Archive for January, 2011

New Storm … Different Flavor
January 31, 2011

A new winter storm is developing and its’ effects will be felt over much of the United States east of the Rockies.

 

The Tuesday morning NASA/GOES satellite image shows the continuing development of the storm over the Plaines states. At the same time, plenty of moisture is being transported northward from the Gulf of Mexico all across the eastern half of the country as indicated by the cloud cover.

Above map updated late Monday night

The National Weather Service Advisories, Watches and Warnings map shows how extensive the effects of this storm will be. Locally a Winter Storm Watch will be in effect through Wednesday morning over the northern tier of Maryland counties into Pennsylvania. Freezing rain with potential ice accumulations of a quarter inch or greater is the main threat.

The NOAA forecast map above (updated Tuesday morning) depicts expected ice accumulations possible into the predawn hours Wednesday morning. The highest values are north of the Maryland/Pennsylvania line.

 

The map above was generated by the National Weather Service at Sterling, Va. and depicts estimated ice accumulation Tuesday and Wednesday. This map does not include data for Cecil and Garrett counties in Maryland or counties in Pennsylvania and Delaware where ice conditions are also expected. Ice accumulation estimates have gone down slightly. This map was updated Tuesday morning.

The reason for the icing threat is high pressure to the north holding dense, cold air in place at the surface over northern Maryland. As the storm moves toward the Ohio River Valley, warm air will be pushed northward. This “less dense” air mass will ride up over the denser cold air at the surface. Rain falling into that shallow layer of cold air will likely freeze on contact with various surfaces, resulting in a coating of ice.

The graph above is a forecast profile (updated at 11:30pm Monday) of what the atmosphere above BWI/Marshall Airport will look like Tuesday morning. The blue and red lines rising from the bottom of the graph depict temperature and dew point at various altitudes, starting near the surface. Temperature is red. The fact that the blue and red lines are are together at the lowest levels of the atmosphere is a sign that the air is saturated. The red line slants to the right up to 825mb (5,700 feet), indicating rising temperatures with altitude. Beyond 6,500 feet, the line slants leftward as temperatures fall. Upon close inspection, the surface temperature at this forecast time(Tuesday 7am) should be 28 degrees whereas the temperature at 5,700 feet is expected to be considerably warmer at 39 degrees. This fits the formula for freezing rain. Colder surface temperatures or a deeper layer of cold air might result in sleet.

The right side of the graph depicts winds. The wind barbs at the surface show an east-northeast wind fetch while the barbs a few thousand feet higher show a southwest wind fetch. This is a signature for the more easterly wind “holding in” the cold temperatures at the surface with the more southerly winds higher up pushing warmer, less dense air  over the top of the colder air. Again, this fits in with the formula for freezing rain.

NOAA forecast map updated late Monday night

The NOAA forecast map above is for Wednesday morning. At this stage in the storm, the weather will be awful in the Great Lakes, including Detroit and Chicago westward into Iowa. Airports in Chicago and elsewhere may be shut down at some stage in this storm, causing air travel disruptions nationwide. In the Mid Atlantic region, freezing rain will likely be transitioning to or already be rain as warmer air squeezes out the remaining pocket of sub-freezing air east of the mountains. The southern limit of the cold air pocket is delineated by the warm/stationary front reaching eastward from West Virginia, then curving up to the DELMARVA Peninsula.

The bottom line, freezing rain should be the main issue with this storm. It should start some time late Monday or early Tuesday and fall intermittently into early Wednesday before becoming all rain. The rainfall should end by the end of the day Wednesday.

Check back with wbaltv.com for storm updates and watch Tom, Tony and Sandra for the latest information on WBAL-TV 11.

By the way, it is summer in the southern hemisphere and while the La Nina weather pattern has contributed to numerous winter storms over the U.S., Australia and New Zealand have been hammered by a series of cyclones.

The latest tropical cyclone in the south Pacific is “Yasi”. As of early Tuesday morning (Baltimore time) the storm is 230 miles northeast of Cairns in northeast Australia with winds clocked at 115 mph. Yasi is expected to make landfall near Cairns by Wednesday morning (Baltimore time) with winds close to 145 mph.

John Collins

Two Clippers Coming
January 28, 2011

Two clippers show up on satellite imagery...click for larger view

Midday Friday 18,000 ft. above sea level...click for larger view

An active northern branch of the jet stream will send two fast moving weather impulses, known as “clippers”, through the mid Atlantic states Friday and Saturday.  These systems will be hard to find on the surface map but can be seen in the upper level wind flow and pressure fields.  The first one looks to be on a better track to produce snow around the Baltimore area; it is headed for central Virginia by midday on Friday, putting Baltimore on the favored north side, where there are colder temperatures and stronger lift.  The second impulse, coming through on Saturday, is forecast to track across Pennsylvania, leaving the Baltimore area on the south side with warmer temperatures and weaker lift.  Unlike Wednesday’s soggy snowmaker, these clippers come out of the drier areas of western Canada and track through the northern plains and Ohio Valley with very little moisture associated with them.  In fact, whereas Wednesday’s storm produced a record 1.82″ of precipitation at BWI-Marshall, Friday’s clipper is forecast to produce less then .10″ of precipitation.  However, with colder temperatures in the middle and upper levels of the atmosphere, the snow to liquid ratio could be around 20:1, producing a quick dusting to perhaps an inch or two of snow as the system moves by.  Current indications are that the snow showers will impact central and eastern Maryland mainly between 9am and 4pm on Friday.

Tom Tasselmyer

Storm Stats: A Couple Records Broken
January 27, 2011

click for larger image

Storm pulling away...click for larger image

As yesterday’s storm continues to pull away from the region, tracking off the coast of Nova Scotia this morning, the record book is being updated here in Baltimore.  The storm broke two records for January 26th:  snowiest and wettest.  The 7.8″ of snow measured at BWI-Marshall was a new record for the day (old record 6.9″ in  1966), and the 1.82″ of total precipitation (melted snow and sleet plus the rain) was also a record for January 26th (old record 1.33″ in 1895).  It is also fascinating to consider that in the city, all that snow fell with temperatures above freezing at ground level; the low temperature for the day was 33F at the National Weather Service’s weather station near the Maryland Science Center!  A testimony to the intensity of the snowfall, which was great enough to overcome the warm low level temperatures.  It is also interesting that the whopping 1.82″ of total precipitation at BWI-Marshall only converted to 7.6″ of snow.  For most storms the liquid to snow ratio is somewhere around 10:1, but yesterday’s storm had a ratio of just 4.2:1 down at BWI-Marshall.  For me, that created a lot of forecasting problems because I did not expect that much snow from an atmosphere that was so warm.  The key was the intense convective snow bursts, accompanied by some thunder, as the upper level low tracked through.  The final snowfall numbers are posted below.  In general, it looks like we saw a 1-6″ snowfall from southern Maryland across the bay to the central eastern shore, and a 6-15″ snowfall from central Maryland to the upper eastern shore and southern PA.

Tomorrow we’ll be tracking a clipper dropping in from the northwest…these storms are typically much drier and it looks like this one will produce just .10″ or less of total precipitation, but that could still produce a quick 1-2″ of snow during the middle of the day and perhaps into the afternoon rush hour.  Stay tuned for more details.

Tom Tasselmyer

PUBLIC INFORMATION STATEMENT
SPOTTER REPORTS
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
911 AM EST THU JAN 27 2011

THE FOLLOWING ARE UNOFFICIAL OBSERVATIONS TAKEN DURING THE PAST
12 HOURS FOR THE STORM THAT HAS BEEN AFFECTING OUR REGION.
APPRECIATION IS EXTENDED TO HIGHWAY DEPARTMENTS...COOPERATIVE
OBSERVERS...SKYWARN SPOTTERS AND MEDIA FOR THESE REPORTS.  THIS
SUMMARY IS ALSO AVAILABLE ON OUR HOME PAGE AT WEATHER.GOV/BALTIMORE

********************STORM TOTAL SNOWFALL********************

LOCATION          STORM TOTAL     TIME/DATE   COMMENTS
                     SNOWFALL           OF
                     /INCHES/   MEASUREMENT

DISTRICT OF COLUMBIA

...DISTRICT OF COLUMBIA...
   NATIONAL ARBORETUM     3.4   908 AM  1/27  CO-OP OBSERVER

MARYLAND

...ALLEGANY COUNTY...
   1 SSE CUMBERLAND      10.0  1150 PM  1/26

...ANNE ARUNDEL COUNTY...
   BWI AIRPORT            7.6   700 AM  1/27  AIRPORT
   1 WNW GREEN HAVEN      7.5   932 PM  1/26  TRAINED SPOTTER
   1 NNE CROFTON          6.5  1000 PM  1/26  TRAINED SPOTTER
   SEVERN                 6.5   913 PM  1/26  SINCE 4...00 PM
   1 NW ANNAPOLIS         6.5  1000 PM  1/26  TRAINED SPOTTER
   1 NNW PAROLE           6.3  1235 AM  1/27  TRAINED SPOTTER
   3 SW LOTHIAN           6.0   740 AM  1/27  TRAINED SPOTTER
   2 NW RIVA              4.0   915 PM  1/26  TRAINED SPOTTER
   EASTPORT               3.0   934 PM  1/26  TRAINED SPOTTER

...BALTIMORE COUNTY...
   1 SE GARRISON         13.4   905 AM  1/27  TRAINED SPOTTER
   1 E OELLA             12.0   803 AM  1/27  TRAINED SPOTTER
   HUNT VALLEY           11.8   802 AM  1/27  BROADCAST MEDIA
   ESSEX                 11.0  1141 PM  1/26  PUBLIC
   JACKSONVILLE          10.0  1143 PM  1/26  PUBLIC
   2 E PERRY HALL         9.5   742 AM  1/27  TRAINED SPOTTER
   1 NNE ROSEDALE         9.2   752 AM  1/27  TRAINED SPOTTER
   1 NE ROSSVILLE         8.7   816 AM  1/27  TRAINED SPOTTER
   PARKVILLE              8.0   942 PM  1/26  TRAINED SPOTTER
   1 WSW GUNPOWDER        7.5  1023 PM  1/26  TRAINED SPOTTER

...BALTIMORE CITY...
   PIMLICO               13.0  1100 PM  1/26  TRAINED SPOTTER
   2 ESE ARLINGTON        9.3   746 AM  1/27  BROADCAST MEDIA
   1 W PARK HEIGHTS       7.0   801 AM  1/27  TRAINED SPOTTER

...CALVERT COUNTY...
   2 N HUNTINGTOWN        4.7   745 AM  1/27  NWS EMPLOYEE
   2 WNW HUNTINGTOWN      4.1   800 AM  1/27  TRAINED SPOTTER
   2 SW HUNTINGTOWN       3.5   941 PM  1/26  TRAINED SPOTTER

...CARROLL COUNTY...
   3 SE WINFIELD         12.7  1149 PM  1/26  TRAINED SPOTTER
   3 WSW LINEBORO        10.0  1130 PM  1/26  TRAINED SPOTTER
   WESTMINSTER            8.0  1100 PM  1/26  NWS EMPLOYEE
   1 W WESTMINSTER        8.0  1135 PM  1/26  NWS EMPLOYEE

...CHARLES COUNTY...
   SAINT CHARLES          6.0  1121 PM  1/26  NWS EMPLOYEE
   2 ESE BRYANS ROAD      5.9  1136 PM  1/26  TRAINED SPOTTER
   2 E BRYANS ROAD        5.7  1000 PM  1/26  TRAINED SPOTTER
   1 SW DENTSVILLE        2.8  1124 PM  1/26  TRAINED SPOTTER

...FREDERICK COUNTY...
   POINT OF ROCKS        11.2  1150 PM  1/26  NWS EMPLOYEE
   2 NE JEFFERSON        10.0  1005 PM  1/26  TRAINED SPOTTER
   NEW MARKET             9.5   747 AM  1/27  TRAINED SPOTTER
   2 NW NEW MARKET        9.0  1000 PM  1/26  TRAINED SPOTTER
   2 ENE MYERSVILLE       9.0  1148 PM  1/26  TRAINED SPOTTER
   2 N LIBERTYTOWN        8.0   714 AM  1/27  TRAINED SPOTTER
   WALKERSVILLE           8.0  1112 PM  1/26  PUBLIC

...HARFORD COUNTY...
   2 E SCARBORO          15.5   751 AM  1/27  TRAINED SPOTTER
   EDGEWOOD              12.0   817 AM  1/27  PUBLIC
   1 NNE BEL AIR          9.5  1247 AM  1/27  TRAINED SPOTTER
   2 E NORRISVILLE        8.0   546 AM  1/27  TRAINED SPOTTER

...HOWARD COUNTY...
   3 WNW WEST FRIENDSHI  12.0   810 AM  1/27  PRIVATE COMPANY
   2 SW SAVAGE           10.5  1102 PM  1/26  TRAINED SPOTTER
   1 SSE SIMPSONVILLE     8.9   749 AM  1/27  TRAINED SPOTTER
   1 N SAVAGE             7.8  1115 PM  1/26  TRAINED SPOTTER
   1 WNW ELKRIDGE         7.5  1051 PM  1/26  TRAINED SPOTTER

...MONTGOMERY COUNTY...
   DAMASCUS              12.1  1003 PM  1/26  TRAINED SPOTTER
   1 N CLARKSBURG        10.5  1100 PM  1/26  BROADCAST MEDIA
   2 WSW GAITHERSBURG     9.0  1015 PM  1/26  TRAINED SPOTTER
   1 W ROCKVILLE          8.2  1116 PM  1/26  TRAINED SPOTTER
   POOLESVILLE            8.0  1015 PM  1/26  TRAINED SPOTTER
   1 ENE POTOMAC          7.8  1119 PM  1/26  TRAINED SPOTTER
   1 ESE NORTH POTOMAC    7.5   951 PM  1/26  TRAINED SPOTTER
   TAKOMA PARK            5.0  1018 PM  1/26  TRAINED SPOTTER
   1 N FOUR CORNERS       4.8   951 PM  1/26  TRAINED SPOTTER

...PRINCE GEORGES COUNTY...
   1 SSE FOREST HEIGHTS   8.0  1150 PM  1/26  CO-OP OBSERVER
   2 NNW BOWIE            8.0  1105 PM  1/26  TRAINED SPOTTER
   1 SW OXON HILL         7.6  1107 PM  1/26  NWS EMPLOYEE
   LAUREL                 7.5   937 PM  1/26  NWS EMPLOYEE
   1 SSW BELTSVILLE       4.5  1149 PM  1/26  TRAINED SPOTTER
   1 SW COLLEGE PARK      4.0   804 AM  1/27  TRAINED SPOTTER
   3 ENE GLENN DALE       3.0   830 AM  1/27  TRAINED SPOTTER

...ST. MARYS COUNTY...
   RIDGE                  1.5   749 AM  1/27  TRAINED SPOTTER
   LEXINGTON PARK         0.5  1145 PM  1/26  TRAINED SPOTTER
   3 ESE PARK HALL        0.5  1153 PM  1/26  TRAINED SPOTTER
DELAWARE

...KENT COUNTY...
   SMYRNA                 3.7   131 AM  1/27
   DOVER                  3.4   211 AM  1/27
   HARRINGTON             2.5   213 AM  1/27
   DOVER SPEEDWAY         2.5   239 AM  1/27
   VIOLA                  1.5   213 AM  1/27

...NEW CASTLE COUNTY...
   HOCKESSIN             12.1   209 AM  1/27
   PRICES CORNER         11.6   209 AM  1/27
   NEWARK                11.5   841 AM  1/27
   GREENVILLE            11.4   206 AM  1/27
   TALLEY BROOK          10.9   207 AM  1/27
   2 NW NEWARK           10.8   207 AM  1/27
   BEAR                  10.4   700 AM  1/27
   WILMINGTON ASOS       10.4   700 AM  1/27
   BLACKBIRD              8.9   210 AM  1/27
   GLASGOW                8.5   210 AM  1/27
   CLAYMONT               8.4   207 AM  1/27
   CHRISTIANA             4.7   431 AM  1/27  SINCE 6 PM

...SUSSEX COUNTY...
   ELLENDALE              3.7   214 AM  1/27
   LAUREL                 2.8   215 AM  1/27
   BRIDGEVILLE            1.5   215 AM  1/27
   LEWES                  0.7   305 AM  1/27
   STOCKLEY               0.4   214 AM  1/27

MARYLAND

...CECIL COUNTY...
   ELKTON                 8.5   121 AM  1/27

...KENT COUNTY...
   GALENA                 8.0   449 AM  1/27
   MILLINGTON             5.6   545 AM  1/27

...QUEEN ANNE`S COUNTY...
   STEVENSVILLE           5.3  1256 AM  1/27
   KENT ISLAND ESTATES    4.0  1147 PM  1/26

...TALBOT COUNTY...
   SAINT MICHAELS         4.5   503 AM  1/27
   EASTON                 3.5   502 AM  1/27
   TRAPPE                 1.5   502 AM  1/27
PENNSYLVANIA

...ADAMS COUNTY...
   2 N ABBOTTSTOWN        6.4   700 AM  1/27  COCORAHS
   CASHTOWN 1S            5.8   800 AM  1/27  COOP
   YORK SPRINGS           5.7   818 AM  1/27  SPOTTER
...LANCASTER COUNTY...
   NEW HOLLAND           12.0   849 AM  1/27  COOP
   2 SE LANCASTER        11.6   846 AM  1/27  COOP
   MILLERSVILLE          11.5   847 AM  1/27  MILLERSVILLE UNIV.
   SAFE HARBOR           10.9   846 AM  1/27  COOP
   LANCASTER             10.0   821 AM  1/27  SPOTTER
   DENVER                 9.0   819 AM  1/27  SPOTTER
   WEST LAMPETER          7.0   822 AM  1/27  SPOTTER
...YORK COUNTY...
   STEWARTSTOWN          11.0   823 AM  1/27  SPOTTER
   1 ENE VALLEY GREEN     7.5   600 AM  1/27  COCORAHS
   LOGANVILLE             7.3   820 AM  1/27  SPOTTER

Part Two Moving In
January 26, 2011

I just wanted to post this beautiful satellite image of today’s storm. Click on it for a larger version.

I didn’t want to mark it up with any reference points. You can visualize the storm center and it is southwest of Baltimore, in North Carolina.

The National Weather Service surface map from mid afternoon shows two low pressure centers combined into one large storm complex that was generating thunder and lightening in the Baltimore area in the four o’clock hour with a combination of snow, sleet and rain. The precipitation shield reached westward into West Virginia.

The map above shows storm tracks for the next three days. The coastal low is headed for the Canadian Maritime Provinces. Two other clipper type disturbances will be headed toward the Great Lakes and Mid Atlantic regions as well.

Snow chances should taper off after midnight. At least several inches of additional snow are likely guaranteed, with more than 6 inches in areas where heavy snow bands develop. Tom’s forecast calls for up to ten inches of snow.

Check out Tom’s detailed forecast this evening tonight on WBAL-TV 11 and stay up to date on wbaltv.com.

John Collins

Round Two On The Way
January 26, 2011

Water vapor satellite from 7:45 a.m...click for larger image

Upper level low crossing the bay at 7pm...click for larger image

Water vapor satellite imagery and radar data show the morning round of rain and snow tracking northeast with the precipitation expected to taper to light rain or drizzle mixed with some sleet or a few flurries through midday.  However, the same satellite imagery is showing what the computer models have been forecasting; part 2 of this storm to our southwest is ready to move toward the mid Atlantic and should arrive during the evening rush hour.  This second part of the storm is the low pressure system tracking through the atmosphere up around 18,000 feet.  It is expected to move across the lower Chesapeake Bay this evening , possibly producing a period of heavy snow between 4pm and midnight, perhaps even kicking up some isolated thundersnow.  The approaching upper level low will help the surface low (still rather disorganized over Georgia and South Carolina) to rapidly intensify, and both systems will head northeast to a position well east of Cape Cod by dawn on Thursday.

RPM total snow forecast by early Thursday a.m...click for larger image

If this forecast scenario holds, snowfall totals (from both parts of the storm) will reach 6-10″ in the colder northern and western suburbs, and 2-6″ east of I-95 by the time the snow winds between midnight and 2:00 a.m.  A fascinating and complicated storm which may still require forecast updates…stay tuned!

Tom Tasselmyer

Late Evening Winter Storm Update
January 26, 2011

1007 millibar low in southern AL...click for larger image

3 hour pressure falls off the NC coast will pull the storm northeast

The winter storm forecast to move into the mid Atlantic region on Wednesday continues to slowly organize over southern Alabama tonight.  The low pressure system at the surface has not intensified very much; the central pressure down to just 1007 millibars as of 10:00 p.m., but the surface pressures are falling rapidly just east of Wilmington, NC, suggesting the storm will be scooting in that direction and gaining strength overnight.

7pm upper air sounding from near Dulles airport...click for larger image

The evening balloon launch near Dulles airport revealed the expected forecast dilemma: temperatures above freezing in the lower levels of the atmosphere.  This will cause a wintry mix of precipitation to fall as the storm arrives in the early morning, most likely rain, sleet, and some snow, but watch for pockets of freezing rain as well.

Upper low tracking through eastern VA 7pm Wednesday

The early evening computer model runs have shifted the main snowband to the southeast and are pointing to the possibility of nasty weather for the evening rush hour as the upper level low tracks across east central Virginia around sunset.  On that track, the upper level low could produce strong upward lift which would rapidly cool the atmosphere and change the mixed precipitation to a period of heavy snow.  Patterns like this can also produce occasional thundersnow, which would create some intense snow showers during the early evening.

Put it all together and a general 3-6″ snowfall looks very possible for much of central and eastern Maryland from late afternoon Wednesday through about 2:00 a.m. Thursday.  Timing the changeover from mixed precipitation to all snow and trying to account for possible convective snow bursts makes this a very tricky forecast which may have to be tweaked further…so as always…stay tuned!

Tom Tasselmyer

Winter Storm Watch Posted
January 25, 2011

Beautiful water vapor image of a potentially ugly storm

Mid week winter storm on Gulf Coast with 1009 mb central pressure

Severe Storms Prediction Center slight risk for Florida

As our mid week winter storm continues to develop on the gulf coast, the National Weather Service has posted a Winter Storm Watch for Wednesday afternoon and night.  The “Watch” means there is a “potential” for significant winter weather within the next 48 hours.  It is interesting that the potential for significant winter weather is increasing even though compared to yesterday’s frigid arctic blast, temperatures have warmed considerably today as the arctic high pressure moves off the Maine coast.  The storm on the Louisiana coast has a central pressure of 1009 millibars and is showing signs of strengthening, kicking up thunderstorms over the gulf waters and prompting the Severe Storms Prediction Center to outlook most of Florida with a “slight risk of severe weather”.

Gulf Coast storm forecast to track up the eastern seaboard

As the storm tracks northeast tonight and tomorrow, our big forecasting dilemma will be trying to figure out how cold the atmosphere will be at various critical heights above the ground.  It seems archaic, but even in the 21st century we still rely on the data gathered by weather balloons launched around the world a couple times each day to help us determine just how warm or cold the atmosphere is.  Around here, the folks up at the Aberdeen Proving Ground will frequently launch a balloon in the early morning, but our closest regular balloon launch is done just outside of Dulles airport in Sterling, Va.  The balloons launched this morning at these two sites revealed temperatures just under freezing (-1.5c at APG and -0.9c at IAD) at the rain/snow critical level of 4500 to 5000 feet above the ground.  In the mid Atlantic region temperatures usually need to stay below freezing at this level for some snow and sleet to fall.  Warmer temperatures at this level usually produce rain.

Freezing line at critical upper level 7:00 a.m. Wednesday

Freezing line at critical level 10:00 a.m. Wednesday

Freezing line at critical upper level 7:00 p.m. Wednesday

So, how cold will this critical level be as the gulf coast storm arrives late tonight and early Wednesday?  The latest run of our in-house RPM model shows the precipitation reaching central Maryland between 2:00 a.m. and 4:00 a.m.  At that time most of Maryland north of the Bay Bridge is forecast to be cold enough for at least some snow and sleet to be in the precipitation mix.  By 10:00 a.m., however, the freezing line at that critical level has pushed farther north and west, meaning rain, or the dreaded freezing rain (rain turning to ice on contact with colder surfaces), will be pushing into areas roughly south and east of I-95.  As the storm intensifies and begins to pull away, the freezing line at 4500-5000 feet above the surface surges back to the south and east and the mixed precipitation, for most areas west of the bay, will likely change to all snow by 7:00 p.m. Wednesday, perhaps continuing into early Thursday morning.

RPM snowfall forecast ending 1:00 p.m. Thursday

So, with multiple precipitation types and a couple of rain/sleet/snow change-overs, it will be very difficult to determine how much of the total precipitation ends up as accumulating snow.  The 12z RPM is painting a stripe of 2-7″ of snow along and to the west of I-95 by early Thursday afternoon.  Right now it looks like the heaviest snow around here (about 7″) will fall in a band extending from the Catoctin Mountains, perhaps clipping northwest Carroll County, and stretching southwest into the Shenandoah Mountains of northern Virginia  where the RPM is forecasting some isolated 10-12″ totals.  For Kent and Cecil Counties on the upper eastern shore the model is showing 2-4″ of snow by Thursday afternoon with just 1-2″ for the rest of the eastern shore from Queen Anne’s County south, and 1-2″ for the western shore south of BWI-Marshall.

This is an early estimate of the snowfall possible with this storm, but due to the “messy” nature of the expected precipitation the forecast will probably need to be tweaked as the system continues to organize and make its approach from the south.

Tom Tasselmyer

Wintry Mix On Wednesday
January 25, 2011

Arctic covers Maryland Monday Morning

Arctic air retreating Monday evening

It is hard to believe that just 48 hours after the coldest temperatures of the winter a storm system will arrive with a messy wintry mix of precipitation instead of just pure snow.  Monday evening surface maps show the arctic air retreating to the northeast as our mid week storm develops near the gulf coast.

RPM 8am Wednesday, 26 Jan 2011...Wintry mix across Maryland

RPM 6pm Wednesday 26 Jan 2011...Wintry mix changing to snow

By the time the storm is on the Carolina coast Wednesday morning, temperatures around here will be just under freezing at ground level and a couple degrees warmer just a few thousand feet above the surface.  That will probably produce a mix of snow and sleet at the storm’s onset with snow, sleet, freezing rain, and rain falling at various times throughout the day Wednesday.  The mixed nature of the precipitation will limit snow accumulations during the daylight hours of Wednesday, but our in-house RPM model is showing the air mass turning colder as the storm intensifies and begins to pull away Wednesday evening.  The arrival of the colder air will probably mean the mix will change to all snow Wednesday night with several inches possible before the storm moves farther away from the region early Thursday morning.

With the Baltimore area positioned right on the rain/snow line, adjustments to the forecast are likely as the system gets closer.  Stay tuned for further updates on Tuesday.

Tom Tasselmyer

New Storm Developing
January 24, 2011

This winter has been very different from last year with its’ three major storms. To date the area has been the target of a series of relatively minor weather disturbances and has been on the outer edges of two major storms. Most notably, it has been cold. Decembers temperatures were 4.3 degrees below average at BWI-Marshall and this month the numbers are running 1.7 degrees below average to date.

This morning was the coldest of the winter season so far. Preliminary low temperatures were:

8    BWI-Marshall

17   Maryland Science Center

10   Aberdeen Proving Ground

16   Annapolis(Naval Academy)

12   Martin State Airport

-7   Elkins, WV

Folks are saying that the cold has been relentless. Perhaps that is because the area has experienced only a few breaks with milder temperatures. Only seven days in December registered above average temperatures with only four days above average so far in January.

In the snowfall category, the numbers are unimpressive:

1.2 inches   December

3.1 inches    January

A new storm is developing and it will be moving up the coast this week. Computer models have been all over the ballpark in the past few days with the track forecast. Those models now seem to be zeroing in on a solution although some of the fine points of the storm are still up for grabs.

It now appears that the storm will be moving past the area on Wednesday. It also appears that the storm will pass closer to the Mid Atlantic coast, allowing warmer air to be drawn in ahead of it. This increases the chances that rain will be a bigger component of the storm.

The current idea is that Baltimore, and areas to the east and south will probably see mostly rain with some snow and sleet while areas to the north and west would see a greater proportion of snow mixed with some rain or sleet. It looks like most if not all of this precipitation will fall on Wednesday.

Keep in mind that it is still early in the forecast cycle regarding this storm. Details still have to be worked out and some adjustments are likely. Keep checking in at wbaltv.com for updates and tune in WBAL-TV 11 for the latest with Tom, Tony and Sandra.

John Collins

Ice Fog at 46 Below Zero
January 21, 2011

Ice fog this morning as the temperature dropped to -46 at Babbitt, MN

The above picture is from Babbitt, Minnesota where a frigid morning low temperature of -46 degrees was recorded on January 21, 2011. The pictures were taken by observer Ryan Scharber. The pictures show ice fog, which is usually a shallow fog consisting of suspended ice crystals. Ice fog usually only occurs when temperatures fall below -22 degrees Fahrenheit (-30 Celsius) according to the AMS Glossary.  Normally, fog consists of tiny water droplets, or supercooled water droplets. However, when temperatures are as cold as they were this morning in parts of northern Minnesota, it becomes too cold for liquid water to exist, and small ice crystals can develop if the amount of water vapor in the air is sufficient.

Fast Facts

  • The lowest temperatures recorded in the NWS Duluth county warning area were -46 degrees at both International Falls, MN (ASOS) and Babbitt, MN (CO-OP).
  • The -46 degree low was tied for the 5th lowest on record at International Falls. Temperature records date back to 1897. The record is -55 degrees which was recorded on January 6, 1909.
  • The -46 degree low was tied for the lowest on record at the International Falls Airport. The official observing station was moved to the airport in 1939. This is tied with the -46 degree reading from January 6, 1968.

List Of Coldest Morning Lows

THE FOLLOWING ARE OBSERVED LOW TEMPERATURES THROUGH 900 AM FRIDAY
JANUARY 21 2011. TEMPERATURES ARE IN DEGREES FAHRENHEIT.

 TEMP    LOCATION                 ST  COUNTY           SOURCE
 ----    -----------------------  --  --------------   -------
 -46     INTERNATIONAL FALLS      MN  KOOCHICHING      ASOS
 -46     BABBITT                  MN  ST LOUIS         COOP
 -43     EMBARRASS                MN  ST LOUIS         COOP
 -43     BIGFORK                  MN  ITASCA           RAWS
 -43     ASHLAKE                  MN  ST LOUIS         MNDOT
 -43     EFFIE                    MN  ITASCA           RAWS
 -40     LITTLEFORK               MN  KOOCHICHING      COOP
 -40     BIRCHDALE                MN  KOOCHICHING      MNDOT

This report was posted on the website of the National Weather Service
Forecast Office in Duluth, MN:  http://www.crh.noaa.gov/dlh/
The arctic air the produced the frigid air in the upper midwest
this morning will sweep through the mid Atlantic and northeast U.S.
this weekend.

Tom Tasselmyer