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Weather Update, November 5, 2008: Rain, Tornadoes, and Blizzards Oh My!

5 Nov 2008, 3:22 pm

What a difference a day makes in the world of weather forecasting! Remember yesterday I stated that the watches and warnings issued by the NWS were from the previous days NAM run, and perhaps some adjustments might be needed? Low and behold, the adjustments have been made. Today the NWS has expanded their areal coverage of winter storm watches, blizzard watches, and blizzard warnings to the general area covered by NAM (again from yesterday’s run as you were previously shown). So now we have various snow advisories and warnings for the majority of North and South Dakota extending a tad south into Nebraska, and east into Wyoming and Montana (note graphic at left, click for full size).

Below is a screen cap of our HAMrad II Precipitation Type Radar product for the Northern Great Plains showing snow in the upper elevations of the Black Hills with liquid precipitation along the Cheyenne River just northwest of the badlands extending outward.

Sampling of Watches and Warnings active as of ~ 1pm November 5, 2008
Blizzard Warning for North Dakota
NATIONAL WEATHER SERVICE BISMARCK ND
1105 AM CST WED NOV 5 2008

A MAJOR WINTER STORM SYSTEM FOR NORTH DAKOTA

A STRONG LOW PRESSURE SYSTEM IN SOUTHEASTERN SOUTH DAKOTA WILL MOVE TO CENTRAL MINNESOTA BY FRIDAY. THIS SLOW MOVING STORM WILL BRING BLIZZARD CONDITIONS TO SOUTHWEST AND SOUTH CENTRAL NORTH DAKOTA TONIGHT…THURSDAY…AND THURSDAY NIGHT. SIX TO TWELVE INCHES OF SNOW…WIND GUSTS TO 50 MPH…AND VISIBILITIES NEAR ZERO ARE LIKELY DURING THE HEIGHT OF THE STORM. DANGEROUS WINTER WEATHER WILL ALSO STRIKE NORTHWEST AND NORTH CENTRAL NORTH DAKOTA TONIGHT THROUGH THURSDAY NIGHT… WITH 4 TO 8 INCHES OF SNOW… WINDS TO 40 MPH AND GREATLY REDUCED VISIBILITIES. THESE DANGEROUS CONDITIONS WILL LIKELY MOVE EAST INTO THE JAMES RIVER AREA THURSDAY.

THE STORM WILL BRING RAIN THIS AFTERNOON…AND THEN THE RAIN WILL CHANGE TO HEAVY WET SNOW…FIRST IN THE NORTHWEST LATE THIS AFTERNOON… AND THEN ACROSS THE REMAINDER OF THE REGION TONIGHT. FREEZING RAIN MAY ALSO PRECEDE THE CHANGE TO SNOW.

TRAVEL WILL LIKELY BECOME IMPOSSIBLE IN THE SOUTHWEST AND SOUTH CENTRAL BY DAYBREAK THURSDAY.

PLEASE RECONSIDER TRAVEL PLANS AND MAKE OTHER PREPARATIONS FOR THE STORM. IF YOU MUST TRAVEL…HAVE A WINTER SURVIVAL KIT WITH YOU. IF YOU GET STRANDED…STAY WITH YOUR VEHICLE.

Blizzard Warning for South Dakota
NATIONAL WEATHER SERVICE RAPID CITY SD
1009 AM MST WED NOV 5 2008

A DEVELOPING UPPER LEVEL LOW IN NORTHWEST WYOMING WILL CONTINUE TO MOVE SOUTHEAST TODAY AND STRENGTHEN OVER NORTHWEST NEBRASKA LATE THIS AFTERNOON. THIS STORM SYSTEM IS EXPECTED TO CONTINUE TO STRENGTHEN AS IT MOVES SLOWLY EAST ACROSS NORTHERN NEBRASKA TONIGHT INTO THURSDAY MORNING.

THIS STORM SYSTEM WILL BRING SIGNIFICANT AMOUNTS OF PRECIPITATION TO WESTERN SOUTH DAKOTA AND THE FAR NORTHEASTERN CORNER OF WYOMING FROM THIS AFTERNOON THROUGH THURSDAY. MUCH OF THE PRECIPITATION WILL FALL AS SNOW. THE HEAVIEST SNOWS WILL BE OVER
THE NORTHERN AND CENTRAL BLACK HILLS WHERE 1 TO 2 FEET OF SNOW IS POSSIBLE BY LATE THURSDAY AFTERNOON. ON THE PLAINS OF WESTERN SOUTH DAKOTA 6 TO 14 INCHES OF SNOW IS EXPECTED BY THURSDAY AFTERNOON.

VERY WINDY CONDITIONS WILL DEVELOP ON THE PLAINS OF WESTERN SOUTH DAKOTA BY MIDDAY…WITH EVEN STRONGER WINDS TONIGHT AND THURSDAY. THE STRONG WINDS AND SNOW WILL LEAD TO GREATLY REDUCED VISIBILITIES AND DIFFICULT TRAVEL CONDITIONS DUE TO BLOWING SNOW TONIGHT AND THURSDAY.

Flood Watch for North Dakota
NATIONAL WEATHER SERVICE GRAND FORKS ND
1151 AM CST WED NOV 5 2008

POTENTIAL FLOODING ACROSS THE RED RIVER VALLEY…

AN UNSEASONABLY STRONG AND SLOW MOVING LOW PRESSURE SYSTEM WILL CONTINUE TO MOVE THROUGH SOUTH DAKOTA TODAY AND TONIGHT. AS THE SYSTEM MEANDERS TO THE EAST OVER THE NEXT FEW DAYS…THERE WILL BE A POTENTIAL OF SEVERAL ROUNDS OF HEAVY PRECIPITATION AFFECTING THE RED RIVER VALLEY. ALTHOUGH THE AREA HAS BEEN RELATIVELY DRY AS OF LATE… SOILS ARE STILL NEARLY SATURATED AS EVAPORATION IS AT A SEASONAL MINIMUM. AS A RESULT… HEAVY PRECIPITATION WILL SATURATE THE SOILS VERY QUICKLY AND GENERATE RUNOFF.

AS THIS RUNOFF MAKES ITS WAY TO THE RIVER SYSTEMS…WHICH ARE NEAR RECORD HIGH BASE FLOWS FOR NOVEMBER…RIVER LEVELS ARE EXPECTED TO RISE. MODERATE FLOODING AT SOME POINTS ALONG THE RED RIVER AND ITS TRIBUTARIES IS POSSIBLE.

Current Model Thoughts
NAM 84 Hour Forecast Snowdepth Product (3 hour increments)
There are some similarities to yesterday’s run with today’s snowdepth animation product (click image at left for full size).

There are some differences with degree and breadth of areal coverage of forecast snowdepth based upon subtle changes in the timing of cold air advection that have been adjusted since yesterday (note below).

NAM 84 Hour Forecast Two Meter Temperatures (3 hour increments)
Notice at left (click for full size) while viewing the NAM 84 Hour 2 meter temperature forecast animation (at 3 hour increments) the “temperature of interest” isotherms plotted onto the graphics. View closely the 32°F isotherm (red line) and the propagation of colder air at the surface. Pockets of “warmer air” are shown to remain (surface – boundary interface) as the air progresses adjusting the timing of associated frozen precipitation (snow). Additionally, progression is slightly different than shown yesterday accounting for adjustments in the breadth and areal coverage of forecast snowdepth above.

However, it is ‘basically the same’ as yesterday =) Will more adjustments in watches and warnings be needed by tomorrow? =)

NAM 84 Hour Forecast Liquid Precipitation (3 hour increments)
Our NAM 84 Hour Liquid Precipitation Forecast Animation (3 hour increments) displays the wet weather ahead for the Pacific Northwest as a respectable warm air mass propagates inland. Additionally our small area of low pressure is forecast to continue sliding northward along the east coast, and the strong precipitation shield that will extend from the enclosed area of lower pressure in the Dakotas is shown, from which tornadoes are very likely (notice the east central great plains and east / south into tomorrow).
Tornadoes, Hail, and Flying Cows Oh My!
SPC Day 1 Convective Outlook SPC Probabilistic Tornado Product
The Storm Prediction Center finally upgraded their Day One Convective Outlook to include a small moderate risk area for the day. Convective Initiation will likely be more westward than they predict, but importantly, those in the forecast area of concern should take extreme caution. The SPC Public Statement is below in its entirety.

NWS STORM PREDICTION CENTER NORMAN OK
1039 AM CST WED NOV 05 2008

SIGNIFICANT SEVERE THUNDERSTORMS EXPECTED OVER PARTS OF THE PARTS OF NORTHERN OKLAHOMA AND SOUTHERN KANSAS LATER THIS AFTERNOON AND EARLY TONIGHT…

THE NWS STORM PREDICTION CENTER IN NORMAN OK IS FORECASTING THE DEVELOPMENT OF A FEW STRONG TORNADOES OVER PARTS OF THE PARTS OF NORTHERN OKLAHOMA AND SOUTHERN KANSAS LATER THIS AFTERNOON AND EARLY TONIGHT.

THE AREAS MOST LIKELY TO EXPERIENCE THIS ACTIVITY INCLUDE SOUTH CENTRAL AND SOUTHEASTERN KANSAS NORTH CENTRAL AND NORTHEASTERN OKLAHOMA ELSEWHERE… SEVERE STORMS ARE ALSO POSSIBLE FROM… EASTERN PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS INTO THE OZARKS AND LOWER MO VALLEY.

A STRONG COLD UPPER TROUGH OVER THE CENTRAL ROCKIES WILL MOVE EWD INTO THE PLAINS TONIGHT. A WARM/MOIST UNSTABLE SOUTHERLY FLOW AHEAD OF THE TROUGH AND ITS ASSOCIATED COLD FRONT NOW LOCATED FROM ERN SD/CENTRAL NEB TO SERN CO WILL FUEL DEVELOPMENT OF SEVERE THUNDERSTORMS LATER THIS AFTERNOON. WITH THE PRESENCE OF THE STRONG UPPER LEVEL JET… CONDITIONS WILL BE FAVORABLE FOR TORNADIC SUPERCELLS TO DEVELOP BY LATER THIS AFTERNOON ACROSS SCENTRAL KS/NCENTRAL OK NEAR THE COLD FRONT/DRY LINE INTERSECTION. ADDITIONAL SUPERCELL DEVELOPMENT IS POSSIBLE SOUTHWARD ALONG DRY LINE TO THE TX/OK BORDER BY THIS EVENING.

THERE IS THE POTENTIAL FOR LONG LIVED SUPERCELLS TRACKING NEWD ACROSS SERN KS/NERN OK THRU THE EVENING WITH POSSIBLE STRONG TORNADOES. IN ADDITION DAMAGING WINDS AND LARGE HAIL WILL ACCOMPANY THE STRONGEST STORMS FROM ERN NEB SWD THRU OK LATER THIS AFTERNOON WITH THE THREAT EXTENDING EWD INTO LOWER MO VALLEY AND THE OZARKS TONIGHT.

THOSE IN THE THREATENED AREA ARE URGED TO REVIEW SEVERE WEATHER SAFETY RULES AND TO LISTEN TO RADIO…TELEVISION…AND NOAA WEATHER RADIO FOR POSSIBLE WATCHES… WARNINGS… AND STATEMENTS LATER TODAY.

As always stay tuned to your favorie weather outlet, stay informed, and stay safe!

cheers,

–patrick

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