FXUS63 KBIS 091011
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
411 AM CST WED DEC 9 2009

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT...

MAIN FORECAST HIGHLIGHT IN THE SHORT TERM PERIOD WILL CONTINUE TO BE 
UNSEASONABLY COLD TEMPERATURES. MODELS REMAIN IN FAIR AGREEMENT SO 
WILL UTILIZE A BLEND.   

CURRENTLY...AS IS TYPICAL WITH LONG DURATION COLD OUTBREAKS ACROSS 
NORTH DAKOTA...THE UPPER LEVEL PATTERN CONSISTS OF A HIGH AMPLITUDE 
RIDGE ACROSS THE US/CANADIAN PACIFIC COAST STRETCHING NORTH TO 
ALASKA...AND A DEEP TROUGH OVER CENTRAL NORTH AMERICA. THIS PATTERN 
HAS AND IS ALLOWING REINFORCED SHOTS OF COLD ARCTIC AIR TO SURGE 
SOUTH INTO THE NORTHERN PLAINS FROM A POLAR VORTEX SPINNING OVER FAR 
NORTH CENTRAL CANADA. THE INTENSE WINTER STORM WHICH DEVELOPED 
ACROSS THE CENTRAL PLAINS TUESDAY HAS MOVED INTO THE MIDWEST WHERE 
IT CONTINUES TO PROMPT WINTER STORM AND BLIZZARD WARNINGS. CLOUD 
COVER ASSOCIATED WITH THIS STORM CONTINUES TO COVER THE EASTERN HALF 
OF ND WITH PERHAPS A FEW FLURRIES YET OVER MY SOUTHEASTERN COUNTIES. 
CLEAR TO PARTLY CLOUDY SKIES WEST AND NORTH UNDER THE AFFECTS OF 
SURFACE HIGH PRESSURE. CURRENT WIND CHILL ADVISORIES ARE WELL 
DESERVED AND WILL ALLOW THEM TO CONTINUE PAST DAYBREAK. 
   
SKIES WILL CONTINUE TO CLEAR/SCATTER OUT THIS MORNING SOUTH AND EAST 
AS THE MIDWEST WINTER STORM PUSHES NORTHEAST INTO THE GREAT LAKES 
REGION...PUTTING ALL OF WEST AND CENTRAL ND MORE UNDER THE AFFECTS 
OF SURFACE HIGH PRESSURE. ANOTHER S/WV IMPULSE ORIGINATING FROM THE 
POLAR VORTEX WILL SLIDE SOUTH-SOUTHEAST ALONG THE FRONT RANGE OF THE 
CANADIAN ROCKIES THIS MORNING...THEN INTO OUR LOCAL REGION LATER 
TODAY AND TONIGHT. THIS FEATURE WILL BRING ANOTHER REINFORCED SHOT 
OF COLD AIR ALONG WITH INCREASING CLOUDS AND SCATTERED SNOW SHOWERS 
SPREADING FROM WEST TO EAST THIS AFTERNOON INTO TONIGHT. WILL NEED 
ANOTHER WIND CHILL ADVISORY TONIGHT...BUT WITH THE CURRENT ADVISORY 
IN EFFECT WILL LET THE DAY CREW DO THE HONORS. ANOTHER S/WV IMPULSE 
QUICKLY FOLLOWS THE FIRST AND PUSHES ACROSS THE STATE THURSDAY/THURS 
NIGHT BRINGING YET ANOTHER SURGE OF ARCTIC AIR ALONG WITH AREAS OF 
LIGHT SNOW. HOWEVER...OUR FLOW ALOFT BEGINS TO TRANSITION TO MORE 
NORTHWESTERLY ON THURSDAY...THEN SLOWLY TRENDS TOWARDS ZONAL 
FRIDAY/FRIDAY NIGHT. THUS DESPITE THIS SECOND IMPULSE...THE CHANGE 
IN FLOW WILL ENABLE SOME WEAK WAA INTO SOUTHWESTERN ND 
THURSDAY...THEN EVEN MORE SO ON FRIDAY AND FURTHER TO THE NORTHEAST 
AS THE CHANGE IN FLOW FINALLY PUSHES THE SFC HIGH OFF TO OUR EAST 
ALLOWING WARMER RETURN FLOW INTO THE FORECAST AREA. DESPITE THIS 
WARM UP...FORECAST HIGHS LOOK TO REMAIN 10-20 DEGREES FAHRENHEIT 
BELOW SEASONAL AVERAGES BOTH THURSDAY AND FRIDAY.

.LONG TERM...SATURDAY THROUGH WEDNESDAY...

THE MAIN DIFFICULTY TODAY CONCERNS THE POSSIBLE ARRIVAL OF FRIGID 
AIR OVER NORTH DAKOTA. 

THE 00 UTC ECMWF/GFS/GEFS MEMBERS ALL UNDERCUT THE BERING SEA OMEGA 
BLOCK WITH LOWER HEIGHTS AND THE SPACING BETWEEN FEATURES LOOKS MUCH 
MORE REASONABLE THAN LAST NIGHTS RUNS. 

THE TREND IN MODELS/ENSEMBLES OVER THE PAST DAY HAS BEEN TO PLACE 
THE POLAR VORTEX OVER SOUTH CENTRAL CANADA FURTHER NORTH BY THE END 
OF THE WEEKEND. THIS WOULD CAUSE FAR LESS COLD ADVECTION IN THE 
NORTHERN PLAINS THAN PREVIOUSLY THOUGHT AS THE CONTINENTAL ARCTIC 
AIRMASS FAILED TO ADVECT MUCH SOUTH OF THE U.S.-CANADIAN BORDER. 
THAT SAID...SUCH A DRASTIC SHIFT FROM CONTINUITY WITH BELOW AVERAGE 
ENSEMBLE SPREAD PRIOR TO TODAY IS NOT NECESSARILY A RELIABLE SHIFT. 
AVOIDING THE POSSIBILITY OF FLIP-FLOPPING SEEMS MORE IMPORTANT...SO 
THE GRIDDED FORECAST HAS ONLY BEEN NUDGED A FEW DEGREES WARMER. 
SHOULD THE TREND BE CONSISTENT...FUTURE FORECASTS WILL BE WARMED 
CONSIDERABLY. 

MODELS ALSO HAVE GREATER CHANCES OF PRECIPITATION WITH THIS 
NORTHWARD PUSH OF THE POLAR VORTEX. THIS IS MAINLY BECAUSE THE 
ASSOCIATED WESTERLIES ALSO MOVE NORTHWARD. LIKE WITH 
TEMPERATURES...GRIDDED FORECASTS HAVE NOT REALLY INCREASED 
PRECIPITATION CHANCES MUCH. SO...THEY MAY NEED TO BE INCREASED IN 
LATER ISSUANCES. 

&&

.AVIATION...

A FEW MVFR CEILINGS ARE POSSIBLE THIS MORNING WITH LIGHT SNOW THAT 
HAS BEEN REPORTED ACROSS SOUTHWEST NORTH DAKOTA. OTHERWISE...VFR 
CONDITIONS THANKS TO HIGH PRESSURE OVER THE DAKOTAS MAY BECOME MVFR 
AGAIN TONIGHT AS A WEAK ALBERTA CLIPPER PASSES THROUGH WESTERN NORTH 
DAKOTA LATE TONIGHT INTO EARLY THURSDAY MORNING. 

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL NOON CST /11 AM MST/ TODAY FOR 
NDZ001>005-009>013-017>023-025-031>037-040>048-050-051.

&&

$$

SHORT TERM...NH
LONG TERM/AVIATION...SCHECK