FXUS63 KBIS 092049 CCA
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
248 PM CST WED DEC 9 2009

.SHORT TERM...
FORECAST MODELS CONTINUE TO BE IN GOOD AGREEMENT THROUGH THE SHORT 
TERM PERIOD. THE MAIN FORECAST CONCERNS ARE DAILY TEMPERATURES AS 
WELL AS WINDS FOR POSSIBLE AFFECTS ON THE WIND CHILL.

CURRENTLY...AN UPPER LEVEL TROUGH CONTINUES TO DOMINATED THE WEATHER 
OVER WESTERN NORTH AMERICA BROUGHT TO YOU BY OMEGA BLOCKING OVER THE 
BERING SEA.  THIS CONTINUES TO HOLD A RIDGE ALONG THE WEST COAST 
WITH A POLAR VORTEX SPINNING IN NORTHWESTERN CANADA. AT THE 
SURFACE...CANADA HIGH PRESSURE CONTINUES TO PUMP ARCTIC AIR 
SOUTHWARD INTO THE NORTHERN PLAINS. WINDS OF 10 TO 20 MPH STATE WIND 
COMBINED WITH SUB ZERO TEMPERATURES TO PUSH WIND CHILL VALUES IN THE 
-20 TO -30 RANGE THIS AFTERNOON SO THE WIND CHILL ADVISORY FROM LAST 
CONTINUES INTO THURSDAY AFTERNOON.

THE FLOW ALOFT OVER THE NORTHERN PLAINS TRANSITIONS TO A MORE 
NORTHWESTERLY FLOW TONIGHT AS A DISTURBANCES BRINGS A TROUGH THROUGH 
NORTH DAKOTA. THE UPPER LEVEL ENERGY IS LOCATED BEHIND THE TROUGH SO 
A FEW FLURRIES MAY BE POSSIBLE THIS EVENING BEFORE SNOW SHOWERS 
DEVELOP TOMORROW. BEHIND THE TROUGH ANOTHER FRIGID SURFACE HIGH 
DROPS INTO NORTH DAKOTA BRINGING ANOTHER REINFORCING SHOT OF COLD 
AIR FOR THURSDAY. MIXING INCREASES BEHIND THE TROUGH SO WINDS ARE 
EXPECTED TO PICK UP EARLY TOMORROW AND CONTINUE INTO THE EVENING. 
THE WIND CHILL ADVISORY MAY NEED TO BE CONTINUED AGAIN TOMORROW THE 
ONLY QUESTION IS HOW MUCH CLOUD COVER AND WINDS WILL AFFECT 
TEMPERATURES DURING THE DAY TOMORROW AND DUE TO THESE FACTORIES IS 
ADVISORY CRITERIA ATTAINABLE. 

A COUPLE MORE DISTURBANCES WITH REINFORCING SHOTS OF COLD AIR MOVE 
THROUGH THE NORTHERN PLAINS ON THURSDAY AND AGAIN ON FRIDAY KEEPING 
THE REGION WELL BELOW NORMAL THROUGH THE END OF THE WORK WEEK.  WIND 
CHILL ADVISORIES MAY ALSO BE NEEDED WITH THESE DISTURBANCES. SNOW 
SHOWERS ARE ALSO POSSBILE WITH THESE DISTURBANCES BUT MOST SNOW 
SHOULD BE LIGHT.

.LONG TERM...
BIGGEST CONCERN IN THE LONG TERM HINGES AROUND WHAT TO DO WITH THE 
TRUE ARCTIC SURGE ASSOCIATED WITH THE UPPER LOW THAT ORIGINATED OVER 
SIBERIA AND THE NORTHERN ARCTIC OCEAN OVER A WEEK AGO. THE GFS 
ENSEMBLES AND DETERMINISTIC/OPERATIONAL MODEL HAVE THE CENTER OF THE 
UPPER LOW MOVING ACROSS SOUTHERN MANITOBA. THE CANADIAN GEMGLB MODEL 
IS ON THE SAME PAGE AS THE GFS...WHICH IF IT DID COME TRUE WE COULD 
SEE SFC TEMPS BETWEEN -15F AND -25F ALONG WITH SFC WINDS OF 30KT 
WITH THE ARCTIC FRONT MONDAY NIGHT. HOWEVER THE 00Z AND 12Z ECMWF 
KEEP THE CENTER OF THE LOW MUCH FURTHER NORTH OVER NORTHERN MANITOBA 
AND HENCE THE COLDEST AIR THERE AS WELL. THE ECMWF DOES REINFORCE 
THE COLD AIR OVER NORTH DAKOTA LATE MONDAY INTO TUESDAY BUT ONLY TO 
THE EXTENT AS OUR CURRENT TEMPS ARE RIGHT NOW...NOTHING LIKE GFS OR 
CANADIAN MODEL. HPC IS LEANING A BIT MORE TOWARD THE GFS AND THEY 
MADE SOME CONTINUITY ADJUSTMENT TOWARD THE ARCTIC SURGE. IN OUR 
GRIDS AND FORECAST...KEPT VERY CLOSE TO PREVIOUS CONTINUITY UNTIL 
THE SOLUTIONS SHOW LESS SPREAD. PERHAPS THAT MIGHT OCCUR TONIGHT OR 
TOMORROW. 

.AVIATION...CURRENT VFR CEILINGS AND VISIBILITIES WILL CONTINUE 
THROUGH 00Z. EXPECT DETERIORATING CEILINGS FROM NORTHWEST TO 
SOUTHEAST OVERNIGHT AS ANOTHER SURFACE COLD FRONT MOVES ACROSS 
WESTERN AND CENTRAL NORTH DAKOTA LATE TONIGHT THROUGH THURSDAY. 
OCCASIONAL FLURRIES OR SOME LIGHT SNOW WILL ACCOMPANY THE FRONT 
TONIGHT INTO THURSDAY WITH MVFR CEILINGS TO LOW VFR CEILINGS. 

&&

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

&&

$$

DC/HW/KS