FXUS63 KFGF 250424 AAA
AFDFGF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GRAND FORKS ND
1024 PM CST THU DEC 24 2009

.DISCUSSION...
THE MAIN FORECAST CHALLENGE IS THE WINTER STORM. WHEN LOOKING AT THE 
LATEST SURFACE ANALYSIS...AN AREA OF LOW PRESSURE IS CENTERED IN S 
MISSOURI WITH AN INVERTED TROF EXTENDING THROUGH CENTRAL 
IA...CENTRAL AND NW MN INTO S MANITOBA. THE LATEST RADAR IMAGERY 
SHOWS THE AREA OF SNOW REFORMING AND EXPANDING QUICKLY TO COVER MUCH 
OF E SD...E ND AND ALL EXCEPT FAR N MN. THE MODELS REMAIN IN GOOD 
AGREEMENT ON THE STORM TRACK AND INTENSITY FOR THE REST OF 
TONIGHT...SO ENDED UP USING A MODEL BLEND FOR THE FORECAST UPDATE.  

WITH STRONG 850MB Q-VECTOR CONVERGENCE AND 700MB LIFT REDEVELOPING 
OVER THE AREA BY 06Z...LATEST RADAR INTENSIFICATION TRENDS APPEAR 
RIGHT ON TRACK FOR WHAT THE MODELS HAVE BEEN EXPECTING. THE ONLY 
DIFFERENCE AT THIS POINT WOULD BE THE SLIGHTLY SLOWER DEVELOPMENT OF 
THE STRONGER WINDS. IT STILL LOOKS LIKE THE WINDS WILL BECOME GUSTY 
IN THE BLIZZARD WARNING AREA CHRISTMAS MORNING. THUS...NO HEADLINE 
CHANGES ARE NEEDED. HOWEVER...DID CHANGE SOME OF THE WEATHER GRIDS 
TO KEEP ANY WORDING OF BLOWING OUT OF THE FORECAST UNTIL AFTER 
MIDNIGHT AND THEN TAPER IT IN WITH AREAS OF BLOWING BEFORE GOING TO 
WIDESPREAD BY 12Z. OTHERWISE...ONLY NEEDED TO MAKE SOME CHANGES TO 
TEMP FORECAST TO ADJUST FOR CURRENT CONDITIONS. MINIMAL CHANGES 
NEEDED TO REST OF FORECAST.  

&&

.AVIATION...
CIGS AND VSBYS CURRENTLY VARYING FROM VFR TO IFR...EXPECTING TO
DROP TO IFR IN MOST AREAS AFTER 06Z AND FOR ALL SITES BY 12Z.
WINDS TO TURN N-NE BY 09Z TO 15Z...INCREASE TO AROUND 20KTS...WITH
GUSTS TO 35 KTS POSSIBLE...ESPECIALLY IN E ND...CREATING LIFR
VSBYS IN SN AND BLSN.

&&

.PREV DISCUSSION... /ISSUED 253 PM CST THU DEC 24 2009/ 

SHORT TERM...
THE MAIN CHALLENGE WILL BE THE THE IMPENDING MAJOR WINTER STORM.
MODELS CONTINUE IN EXCELLENT AGREEMENT WITH NO MAJOR DIFFERENCES
AT ALL NOTED. ALL PARAMETERS ARE IN PLACE FOR A CHRISTMAS BLIZZARD
FOR THE VALLEY AND AT LEAST A FOOT OF ADDITIONAL SNOW FOR ALL
AREAS TONIGHT THROUGH SAT.

FOR TONIGHT...STRONG MID LAYER MOIST/WARM ADVECTION WILL MOVE
N INTO A DEVELOPING TROWAL ALOFT. SNOW SHOULD DEVELOP FAIRLY
QUICKLY THIS EVENING IN THE S...SPREADING QUICKLY N THEREAFTER.
SNOW MAY BECOME HEAVY LATE TONIGHT ALONG WITH SOME BLOWING AND
DRIFTING IN THE VALLEY AND WILL MENTION.

ON CHRISTMAS THROUGH NOON SAT...CONDITIONS WILL DETERIORATE
RAPIDLY BEFORE SUNRISE ON CHRISTMAS WITH BLIZZARD CONDITIONS
DEVELOPING IN THE VALLEY BY DAWN. THERE WILL BE 35KT TO MIX FROM
925MB...AND THE PRESSURE GRADIENT FORCE WILL STRENGTHEN. N WINDS
WILL INCREASE TO BETWEEN 25 TO 30 MPH WITH GUSTS OVER 35 MPH IN
THE VALLEY DURING CHRISTMAS MORNING. THESE WINDS WILL ALSO
COINCIDE WITH A LARGE SWATH OF MODERATE TO HEAVY SNOW FOR A
PROLONGED PERIOD...WITH LOCALIZED INTENSE SNOW BANDS WITH 1-2
INCH/HR RATES POSSIBLE. GIVEN THE SEVERE IMPACTS AND PROLONGED
ZERO VSBY...EXPECT BLIZZARD CONDITIONS IN THE VALLEY. THIS WILL
CAUSE SOME ROADS TO BECOME IMPASSABLE INTO SAT MORNING WITH
SIGNIFICANT DRIFTING IN OPEN AREAS. TRAVEL WILL BECOME IMPOSSIBLE
IN OPEN COUNTRY ON CHRISTMAS AT TIMES...AND MAY EVEN BE TOUGH IN
TOWNS WITH POOR VISIBILITY AND DRIFTING.

A TREMENDOUS FETCH OF MOISTURE FROM THE GULF WILL ADVECT OVER THE
COLD DOME...AS LOW PRESSURE DEEPENS RAPIDLY AND STALLS OUT IN
IA. THIS WILL CAUSE A PROLONGED PERIOD OF SNOW AND BLOWING SNOW.
MOST AREAS WILL RECEIVE AT LEAST A FOOT OF ADDITIONAL SNOW...WITH
ISOLATED AMOUNTS OF UP TO 2 FEET NOT OUT OF THE QUESTION WHERE
BANDING OCCURS. GIVEN THE DRIFTING THAT WILL OCCUR THOUGH...
MEASURING SNOW WILL BE DIFFICULT AND WITH THIS MUCH SNOW. NEEDLESS
TO SAY...ALL FORMS OF TRAVEL WILL LIKELY COME TO A HALT ON
CHRISTMAS INTO EARLY SAT. TEMPS WON/T BE THAT COLD THOUGH...SO
SEVERE WIND CHILLS ARE NOT EXPECTED.

WINDS WILL SLOWLY SUBSIDE SOME SAT AFTERNOON...ALTHOUGH SOME SNOW
WILL CONTINUE WITH LOW VSBYS IN OPEN AREAS WITH BLOWING SNOW. BY
SUN...THE LOW SHOULD SLOWLY PULL AWAY WITH SOME FLURRIES POSSIBLE.

LONG TERM (SUN NIGHT-THU)...

EXTENDED PERIOD WILL FEATURE AN ACTIVE S STREAM ONCE AGAIN AS THE
N PLAINS ENTERS A WELL DESERVED PERIOD OF RELIEF TO RECOVER FROM
CHRISTMAS BLIZZARD. GUIDANCE IN FAIR AGREEMENT WITH A MEAN RIDGE
OVER THE FAR W AND POLAR VORTEX WELL N TO BEGIN THE PERIOD. ANY
PCPN CHANCES UNDER THIS REGIME WILL BE HARD TO PINPOINT...THUS
LEAVING ENTIRE FORECAST DRY AT THIS TIME. GOOD INDICATION THAT THE
VORTEX WILL DRIFT S TOWARD UPPER MIDWEST BY END OF PERIOD...RESULTING
IN BELOW NORMAL TEMPERATURE SCENARIO BY DAY 7/NEW YEARS EVE.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...WINTER STORM WARNING UNTIL 6 AM CST FRIDAY FOR NDZ006>008-
     014>016-024-026>030-038-039-049-052>054.

     BLIZZARD WARNING FROM 6 AM FRIDAY TO NOON CST SATURDAY FOR 
     NDZ006>008-014>016-024-026>030-038-039-049-052>054.

MN...WINTER STORM WARNING UNTIL 6 AM CST FRIDAY FOR MNZ001>004-007-
     029-030-040.

     BLIZZARD WARNING FROM 6 AM FRIDAY TO NOON CST SATURDAY FOR 
     MNZ001>004-007-029-030-040.

     WINTER STORM WARNING UNTIL NOON CST SATURDAY FOR MNZ005-006-008-
     009-013>017-022>024-027-028-031-032.

&&

$$
NG