FXUS63 KFGF 242053
AFDFGF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
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 SATURDAY.
FOR TONIGHT...STRONG MID LAYER MOIST/WARM ADVECTION WILL MOVE
NORTH INTO A DEVELOPING TROWAL ALOFT. SNOW SHOULD DEVELOP FAIRLY
QUICKLY THIS EVENING IN THE SOUTH...SPREADING QUICKLY NORTH
THEREAFTER. SNOW MAY BECOME HEAVY LATE TONIGHT ALONG WITH SOME
BLOWING AND DRIFTING IN THE VALLEY AND WILL MENTION.
ON CHRISTMAS THROUGH NOON SATURDAY...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. NORTHERLY
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 SATURDAY 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
IOWA. 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
SATURDAY. TEMPS WON/T BE THAT COLD THOUGH...SO SEVERE WIND CHILLS
ARE NOT EXPECTED.
WINDS WILL SLOWLY SUBSIDE SOME SATURDAY AFTERNOON...ALTHOUGH SOME
SNOW WILL CONTINUE WITH LOW VSBYS IN OPEN AREAS WITH BLOWING SNOW.
BY SUNDAY...THE LOW SHOULD SLOWLY PULL AWAY WITH SOME FLURRIES
POSSIBLE.
.LONG TERM (SUN NIGHT-THURSDAY)...
EXTENDED PERIOD WILL FEATURE AN ACTIVE SOUTHERN STREAM ONCE
AGAIN AS THE NORTHERN PLAINS ENTERS A WELL DESERVED PERIOD OF RELIEF
TO RECOVER FROM CHRISTMAS BLIZZARD. GUIDANCE IN FAIR AGREEMENT WITH
A MEAN RIDGE OVER THE FAR WEST AND POLAR VORTEX WELL NORTH 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 SOUTH TOWARD UPPER MIDWEST BY
END OF PERIOD...RESULTING IN BELOW NORMAL TEMPERATURE SCENARIO BY
DAY 7/NEW YEARS EVE.
&&
.AVIATION...
MVFR CIGS WITH IMPROVING VISIBILITY THE NEXT SEVERAL HOURS
BETWEEN PREVIOUS SNOWFALL AND THE POWERFUL SYSTEM TO COME.
SNOW AND WIND TO PICK UP FROM SOUTHEAST TO NORTHWEST OVERNIGHT
WITH LIFR CONDITIONS TO DOMINATE THROUGH CHRISTMAS DAY.
&&
.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.
&&
$$
DK/WJB
