FXUS63 KFGF 232106
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
306 PM CST WED DEC 23 2009

.SHORT TERM...
THE IMPENDING MAJOR STORM WILL BE THE CHALLENGE THROUGH THE
CHRISTMAS HOLIDAY. MODELS ARE IN EXCELLENT AGREEMENT OVERALL AND A
FEW DIFFERENCES ON WHO GETS THE MOST SNOW. THE GFS SCENARIO MAKES
THE MOST SENSE WITH THE SOUTH GETTING THE MOST WITH LOWER AMOUNTS
TO THE NORTH. NO MATTER WHAT THOUGH...IT IS BECOMING CLEAR THAT
THIS WILL BE A MAJOR STORM WITH SOME AREAS SEEING WELL OVER A FOOT
OF SNOW.

FOR TONIGHT...SFC INVERTED TROUGH WILL MOVE INTO THE VALLEY...AND
STRONG ISENTROPIC LIFT AND DEEP MOISTURE ADVECTION WILL BEGIN.
EXPECT SNOW TO DEVELOP THIS EVENING IN THE SOUTH AND SPREAD NORTH
AND EAST THROUGH THE NIGHT. EXPECT GENERAL SNOW AMOUNTS FROM 1 TO
3 INCHES FOR MOST AREAS WITH THE HIGHEST TOTALS IN THE SOUTH.

FOR CHRISTMAS EVE...THE INVERTED THROUGH WILL PIVOT OVER THE
REGION. THE FIRST WAVE OF SNOW SHOULD LIFT NORTH THROUGH THE
DAY...AND THERE COULD BE A BREAK FROM ACCUMULATING SNOW BY THE
AFTERNOON/EVENING BUT SEVERAL MORE INCHES SHOULD PILE UP THROUGH
THE DAY.

FOR THURSDAY NIGHT THROUGH CHRISTMAS DAY...IT APPEARS THAT THE
BIGGEST IMPACTS WILL OCCUR DURING THIS TIMEFRAME. SFC LOW PRESSURE
WILL DEEPEN AND BECOME VERTICALLY STACKED NEAR IOWA. THIS WILL
ENHANCE ISENTROPIC LIFT AND VERY STRONG MID LEVEL CONVERGENCE. THE
850MB JET WILL INCREASE TO NEAR 60KT FROM THE EAST OVER THE
ARROWHEAD OF MN AND A 50KT NORTHERLY JET OVER CENTRAL ND. THERE
WILL ALSO BE AMPLE DEEP LAYER MOISTURE/OMEGA THROUGH 250MB AND
PWATS NEAR 0.50 INCHES OR SLIGHTLY HIGHER. WILL MENTION HEAVY SNOW
FOR CHRISTMAS DAY. 

THE NEXT CHALLENGE WILL BE BLIZZARD POTENTIAL ON CHRISTMAS DAY
INTO FRIDAY NIGHT. THERE WILL BE A TIGHTENING PRESSURE GRADIENT
AND NORTHERLY WINDS INCREASING WITH ABOUT 30-35KT TO MIX FROM
925MB. THERE WILL BE PLENTY OF WARM ADVECTION THROUGH THE LAYER
THOUGH...BUT THE FAVORABLE NORTHERLY COMPONENT WILL LIKELY CAUSE
GUSTS OVER 30MPH AT TIMES. WHEN THE HEAVY SNOW COMBINES WITH THE
WIND...THEN BLIZZARD LIKE CONDITIONS WILL BE POSSIBLE. WE STILL
HAVE SOME TIME TO UPGRADE TO A BLIZZARD WARNING IN THE VALLEY WEST
THOUGH...AND WILL CONTINUE TO MONITOR THIS POTENTIAL. NEEDLESS TO
SAY...SIGNIFICANT IMPACTS WILL BE FELT ON CHRISTMAS DAY AND TRAVEL
MAY COME TO A STANDSTILL FOR THE REGION.

THE GFS/NAM/ECMWF INDICATE LIQUID EQUIVALENT QPF VALUES OF AROUND
1.50 INCHES IN THE SOUTH AND UPWARDS OF 1 INCH IN THE NORTH. THERE
GIVEN THE SNOW RATIOS AROUND 12:1 IN THE SOUTH AND 14:1 IN THE
NORTH WILL YIELD MOST AREAS SEEING AROUND A FOOT OF SNOW...WITH
AREAS IN THE SOUTH SEEING MORE. WE WOULD NOT BE SURPRISED TO SEE
LOCALIZED AREAS RECEIVING UP TO 2 FEET THROUGH THE EVENT IF
BANDING CAN OCCUR GIVEN THE SLOW MOVEMENT ONCE IT BECOMES
VERTICALLY STACKED. SNOW WILL BE HARD TO MEASURE ON FRIDAY AND
ROADS MAY BECOME IMPASSABLE WITH SIGNIFICANT DRIFTING. IT IS
IMPORTANT TO NOTE THAT THIS WILL BE A LONG DURATION EVENT THAT
WILL LAST 48 TO 60HR...AND THERE MAY BE BREAKS IN THE SNOW
ESPECIALLY THURSDAY AFTERNOON AND EVENING.

FOR SATURDAY...THE STORM SHOULD BE SLOWLY WINDING DOWN WITH SOME
SNOW POSSIBLE FOR THE REGION. IF THE STORM IS ANY SLOWER...SAT
MORNING COULD ALSO FEATURE SOME BLOWING/DRIFTING SNOW AS WELL. 

.LONG TERM...
PCPN CHANCES WERE INCREASED FOR SAT AFTERNOON AND EVENING TO ACCOUNT 
FOR THE SLIGHTLY SLOWER TRACK OF THE CHRISTMAS STORM EVENT. AFTER 
THE PCPN FINALLY MOVES OUT OF THE AREA THIS WEEKEND...CONDITIONS 
WILL BE RELATIVELY QUIET THROUGHOUT THE REMAINDER OF THE PERIOD. ALL 
LONG TERM MODELS INDICATE HIGH PRESSURE SETTLING OVER THE REGION 
LATE IN THE WEEKEND AND INTO EARLY NEXT WEEK. BOTH THE ECMWF AND GFS 
DEPICT A WEAK CLIPPER SYSTEM BRINGING THE NEXT CHANCE FOR PCPN 
DURING THE MIDDLE OF NEXT WEEK.

TEMPERATURES WILL REMAIN NEAR NORMAL VALUES THROUGHOUT THE LONG TERM 
WITH THE POSSIBILITY OF A SLIGHT COOLING TREND TOWARDS THE END OF 
THE PERIOD.

&&

.AVIATION...
-SN AND REDUCED VSBYS HAVE ALREADY CREATED IFR CONDITIONS AT KDVL 
AND KFAR. IFR CIGS AND -SN CHANCES WILL CONTINUE TO CREEP ACROSS THE 
AREA AND AFFECT THE REMAINING TAF SITES BY EARLY EVENING. SE WINDS 
WILL GRADUALLY SHIFT MORE TO THE E/NE AND STRENGTHEN BY THUR MORNING.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM CST SATURDAY 
     FOR NDZ006-014-015-024-026-028-038-049-052-053.

     WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 AM CST SATURDAY 
     FOR NDZ007-008-016-027-029-030-039-054.

MN...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM CST SATURDAY 
     FOR MNZ029.

     WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 AM CST SATURDAY 
     FOR MNZ001>003-007-027-028-030>032-040.

     WINTER STORM WARNING FROM 6 AM THURSDAY TO 6 AM CST SATURDAY FOR 
     MNZ004>006-008-009-013>017-022>024.

&&

$$
DK/HOMANN