FXUS63 KFGF 281641 AAA
AFDFGF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GRAND FORKS ND
1041 AM CST SAT NOV 28 2009

.DISCUSSION...

THE MAIN CHALLENGE TODAY IS FIGURING OUT PCPN CHANCES THROUGH THIS
EVENING AS A SHORTWAVE WORKS ITS WAY OUT OF SOUTHERN SASKATCHEWAN
TO THE NORTHERN PLAINS. THE PREVIOUS FORECAST CALLED FOR THE
GREATEST CHANCES OF PRECIPITATION ACROSS NORTHEASTERN NORTH DAKOTA
AND NORTHERN MINNESOTA. HOWEVER...NOT ONLY IS THE LATEST GUIDANCE
LOOKING LESS IMPRESSIVE OVERALL FOR PRECIPITATION...BEST CHANCES
NOW LOOK TO BE ACROSS EASTERN NORTH DAKOTA DURING THE
AFTERNOON...AND THE SOUTHERN VALLEY AND WEST CENTRAL MINNESOTA
DURING THE EARLY EVENING. BOTH THE GFS90 AND NAM80 ARE SHOWING THE
BEST H20...BEST DIV Q...AND BEST 850-700 MB FRONTOGENESIS ACROSS
THE SOUTHERN FORECAST AREA DURING THE LATE AFTERNOON AND EARLY
EVENING. PLUS...NAM40 INDICATES THE 700 MB VORTICITY ASSOCIATED
WITH THE SASKATCHEWAN SHORTWAVE WILL SWEEP ACROSS THE CENTRAL AND
SOUTHERN VALLEY RATHER THAN THE NORTHERN VALLEY. SNOWFALL AMOUNTS
LOOK VERY LOW OVERALL...AND CANNOT RULE OUT FLURRIES FOR MUCH OF
THE AREA. THE MAIN POINT IS THAT THE EMPHASIS FOR SNOW IS NOW
ACROSS THE SOUTH RATHER THAN THE NORTH.

THE COLD AIR ADVECTION...NORTHERLY WINDS...AND INCREASING SKY
COVER CONVINCED US TO LOWER TEMPERATURES A BIT. THE 9Z SREF
GUIDANCE APPEARED THE BEST.

&&

.AVIATION...

VFR CONDS ARE MAINLY EXPECTED THROUGH THE EARLY AFTERNOON. A MID
LEVEL CIG WILL EXPAND EAST AND LOWER THROUGHOUT THE DAY WITH SNOW
FLURRIES EXPECTED AT MOST TAF SITES. MOST TAF SITES SHOULD SEE
PERIODS OF MVFR CIGS DURING THE LATE AFTERNOON AND INTO MUCH OF
TONIGHT. WINDS WILL REMAIN LIGHT AT AROUND 5 TO 12 KNOTS OUT OF
THE NORTHWEST.

&&

.PREV DISCUSSION... /ISSUED 349 AM CST SAT NOV 28 2009/ 

DISCUSSION...
THE MAIN CHALLENGE WITH THIS MORNINGS FORECAST WILL BE
PRECIPITATION CHANCES TODAY AND THE TIMING OF A LOW PRESSURE SYSTEM
EXPECTED TO PASS THROUGH THE AREA EARLY TO MID NEXT WEEK. GFS AND
NAM ARE FAIRLY SIMILAR EARLY...SO WILL USE A FORECAST BLEND FOR
TODAY AND SUNDAY. FOR CONTINUITY...WILL CONTINUE TO LEAN TOWARD
THE ECMWF SOLUTION FOR OUR TUESDAY SYSTEM AS IT REMAINS SLOWER
THAN THE GFS.

FOR TODAY AND TONIGHT...AN UPPER LEVEL WAVE WILL MOVE ACROSS THE
DAKOTAS AND INTO NORTHERN MINNESOTA. THE NAM REMAINS DRIER THAN
THE GFS BUT 00Z NAM SOUNDINGS ARE MOISTURE THAN THE PREV OOZ NAM
RUN. BEYOND PVA ASSOCIATED WITH THE WAVE...MODELS INDICATE RATHER
WEAK FRONTOGENETIC FORCING ACROSS THE NORTHERN ZONES AND WEAK TO
MODERATE Q VECTOR CONVERGENCE JUST NORTH OF THE INTERNATIONAL
BORDER. THUS WITH ONLY WEAK FORCING...IT CONTINUES TO LOOK LIKE WE
SHOULD SEE NO MORE THAN A COUPLE TENTHS OF AN INCH ACROSS THE
NORTHERN ZONES. MY CONCERN CONTINUES TO BE GROUND TEMPS AND SLIGHTLY
ABOVE FREEZING SFC TEMPS. DO NOT EXPECT SNOWFALL RATE TO BE FAST
ENOUGH TO GET ANY ACCUMULATION DRG THE DAY...BUT STILL APPEARS
BEST CHANCE WOULD BE AFT SUNSET THIS EVENING AS THE AIR TEMP DROPS
BACK BELOW FREEZING. LIGHT FLURRIES ARE EXPECTED ACROSS THE REST
OF THE FA...ALTHOUGH THE EXTREME SOUTHERN ZONES MAY BE DRY ENOUGH
TO ESCAPE FLURRY ACTIVITY.

FOR SUNDAY AND MONDAY...LACK OF ANY SNOW ON THE GROUND AND DRIER
AIR MASS WITH WESTERLY WINDS SHOULD RESULT IN TEMPS SLIGHTLY ABOVE
NORMAL FOR LATE NOVEMBER.

TUESDAY...MODELS DIFFER IN TIMING OF NEXT WAVE PUSHING
THROUGH...WITH GFS CONTINUING TO BE FASTER WITH THIS WAVE. AS
MENTIONED EARLIER...CONT TO LEAN TOWARD SLOWER ECMWF SOLUTION FOR
CONTINUITY. HAVE BUMPED POPS IN THE NE UP TO THE CHANCE CATEGORY
ON TUE NIGHT...AS THAT BEST DEPICTS THE OVERLAP OF TWO MODELS QPF. THE
ECMWF CONTINUES TO KEEP THE HIGHEST QPF NORTH OF THE BORDER BUT
CLIPPING LAKE OF THE WOODS COUNTY. OTHER CHALLENGE ASSOCIATED WITH
THE TIMING OF THIS SYSTEM IS WHEN TO BRING POST FROPA WINDS UP IN
THE DVL LAKE REGION...AND AGAIN...LEANING TOWARD THE SLOWER SOLUTION
THUS AM NOT INCREASING WINDS UNTIL TUE EVENING.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...NONE.
MN...NONE.
&&

$$
GROCHOCINSKI