Area Forecast Discussion
Issued by NWS Grand Forks, ND

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000
FXUS63 KFGF 231148
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
648 AM CDT WED APR 23 2014

.UPDATE...
ISSUED AT 641 AM CDT WED APR 23 2014

MAIN UPDATE CHALLENGES THROUGH THE DAY WILL BE ADJUSTING POPS AS
RAIN BAND LIFTS SLOWLY NE. IT WILL BE A BATTLE WITH DRIER AIR AS
DEW POINTS NORTH AND EAST OF THE RAIN ARE STILL IN THE 20S. BAND
IS CURRENTLY MOVING NE AROUND 10-15KTS. AS A RESULT BACKED OFF ON
POPS FARTHER NORTHEAST. NO OTHER CHANGES.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 330 AM CDT WED APR 23 2014

FORECAST CHALLENGE CONCERNS UPCOMING PCPN EVENT AND TEMPERATURES.
MODELS IN FAIR AGREEMENT THROUGH MOST OF THE PERIOD AND USED A
BLEND.

RAIN BAND GETTING ORGANIZED ACROSS THE SW FA AS UPPER WAVE
APPROACHES. GFS CURRENTLY A LITTLE TOO QUICK IN BRINGING DEEPER
MOISTURE NE THROUGH THE FA SO TRIMMED POPS ESPECIALLY ACROSS THE
NE FA WHICH WILL TAKE LONGEST TO MOISTEN UP. OTHERWISE CURRENT
POPS GOOD AS RAIN BAND LIFTS NE DURING THE DAY IN BROAD ZONE OF
IMPRESSIVE ISENTROPIC LIFT. ALTHOUGH MIXED LAYER SHALLOW TIGHT
SURFACE PRESSURE GRADIENT SETS UP WITH UP TO 35KTS THROUGH LAYER.
AS A RESULT HAVE ISSUED WIND ADVISORY ACROSS SW THIRD OF FA AND
LATER SHIFTS CAN MONITOR. AIRMASS REMAINS STABLE WITH UNFAVORABLE
LAPSE RATES SO TRIMMED T MENTION TODAY EXCEPT FOR THE FAR SOUTH
AND STILL THIS MARGINAL AT BEST.

RAIN WILL CONTINUE TO LIFT NE TONIGHT WITH BEST CHANCES ACROSS NE
HALF OF FA IN FAVORED ZONE OF ISENTROPIC LIFT AND LOWEST
CONDENSATION PRESSURE DEFICITS. SOME DRYING WORKS INTO THE WESTERN
FA LATE TONIGHT SO CHANCE POPS REASONABLE IN THIS AREA.

ALL MODELS BRINGING DRY SLOT INTO AREAS GENERALLY WEST OF THE
VALLEY. FROM VALLEY EAST RAIN BAND SHOULD SLOWLY SHIFT EAST WITH
UPPER LOW. TEMPERATURES WILL BE TRICKY DEPENDENT ON DEGREE OF
CLOUD COVER.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 330 AM CDT WED APR 23 2014

AS LOW EXITS COLDER AIR BEGINS TO FILTER SOUTHWARD THURSDAY NIGHT.
OVERALL PCPN CHANCES DO NOT LOOK GREAT. FAR NE CORNER OF FA THE
EXCEPTION AND COLUMN DOES SUPPORT SNOW SO THERE IS THE POTENTIAL
FOR SOME ACCUMULATIONS AND THIS WILL NEED TO BE MONITORED.

GFS MOST AGGRESSIVE IN DROPPING COLD AIR SOUTHWARD ON FRIDAY WHERE
AS ECMWF AND NAM WARMER. THIS WILL HAVE IMPACT ON BOTH
TEMPERATURES AND PHASE OF ANY PCPN WHICH OCCURS. WITH SIGNIFICANT
MODEL DIFFERENCES DID NOT MAKE MANY CHANGES THIS PERIOD.

SATURDAY TO TUESDAY NIGHT...CONFIDENCE IS FAIR TO START AND
DECREASES WITH TIME IN THIS HALF OF THE FORECAST AS EVOLUTION OF
500MB FLOW REMAINS UNCERTAIN. GIVEN THE OMEGA TYPE BLOCK THAT
SETS UP SATURDAY INTO SUNDAY WITH RIDGING ORIENTED SUNDAY FROM THE
OHIO VALLEY NW OVER THE NORTHERN PLAINS CAN EXPECT COOLER THAN
NORMAL TEMPS WITH DRY EASTERLY SFC FLOW IMPEDING APPROACHING PRECIP
SHIELD SUNDAY AND MONDAY. EC BREAKS RIDGE DOWN WITH MERGER OF 500MB
TROUGHS BY A RETROGRESSION OF HUDSON BAY LOW AND ITS ASSOCIATED COLD
POOL BY TUESDAY WHEREAS THE GFS ENSEMBLE IS MORE PROGRESSIVE WITH
THE OVERALL 500MB FLOW WITH NO MERGER AND MUCH WARMER TEMPS FOR THE
BEGINNING OF NEXT WEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 641 AM CDT WED APR 23 2014

TAF FORECASTS WILL BE CHALLENGING TODAY WITH TIMING OF RAIN AREA
LIFTING SLOWLY NE. SO FAR CIGS WITHIN THE RAIN REMAINING VFR WITH
VSBY DOWN TO 3-4MILES AT TIMES. BIT QUESTION IS HOW THIS RAIN WILL
HOLD TOGETHER AS IT MOVES INTO DRIER AIR. I COULD POSSIBLY BE TO
PESSIMISTIC WITH THE FORECAST BUT TOUGH. UPDATES LATER THIS
MORNING COULD BE POSSIBLE. SE WIND WILL INCREASE AND BECOME WINDY
BY NOON.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...WIND ADVISORY FROM 10 AM THIS MORNING TO 7 PM CDT THIS EVENING
     FOR NDZ006-014-015-024-026-028-029-038-039-049-052-053.

MN...WIND ADVISORY FROM 10 AM THIS MORNING TO 7 PM CDT THIS EVENING
     FOR MNZ003-029.

&&

$$

UPDATE...VOELKER
SHORT TERM...VOELKER
LONG TERM...JK/VOELKER
AVIATION...VOELKER






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