Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 231745
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
1245 PM CDT WED APR 23 2014

.UPDATE...
ISSUED AT 1245 PM CDT WED APR 23 2014

STILL ANTICIPATE THAT THE CURRENT BAND OF RAINFALL WILL GRADUALLY
DISSIPATE OVER THE NEXT SEVERAL HOURS...WITH EASTWARD EXTENT
LIMITED. AT THE SAME TIME...SHOWERS WILL INCREASE IN AREAL
COVERAGE TO THE WEST (THROUGH THE AFTERNOON HOURS) AS FORCING
AGAIN INCREASES. THE MAIN UPDATE CHANGE WAS TO LOWER MAX TEMPS
ACROSS A PORTION OF THE REGION CURRENTLY RECEIVING RAINFALL.

UPDATE ISSUED AT 1000 AM CDT WED APR 23 2014

WILL MAKE A MINOR UPDATE TO THE POP/WX GRIDS FOR TODAY INTO THIS
EVENING. LATEST MODEL GUIDANCE INDICATES THAT THE CURRENT BAND OF
SHOWERS IS ASSOCIATED WITH 700MB WARM AIR ADVECTION/FRONTOGENESIS.
THIS FORCING WILL WEAKEN AFTER 18Z AS THE 700MB BAROCLINIC ZONE
WEAKENS (SINCE THE MAIN UPPER LOW TO THE WEST IS PROPAGATING VERY
SLOW). THUS...DO NOT EXPECT THIS CURRENT BAND OF SHOWERS TO MAKE
MUCH MORE PROGRESS TO THE EAST/NORTHEAST. LATER THIS AFTERNOON AND
INTO THIS EVENING...AS UPPER LEVEL ENERGY LIFTS INTO THE REGION
(UPPER FLOW BECOMES MORE SOUTHWEST)...850MB WARM AIR
ADVECTION/FRONTOGENESIS FORCING WILL PROPAGATE THROUGH THE FA...AND
ANTICIPATE ANOTHER BAND OF SHOWERS WILL INITIATE AND MOVE THROUGH
THE ENTIRE FA. UPDATES POPS/WX TO ACCOUNT FOR THE THINKING ABOVE.

THE OTHER ASPECTS OF THE FORECAST ARE IN GOOD SHAPE...INCLUDING
THE WIND ADVISORY.

&&

.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 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1245 PM CDT WED APR 23 2014

FIRST BAND OF LIGHT RAIN SHOWERS FROM CANDO TO GRAND FORKS/FARGO TO
FERGUS FALLS WILL CONTINUE TO MOVE NORTHEASTWARD AROUND 20 MPH.
CEILINGS ARE MAINLY VFR...BUT THERE ARE SOME BRIEF MVFR/IFR POCKETS.
THERE SHOULD BE A SHORT BREAK IN PRECIP LATER THIS AFTERNOON BEFORE
A SECONDARY BAND OF LIGHT RAIN MOVES THROUGH THE REGION THIS EVENING
INTO THE EARLY OVERNIGHT HOURS. BETTER CHANCES FOR WIDESPREAD MVFR
CEILINGS WITH THIS SECOND BAND. BREEZY EAST-SOUTHEAST WIND WILL
CONTINUE...GUSTING AT TIMES TO 30 KTS MAINLY ALONG AND WEST OF THE
VALLEY. WINDS WILL REMAIN ELEVATED OVERNIGHT...BUT SUBSIDE SLIGHTLY
AFTER SUNSET.

&&

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

MN...WIND ADVISORY UNTIL 7 PM CDT THIS EVENING FOR MNZ003-029.

&&

$$

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




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