Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 221151
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
651 AM CDT TUE APR 22 2014

.UPDATE...
ISSUED AT 647 AM CDT TUE APR 22 2014

NO FORECAST CHANGES THIS UPDATE PERIOD.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 340 AM CDT TUE APR 22 2014

FORECAST CHALLENGE CONCERNS UPCOMING EXTENDED RAIN EVENT AND
TEMPERATURES. FAIRLY COMPLEX SYSTEM TO AFFECT THE FA FROM
WEDNESDAY THROUGH THURSDAY SO NOT SURPRISING THAT MODELS SHOWING
SOME DIFFERENCES. MAIN DIFFERENCE IS ON THURSDAY WITH STRENGTH OF
SECONDARY LOW PASSAGE. OTHERWISE MODELS IN PRETTY GOOD AGREEMENT
WITH INCREASING CONFIDENCE WITH FORECAST.

IN THE NEAR TERM WITH SURFACE HIGH OVERHEAD AND LIGHT WINDS WILL
MONITOR FOR ANY BR DEVELOPMENT. WITH ADVANCING CI SHIELD THINK ANY
DEVELOPMENT WILL BE FAIRLY LOCALIZED. OTHERWISE SURFACE HIGH WILL
SHIFT EAST TODAY SETTING UP SOME MODEST RETURN FLOW/WARM
ADVECTION. THIS SHOULD ALLOW TEMPERATURES TO RECOVER CLOSE TO
AVERAGE WITH THE NE THE COOLEST UNDER COOLER AIR.

SURFACE LOW PRESSURE WILL ORGANIZE OVER THE NORTHERN HIGH PLAINS
SHIFTING TO THE WESTERN DAKOTAS BY MORNING. PRECIPITABLE H2O
VALUES NEAR AN INCH WORK INTO THE SW FA AROUND 06Z SLOWLY LIFTING
NE OVERNIGHT. FEEL IT WILL TAKE INFLUENCE FROM LOW LEVEL JET
CONVERGENCE LATE EVENING TO GET ANY PCPN GOING SO KEPT LOW POPS
GOING THROUGH THE EVENING THEN INCREASING AFTER MIDNIGHT.

BETTER SUPPORT ARRIVES WEDNESDAY AND EXPECT ARC OF RAIN TO LIFT
SLOWLY NE THROUGH THE DAY AHEAD OF APPROACHING BOUNDARY. DRIER
E-SE FLOW WILL LIKELY KEEP NE 1/3 OF FA DRY MOST OF THE DAY AND
BACKED OFF ON POPS THIS AREA. AIRMASS REMAINS STABLE SO NO MENTION
OF THUNDER.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 340 AM CDT TUE APR 22 2014

BAND OF RAIN WILL CONTINUE TO LIFT SLOWLY NE OVERNIGHT WEDNESDAY AS
UPPER LOW CROSSES THE FA. DRY SLOTTING WILL BRING A BREAK TO THE RAIN
FOR AREAS WEST OF THE VALLEY. COLUMN FAIRLY MILD SO NO THREAT FOR
FREEZING TEMPERATURES.

MODELS SHOWING SIGNIFICANT DIFFERENCES ON STRENGTH OF SECONDARY
SURFACE/UPPER LOW PASSAGE THURSDAY. GFS DEEPEST WITH THE SURFACE
FEATURE. WITH BETTER DEVELOPED LOW WARMER/MORE UNSTABLE AIR GETS
PULLED NORTHWARD FOR MUCH BETTER POTENTIAL FOR CONVECTION THAN THE
ECMWF. ECMWF ALSO COLDER LEADING TO BETTER POTENTIAL FOR MIXED
PCPN/SNOW THURSDAY NIGHT ACROSS THE NORTH. WITH DIFFERENCES DID NOT
MAKE SIGNIFICANT CHANGES.

FRIDAY TO MONDAY NIGHT...NORTHERN PLAINS STORMS SYSTEM MOVES INTO
THE GREAT LAKES REGION WITH EXITING DIFFUSE DEFZONE BAND OF RASN
SHOWERS DURING THE DAY FRIDAY. IN ITS WAKE CANADIAN SFC HIGH
PRESSURE AXIS WILL CREATE IDEAL DIURNAL COOLING AND SAT AM TEMPS
WILL BE SEASONALLY COOL WITH LOWS IN THE 20S AND 30S. FOG
DEVELOPMENT SAT MORNING MAY LIMIT TEMPS FROM BOTTOMING OUT. COOL DRY
EASTERLY WINDS ON SOUTHERN EDGE OF SFC HIGH AND A PSEUDO OMEGA BLOCK
DEVELOPS WITH RIDGING OVER THE UPPER MISS VALLEY LIMITING
PROGRESSION OF NEXT 500MB TROUGH. THUS DELAYING THE NEXT CHC OF PCPN
INTO MONDAY AND PROBABLY LONGER. THIS BLOCKING WILL KEEP THE
SEASONALLY COOL AIRMASS IN PLACE AND KEEP MAX TEMPS AROUND 10
DEGREES BELOW NORMAL.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 647 AM CDT TUE APR 22 2014

ANY LOCALIZED AREAS OF BR CURRENTLY NOT AFFECTING TAF SITES SHOULD
DISSIPATE MID MORNING. A SMALL BAND OF VFR CIGS MAY CLIP THE TVF
AND BJI SITES THIS MORNING. OTHERWISE ONLY EXPECTING CI ACROSS THE
REGION. CLOUDS WILL THICKEN THIS EVENING WITH ANY SHRA OVER SW FA
LATE TONIGHT.

&&

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

$$

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






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