Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 311743
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
1243 PM CDT SUN AUG 31 2014

.UPDATE...
ISSUED AT 1243 PM CDT SUN AUG 31 2014

THE FIRST UPPER WAVE CONTINUES TO SLOWLY PROPAGATE E/NE AND
ASSOCIATED SHOWERS ARE LIFTING INTO CANADA. LIGHT RAIN WILL BE
POSSIBLE ACROSS NW MN INTO THE EARLY AFTERNOON HOURS.

THE NEXT AREA OF CONCERN WILL BE AN UPPER WAVE CURRENTLY ACROSS
CENTRAL SOUTH DAKOTA (RADAR IMAGERY SHOWS ASSOCIATED PRECIP) THAT
WILL MOVE INTO THE SOUTHERN FA THIS AFTERNOON. AS THE FORCING FROM
THIS FEATURE SPREADS INTO THE FA...STRONG THUNDERSTORMS SHOULD BE
INITIATING ACROSS NEBRASKA/IOWA. THIS MAY CUT-OFF THE MOISTURE
FEED AND ANY SHOWERS THAT ADVECT INTO THIS FA SHOULD DISSIPATE.

ATTEMPTED TO ADJUST POPS/WX TO ABOVE THINKING...NOT MUCH CHANGE
NEEDED.

LOWERED MAX TEMPS TODAY A FEW DEGREES ACROSS THE NORTHERN FA
BASED ON CONTINUED THICKER CLOUD COVER.

ISOLD SHOWERS/THUNDER WILL REMAIN POSSIBLE ALONG AND
AHEAD OF THE SFC TROUGH....BUT STRONGER STORMS ARE NOT EXPECTED.
CLEARING HAS REMAINED SOUTH...AND WILL NEED SOME HEATING TO OBTAIN
STRONG ENOUGH INSTABILITY FOR SEVERE STORMS.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 330 AM CDT SUN AUG 31 2014

FOR THE NEXT 6 TO 12 HOURS THE MAIN CONCERN IS THE CONVECTION AND
RISK FOR SEVERE. AS OF 08Z A LINE OF TSRA EXTENDED FROM
KDVL...KS32 TO KGWR MOVG EAST 35 KTS. THIS LINE IS MOVING INTO AN
AREA OF INCREASINGLY STABLE AIR AND APPEARS TO BE OUTRUNNING THE
LOWER LEVEL FORCING. THE NAM12 AND GFS40 HAD BEEN INCREASING THE
BULK 0-6KM SHEAR TO NEAR 50KTS IN THE DEVILS LAKE BASIN...WHICH
DOES NOT YET APPEAR TO BE THE CASE. HAVE TRIED TO TIME THE TSRA
ACROSS THE CWFA THIS FIRST 12 HOURS BLENDING INHERITED FCST AND
HRRR/NAM/WRF MODEL MOVEMENT.

THE FIRST WAVE ASSOCIATED WITH CONVECTION MOVES EAST BY
18Z...WITH SECOND FAST WAVE MOVING INTO WY AS OF 08Z. AS THE UPPER
WAVES ARE PROGRESSIVE AND THE SYNOPTIC SCALE MODELS ARE IN FAIR
AGREEMENT WITH THE HIGH-RES MODELS...HAVE TRENDED THE BULK OF THE
TSRA/RASH OVER THE EASTERN HALF CWFA BY 00Z. MAY HAVE HELD ON TO
POPS TOO LONG POST 18Z...BUT THIS IS DIFFICULT TO ASCERTAIN ATTM.
THE FCST PRESENCE OF THE LOW LEVEL BOUNDARY AND INSTABILITY 18Z-
00Z ARGUES FOR HOLDING ONTO POPS.

SECOND SHORT WAVE FORECAST TO MOVE ACROSS THE SOUTHERN HALF OF
THE FA 00Z TO 06Z MONDAY SO HAVE HELD ON TO CHC POPS THROUGH 06Z
THEN ENDED RAIN RISK FOR MONDAY. HIGH TEMPERATURES TODAY WILL BE
HIGHLY DEPENDENT ON THE CLOUD COVER...THICKNESSES ARE HIGH ENOUGH
OVER THE SOUTH TO SUPPORT UPPER 70S TO LOWER 80S. HAVE USED THE
LOCAL BIAS CORRECTED TEMPERATURE MODEL FOR TODAY - TUESDAY AS IT
SEEMS TO HAVE SUPERIOR SKILL OF LATE.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 330 AM CDT SUN AUG 31 2014

FLOW ALOFT TURNS FLAT WEST-NORTHWEST BEHIND SECOND WAVE BUT
HEIGHTS DO NOT FALL APPRECIABLY. THE NEXT SHORTWAVE AND ASSOCIATED
SURFACE REFLECTION IMPACTS THE SOUTHERN CWFA MONDAY NIGHT. MODELS
SUGGEST NEXT WAVE FOR TUESDAY FOCUSED MORE ALONG AND NORTH OF THE
HIGHWAY 2 CORRIDOR FOR TUESDAY AFTERNOON AND EVENING...WITH ONLY
CHC POPS.

WEDNESDAY THROUGH SATURDAY...THE NEXT UPPER TROUGH WILL MOVE INTO
THE NORTHERN ROCKIES AT THE START OF THE PERIOD...THEN MOVING OFF
INTO MANITOBA BY THURSDAY. THE SFC LOW WILL MOVE BY TO OUR SOUTH AND
WE SHOULD SEE PLENTY OF PRECIP WITH A BOUNDARY NEARBY...ALTHOUGH THE
MODELS DIFFER ON EXACT TIMING AND PLACEMENT OF THE LOW. WILL
CONTINUE TO KEEP FAIRLY HIGH POPS FOR WEDNESDAY NIGHT AND SOME
LINGERING IN THE EST INTO THURSDAY AS A COLD FRONT COMES THROUGH.
SFC HIGH PRESSURE BUILDING IN FOR THE END OF THE PERIOD WILL BRING
DRY CONDITIONS AND COOLER TEMPERATURES. THE ECMWF AND GFS START TO
DIVERGE BY SATURDAY...SO KEPT ALLBLEND POPS FOR THE TIME BEING.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1243 PM CDT SUN AUG 31 2014

AFTN CIGS EXPECTED TO BE IN THE LOWER END OF THE MVFR RANGE WITH
SOME SPOTTY AREAS OF IFR CIGS. IFR CIGS GENERALLY IN THE 005-009
RANGE SO SHOULD LIFT INTO MVFR RANGE BY MID AFTN. MODEL GUIDANCE
APPEARS TO FAST IN SCATTERING SKIES OUT TONIGHT SO WILL HOLD ON TO
MVFR CIGS A BIT LONGER THAN MODELS SUGGEST...GENERALLY GOING VFR BY
MID EVENING AT ALL SITES EXCEPT BJI...WHERE MVFR CIGS ARE EXPECTED
TO STAY IN PLACE OVERNIGHT.

&&

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

$$

UPDATE...TG
SHORT TERM...EWENS
LONG TERM...JR/EWENS
AVIATION...SPEICHER




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