Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 041435
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
935 AM CDT SAT JUL 4 2015

.UPDATE...
ISSUED AT 935 AM CDT SAT JUL 4 2015

MADE A FEW TWEAKS TO POPS THIS AFTERNOON AS THE CAM MODELS STILL
ARE BREAKING OUT SOME STORMS WITH THE LEAD SHORTWAVE TROUGH COMING
OUT. BEFORE THAT KEPT IN THE AREAS OF SMOKE MENTION FOR THE REST
OF THE MORNING AS VIS CONTINUE TO BE REDUCED. THINK THERE SHOULD
BE SOME IMPROVEMENT BY AFTERNOON AS SOUTH WINDS PICK UP.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY NIGHT)
ISSUED AT 330 AM CDT SAT JUL 4 2015

SEVERE T-STORM POTENTIAL TODAY...AND THEN AGAIN ON SUNDAY WILL BE
THE MAIN CONCERNS. 00Z MODELS IN DECENT AGREEMENT WITH SYNOPTIC
FEATURES.

TODAY-TONIGHT...SPC HAS ADDED A SLIGHT RISK OF SEVERE STORMS FOR
EASTERN NORTH DAKOTA. WATER VAPOR IMAGERY INDICATES A LEAD
SHORTWAVE ACROSS EASTERN MONTANA THAT WILL PROVIDE FORCING ACROSS
EASTERN NORTH DAKOTA DURING THE AFTERNOON HOURS. ADDITIONAL STORMS
ARE EXPECTED TO DEVELOP ACROSS WESTERN NORTH DAKOTA ALONG A COLD
FRONT AND THEN MOVE INTO THIS AREA. CAM GUIDANCE SUGGESTS COVERAGE
WILL REMAIN ISOLD/SCATTERED. MOST GUIDANCE SUGGESTS MLCAPE
1000-2000 J/KG...WITH INCREASING 0-6KM BULK SHEAR (TO AROUND 30
KNOTS) THROUGH THE AFTERNOON AS THE MORE SUBSTANTIAL TROUGH IN
CANADA APPROACHES. THIS INSTABILITY/SHEAR COMBINATION SHOULD LEAD
TO ORGANIZED STORMS WITH MARGINALLY SEVERE HAIL AND WIND THE MAIN
THREATS.

THE SURFACE SMOKE REDUCING VSBY SHOULD DISPERSE A BIT DURING THE
AFTERNOON AS LOW LEVEL WINDS INCREASE.

SUNDAY-SUNDAY NIGHT...ECMWF/GEM HAVE SLOWED DOWN THE PROGRESSION
OF THE COLD FRONT ON SUNDAY...AND LIKEWISE ARE FURTHER NORTH WITH
AN UPPER WAVE SUNDAY NIGHT (COMPARED TO THE GFS/NAM). THE
ECMWF/GEM SOLUTION WOULD INCREASE THE SEVERE POTENTIAL FOR SUNDAY
AFTERNOON...AND ALSO LEAD TO A GREATER THREAT FOR HEAVY RAINFALL
(FLASH FLOODING) POTENTIAL ACROSS THE SOUTHERN FA SUNDAY NIGHT.
REGARDING THE SEVERE POTENTIAL ON SUNDAY...THE MAIN QUESTION STILL
REMAINS HOW QUICKLY THE STRONGER DEEP LAYER SHEAR CAN OVERSPREAD
THE REGION. THERE WILL BE MODERATE INSTABILITY ALONG AND AHEAD OF
THE SFC BOUNDARY SUNDAY AFTERNOON...IT IS JUST A MATTER HOW
QUICKLY THE SFC BOUNDARY MOVES TO THE SOUTHEAST (WILL IT REMAIN
AHEAD OF THE STRONGER DEEP LAYER SHEAR?). WOULD NOT BE SURPRISED
TO SEE SPC UPGRADE THE MARGINAL RISK TO A SLIGHT RISK EVENTUALLY.
STORM MOTION WILL LIKELY BE PARALLEL TO THE SURFACE BOUNDARY
SUNDAY AFTERNOON/EVENING...AND WITH PWATS ABOVE 1.5 INCHES ANY
TRAINING TYPE STORMS COULD LEAD TO HEAVY RAINFALL. IF THIS
OCCURS...WILL BE VERY CONCERNED FOR AN ADDITIONAL 1-3 INCHES THAT
COULD OCCUR TOWARD MONDAY MORNING IF THE ECMWF/GEM ARE CORRECT.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 330 AM CDT SAT JUL 4 2015

MONDAY...MUCH COOLER AIRMASS WILL INVADE THE REGION LEADING TO MAX
TEMPS BARELY REACHING 70F. COLD POOL ALOFT SHOULD LEAD TO AT LEAST
ISOLD AFTERNOON SHOWERS/T-STORMS.

TUESDAY-FRIDAY...MEDIUM RANGE MODELS STILL AGREE ON STARTING OUT
EXTENDED PERIOD AS DRY WITH BELOW AVERAGE TEMPERATURES AS HIGH
PRESSURE BUILDS INTO THE UPPER MIDWEST. SPLIT FLOW RULES AS THE
NEXT SHORTWAVE TROUGH ENTERS THE NORTHERN PLAINS ON WEDNESDAY
SPAWNING ANOTHER ROUND OF AT LEAST SCATTERED THUNDERSTORMS. THE
ECMWF REMAINS FASTER THAN THE GFS IN TIMING THE WAVE THROUGH THE
REGION. BLENDING PROTOCOLS YIELD HIGHER POPS ON
WEDNESDAY/WEDNESDAY NIGHT...WITH WEAK FRONTAL BOUNDARY CLEARING
THE REGION SOMETIME ON THURSDAY. BELOW NORMAL TEMPERATURES
SUCCEEDING EARLY WEEK COLD FRONT WILL EDGE TOWARD AVERAGE VALUES
BY THURSDAY AND FRIDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 620 AM CDT SAT JUL 4 2015

REDUCED VSBY DUE TO SMOKE AND/OR FOG WILL CONTINUE INTO THE LATE
MORNING HOURS...THEN IMPROVE BY THIS AFTERNOON AS LOW LEVEL FLOW
INCREASES. THUNDERSTORMS POSSIBLE THIS AFTERNOON AND
OVERNIGHT...BUT COVERAGE LIKELY NOT ENOUGH TO MENTION IN THE TAF.


&&

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

$$

UPDATE...JR
SHORT TERM...TG
LONG TERM...WJB/TG
AVIATION...TG


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