000
FXUS63 KFGF 171743
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
1243 PM CDT FRI MAY 17 2013

.UPDATE...
ISSUED AT 1243 PM CDT FRI MAY 17 2013

SCATTERED SHOWERS ACROSS THE NW FA WILL EXIT BY LATER THIS
AFTERNOON AS ASSOCIATED UPPER WAVE PROPAGATES INTO CANADA.
CLEAR SKIES REMAIN ACROSS PORTIONS OF THE SOUTHERN FA...AND
TEMPERATURES WITHIN THIS AREA ARE NOW INTO THE 70S. THE TREND OF
BECOMING CLOUDY STILL LOOKS GOOD...BUT IT WILL TAKE SOME TIME.
INCREASED MAX TEMPS INTO THE MID-UPPER 70S WITHIN THE CLEAR
AREA...AND SLOWED DOWN THE PROGRESSION OF THIS AREA BECOMING
CLOUDY. THE OTHER ISSUE WILL BE THUNDER CHANCES TONIGHT. FOLLOWING
THE LATEST RAP/HRRR GUIDANCE AND 12Z NAM/GFS...THERE WILL BE A
SURGE OF INSTABILITY AS 850MB WINDS AND WARM AIR ADVECTION
INCREASE (ALONG ELEVATED WARM FRONT). THIS WILL HAPPEN CLOSER TO
03Z-06Z ACROSS THE SOUTHERN FA. THE RAP INDICATES 850MB CAPE ABOVE
1000 J/KG ALONG WITH AROUND 35 KNOTS OF DEEP LAYER SHEAR...WHICH
COULD POSSIBLY LEAD TO ISOLATED SEVERE HAIL (SEVERE HAIL POTENTIAL
IS DEPENDENT ON STRENGTH OF INSTABILITY). THIS COMPLEX WILL LIKELY
WEAKEN AS IT MOVES TO THE NORTH...BUT THUNDER/SHOWER CHANCES
SHOULD HOLD TOGETHER AND EXIT THE NORTHERN FA SATURDAY MORNING.
UPDATED THE GRIDS THROUGH TONIGHT FOR THIS THINKING (AND WILL
CONCENTRATE ON SATURDAY THROUGH MONDAY FOR THE NEXT FORECAST
ISSUANCE).

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 325 AM CDT FRI MAY 17 2013

FORECAST CHALLENGE CONCERNS PCPN CHANCES/AMOUNTS AND TEMPERATURES.
MODELS IN GENERAL AGREEMENT WITH MAIN FEATURES HOWEVER ALL DIFFER
ON QPF SCENARIOS THROUGH THE SHORT TERM. AT THIS POINT WILL USE A
GENERAL BLEND.

PERSISTENT BAND OF -SHRA ASSOCIATED WITH ELEVATED ZONE OF
ENHANCED WARM ADVECTION AND H7 CONVERGENCE SHOULD GRADUALLY WEAKEN
THROUGH THE MORNING AS ABOVE FEATURES WEAKEN AND SHIFT NE. WILL GO
WITH HIGH POP/LOW QPF INTO MID MORNING THEN TRIM BACK ON POPS.
ELSEWHERE CONFIDENCE LOW ON ANY PCPN POTENTIAL THROUGH THE BULK OF
THE DAY. SURFACE LOW AND E-W ORIENTED WARM FRONTAL BOUNDARY ALONG
SD/NE BORDER INTO IA LIFTS SLOWLY THROUGH SD DURING THE DAY.
EXPECT MOST PCPN WILL BE ORIENTED CLOSER TO LOW LEVEL BOUNDARY TO
OUR SOUTH. WILL INCREASE POPS SOMEWHAT LATER IN THE AFTERNOON AS
BOUNDARY APPROACHES. TEMPERATURES WILL BE HIGHLY INFLUENCED BY
CLOUDS. RAISED TEMPERATURES SLIGHTLY ACROSS THE SOUTH WHERE SOME
THINNER CLOUD COVER EXISTS OTHERWISE WILL STICK WITH PERSISTENCE.

AS WARM FRONT LIFTS NORTH TONIGHT EXPECT RAIN CHANCES TO INCREASE
AND BY MID EVENING SOUTHERN AND WESTERN FORECAST AREAS LOOK TO BE
FAVORED AREAS FOR SHRA/TSRA. BEST THUNDER POTENTIAL WILL BE ACROSS
THE SOUTH AS NORTHERN AREAS STILL PRETTY STABLE. BAND OF PCPN
SHOULD LIFT NORTHWARD OVERNIGHT NIGHT AND ADJUSTED POPS
ACCORDINGLY.

FRONTAL BOUNDARY WILL BE ORIENTED ACROSS FA SATURDAY SO INCREASED
POPS. SEVERE POTENTIAL LOOKS BEST LATE IN THE AFTERNOON ACROSS THE
SOUTH HALF OF THE FA WITH FAVORABLE CONVECTIVE PARAMETERS.

.LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 325 AM CDT FRI MAY 17 2013

SEVERE CONVECTIVE THREAT WILL CONTINUE INTO THE EVENING. WITH
PRECIPITABLE H2O VALUES AROUND 1.5 INCHES HEAVY RAIN WILL BE A
POSSIBILITY. INITIALLY FAVORED AREA FOR HEAVY RAIN LOOKS TO BE
ACROSS S HALF OF FA LIFTING NORTHWARD DURING THE OVERNIGHT.

WITH CUT OFF LOW DEVELOPING VCNTY OF FA POTENTIAL FOR SIGNIFICANT
RAIN WILL CONTINUE THROUGH THE WEEKEND AND WILL NEED TO MONITOR
RAIN AMOUNTS CLOSELY. AT THIS POINT LONG DURATION RAIN EVENT FOR
SURE BUT NOT ENOUGH CONFIDENCE ON ANY PARTICULAR LOCATION FOR
FLOOD/FLASH FLOOD WATCH.

0 UTC GFS/ECMWF/GEM IN GOOD OVERALL AGREEMENT NEXT WEEK...SHOWING A
CLOSED 500 HPA LOW ACROSS SOUTHEAST SD MONDAY MORNING CRAWLING
PAINFULLY SLOW TO THE EAST THROUGH WEDNESDAY. THIS FIRMLY ENTRENCHES
THE FORECAST AREA IN WRAP-AROUND RAIN SHOWERS THROUGH TUESDAY...
SLOWLY DRYING OUT WEDNESDAY AND A RETURN TO DRY CONDITIONS ON THURSDAY.
WILL KEEP THUNDER MENTION THROUGH MONDAY...BUT MOST INSTABILITY
SHOULD MOVE TO THE SOUTH BY TUESDAY. WITH CLOUD COVER AND RAIN...
TEMPERATURES WILL BE NEAR OR SLIGHTLY BELOW MID-MAY NORMALS WITH
HIGHS IN THE UPPER 50S AND 60S AND LOWS IN THE 40S/LOWER 50S. WITH
GREATER SUNSHINE AND DRY CONDITIONS...SHOULD SEE SOME AREAS REACHING
70 DEGREES BY THURSDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1243 PM CDT FRI MAY 17 2013

QUESTION FOR THIS PERIOD WILL BE HOW FAR NORTH THE MVFR CLOUDS
SPREAD DURING THE NIGHT INTO SATURDAY MORNING AND PRECIPITATION
(THUNDER) CHANCES.  THRU 00Z FORSEE ALL SITES STAYING VFR..BUT
WATCHING AN AREA OF HIGHER DEW POINTS ALONG WITH 25-35K FT CLOUD
DECK MOVING SLOWLY NORTHWEST FROM WCNTRL MN AND ECNTRL SD.  TIMING
OF THIS MOVEMENT NORTHWEST INTO FARGO AREA IS SUSPECT...BUT LATEST
RAP MODEL SUGGEST 03Z-06Z PERIOD.  THESE CONDITIONS MAY REACH THE
OTHER TAF SITES TOWARD 12Z.  PRECIP (THUNDER) CHANCES LATER TONIGHT
INTO SATURDAY MORNING AND WHEN/HOW IT AFFECTS ANY TAF SITE IS QUITE
DIFFICULT TO DETERMINE NOW.  FOR NOW JUST INCLUDED A TEMPO GROUP FOR
FARGO AS BEST CHANCE APPEARS THERE OVERNIGHT.  WINDS WILL REMAIN
SOUTHEAST MOSTLY 10 TO 20 KTS.

&&

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

$$

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