Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 040833
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
333 AM CDT FRI SEP 4 2015

.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 333 AM CDT FRI SEP 4 2015

THE MAIN CONCERN WILL BE SEVERE THUNDERSTORM AND HEAVY RAIN
POTENTIAL THIS AFTERNOON AND EVENING.

SOUTHWEST FLOW ALOFT CONTINUES...WITH A STRONGER UPPER LEVEL WAVE
APPROACHING THE REGION (AND MOVING THROUGH THIS
AFTERNOON/EVENING). THE HOT AND HUMID AIRMASS WILL REMAIN IN
PLACE AS THE SFC BOUNDARY REMAINS LOCATED THROUGH CENTRAL ND. THE
FORCING FROM THIS SHORTWAVE WILL INTERACT WITH STRONG INSTABILITY
LIKELY LEADING TO A CLUSTER OF STRONG STORMS. 0-6KM BULK SHEAR
REMAINS RELATIVELY WEAK...BUT DOES INCREASE IN ASSOCIATION WITH
THE SHORTWAVE. THE COMBINATION OF INSTABILITY AND DEEP LAYER SHEAR
SHOULD BE SUFFICIENT FOR SEVERE STORMS (SPC INDICATES A SLIGHT
RISK). CAM GUIDANCE IS IN GOOD AGREEMENT AS THE 00Z SPC SSEO
INDICATES VERY HIGH PROBABILITIES OF STRONG UPDRAFT HELICITY AND
WIND GUST POTENTIAL FROM THE DEVILS LAKE BASIN INTO THE NORTHERN
RED RIVER VALLEY. THIS WOULD APPEAR TO BE THE MOST LIKELY AREA
GIVEN WHERE THE SFC BOUNDARY IS CURRENTLY LOCATED. TO THE
SOUTH...NOT SURE THE EXTENT OF STORMS GIVEN THE WARM MID-LEVEL
TEMPS (CAPPING) AND WEAKER FORCING. DID KEEP CHC POPS SINCE IF A
STORM OR TWO CAN DEVELOP THEY SHOULD BE SEVERE. DAMAGING HAIL AND
WINDS APPEAR TO BE THE MAIN THREATS. LOW LEVEL SHEAR IS RELATIVELY
WEAK WHICH LIMITS TORNADO POTENTIAL (ALTHOUGH STILL NOT
IMPOSSIBLE).

HEAVY RAINFALL WILL ALSO BE A CONCERN...AND WPC INDICATES A
SLIGHT RISK FOR EXCESSIVE RAINFALL. ALTHOUGH THE FORCING SIGNALS
FOR WIDESPREAD HEAVY RAINFALL ARE WEAK...MOISTURE IS VERY HIGH
WITH MODELS SUGGESTING PWATS OVER 2 INCHES. CAM GUIDANCE INDICATES
HIGH RAINFALL RATES (> 1 INCH/HOUR). GIVEN THESE FACTORS WILL
MENTION LOCALLY HEAVY RAINFALL POSSIBLE (RW+) ACROSS THE DVL BASIN
AND NORTHERN VALLEY. TRAINING STORMS ALONG THE LOW LEVEL BOUNDARY
COULD LEAD TO ISOLATED FLASH FLOODING...BUT THE PROGRESSIVE NATURE
OF THIS SYSTEM COMBINED WITH NORMAL SOIL MOISTURE WILL LIMIT
WIDESPREAD FLASH FLOOD POTENTIAL.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 333 AM CDT FRI SEP 4 2015

SATURDAY-SUNDAY...SEVERE THUNDERSTORMS AND HEAVY RAIN POTENTIAL
WILL CONTINUE TO BE THE CONCERNS. THERE WILL A BREAK EARLY
SATURDAY BEFORE THE NEXT STRONGER SHORTWAVE MOVES THROUGH THE
REGION...LEADING TO LIKELY THUNDERSTORM CHANCES...AND THE
POTENTIAL FOR STRONG TO SEVERE STORMS. WILL NEED TO WAIT AND
ATTEMPT TO FIGURE OUT DETAILS GIVEN SUBTLE MODEL DIFFERENCES THAT
REMAIN. THE MAIN UPPER LOW SWINGS INTO SOUTH CENTRAL CANADA BY
SUNDAY EVENING...SENDING A STRONGER COLD FRONT THROUGH THE REGION
SOMETIME ON SUNDAY...WHICH COULD AGAIN LEAD TO AN AREA OF STRONGER
THUNDERSTORMS.

MONDAY-THURSDAY...THE MUCH COOLER TEMPS WILL BE THE MAIN STORY FOR
THE START OF THIS PERIOD. IT WILL BE BREEZY ON MONDAY AS THE SFC LOW
PULLS AWAY...WITH HIGHS IN THE 60S AND 70S. TEMPS ON TUESDAY LOOK TO
REMAIN IN THE 60S FOR MOST AREAS...WITH AREAS NEAR THE CANADIAN
BORDER POSSIBLY STRUGGLING TO HIT 60. IN GENERAL...MUCH OF THE
PERIOD LOOKS TO BE QUIET UNDER THE INFLUENCE OF HIGH
PRESSURE...ALTHOUGH THE GFS/ECMWF ARE AT ODDS WITH EACH OTHER WITH
THE DEGREE OF AMPLIFICATION IN THE PATTERN BY THE MIDDLE OF NEXT
WEEK...WHICH WOULD IMPACT TEMP TRENDS AND MINOR RAIN CHANCES WITH
EMBEDDED IMPULSES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1138 PM CDT THU SEP 3 2015

AT THIS TIME LOOKS LIKE THUNDER CHANCES SLIM AT ANY OF THE TAF
SITES OVERNIGHT. ST/FG WILL AGAIN BE A BIG CHALLENGE. LATEST
GUIDANCE BRINGS SOME PATCHY IFR CIGS INTO THE NORTHERN AND EASTERN
HALF OF THE FA LATE TONIGHT AND INCLUDED IN LATEST TAF SETS. BEST
T POTENTIAL TOMORROW SHOULD BE LATE AFTERNOON FIRST IN THE DVL
AREA AND INTO THE VALLEY BY EVENING.

&&

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

$$

SHORT TERM...TG
LONG TERM...TG/MAKOWSKI
AVIATION...VOELKER



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