Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 311137
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
637 AM CDT MON AUG 31 2015

.UPDATE...
ISSUED AT 632 AM CDT MON AUG 31 2015

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE TO LIFT
NORTHEAST ACROSS NORTHERN AND EASTERN NORTH DAKOTA. CONVECTION HAS
EXITED THE SOUTHWEST QUARTER OF THE STATE. MAIN UPDATE WAS TO POPS
BASED ON LATEST RADAR AND THE TIME LAGGED HRRR OUTPUT THROUGH THIS
MORNING. OTHERWISE NO SIGNIFICANT UPDATES NEEDED.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 335 AM CDT MON AUG 31 2015

SHOWERS AND THUNDERSTORMS ENDING BY NOON. THEN BREEZY WEST WINDS
BRING A DRIER AND COOLER AIRMASS INTO THE STATE.

A SURFACE COLD FRONT EXTENDED FROM AROUND LAKE WINNIPEG
SOUTHWESTWARD TO THE TURTLE MOUNTAIN AND DEVILS LAKE AREA...TO NEAR
BISMARCK TO THE BLACK HILLS AREA IN WESTERN SOUTH DAKOTA. SCATTERED
SHOWERS AND THUNDERSTORMS CONTINUED TO DEVELOP ALONG AND WEST OF THE
SURFACE FRONT...MOVING NORTHEASTWARD ALONG THE UPPER LEVEL FLOW. AT
UPPER LEVELS...A SERIES OF UPPER LEVEL IMPULSES WERE MOVING
NORTHEASTWARD FROM WYOMING INTO THE CENTRAL AND WESTERN DAKOTAS. A
STRONG UPPER LEVEL SHORTWAVE WAS FARTHER WEST OVER CENTRAL
MONTANA/SOUTHERN SASKATCHEWAN...AND IS FORECAST TO CONTINUE LIFTING
NORTHEASTWARD ACROSS NORTHWESTERN NORTH DAKOTA AND INTO SOUTHERN
MANITOBA.

THE SURFACE COLD FRONT IS FORECAST TO MOVE EAST...REACHING THE RED
RIVER VALLEY AREA AROUND NOON. THE SHOWERS AND THUNDERSTORMS SHOULD
BE ENDING IN THE SOUTHWEST EARLY THIS MORNING...AND ENDING BY EARLY
AFTERNOON IN THE FAR NORTH AND JAMES RIVER VALLEY. THIS SHOULD OCCUR
AS THE LAST OF THE UPPER LEVEL IMPULSES AND STRONG SHORTWAVE MOVE
EAST OUT OF WESTERN AND CENTRAL NORTH DAKOTA.

A SECONDARY SURGE OF COOLER AND DRIER AIR WELL BEHIND THE FRONT
IS PROGGED TO PUSH INTO FAR WESTERN NORTH DAKOTA BEFORE DAYBREAK
THIS MORNING...WITH H850 WINDS OF 25 TO 35 KNOTS AT THE LEADING EDGE
OF THE AIRMASS. THIS IS DRY AIR MOVING ACROSS THE ROCKIES AND INTO
THE FRONT RANGE. CURRENT DEWPOINT TEMPERATURES IN THE WEST WERE IN
THE 50S WITH 60S IN THE EASTERN HALF OF THE STATE. THIS AFTERNOON
THE DEWPOINTS SHOULD BE AS LOW AS THE LOW TO MID 30S IN WESTERN
NORTH DAKOTA...AND IN THE 40S AND 50S EAST. HIGHS IN THE UPPER 70S
WEST WILL RESULT IN AFTERNOON MINIMUM RELATIVE HUMIDITY VALUES
AROUND 20 PERCENT. WEST WINDS OF 20 TO 25 MPH WITH GUSTS TO 30 MPH
CAN BE EXPECTED LATER THIS MORNING...BUT SHOULD DIMINISH SOMEWHAT
THIS AFTERNOON AFTER THE INITIAL PUSH OF DRY AIR. THUS THE STRONGEST
WINDS TODAY SHOULD NOT COINCIDE WITH THE LOWEST RELATIVE HUMIDITY
VALUES...AND RED FLAG CRITERIA ARE NOT EXPECTED TO BE MET.

LOOK FOR BREEZY WEST WINDS TO DEVELOP TODAY WITH DECREASING CLOUDS
FROM SOUTHWEST TO NORTHEAST. HIGHS SHOULD RANGE FROM THE UPPER 70S
NORTH AND WEST TO THE LOW TO MID 80S SOUTH CENTRAL.

DECREASING WINDS THIS EVENING WITH CLEAR SKIES. LOWS SHOULD BE
MAINLY IN THE 50S.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 335 AM CDT MON AUG 31 2015

CONTINUED WARM TEMPERATURES AND SLIGHT/PERIODIC THUNDERSTORM CHANCES
WILL HIGHLIGHT THE EXTENDED FORECAST PERIOD THROUGH THE WORK WEEK.
MODEL DIFFERENCES APPEAR BY THE WEEKEND WITH A POSSIBLE PATTERN
CHANGE INTO THE EARLY PORTIONS OF NEXT WEEK.

ON TUESDAY...MAINTAINED A SLIGHT CHANCE OF MAINLY EVENING AND
OVERNIGHT THUNDERSTORMS FOR THE DEVILS LAKE BASIN AND JAMES RIVER
VALLEY WITH MODELS STILL SHOWING INCREASING INSTABILITY WITH DAYTIME
HEATING COUPLED WITH AN INCREASING LOW LEVEL JET ACROSS THE EASTERN
HALF OF THE STATE. CAPPING DURING THE DAY MAY HOLD OFF ON CONVECTION
UNTIL AFTER 00Z.

BEYOND TUESDAY...OUR SOUTHWEST UPPER FLOW WILL CONTINUE THROUGH THE
END OF THE WORK WEEK WITH TROUGHING ACROSS THE PACIFIC NORTHWEST AND
RIDGING OFF TO OUR EAST. A QUASI-STATIONARY SURFACE TROUGH COMBINED
WITH ANY EMBEDDED WAVES ALOFT WILL PROVIDE A FOCUS FOR MAINLY
ISOLATED DAILY SHOWER AND THUNDERSTORM ACTIVITY. BEST CHANCES APPEAR
TO BE TOWARDS THE END OF THE WORK WEEK AND INTO NEXT WEEKEND WHEN A
STRONG UPPER JET APPROACHES THE NORTHERN PLAINS. TEMPERATURES WILL
REMAIN NEAR TO SLIGHTLY ABOVE NORMAL THROUGH THE WORK WEEK.

DISAGREEMENT IN DETERMINISTIC MODELS CROPS UP BY THE WEEKEND
REGARDING THE STRONG UPPER LEVEL TROUGH TO OUR WEST. THE 00 UTC 31
AUG GFS IS NOW MUCH MORE PROGRESSIVE AND WEAKER WITH THIS FEATURE.
THUS COOLER CONDITIONS ENTER THE NORTHERN PLAINS SATURDAY AND SUNDAY
WITH A WARM-UP RETURNING BY THE BEGINNING OF NEXT WEEK. THE ECMWF
IS MUCH SLOWER AND STRONGER...KEEPING IT MILD THROUGH THE FIRST
HALF OF THE WEEKEND...THEN COOLING SUNDAY INTO EARLY NEXT WEEK AND
WITH MUCH COLDER TEMPERATURES OVER THE AREA EARLY NEXT WEEK. THE
GLOBAL GEM WAS ALSO SHOWING A SLOWER SOLUTION THAN THE GFS THROUGH
SUNDAY. THE GFSENSEMBLE SPREAD WAS MUCH GREATER LATE IN THE
WEEKEND COMPARED TO THE ECMWF ENSEMBLE...THUS MAYBE AN INDICATION
THAT THE SLOWER SOLUTION WILL PREVAIL. BUT FOR NOW WILL HOLD
STEADY WITH OUR CURRENT MODEL BLEND SOLUTION WHICH IS STILL
TRENDING COOLER FOR THE WEEKEND.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 632 AM CDT MON AUG 31 2015

SCATTERED THUNDERSTORMS ARE POSSIBLE AT KISN/KMOT/KJMS THIS MORNING.
THOUGH NOT OUT OF THE QUESTION...IT APPEARS THAT THE THUNDERSTORM
THREAT AT KDIK AND KBIS HAS PASSED. A COLD FRONT EXTENDED FROM NEAR
DEVILS LAKE TO NEAR STEELE TO LINTON...TO NEAR MOBRIDGE IN SOUTH
DAKOTA. COOLER AND DRIER AIR WAS PUSHING INTO THE WESTERN PART OF
NORTH DAKOTA. NORTHWEST WINDS HAD JUST BEGUN TO INCREASE AT CROSBY.
INCREASE OF NORTHWEST WINDS SHOULD SPREAD FROM NORTHWEST TO
SOUTHEAST AT TAF SITES...BEGINNING AT KISN SOON AFTER 12Z AND
REACHING KJMS BY AROUND 18Z. DECREASING WINDS AFT 00Z.

SMOKE MAY BECOME MORE WIDESPREAD AND THICKER THROUGH THE
DAY...BUT NOT CONFIDENT REGARDING AFFECTS AT THE SURFACE AT MOST TAF
SITES. MENTIONED VSBY REDUCTION AT KBIS WITH 4SM REPORTED AT 6 AM
CDT BECAUSE OF SMOKE.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...TWH
SHORT TERM...JV
LONG TERM...TWH
AVIATION...JV



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