Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 220253
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
953 PM CDT THU AUG 21 2014

.UPDATE...
ISSUED AT 949 PM CDT THU AUG 21 2014

SO FAR COOP REPORTS OF THUNDERSTORMS HAVE HEAVY RAINFALL FROM THE
BOWMAN COUNTY STORMS THIS EVENING. SEVERAL REPORTS IN EXCESS ON ONE
INCH. SO THE ATMOSPHERE IS PRIMED FRO HEAVY RAINFALL. TRENDS LOOK
GOOD SO FAR FOR POPS AND TEMPERATURES SO WILL ONLY MAKE COSMETIC
TWEAKS.

UPDATE ISSUED AT 654 PM CDT THU AUG 21 2014

LARGE AREA OF SHOWERS WITH EMBEDDED THUNDERSTORMS SWINGING THROUGH
EASTERN MONTANA AT THIS TIME. THESE WILL BEGIN TO MOVE INTO WESTERN
NORTH DAKOTA AFTER 9-10 PM. AHEAD OF THIS AREA SOME WIDELY
SCATTERED SHOWERS AND A FEW THUNDERSTORMS ARE OVER WEST CENTRAL
NORTH DAKOTA BUT LOOKING PRETTY WEAK AT THIS TIME. WILL MOST
LIKELY NEED TO WAIT UNTIL THE MAIN UPPER WAVE MOVES CLOSER TO
WESTERN ND LATE THIS EVENING TO SEE SUBSTANTIAL RAIN ACTIVITY.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)

ISSUED AT 335 PM CDT THU AUG 21 2014

MAIN FORECAST HIGHLIGHT IN THE SHORT TERM PERIOD WILL BE THE NEXT
WAVE OF PRECIPITATION LATER TODAY THROUGH TONIGHT.

CURRENTLY...ACTIVE SOUTHWESTERLY FLOW ALOFT REMAINS OVER THE
NORTHERN PLAINS. TROUGH OF LOW PRESSURE CONTINUES SLOWLY EAST OVER
THE EASTERN DAKOTAS...WITH CONVECTION FIRING UP NEAR THIS FEATURE
OVER EASTERN PORTIONS OF THE STATE...EXTENDING INTO THE TURTLE
MOUNTAIN REGION. ANOTHER AREA OF THUNDERSTORMS CONTINUES OVER FAR
EASTERN MONTANA AHEAD OF A S/WV IMPULSE EJECTING NORTHEAST OUT OF
THE WYOMING ROCKIES. A STRONGER STORM FOR ANY OF THESE AREAS NOT
OUT OF THE QUESTION CONSIDERING THE AMOUNT OF INSTABILITY PRESENT.
WIDESPREAD SEVERE NOT EXPECTED.

MAIN AREA OF HEAVY RAIN FORECAST TO DEVELOP ACROSS THE WEST AFTER
00Z WHEN MODELS PROJECT A STRONGER MID LEVEL IMPULSE TO MOVE
THROUGH THE LOCAL AREA AND AS A SFC BOUNDARY DEVELOPS NEAR THE
ND/SD BORDER. FORCING WILL BE ENHANCED AS WELL BY AN UPPER LEVEL
JET STREAK. COUPLED WITH RICH BOUNDARY LAYER MOISTURE WITH
PRECIPITABLE WATER VALUES IN THE 99TH PERCENTILE...SHOULD SEE A
FEW HEAVY RAINERS ACROSS THE AREA...ESPECIALLY SOUTHWEST INTO
PARTS OF THE CENTRAL TONIGHT INTO FRIDAY MORNING.

ANOTHER BREAK IN THE ACTION FRIDAY DAYTIME...SIMILAR TO
TODAY WITH CONTINUED HIGH HUMIDITY AND LIKELY LOW TO MID CLOUD
COVER THROUGH THE DAY...WITH THE NEXT WAVE OF RAIN LATER IN THE
DAY INTO FRIDAY NIGHT.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 335 PM CDT THU AUG 21 2014

THE MAIN CONCERN IN THE LONG TERM IS THE POTENTIAL FOR WIDESPREAD
HEAVY RAIN AND FLOODING FRIDAY NIGHT THROUGH THIS WEEKEND.

AN ACTIVE SOUTHWESTERLY FLOW ALOFT WILL CHARACTERIZE THE UPPER
PATTERN OVER THE NORTHERN PLAINS THROUGH THE WEEKEND. QUASI-ZONAL
FLOW IS THEN PROGGED TO DEVELOP DURING THE FIRST PART OF NEXT
WEEK...WITH UPPER LEVEL RIDGING POSSIBLE BY THE MIDDLE OF NEXT WEEK.
BELOW AVERAGE TEMPERATURES WILL CONTINUE THROUGH THE EXTENDED PERIOD.

FRIDAY NIGHT THROUGH SUNDAY:
A LONGWAVE TROUGH WELL-ESTABLISHED OVER THE ROCKIES WILL BEGIN
MOVING EAST AND A SIGNIFICANT EMBEDDED SHORTWAVE WILL LIFT
NORTHEASTWARD INTO THE DAKOTAS FRIDAY NIGHT AND SATURDAY...FOLLOWED
BY THE PARENT UPPER LEVEL LOW SATURDAY NIGHT THROUGH SUNDAY. THIS
TIME PERIOD WILL BE CHARACTERIZED BY WIDESPREAD SHOWERS AND
THUNDERSTORMS WITH HEAVY RAIN ACROSS ALL OF WESTERN AND CENTRAL
NORTH DAKOTA.

AT THIS TIME...THE MODEL CONSENSUS IS FOR THE OVERALL HEAVIER TOTALS
TO BE HIGHER OVER THE WESTERN HALF OF THE STATE FRIDAY NIGHT THROUGH
SUNDAY...WITH 1-2.5 INCHES AVERAGED OVER THE ENTIRE WESTERN HALF OF
THE STATE. THE HIT-AND-MISS CHARACTER OF WARM-SEASON THUNDERSTORMS
WILL LIKELY RESULT IN SOME AREAS RECEIVING HIGHER AMOUNTS...WHILE
OTHER LOCALES WILL LIKELY RECEIVE LESS THAN THE ANTICIPATED
AREA-WIDE AVERAGE. OVERLAND FLOODING WILL BE LIKELY IN THOSE LOCALES
WHICH RECEIVE MORE THAN AN INCH OR TWO OF RAIN.

SUNDAY NIGHT THROUGH THURSDAY:
AS THE PARENT UPPER LEVEL LOW LIFTS NORTHEASTWARD INTO
CANADA...CHANCES OF SHOWERS CONTINUE ACROSS NORTH DAKOTA - BUT THE
THREAT OF WIDESPREAD HEAVY RAINS SHOULD BE OVER. BY WEDNESDAY ZONAL
WEST-TO-EAST FLOW ALOFT WILL BRING DRY WEATHER OR ONLY SMALL CHANCES
FOR SHOWERS OR THUNDERSHOWERS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 949 PM CDT THU AUG 21 2014

A LARGE UPPER LEVEL LOW PRESSURE PATTERN WILL BECOME
PREDOMINATE OVER THE NORTHERN PLAINS. THIS WILL BRING WIDESPREAD
SHOWERS AND THUNDERSTORMS TO THE REGION LATER TONIGHT AND FRIDAY.
THE MAIN THREATS TO AVIATION ARE THUNDERSTORMS AND MVFR TO IFR
CONDITIONS ASSOCIATED WITH THE PRECIPITATION AND AREAS OF FOG. VFR
CONDITIONS WILL GRADUALLY DETERIORATE TO MVFR BY EARLY MORNING
ACROSS THE WEST IMPACTING KISN-KDIK-KMOT-KBIS. VFR EXPECTED AT
KJMS UNTIL SOME FOG SETS IN WITH AT LEAST MVFR CONDITIONS LATE
TONIGHT THROUGH MID MORNING FRIDAY.

&&

.HYDROLOGY...

ISSUED AT 335 PM CDT THU AUG 21 2014

ABOUT A THIRD OF THE AREA HAS RECEIVED MORE THAN THREE TIMES
THEIR NORMAL AMOUNT OF PRECIPITATION OVER THE PAST TWO WEEKS. SOIL
MOISTURE IS ANOMALOUSLY HIGH...AND THE LIKELIHOOD OF RAINFALL
CAUSING EXCESSIVE RUNOFF AND OVERLAND/SMALL STREAM FLOODING GROWS
WITH EACH PASSING THUNDERSTORM.

WILL CONTINUE TO USE THE HYDROLOGIC OUTLOOK/ESF TO HIGHLIGHT
FLOOD POTENTIAL WITH THIS FORECAST ISSUANCE. PRECIPITATION FOR
TONIGHT IS NOT EXPECTED TO BE AS WIDESPREAD AS WE WILL SEE DURING
THE FRIDAY NIGHT-SUNDAY TIME PERIOD. THE PLACEMENT OF ADDITIONAL
RAINFALL TONIGHT...COUPLED WITH FORECAST MODEL GUIDANCE BECOMING
MORE IN AGREEMENT...WILL HOPEFULLY SHED A BETTER LIGHT ON THE
POTENTIAL FOR A FLOOD WATCH PRODUCT OVER THE WEEKEND.

&&

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

$$

UPDATE...WAA
SHORT TERM...NH
LONG TERM...JV
AVIATION...WAA
HYDROLOGY...NH






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