Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 041825
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
125 PM CDT TUE AUG 4 2015

.UPDATE...
ISSUED AT 120 PM CDT TUE AUG 4 2015

THE 12 UTC GLOBAL AND HIGH RESOLUTION SUITES CONTINUE TO SLOW THE
PROPAGATION AND WEAKEN THE OVERALL STRENGTH OF CONVECTION THAT IS
EXPECTED TO ENTER WESTERN NORTH DAKOTA THIS EVENING. THUS...HAVE
REMOVED POPS FOR THIS AFTERNOON FAR WEST...WITH 06 UTC APPEARING
TO BE THE FAVORED TIMEFRAME FOR POTENTIAL STORMS TO ENTER THE WEST
AS MOISTURE RETURN INTO EASTERN MONTANA HAS BEEN SLOW TO DEVELOP
SO FAR TODAY.

UPDATE ISSUED AT 928 AM CDT TUE AUG 4 2015

NO SIGNIFICANT CHANGES WITH THIS UPDATE OTHER THAN TO BLEND TO
OBSERVED TRENDS THROUGH 14 UTC. THE 00 UTC WRF-ARW/NMM...12-13 UTC
HRRR RUNS AND 12 UTC NAM ARE ALL IN AGREEMENT ON CONVECTION
REMAINING IN EASTERN MONTANA THROUGH 00 UTC IN ASSOCIATION WITH A
NARROW AXIS OF MID TO UPPER 60S DEWPOINTS CURRENTLY ACROSS
SOUTHERN SOUTH DAKOTA AND NEBRASKA THIS MORNING THAT WILL
ADVECT NORTHWEST AHEAD OF THE WARM FRONTAL BOUNDARY THROUGH THE
AFTERNOON.

UPDATE ISSUED AT 642 AM CDT TUE AUG 4 2015

CONSIDERED ADDING A BRIEF MENTION OF PATCHY FOG FOR AN HOUR OR TWO
THIS MORNING TOWARDS THE SOUTHERN JAMES RIVER VALLEY. KJMS AND
KBAC BRIEFLY REPORTED VISIBILITY RESTRICTIONS IN FOG...BUT THEY
HAVE SINCE CLIMBED BACK TO 10SM...AND AREA WEBCAMS DO NOT SHOW
REDUCED VISIBILITIES. DECIDED TO LEAVE OUT THE FOG MENTION FOR
NOW SINCE ANY FOG SHOULD BE VERY ISOLATED...AND IS NOT EXPECTED
TO PERSIST.

BLENDED CURRENT OBSERVATIONS INTO THE GRIDS...WITH THE FORECAST
GENERALLY STILL ON TRACK.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 305 AM CDT TUE AUG 4 2015

CURRENTLY...SURFACE HIGH PRESSURE EXTENDED FROM MANITOBA SOUTHWARD
THROUGH THE RED RIVER VALLEY. LOW PRESSURE CONTINUED TO DEVELOP IN
THE LEE OF THE ROCKIES. AT UPPER LEVELS...A RIDGE WAS MAINTAINED
OVER THE CANADIAN ROCKIES AND FRONT RANGE...BUT WAS BEING UNDERCUT BY
A SHORTWAVE LOW/TROUGH MOVING NORTHEASTWARD OUT OF UTAH INTO
WYOMING. A LOW LEVEL JET WAS ESTABLISHED ACROSS THE HIGH PLAINS OF
EASTERN CO/WY AND WESTERN NE/SD NUDGING INTO EASTERN MONTANA. A LINE
OF THUNDERSTORMS HAD DEVELOPED ALONG THE NOSE OF THE H850
JET...ARCING FROM THE BLACK HILLS SOUTHEASTWARD INTO NORTHEASTERN
NEBRASKA.

THE MODELS MOVE THE UPPER LEVEL RIDGE EASTWARD TODAY...REACHING
EASTERN SASKATCHEWAN/WESTERN DAKOTAS BY THIS EVENING. THE MODELS
CONTINUE ITS EASTWARD MARCH ACROSS THE STATE...WITH THE RIDGE
FLATTENING AS A STRONG UPPER LEVEL IMPULSE...EXTENDING FROM CENTRAL
SASKATCHEWAN SOUTHWARD INTO NEBRASKA...ENTERS FAR WESTERN NORTH
DAKOTA EARLY THIS EVENING AND MOVES INTO CENTRAL NORTH DAKOTA BEFORE
DAYBREAK WEDNESDAY MORNING.

EXPECT MOSTLY SUNNY SKIES OVER CENTRAL NORTH DAKOTA WITH EAST WINDS
BECOMING SOUTHEAST...BRINGING HIGHER SURFACE DEWPOINTS INTO THE
REGION. CHANCES OF THUNDERSTORMS BEGIN LATE THIS AFTERNOON IN THE
FAR WEST...WITH INCREASING CHANCES THIS EVENING IN THE WEST AND
SPREADING TO CENTRAL NORTH DAKOTA LATE TONIGHT. INCREASING
CAPE/INSTABILITY WITH THE APPROACH OF THE UPPER LEVEL IMPULSE. BULK
SHEAR VALUES ARE MODEST AND WE MAY SEE A STRONG STORM OR TWO...BUT
NOT EXPECTING A SEVERE WEATHER OUTBREAK WITH THIS SCENARIO.

LOOK FOR HIGHS TODAY IN THE LOWER 80S NORTH CENTRAL THROUGH THE
JAMES VALLEY TO THE UPPER 80S IN THE SOUTHWEST. LOWS TONIGHT SHOULD
BE IN THE UPPER 50S TO LOWER 60S.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 305 AM CDT TUE AUG 4 2015

SHOWERS AND THUNDERSTORMS FROM TUESDAY NIGHT WILL CONTINUE INTO
WEDNESDAY AS AN H5 WAVE MOVES ACROSS THE STATE. INSTABILITY
INCREASES WEDNESDAY AFTERNOON...ESPECIALLY ACROSS THE EASTERN
HALF OF THE FORECAST AREA...WHILE 0-6KM SHEAR IS FORECAST TO BE
35 TO 40 KTS. THE LATEST DAY 2 SPC OUTLOOK PLACES EASTERN PORTIONS
OF THE FORECAST AREA IN A MARGINAL RISK FOR SEVERE
THUNDERSTORMS...AND WILL MENTION THE POTENTIAL FOR A FEW STRONG
STORMS IN THE HAZARDOUS WEATHER OUTLOOK.

THUNDERSTORM CHANCES DIMINISH BEHIND THIS INITIAL WAVE...BUT THE
NEXT WAVE IS ALREADY MOVING INTO EASTERN MONTANA / WESTERN NORTH
DAKOTA LATER WEDNESDAY NIGHT INTO THURSDAY.  THE MODEL BLEND PAINTS
40-50 PERCENT POPS ACROSS MUCH OF WESTERN AND CENTRAL NORTH
DAKOTA ON THURSDAY...AND COULD SEE THOSE RISING IN PARTS OF THE
FORECAST AREA WITH RELATIVE AGREEMENT ALREADY SEEN AMONG THE
DETERMINISTIC RUNS OF THE NAM / GFS AND ECMWF.

A WEAK H5 RIDGE MOVES INTO THE NORTHERN PLAINS THIS WEEKEND...BUT
THE PROGRESSION OF WAVES CONTINUES. THERE IS SOME DISAGREEMENT
AMONG THE VARIOUS MODEL SOLUTIONS IN THE DETAILS...AND WILL AGAIN
FAVOR THE BLENDED MODEL APPROACH WHICH KEEPS MUCH OF SATURDAY
DRY...WITH THUNDERSTORM CHANCES INCREASING SATURDAY NIGHT INTO
SUNDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 120 PM CDT TUE AUG 4 2015

VFR CONDITIONS ARE EXPECTED THROUGH THE FORECAST PERIOD OUTSIDE OF
THUNDERSTORMS. SHOWERS AND THUNDERSTORMS ARE EXPECTED TO MOVE
INTO FAR WESTERN NORTH DAKOTA LATE THIS EVENING...APPROACHING
KISN/KDIK AROUND 06-07Z AND KBIS/KMOT AROUND 12-14 UTC.

&&

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

$$

UPDATE...AYD
SHORT TERM...JV
LONG TERM...CK
AVIATION...AYD


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