Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 010539
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
1239 AM CDT FRI AUG 1 2014

.UPDATE...
ISSUED AT 1239 AM CDT FRI AUG 1 2014

A SMALL CLUSTER OF THUNDERSTORMS OVER SOUTH CENTRAL SASKATCHEWAN...IN
THE SWIFT CURRENT AREA...CONTINUED TO SUSTAIN ITS CONVECTION THROUGH
SUNSET. THE MODELS DEPICT A WEAK UPPER LEVEL IMPULSE IN THE AREA
WHERE CURRENT THUNDERSTORM ACTIVITY WAS OCCURRING. THE NAM DEPICTS
THE WEAK UPPER LEVEL IMPULSE MOVING SOUTHEASTWARD
SLOWLY...APPROACHING NORTHWESTERN NORTH DAKOTA BEFORE/AROUND
DAYBREAK...THEN MOVING THROUGH SOUTHWESTERN NORTH DAKOTA FRIDAY
AFTERNOON.

HAVE INTRODUCED SOME SLIGHT CHANCE PRECIP PROBABILITIES IN
NORTHWESTERN NORTH DAKOTA BEFORE DAYBREAK.

OTHERWISE CURRENT FORECAST LOOKS ON TRACK.

UPDATE ISSUED AT 949 PM CDT THU JUL 31 2014

SHORT TERM HOURLY GRIDS HAVE BEEN UPDATED WITH NO CHANGES MADE.

UPDATE ISSUED AT 637 PM CDT THU JUL 31 2014

WE REMAIN MODERATELY UNSTABLE WITH CAPES GENERALLY 1000-1500
J/KG...HOWEVER...NOTHING YET HAS IGNITED CONVECTION. WEAK IMPULSES
SLIDING DOWN THE UPPER RIDGE COULD YET SPARK A STRAY THUNDERSTORM
BUT THIS SMALL LIKELIHOOD WILL DIMINISH EVEN MORE AS WE HEAD INTO
THE EVENING. LATEST MESO-SCALE MODELS DO NOT INDICATE ANYTHING OF
SIGNIFICANCE OVER CENTRAL NORTH DAKOTA THIS EVENING. THE LATEST
HRRR DOES BRING CONVECTION INTO THE FAR WEST THIS EVENING BUT
SEEMS OVERDONE WITH INITIALIZED CONVECTION COMPARED TO CURRENT
CONDITIONS. WILL KEEP OUR INHERITED SLIGHT CHANCE POPS...WHICH
DIMINISH THROUGH THE EVENING.

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 311 PM CDT THU JUL 31 2014

CURRENT SURFACE ANALYSIS PLACES LOW OVER NORTHEAST MONTANA WHILE
BROAD HIGH STRETCHES THROUGH THE EASTERN DAKOTAS INTO THE MIDWEST.
UPPER LEVEL ANALYSIS PLACES RIDGE FROM THE GREAT BASIN INTO THE
NORTHERN ROCKIES WHILE LOW SPINS NEAR JAMES BAY BRINGING NORTH-
NORTHWESTERLY FLOW TO OUR AREA WITH A VARIETY OF WEAK IMPULSES
SLIDING THROUGH.

FOR THE REST OF THIS AFTERNOON INTO TONIGHT...PARADE OF WEAK
IMPULSES CONTINUE TO SLIDE THROUGH THE FLOW WHILE A WARM FRONT
CONTINUES TO DEVELOP AND LIFT INTO SOUTHWESTERN NORTH DAKOTA. WITH
THE COMBINATION OF THESE...WILL KEEP LOW SHOWER/THUNDERSTORM
CHANCES GOING OVERNIGHT...MAINLY OVER SOUTHERN NORTH DAKOTA.

ON FRIDAY...SIMILAR SCENARIO CONTINUES AS VARIETY OF WEAK WAVES
MOVE THROUGH NORTH-NORTHWESTERLY FLOW WHILE SURFACE LOW SHIFTS
INTO WESTERN SOUTH DAKOTA. WILL KEEP LOW POPS MAINLY OVER THE
SOUTH/WEST WITH THESE FEATURES. EARLIER HI-RES MODEL RUNS DEPICTED
SOME STRONGER CONVECTION OVER PARTS OF THE AREA...BUT HAVE SINCE
BACKED OFF SO DID NOT INCORPORATE THIS INTO THE FORECAST. IF THIS
RE-APPEARS IN SUBSEQUENT RUNS LATER SHIFTS WILL HAVE TO TAKE THIS
INTO CONSIDERATION.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 311 PM CDT THU JUL 31 2014

THE GFS/ECMWF/GEFS/GEM GLOBAL ARE IN AGREEMENT THAT THE LARGE
HUDSON BAY CYCLONE WILL WEAKEN AND LIFT AS WEAK BLOCKING FLOW
DEVELOPS AND REPLACES NORTHWEST FLOW OVER THE NORTHERN HIGH
PLAINS. ASSORTED WEAK MID LEVEL SHORTWAVES MEANDERING AROUND THE
REX BLOCK...ALONG WITH GENERAL DYNAMIC SUPPORT FROM THE ASSOCIATED
CUT OFF LOW...JUSTIFY DAILY CHANCES OF THUNDERSTORMS ACROSS THE
REGION.

PERHAPS THE BEST DAY FOR MORE ORGANIZED CONVECTION IS
MONDAY...WHEN THE 12 UTC GEM GLOBAL/GFS/ECMWF ALL HAVE QPF OVER
TWO-THIRDS OF THE STATE. PREDICTABILITY IS TOO LOW...HOWEVER...TO
BEGIN MENTIONING THE POTENTIAL FOR SEVERE THUNDERSTORMS.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 311 PM CDT THU JUL 31 2014

CURRENT SURFACE ANALYSIS PLACES LOW OVER NORTHEAST MONTANA WHILE
BROAD HIGH STRETCHES THROUGH THE EASTERN DAKOTAS INTO THE MIDWEST.
UPPER LEVEL ANALYSIS PLACES RIDGE FROM THE GREAT BASIN INTO THE
NORTHERN ROCKIES WHILE LOW SPINS NEAR JAMES BAY BRINGING NORTH-
NORTHWESTERLY FLOW TO OUR AREA WITH A VARIETY OF WEAK IMPULSES
SLIDING THROUGH.

FOR THE REST OF THIS AFTERNOON INTO TONIGHT...PARADE OF WEAK
IMPULSES CONTINUE TO SLIDE THROUGH THE FLOW WHILE A WARM FRONT
CONTINUES TO DEVELOP AND LIFT INTO SOUTHWESTERN NORTH DAKOTA. WITH
THE COMBINATION OF THESE...WILL KEEP LOW SHOWER/THUNDERSTORM
CHANCES GOING OVERNIGHT...MAINLY OVER SOUTHERN NORTH DAKOTA.

ON FRIDAY...SIMILAR SCENARIO CONTINUES AS VARIETY OF WEAK WAVES
MOVE THROUGH NORTH-NORTHWESTERLY FLOW WHILE SURFACE LOW SHIFTS
INTO WESTERN SOUTH DAKOTA. WILL KEEP LOW POPS MAINLY OVER THE
SOUTH/WEST WITH THESE FEATURES. EARLIER HI-RES MODEL RUNS DEPICTED
SOME STRONGER CONVECTION OVER PARTS OF THE AREA...BUT HAVE SINCE
BACKED OFF SO DID NOT INCORPORATE THIS INTO THE FORECAST. IF THIS
RE-APPEARS IN SUBSEQUENT RUNS LATER SHIFTS WILL HAVE TO TAKE THIS
INTO CONSIDERATION.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 311 PM CDT THU JUL 31 2014

THE GFS/ECMWF/GEFS/GEM GLOBAL ARE IN AGREEMENT THAT THE LARGE
HUDSON BAY CYCLONE WILL WEAKEN AND LIFT AS WEAK BLOCKING FLOW
DEVELOPS AND REPLACES NORTHWEST FLOW OVER THE NORTHERN HIGH
PLAINS. ASSORTED WEAK MID LEVEL SHORTWAVES MEANDERING AROUND THE
REX BLOCK...ALONG WITH GENERAL DYNAMIC SUPPORT FROM THE ASSOCIATED
CUT OFF LOW...JUSTIFY DAILY CHANCES OF THUNDERSTORMS ACROSS THE
REGION.

PERHAPS THE BEST DAY FOR MORE ORGANIZED CONVECTION IS
MONDAY...WHEN THE 12 UTC GEM GLOBAL/GFS/ECMWF ALL HAVE QPF OVER
TWO-THIRDS OF THE STATE. PREDICTABILITY IS TOO LOW...HOWEVER...TO
BEGIN MENTIONING THE POTENTIAL FOR SEVERE THUNDERSTORMS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1239 AM CDT FRI AUG 1 2014

VFR CONDITIONS EXPECTED THROUGH THE FORECAST PERIOD. CONVECTION
POSSIBILITIES ARE LOW ENOUGH THAT WE WILL NOT CARRY ANY VCTS WITH
THE 06 UTC TAF ISSUANCE. WATCHING A SMALL CLUSTER OF THUNDERSTORMS
OVER SOUTH CENTRAL SASKATCHEWAN...AND WILL MONITOR IN CASE
THUNDERSTORMS APPROACH KISN AFT 09Z. LIGHT AND VARIABLE SURFACE FLOW
TONIGHT BECOMING MORE EASTERLY ON FRIDAY...YET REMAINING UNDER 15
KNOTS.

&&

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

$$

UPDATE...JV
SHORT TERM...JJS
LONG TERM...SCHECK
AVIATION...JV






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