007
FXUS63 KBIS 221950
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
250 PM CDT MON JUL 22 2019
SHORT TERM
(THIS EVENING THROUGH TUESDAY)
ISSUED AT 205 PM CDT MON JUL 22 2019
QUIET CONDITIONS CONTINUE THROUGH THE SHORT TERM PERIOD.
ABUNDANT SUNSHINE TODAY AS SURFACE HIGH PRESSURE IS SITUATED OVER
THE NORTHERN PLAINS. EXPECT HIGHS IN THE UPPER 70S TO MID 80S.
CLEAR AND QUIET CONDITIONS ARE EXPECTED TONIGHT AS THE SURFACE
HIGH CURRENTLY OVER CENTRAL ND, PROPAGATES INTO WESTERN MINNESOTA
BY 12 UTC TUESDAY. RETURN FLOW BEGINS TO SET UP OVERNIGHT, BUT
OVERALL SURFACE WINDS WILL REMAIN LIGHT. MESOSCALE MODELS ARE NOT
REALLY HINTING AT ANY FOG TONIGHT AND WILL NOT ADD ANY AT THIS
TIME, BUT SOME PATCHY LOW LYING FOG CAN NOT BE RULED OUT OVER THE
SOUTH CENTRAL INTO THE JAMES RIVER VALLEY.
MOSTLY SUNNY AND WARMER ON TUESDAY WITH HIGHS IN THE 80S. WE DO
SEE SOME ELEVATED CAPE TUESDAY AFTERNOON, BUT VERY WARM AND DRY
LOWER LAYER ATMOSPHERE SHOULD INHIBIT ANY CONVECTION. THERE IS A
WEAK SHORTWAVE TRYING TO SLIDE DOWN THE BUILDING UPPER RIDGE OVER
CENTRAL AND EASTERN MONTANA, THAT MAKES IT'S WAY INTO WESTERN ND
TUESDAY AFTERNOON, BUT THINK THE CONVECTIVE INHIBITION WILL WIN
OUT. A BLEND OF MODEL GUIDANCE IS GIVING SUB-15% POPS AND SEE NO
REASON TO BUMP THIS UP AT THIS TIME.
WE WILL SEE AN INCREASE IN SOUTHERLY WINDS OVER WESTERN ND TUESDAY
AFTERNOON, WHICH WILL BRING INCREASING LOW LEVEL MOISTURE INTO
THE REGION.
LONG TERM
(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 205 PM CDT MON JUL 22 2019
THE UPPER LEVEL RIDGE OVER CENTRAL AND EASTERN MONTANA, PUSHES
INTO WESTERN ND TUESDAY NIGHT, WHICH WILL HELP TO INHIBIT ANY
CONVECTION. A SHORTWAVE TROUGH MOVING ONTO THE NORTHWEST U.S.
COAST TUESDAY NIGHT WILL AID IN BREAKING DOWN THE WESTERN ND RIDGE
BY WEDNESDAY AFTERNOON AND NIGHT. LATE WEDNESDAY AFTERNOON MODELS
DEPICT A PRE-FRONTAL TROUGH DEVELOPING OVER FAR EASTERN MONTANA,
AND MOVES IT INTO WESTERN ND WEDNESDAY EVENING. THIS WILL BE A
FOCUS FOR THUNDERSTORM DEVELOPMENT ON WEDNESDAY AFTERNOON/EVENING.
AT THIS TIME IT APPEARS THE MOST VOLATILE CONDITIONS WILL EXIST
OVER WESTERN ND WHERE CAPE VALUES IN EXCESS OF 2000 J/KG WILL
EXIST IN AN AREA OF 35 TO 45 KNOTS OF DEEP LAYER SHEAR. THERE IS
SOME LOW LEVEL CAPPING PRESENT, SO THE QUESTION WILL BE IF THE
CONVERGENCE ALONG THE TROUGH AND THE FORCING FROM THE APPROACHING
SHORTWAVE WILL BE ENOUGH TO FIRE LATE AFTERNOON/EARLY EVENING
CONVECTION OVER WESTERN ND. IF SO, THE ALIGNMENT OF THE SHEAR
VECTORS, PERPENDICULAR TO THE TROUGH INDICATE THE POTENTIAL FOR
DISCRETE SUPERCELLS. LATER IN THE EVENING, CONVECTION LOOKS MORE
LIKELY OVER SOUTHERN SASKATCHEWAN, AND POTENTIALLY SOME CLUSTERS
PROPAGATING ENOUGH SOUTHWARD TO CROSS INTO NORTHERN ND, BUT BY
THIS TIME THE CAPE/SHEAR WILL BE DIMINISHING AND THE THREAT OF
DISCRETE SUPERCELLS WILL BE WANING.
WITH THAT SAID, SEVERE WEATHER CERTAINLY LOOKS POSSIBLE AND THE
STORM PREDICTION CENTER HAS PLACED AREAS ALONG AND WEST OF THE
HIGHWAY 83 CORRIDOR IN A MARGINAL RISK OF SEVERE WEATHER IN THE
LATEST DAY THREE CONVECTIVE OUTLOOK. BECAUSE OF THE UNCERTAINTY,
HAVE NOT YET INCLUDED THE MENTION OF SEVERE IN THE GRIDDED
FORECAST BUT HAVE STARTED MESSAGING THE POTENTIAL IN THE HAZARDOUS
WEATHER OUTLOOK.
SHOWERS AND STORMS ARE LIKELY TO REMAIN ONGOING LATE WEDNESDAY
NIGHT AND INTO THURSDAY AS THE FOCUS SHIFTS EAST TOWARDS THE JAMES
RIVER VALLEY. QUIET WEATHER IS EXPECTED TO RETURN ON FRIDAY, WITH
A FEW WEAK DISTURBANCES PROGGED TO MOVE THROUGH AREA DURING THE
WEEKEND, BRINGING LOW THUNDERSTORM CHANCES SATURDAY THROUGH
MONDAY.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 205 PM CDT MON JUL 22 2019
VFR CONDITIONS ARE EXPECTED THROUGH THE 18Z FORECAST PERIOD WITH
MOSTLY CLEAR SKIES. ONLY ISSUE WILL BE THE POTENTIAL FOR PATCHY
FOG TUESDAY MORNING. PROBABILITY LOOKS SMALL AS THE SURFACE RIDGE
WILL BE EAST OF THE AREA WITH A SOUTHERLY RETURN FLOW SETTING UP,
BUT CAN'T COMPLETELY RULE OUT SOME PATCHY FOG, MOST LIKELY AT
KBIS OR KJMS. TOO UNCERTAIN TO ADD TO A MENTION AT THIS TIME.
OTHERWISE LIGHT AND VARIABLE WINDS TODAY BECOME SOUTHERLY ACROSS
THE FORECAST AREA ON TUESDAY, INCREASING TO AROUND 10-15 KNOTS AT
KISN AND KDIK 15-15 UTC.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...TWH
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