000
FXUS63 KBIS 130250
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
950 PM CDT WED JUN 12 2013

.UPDATE...
ISSUED AT 946 PM CDT WED JUN 12 2013

SHOWERS AND THUNDERSTORMS ACROSS EASTERN MONTANA AND NORTHEAST
WYOMING CONTINUE TO STRUGGLE TO MAKE PROGRESS EAST THIS EVENING.
THEY ARE BEING WEAKENED SUBSTANTIALLY AS THEY MIGRATE CLOSER TO
SURFACE HIGH PRESSURE AND A RIDGE AT H5. THE 13.00Z NAM GENERALLY
CAPTURES THIS TREND BY KEEPING THE FORECAST AREA DRY
OVERNIGHT...BUT THERE ARE STILL HINTS AN ISOLATED SHOWER OR STORM
COULD MAKE IT INTO SOUTHWEST NORTH DAKOTA. HAVE KEPT THE SLIGHT
CHANCE POPS IN THE FAR SOUTHWEST...BUT COULD SEE THEM GETTING
PULLED WITH LATER UPDATES IF RADAR TRENDS CONTINUE TO SHOW THE
CONVECTION DIMINISHING AS IT TRIES TO PROGRESS EAST.

UPDATE ISSUED AT 701 PM CDT WED JUN 12 2013

CURRENT FORECAST IS ON TRACK. SHOWERS IN THE FAR EASTERN PORTION
OF THE FORECAST AREA HAVE ENDED...WITH DRY CONDITIONS NOW IN
PLACE.

SHOWERS AND THUNDERSTORMS DEVELOPED IN EASTERN MONTANA THIS
AFTERNOON...AND THEY HAVE BEEN MAKING GRADUAL PROGRESS EAST
TOWARDS SOUTHWEST NORTH DAKOTA. THE LATEST RAP SUGGESTS MOST OF
THE ACTIVITY WILL FALL APART BEFORE REACHING THE FORECAST
AREA...THOUGH IT WILL BE CLOSE. HAVE LEFT THE SLIGHT CHANCES OF
THUNDERSTORMS IN THE FAR SOUTHWEST JUST IN CASE A STRAY SHOWER OR
THUNDERSTORM MAKES IT THAT FAR.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 343 PM CDT WED JUN 12 2013

THERE SHOULD BE NO MAJOR WEATHER CONCERNS FOR THE PERIOD AS NORTH
DAKOTA WILL BE UNDER SYNOPTIC SUBSIDENCE AS A RESULT OF AN UPPER
LEVEL RIDGE OVER THE NORTHERN PLAINS.

FOR THIS AFTERNOON...SCATTERED LIGHT RAIN SHOWERS WILL CONTINUE
TO TAPER OFF TO THE SOUTHEAST. THIS ACTIVITY SHOULD BE OUT OF THE
CWA BY EARLY EVENING.

FOR TONIGHT...CONVECTION OVER MONTANA COULD NOSE ITS WAY INTO
EXTREME SOUTHWESTERN NORTH DAKOTA AFTER MIDNIGHT.
HOWEVER...CONFIDENCE IS LOW IN THIS MATERIALIZING SO ONLY
MENTIONED A SLIGHT CHANCE EXTREME SOUTHWEST TONIGHT.
FURTHERMORE...HIGH PRESSURE IS FORECAST TO CREST ACROSS THE
REGION. THE SURFACE RIDGE AXIS IS EXPECTED TO BE OVER THE JAMES
RIVER VALLEY BY 12Z THURSDAY. GIVEN THE COMBINATION OF LIGHT
WINDS...NEAR SATURATED SURFACE CONDITIONS...AND MOSTLY CLEAR
SKIES...ADDED PATCHY FOG WORDING FROM THE TURTLE MOUNTAIN AREA
SOUTH TO THE JAMES RIVER VALLEY.

FOR THURSDAY...DRY CONDITIONS ARE EXPECTED TO PERSIST ACROSS MOST
OF THE CWA. AN UPPER LEVEL WAVE IN THE SOUTHWESTERLY FLOW ALOFT
MAY SPARK THUNDERSTORM ACTIVITY OVER EASTERN MONTANA THURSDAY
AFTERNOON. SOME OF THIS ACTIVITY COULD MAKE IT INTO WESTERN NORTH
DAKOTA...MAINLY ALONG AND WEST OF HIGHWAY 85. HOWEVER...CONFIDENCE
IS LOW IN THIS MATERIALIZING AS WELL. THEREFORE...ONLY INDICATED
SLIGHT CHANCE FOR THUNDER ALONG AND WEST OF HIGHWAY 85 THURSDAY
AFTERNOON.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 343 PM CDT WED JUN 12 2013

THE HIGHLIGHT OF THE EXTENDED FORECAST IS THE POTENTIAL FOR SEVERE
THUNDERSTORMS THURSDAY NIGHT INTO FRIDAY.

A STRENGTHENING LOW LEVEL JET AHEAD OF DEEPENING LOW PRESSURE INTO
NORTHWEST SOUTH DAKOTA ON THURSDAY NIGHT IS EXPECTED TO LEAD TO A
POTENTIAL ROUND OF ELEVATED CONVECTION. 850 MB CAPE VALUES OF
800-1000 J/KG WITH DEEP LAYER SHEAR OF 40-50 KTS SUPPORT A
POTENTIAL LARGE HAIL THREAT THURSDAY NIGHT ACROSS THE AREA.
HOWEVER...700 MB TEMPERATURES OF 12 C OR GREATER DO ADVECT NORTH
THROUGH THE NIGHT WHICH MAY BE A LIMIT TO HAIL GROWTH POTENTIAL.
ON FRIDAY...AN OCCLUDED FRONT EXTENDED FROM THE NOW FILLING
SURFACE LOW ACROSS NORTH CENTRAL SOUTH DAKOTA THROUGH THE PRIMARY
LOW ACROSS SASKATCHEWAN IS FORECAST TO PROPAGATE INTO CENTRAL
NORTH DAKOTA THROUGH THE AFTERNOON. STILL UNCERTAINTY IN THE EXACT
POSITIONING OF THE FRONT DURING PEAK HEATING...WITH THE 12 UTC
GFS/ECMWF/GEM CLOSER TO HIGHWAY 83...WITH THE 12 UTC NAM AND 15
UTC SREF ON THE EASTERN FRINGES OF THE CWA. THIS DIFFERENCE IN
FRONTAL POSITIONING COMBINED WITH UNCERTAINTY IF SKIES WILL CLEAR
TO DESTABILIZE THE BOUNDARY LAYER LEAD TO UNCERTAINTY IN HOW
WIDESPREAD THE SEVERE THREAT MAY BE ON FRIDAY AFTERNOON AND
EVENING. IF SKIES CAN CLEAR...BOUNDARY LAYER DEWPOINTS OF 65-70 F
AHEAD OF THE FRONT AND SUFFICIENT DEEP LAYER SHEAR ARE FORECAST TO
BE AVAILABLE. THEREAFTER...A DRY BUT WINDY SATURDAY IS FORECAST IN
THE DRY SLOT OF THE UPPER LOW ACROSS SOUTHERN CANADA...WITH A
BREAK IN THE THUNDERSTORM THREAT THROUGH AT LEAST TUESDAY UNDER AN
UPPER LEVEL RIDGE WITH NEAR NORMAL TEMPERATURES ANTICIPATED.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 701 PM CDT WED JUN 12 2013

VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE 00Z TAF PERIOD.
SCATTERED TO AT TIMES BROKEN CUMULUS CONTINUES ACROSS CENTRAL AND
WESTERN NORTH DAKOTA...BUT EXPECT THAT TO BECOME LESS PREVALENT
AS THE EVENING WEARS ON. SURFACE HIGH PRESSURE WILL BRING LIGHT
AND VARIABLE WINDS TO MOST AERODROMES TONIGHT...BUT WINDS WILL
BECOME GUSTY FROM THE SOUTHEAST ON THURSDAY AS THE HIGH SHIFTS
EAST OF THE REGION.

&&

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

$$

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