000
FXUS63 KBIS 182024
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
324 PM CDT TUE JUN 18 2013

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 324 PM CDT TUE JUN 18 2013

SURFACE TROUGH AND ASSOCIATED WARM FRONTAL BOUNDARY IN EASTERN
MONTANA WILL BE THE FOCUS FOR SCATTERED THUNDERSTORMS LATE TONIGHT
AND WEDNESDAY AFTERNOON. ANTICIPATE SOME THUNDERSTORMS WILL FIRE
OVER THE HIGHER ELEVATION AREAS IN WYOMING/MONTANA/SOUTH DAKOTA
AND DRIFT INTO SOUTHWEST NORTH DAKOTA LATE TONIGHT. ON WEDNESDAY ONE
LIMITING FACTOR WILL BE A SLOWING EVOLVING ELEVATED MIXED LAYER
THAT MAY CAP THUNDERSTORMS OVER WESTERN NORTH DAKOTA WEDNESDAY
AFTERNOON. HOWEVER BELIEVE THE INCREASING LOW LEVEL JET AND
SIGNIFICANT CAPE VALUES JUSTIFY SCATTERED THUNDERSTORMS ACROSS
WEST AND CENTRAL NORTH DAKOTA WEDNESDAY AFTERNOON. WINDS ON
WEDNESDAY SHOULD APPROACH BUT REMAIN BELOW WIND ADVISORY CRITERIA
SOUTHWEST...PROBABLY 20 TO 35 MPH.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 324 PM CDT TUE JUN 18 2013

THE MAIN FORECAST ISSUE THROUGH THE LONG TERM PERIOD IS CONVECTIVE
TRENDS AND POTENTIAL FOR PERIODS OF STRONG TO SEVERE STORMS...SOME
ACCOMPANIED BY HEAVY RAINFALL.

THE RUNS OF THE GFS/ECMWF ARE IN GENERAL AGREEMENT WITH A SLOWER
PROGRESSION OF A LARGE CLOSED UPPER LOW IN THE PACIFIC NORTHWEST
EARLY IN THE PERIOD...WITH THE NAM FASTEST IN BRINGING THE MAIN
SYNOPTIC FEATURES EASTWARD. HAVE FAVORED THE GFS/EC SOLUTIONS FOR
POPS WEDNESDAY NIGHT AND THURSDAY. THERE IS SOME POTENTIAL FOR AN
MCS TO CLIP NORTHWEST COUNTIES LATE WEDNESDAY NIGHT INTO THURSDAY
MORNING...FUELED BY A 40-50 KT LOW LEVEL JET. THE MAIN
DECISION-MAKING ELEMENT WAS WHEN/WHERE THE STRONG MID-LEVEL CAP
WOULD INHIBIT CONVECTION...BECAUSE OTHERWISE PLENTY OF CAPE AND
SHEARING FOR SEVERE THUNDERSTORMS.

WEDNESDAY EVENING THE AXIS OF THE MID-LEVEL CAP OF 10-14C IS
SITUATED OVER WYOMING/EASTERN MONTANA AND NUDGING INTO SOUTH DAKOTA
AND FAR SOUTHWESTERN NORTH DAKOTA. THE CAP BUILDS DURING THE EVENING
NORTHWARD AND EASTWARD ACROSS THE DAKOTAS. AT THIS TIME IT APPEARS
THE BEST CHANCE OF SEVERE THUNDERSTORMS BEGINS IN FAR WESTERN NORTH
DAKOTA LATE EVENING WEDNESDAY OR EARLY MORNING THURSDAY...WITH
SEVERE THUNDERSTORMS POSSIBLE. THE STORMS MOVE EASTWARD INTO
CENTRAL NORTH DAKOTA BETWEEN MIDNIGHT AND DAYBREAK THURSDAY MORNING.

THURSDAY THE ACCOMPANYING SURFACE FRONT IS PROGGED TO BE ORIENTED
NORTH-SOUTH ACROSS CENTRAL NORTH DAKOTA...WITH THE BEST CHANCES OF
THUNDERSTORMS IN NORTHWEST AND CENTRAL NORTH DAKOTA THURSDAY
MORNING...AND SHIFTING TO CENTRAL NORTH DAKOTA THURSDAY AFTERNOON
AND INTO THURSDAY EVENING. THE BEST CHANCE FOR SEVERE WEATHER
THURSDAY IS IN THE NORTHWEST AND CENTRAL.

FRIDAY AND FRIDAY NIGHT LOOKS TO BE THE TIME FRAME FOR WIDESPREAD
MODERATE TO HEAVY RAINFALL. CONTINUED UPPER LEVEL ENERGY AND LOW
LEVEL MOISTURE WITH A SURFACE LOW BECOMING ESTABLISHED OVER THE
CENTRAL PLAINS AND OVERRUNNING PRECIPITATION NORTH OF THE LOW IS
FAVORED FOR THE HEAVIEST RAINFALL. WIDESPREAD RAINFALL AMOUNTS OF 1
TO 2 INCHES IS POSSIBLE.

THE MODELS CONTINUE TO DEPICT THE UPPER LEVEL LOW MAINTAINING ITS
PRESENCE OVER THE ROCKIES WITH SOUTHWEST FLOW OVER NORTH DAKOTA WITH
MULTIPLE UPPER LEVEL ENERGY IMPULSES MOVING ACROSS THE STATE IN THE
UPPER FLOW. THE MODELS BRING THE UPPER LOW ACROSS THE STATE SUNDAY.

PRECIPITATION CHANCES LESSEN MONDAY AND TUESDAY...BUT ZONAL FLOW
ALOFT WOULD ALLOW SOME UPPER LEVEL IMPULSES TO SUPPORT SHOWERS AND
THUNDERSHOWERS INTO EARLY NEXT WEEK.

TEMPERATURES ARE EXPECTED TO BE SEASONABLE THROUGH THE PERIOD...WITH
HIGHS IN THE 70S/LOWER 80S...AND LOWS GENERALLY IN THE 50S AND 60S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 324 PM CDT TUE JUN 18 2013

A SURFACE TROUGH IN EASTERN MONTANA WITH AN ASSOCIATED WARM FRONT
WILL BE THE FOCUS FOR INCREASING CHANCES FOR THUNDERSTORMS OVER
WEST AND CENTRAL NORTH DAKOTA TONIGHT AND WEDNESDAY. INITIALLY
THE THUNDERSTORMS WILL BE WIDELY SCATTERED ACROSS SOUTHWEST NORTH
DAKOTA AFTER 00Z. HAVE NOT INCLUDED IN THE KDIK TAF DUE TO LOW
PROBABILITY AND UNCERTAIN TIMING. ON WEDNESDAY...SOUTHERLY WINDS
WITH THE APPROACHING WARM FRONT FOR KDIK- KISN- KBIS WITH
INCREASING SOUTHEAST WINDS TO 25 KTS AFTER 14Z. MAIN THREAT OF
THUNDERSTORMS AFTER 18Z SO DID NOT INCLUDE IN TAF FORECASTS...BUT
FOR AVIATION PLANNING MORE NUMEROUS STORMS WEDNESDAY AFTERNOON AND
NIGHT.


&&

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

$$

SHORT TERM...WAA
LONG TERM...JV
AVIATION...WAA