Severe Thunderstorm Warning 146, NWS Bismarck, ND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
150 PM WED AUG 6 2003

THE HIGHLY AMPLIFIED YET SLIGHTLY PROGRESSIVE PATTERN ACROSS THE
CONUS WILL CONTINUE FOR THE NEAR FUTURE...WHICH WILL MAKE CHANCES
OF CONVECTION AS WELL AS HIGH TEMPS THE MAIN FCST CONCERNS.  THE ETA
AND GFS ARE IN DECENT AGREEMENT AND A BLEND WILL BE USED FOR THE
FCST...THOUGH THE EXCEPTION WILL BE THE FRI NIGHT TIMEFRAME...WHEN
THE GFS CONTINUES TO HAVE FEEDBACK PROBLEMS.

EARLY AFT H20 VAPOR IMAGES AS WELL AS 12Z UPPER AIR DATA SHOWS WELL
THE UPPR RIDGE AXIS ALONG THE MT/ND BORDER.  MEANWHILE...A COUPLE OF
WEAK S/WS THAT WL EVENTUALLY PLAY A ROLE IN OUR TSTM CHANCES ARE
MOVING UP THE BACKSIDE OF THE RIDGE AXIS IN THE NORTHERN ROCKIES.
H85 WINDS WILL CRANK UP TO 40 KTS IN THE WEST TONIGHT AS STRONG
THETA-E ADVECTION OCCURS...HOWEVER LACK OF A FOCUSING MECHANISM AND
ONLY WEAK AVAILABLE MUCAPE VALUES SHOULD PRECLUDE MUCH CHANCE OF
STORMS.  A PERSISTENT LEE TROUGH WILL MOVE SLOWLY EAST DURING THE
DAY THU...ALLOWING SFC MOISTURE TO CONTINUE TO INCREASE AND
CONTRIBUTE TO A RATHER UNSTABLE BUT CAPPED AIRMASS ACROSS WESTERN
ND...AS SHOWN BY SBCAPE VALUES OF 1500 TO 3000 J/KG. SFC TEMPS IN
THE 90S COMBINED WITH CONVERGENCE ALONG THE TROF AND PRESENCE OF ANY
WEAK S/WS MAY BE ENOUGH TO ALLOW A FEW UPDRAFTS TO BREACH THE
CAP...PERHAPS AFTER DVLPING ON THE HIGHER TERRAIN TO THE WEST.  A
FEW STORMS MAY CONTINUE OVERNIGHT GIVEN SUFFICIENT MUCAPE VALUES.
IF STORMS ARE ABLE TO FORM...HAIL AND WIND AT SVR CRITERIA WOULD BE
POSSIBLE GIVEN EXPECTED CAPE AND VEERING WIND PROFILES.

ALSO OF CONCERN THURSDAY AFTERNOON IS THE POTENTIAL FOR FIRE
PROBLEMS...AS A STRENGTHENING WIND IN THE 925-850 MB LAYER WILL
LIKELY AT LEAST PARTIALLY MIX TO THE SFC...ESPECIALLY IN THE SW
CORNER OF THE STATE...WHICH HAPPENS TO BE THE DRIEST AREA.
HOWEVER...THERE IS SOME QUESTION AS TO HOW LOW RH VALUES WILL BE
GIVEN SFC TDS BTWN 55 AND 60...THUS WE WILL HOLD OFF ON ANY FIRE WX
HIGHLIGHTS AT THIS TIME.

MUCH THE SAME STORY FRIDAY...WELL HEAT UP NICELY AS H85 TEMPS
REMAIN BTWN 21 AND 26 C...THEN A PASSING WAVE LATE IN THE DAY MAY BE
ENOUGH TO INITIATE CONVECTION.  AGAIN WE WILL BE VERY MOIST AND
UNSTABLE...AND THE SUGGESTION OF A STRONGER S/W WOULD SEEM TO POINT
TO A BETTER CHANCE OF CONVECTION AND POSSIBLE SVR WX THAN THAT ON
THU.  HOWEVER...THE GFS SOLUTION FOR THIS TIMEFRAME LOOKS SUSPICIOUS
AND HAS BEEN DISCOUNTED FOR THE MOST PART.

IN THE LONGER RANGE...MEDIUM RANGE GUIDANCE SUGGESTS A CONTINUATION
OF THE SAME PATTERN AS OF LATE...THOUGH THE UPPR LVL RIDGE AMPLIFIES
ENOUGH LATE IN THE WEEKEND TO MITIGATE THE THREAT OF STORMS FOR A
WHILE.  EARLY NEXT WEEK...INCREASING SW FLOW ALOFT WOULD SEEM TO
POINT TO SOME THREAT OF CONVECTION...HOWEVER LARGE SCALE CAPPING AND
THE LIKELIHOOD OF TIMING ISSUES MEANS WE WILL KEEP THE FCST DRY.

.BIS...NONE.

SCHULTZ/TWH

NDZ001>005-009>013-017>023-025-031>037-040>048-050-051-070945-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
450 AM CDT WED AUG 6 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL NORTH
DAKOTA.

.DAY ONE...TODAY AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THERE IS A CHANCE OF THUNDERSTORMS IN WESTERN NORTH DAKOTA ON
THURSDAY AND A CHANCE OF THUNDERSTORMS STATEWIDE ON FRIDAY AND
SATURDAY.  SOUTHEAST WINDS THROUGH THE PERIOD WILL BRING MOISTURE
INTO THE REGION AND IF THUNDERSTORMS DEVELOP...SOME COULD BE SEVERE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY...BUT SPOTTERS MAY BE
NEEDED THURSDAY THROUGH SATURDAY.