Flash Flood Watch 2, NWS Bismarck, ND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
229 PM CDT MON JUL 13 2009

.SYNOPSIS...HEAVY RAIN A MAIN CONCERN WITH ONGOING CONVECTION
ACROSS THE SOUTH CENTRAL. CURRENT TRENDS SHOW CONVECTION FORMING
ALONG AND NORTH OF WARM FRONTAL BOUNDARY IN LOW LEVEL WARM
ADVECTION WITH AID FROM SHORTWAVE TROUGH. THIS CONVECTION IS WARM
TOPPED AND SHOULD RESULT IN EFFICIENT RAIN PRODUCERS. A SECONDARY
CONCERN WILL BE SHORT WAVE TROUGH CURRENTLY MOVING THROUGH WYOMING
AND CENTRAL MONTANA. WITH CURRENT CLOUD TRENDS CLEARING ACROSS THE
SOUTHWEST SHOULD GET WARMING THROUGH LATE AFTERNOON AND EARLY
EVENING. THIS SHOULD AID IN DESTABILIZATION FOR AIDING IN SEVERE
WEATHER THREAT THIS EVENING AND OVERNIGHT.

&&

.SHORT TERM...MONDAY NIGHT THROUGH THURSDAY NIGHT...

THE FORECAST CONCERNS ARE SEVERE WEATHER POTENTIAL THIS EVENING AND
THUNDERSTORM CHANCES INTO TUESDAY.  THE FOCUS THEN SHIFTS TOWARDS
WINDS FOR TUESDAY AFTERNOON AND NIGHT AND ALSO COOL TEMPERATURES
TUESDAY. MODELS ARE IN BETTER OVERALL AGREEMENT TODAY.

UPPER LEVEL LOW IS PROGRESSING THROUGH THE NORTHERN ROCKIES AND
CYCLOGENESIS HAS BEGUN TO TAKE SHAPE IN MONTANA. LOW AND MID LEVEL
CLOUDS HAVE OVERSPREAD MOST OF WESTERN AND CENTRAL NORTH DAKOTA WITH
SOME BREAKS BEGINNING TO SHOW UP ON VISIBLE SATELLITE IN THE WEST
MAINLY BETWEEN THE LITTLE MISSOURI RIVER AND INTERSTATE 94. SHOWERS
AND THUNDERSTORMS CONTINUE ACROSS THE SOUTHWEST AND SOUTH CENTRAL
PORTIONS OF NORTH DAKOTA. CLOUD COVER HAS WORKED TO EFFECTIVELY
CAP THE ATMOSPHERE BUT AREAS THAT HAVE CLEARED WILL PROVIDE SOME
DIFFERENTIAL HEATING LEADING TO THUNDERSTORM DEVELOPMENT. PRIMARY
THUNDERSTORM DEVELOPMENT IS STILL EXPECTED ACROSS CENTRAL MONTANA
LATE THIS AFTERNOON AND IS FORECAST TO PROGRESS EASTWARD INTO
WESTERN NORTH DAKOTA THIS EVENING. SEVERE THUNDERSTORMS MAY COME
IN TWO WAVES AS SPC ALSO EXPECTS A LINE OF THUNDERSTORMS TO
DEVELOP ACROSS THE HIGHER TERRAIN OF MONTANA. STRONG DEEP LAYER
SHEAR AND MOST UNSTABLE CAPE VALUES BETWEEN 2000 TO 3000 J/KG ARE
STILL PRESENT. AGAIN THE BEST THERMODYNAMICS AND SHEAR ARE
EXPECTED TO BE ACROSS THE SOUTHWEST LATE THIS AFTERNOON AND THIS
EVENING. THE PRIMARY SEVERE WEATHER THREAT IS FORECAST TO BE LARGE
HAIL BUT STRONG WINDS AND A FEW TORNADOES MAY STILL BE POSSIBLE IN
THE LATE AFTERNOON AND EARLY EVENING. HODOGRAPH ACROSS WESTERN AND
CENTRAL NORTH DAKOTA STILL SHOW STRONG LOW LEVEL CURVATURE THIS
EVENING. HEAVY RAIN LIKELY WITH PWAT VALUES NEAR 1.50 INCHES.

BY 12 UTC TUESDAY THE OCCLUDED FRONT/INVERTED SURFACE TROUGH MOVES
INTO WESTERN NORTH DAKOTA AND THROUGH INTO FAR EASTERN PARTS OF THE
STATE BY 00 UTC WEDNESDAY. IN THE WAKE OF THIS FRONT...PRESSURE
GRADIENTS ACROSS WESTERN AND CENTRAL NORTH DAKOTA STRENGTHEN AS A
SURFACE HIGH DROPS INTO CENTRAL MONTANA. MODELS SHOW 850 HPA WINDS
BETWEEN 30 AND 40 KNOTS DURING THE LATE AFTERNOON AND EVENING
TOMORROW. THE PRESSURE GRADIENT BEGINS TO WEAKEN AS IT MOVES INTO
CENTRAL AND EASTERN PORTIONS OF THE STATE TUESDAY NIGHT. SOME
LINGERING THUNDERSTORMS ARE EXPECTED TUESDAY WITH COLD AIR ALOFT
ASSOCIATED WITH THE UPPER LEVEL LOW MOVING THROUGH THE REGION AND
DISTURBANCES ROTATING AROUND IT. TEMPERATURES ARE ALSO EXPECTED TO
BE MUCH BELOW NORMAL TOMORROW WITH CLOUD COVER AREA WIDE AND SOME
COOL ADVECTION ACROSS THE NORTHERN TIER STATES.

BY WEDNESDAY...THE UPPER LEVEL LOW IS MOVING INTO WESTERN ONTARIO
AND THE SOUTHERN RIDGE BEGINS TO BUILD NORTHWARD INTO THE ROCKIES.
THIS IS FORECAST TO BEGIN A GRADUAL WARMING TREND STARTING MID WEEK.
ONE FLY LEFT IN THE OINTMENT AS A SHORTWAVE MOVING THROUGH THE FLOW
MOVES THROUGH THE FORECAST AREA LATE WEDNESDAY.

.LONG TERM...FRIDAY THROUGH MONDAY NIGHT
FOUR CORNERS RIDGE STILL ON TRACK TO BUILD NORTH THROUGH SATURDAY
THEN PROGRESS EAST AND FLATTEN AS IT MOVES ACROSS NORTH DAKOTA LATE
SUNDAY INTO MONDAY. NORTHWEST FLOW WILL DOMINATE AHEAD OF THE RIDGE
WITH MOSTLY DRY WEATHER. SOME DISTURBANCES WILL MIGRATE THROUGH BUT
OVERALL FORECAST IS DRY. BOTH THE EC AND GFS BRING A SHORTWAVE OVER
THE TOP OF THE RIDGE AND INTO NORTH DAKOTA FRIDAY NIGHT FOR A SLIGHT
CHANCE OF SHOWERS/THUNDERSTORMS. AS THE RIDGE FLATTENS SUNDAY NIGHT
AND MONDAY...A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS WILL
COMMENCE. TEMPERATURES WILL SLOWLY WARM THROUGH THE PERIOD.
&&

.AVIATION...SEVERE THUNDERSTORMS LIKELY THIS EVENING INTO TONIGHT.
LARGE HAIL/DAMAGING WINDS/HEAVY RAINFALL WILL OCCUR WITH THESE
THUNDERSTORMS. AN ISOLATED TORNADO THREAT APPEARS CONFINED MAINLY TO
SOUTHWEST NORTH DAKOTA...WHICH INCLUDES KDIK. MVFR CEILINGS AND
VISIBILITIES WILL ALSO ACCOMPANY THE SHOWERS AND THUNDERSTORMS.
SCATTERED SHOWERS AND THUNDERSTORMS ALONG WITH GUSTY NORTHWEST WINDS
BETWEEN 15 AND 30 MPH WILL ARRIVE FOR TUESDAY.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH TUESDAY MORNING FOR NDZ020-033>037-
040>048-050-051.

&&

COUSINS/WAA/KS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
447 AM CDT MON JUL 13 2009

NDZ001>005-009>013-017>023-025-031>037-040>048-050-051-141000-
DIVIDE-BURKE-RENVILLE-BOTTINEAU-ROLETTE-WILLIAMS-MOUNTRAIL-WARD-
MCHENRY-PIERCE-MCKENZIE-DUNN-MERCER-OLIVER-MCLEAN-SHERIDAN-WELLS-
FOSTER-GOLDEN VALLEY-BILLINGS-STARK-MORTON-BURLEIGH-KIDDER-
STUTSMAN-SLOPE-HETTINGER-GRANT-BOWMAN-ADAMS-SIOUX-EMMONS-LOGAN-
LA MOURE-MCINTOSH-DICKEY-
447 AM CDT MON JUL 13 2009 /347 AM MDT MON JUL 13 2009/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
NORTH DAKOTA...NORTHWEST NORTH DAKOTA...SOUTH CENTRAL NORTH
DAKOTA...SOUTHEAST NORTH DAKOTA AND SOUTHWEST NORTH DAKOTA.

.DAY ONE...TODAY AND TONIGHT

A POTENT STORM SYSTEM IS EXPECTED TO AFFECT THE NORTHERN PLAINS
TODAY THROUGH TUESDAY. SCATTERED THUNDERSTORMS WILL MOVE ACROSS
PORTIONS OF WESTERN AND CENTRAL NORTH DAKOTA DURING THE MORNING
HOURS. HOWEVER...ADDITIONAL THUNDERSTORMS ARE EXPECTED TO DEVELOP
ACROSS WESTERN NORTH DAKOTA LATER THIS AFTERNOON. THE ENVIRONMENT
IN WHICH THESE STORMS DEVELOP WILL ALLOW THESE STORMS TO QUICKLY
BECOME SEVERE AS THEY MOVE ACROSS WESTERN NORTH DAKOTA LATER
TODAY. THE GREATEST RISK OF SEVERE WEATHER THIS AFTERNOON AND
EARLY EVENING WILL BE ACROSS THE SOUTHWEST...WHERE LARGE HAIL
DAMAGING WINDS AND TORNADOES ARE POSSIBLE. THESE STORMS ARE
EXPECTED TO SPREAD EAST ACROSS MUCH OF CENTRAL NORTH DAKOTA THIS
EVENING AND OVERNIGHT...AND WILL BRING A TREAT FOR HAIL AND
DAMAGING WINDS TO CENTRAL NORTH DAKOTA. IN ADDITION TO THE SEVERE
THREAT...THESE THUNDERSTORMS WILL ALSO BE CAPABLE OF PRODUCING
LOCALLY HEAVY RAINFALL.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

SCATTERED THUNDERSTORMS ARE EXPECTED AGAIN ON TUESDAY AS THE UPPER
LEVEL SYSTEM MOVES ACROSS THE AREA. WINDS WILL ALSO BECOME STRONG
ACROSS THE WEST DURING THE DAY ON TUESDAY IN THE WAKE OF THIS
STORM SYSTEM. CURRENTLY...IT APPEARS THE STRONGEST WINDS WILL
OCCUR ACROSS THE SOUTHWEST...WHERE WINDS OF 25 TO 35 MPH ARE POSSIBLE.
SLIGHTLY LIGHTER WINDS CAN BE EXPECTED FARTHER NORTH AND EAST.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE NEEDED LATER TODAY AND TONIGHT.

KJB

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