Severe Thunderstorm Warning 321, NWS Bismarck, ND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
101 PM CDT THU JUL 29 2010

.SYNOPSIS...

BROAD SCALE UPPER LEVEL RIDGING OVER THE SOUTHEASTERN THREE
QUARTERS OF CONUS WILL KEEP THE NORTHERN PLAINS BENEATH A BARRAGE
OF SHORTWAVES AS THEY EJECT OUT OF THE NORTHWESTERN U.S. TROUGH
INTO COMPLEX MULTI-STREAM FLOW ALONG THE NORTHERN TIER.
TEMPERATURES NEAR TO ABOVE AVERAGE ARE EXPECTED...AS ARE ABOVE
AVERAGE CHANCES FOR PRECIPITATION.

&&

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT...

MAIN FORECAST CONCERNS/HIGHLIGHTS THROUGH THE SHORT TERM PERIOD DEAL
PRIMARILY WITH CONVECTIVE CHANCES AND THE ATTENDANT THREAT FOR
SEVERE WEATHER ACROSS WESTERN AND CENTRAL ND THROUGH TONIGHT. MODEL
MASS FIELDS ARE IN GOOD AGREEMENT THROUGH THE PERIOD. WILL UTILIZE A
GENERAL MODEL BLEND FOR FORECAST DETAILS.

THE MAIN FOCUS IN THE NEAR TERM CONCERNS THE POTENTIAL FOR STRONG TO
SEVERE CONVECTION ACROSS WESTERN AND CENTRAL ND THROUGH THE
REMAINDER OF THE AFTERNOON AND INTO THE EVENING. THE TIMING OF
CONVECTIVE INITIATION REMAINS QUITE UNCERTAIN THIS AFTERNOON AS A
FAIRLY STRONG EML CONTINUES TO ADVECT INTO THE NORTHERN PLAINS WITH
H7 TEMPERATURES IN EXCESS OF 10C ACROSS PORTIONS OF SOUTHWEST AND
SOUTH CENTRAL ND RESULTING IN NOTABLE CAPPING. CONTINUED LOW-LEVEL
WARM/MOIST ADVECTION IN RESPONSE TO PERSISTENT SOUTHEASTERLY
NEAR-SURFACE FLOW SHOULD CONTRIBUTE TO CONTINUED DESTABILIZATION
WITH SBCAPES RANGING FROM 1500 TO 2500 J/KG ALONG AND AHEAD OF THE
SURFACE TROUGH MARCHING EASTWARD INTO WESTERN ND. AS THIS
OCCURS...INHIBITION SHOULD GRADUALLY WEAKEN WITH CAPPING ERODING
SUFFICIENTLY TO ALLOW FOR CONVECTIVE INITIATION BY ABOUT 21 UTC
TODAY. CONVECTION SHOULD INITIALLY DEVELOP ACROSS WESTERN ND...AIDED
BY LOW-LEVEL CONVERGENCE IN THE VICINITY OF THE AFOREMENTIONED
SURFACE TROUGH. THE THREAT FOR CONVECTION IS EXPECTED TO SPREAD
EASTWARD INTO CENTRAL ND THROUGH THE REMAINDER OF THE
AFTERNOON/EVENING AS FORCED ASCENT INCREASES WITH THE ARRIVAL OF A
NOTABLE MID-LEVEL DISTURBANCE MOVING THROUGH CENTRAL MT. ONCE
INITIATION OCCURS...AVAILABLE MOISTURE/INSTABILITY COMBINED WITH
STRONG DEEP LAYER VERTICAL SHEAR ON THE ORDER OF 40 TO 50 KNOTS WILL
SUPPORT SUPERCELL THUNDERSTORMS CAPABLE OF PRODUCING VERY LARGE HAIL
AND DAMAGING WINDS. ISOLATED TORNADOES ARE ALSO POSSIBLE WITH ANY
SURFACE-BASED STORMS GIVEN BACKED LOW-LEVEL FLOW CONTRIBUTING TO
ENHANCED LOW-LEVEL SHEAR ACROSS PORTIONS OF WESTERN AND CENTRAL ND.
CONVECTION WILL LIKELY MERGE INTO ONE OR MORE MCS/S ACROSS THE
CENTRAL AND EASTERN DAKOTAS OVERNIGHT THURSDAY INTO FRIDAY.

.LONG TERM...FRIDAY THROUGH THURSDAY NIGHT...

WITH THE MAIN THREAT OF SEVERE WEATHER
TODAY...NCEP/HYDROMETEOROLOGICAL PREDICTION CENTER EXTENDED
FORECAST WAS HEAVILY RELIED ON. IN GENERAL...CHANGES WERE MINOR
WITH PRECIPITATION CHANCES INCREASED WHEN THE 12 UTC GFS/GEM
GLOBAL AND 00 UTC ECMWF HAD BETTER AGREEMENT ON LARGE-SCALE
SUPPORT FOR UPWARD VERTICAL MOTION AND CORRESPONDING ENHANCEMENT
OF MODEL PRECIPITATION AMOUNTS.

LOOK FOR TEMPERATURES TO GENERALLY BE AT OR ABOVE AVERAGE AS
COOLER AIR MASSES REMAIN WELL TO THE NORTH IN CENTRAL/NORTHERN
CANADA.

&&

.AVIATION...

SURFACE LOW PRESSURE CENTERED OVER EASTERN MONTANA. UPPER LEVEL
DISTURBANCES ARE FORECAST TO MOVE ACROSS NORTH DAKOTA FROM WEST TO
EAST BEGINNING AROUND 21Z TODAY. EXPECT THUNDERSTORM INITIATION OVER
WESTERN NORTH DAKOTA AROUND 21Z AND SPREADING EAST ACROSS THE STATE.
THUNDERSTORM ACTIVITY SHOULD END AROUND 06Z IN WESTERN TAF SITES AND
BY 12Z FRIDAY IN THE KJMS AREA. SEVERE STORMS ARE EXPECTED MAINLY
LATE THIS AFTERNOON IN THE WEST AND SPREADING INTO CENTRAL NORTH
DAKOTA THIS EVENING. AFTER UPPER LEVEL DISTURBANCES PASS...ONLY SCT
TO BKN MIDDLE CLOUDS EXPECTED.

SOUTH WINDS AHEAD OF THE SURFACE LOW...AND AS THE LOW MOVES INTO
WESTERN NORTH DAKOTA AFTER 06Z WINDS WILL BE LIGHT AND FROM THE
NORTH/NORTHWEST.

&&

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

SYNOPSIS...SCHECK
SHORT TERM...HAMMER/SCHECK
LONG TERM...SCHECK
AVIATION...JV

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
1217 PM CDT THU JUL 29 2010

NDZ001>005-009>013-017>023-025-031>037-040>048-050-051-301730-
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-
1217 PM CDT THU JUL 29 2010 /1117 AM MDT THU JUL 29 2010/

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...THIS AFTERNOON AND TONIGHT...

ANOTHER STORM SYSTEM WILL SLIDE INTO WESTERN NORTH DAKOTA LATE
THIS EVENING. AMPLE MOISTURE AND INSTABILITY WILL SUPPORT
SCATTERED TO NUMEROUS THUNDERSTORMS LATE THIS AFTERNOON INTO
TONIGHT WITH VERY HEAVY RAIN POSSIBLE...ESPECIALLY AFTER DARK.
SOME STORMS WILL BE SEVERE WITH DESTRUCTIVE HAIL AND DAMAGING
WINDS THE MAIN THREATS...THOUGH ISOLATED TORNADOES CANNOT BE RULED
OUT BEFORE SUNSET.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY...

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS FRIDAY MORNING...THEN A
CHANCE OF THUNDERSTORMS SATURDAY THROUGH TUESDAY AS THE WEATHER
PATTERN REMAINS ACTIVE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE NEEDED TONIGHT AND POSSIBLY LATER IN
THE WEEK.

SCHECK

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