Tornado Warning 22, NWS Glasgow, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
434 PM MDT WED AUG 11 2010

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH FRIDAY...
MORE SEVERE WEATHER POTENTIAL EXPECTED. SEVERE WEATHER POTENTIAL
APPEARS TO BE IN THE MIX FOR TONIGHT AND POSSIBLY LINGERING INTO
THURSDAY MORNING.

MODELS ARE INCREASING OUR SHEAR POTENTIAL FOR TONIGHT WHICH LOOKS
REASONABLE GIVEN THE PLACEMENT OF A SURFACE LOW AND UPPER TROUGH
TODAY. CONVECTION HAS BEGUN TO FIRE UP TO OUR SOUTHWEST OVER THE
MOUNTAINS IN NORTHERN WY AND SOUTHERN MT.  MORE IMPORTANTLY CAPE AND
OTHER STABILITY PARAMETERS ARE SIGNALING THAT THUNDERSTORMS HAVE A
GOOD POSSIBILITY OF BECOMING SEVERE WITH LARGE HAIL AND DAMAGING
WINDS BEING THE MAIN THREATS. WEAK BOUNDARIES CURRENTLY OVER EASTERN
MONTANA MAY HELP TO FOCUS STORMS THIS EVENING AND WILL HAVE TO BE
MONITORED WHEN/IF THE SEVERE WEATHER OCCURS.

AS THE UPPER TROUGH DRIFTS CLOSER FROM THE WEST THROUGH
THURSDAY...THE UPPER DYNAMICS MAY KEEP THINGS UNSTABLE ENOUGH FOR AN
ISOLATED SEVERE STORM OR TWO INTO THURSDAY MORNING. BUT SURFACE
SUPPORT WILL BE WELL TO OUR EAST AS THE SAID SURFACE LOW DRIFTS INTO
THE DAKOTAS. WIDESPREAD PRECIP DOESN/T LOOK LIKELY SO LOWERED POPS.

THEN A COLD FRONT CROSSES THE AREA LATE THURSDAY NIGHT/EARLY FRIDAY
AND BRINGS A FEEL OF FALL. TEMPS ARE EXPECTED TO BE SOME 15 TO 20
DEGREES COOLER THAN TODAY. NW WINDS MAY BE A BIT OF A HAZARD THOUGH
ESPECIALLY TO BOATERS. WILL HIGHLIGHT THIS IN AN HWO. AREAS OF
SHOWERS AND ISOLATED THUNDERSTORMS WILL DROP INTO THE REGION AND
THUS HAVE RAISED POPS SLIGHTLY. JAMBA

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...

ABRUPT END TO THE PRECIP IS SLATED FOR SATURDAY AFTERNOON INTO
SATURDAY EVENING AFTER THE LAST PINWHEELING SHORT WAVE LOBE OF THE
MAIN UPPER LOW SLIDES EAST OF OUR CWA. LATE SATURDAY NIGHT THROUGH
EARLY MONDAY...A DRY AND PERSISTENT NORTHWEST FLOW ALOFT SETS UP
OVER OUR AREA. VERY SUBTLE AND SMALL DISTURBANCES EMBEDDED WITHIN
THIS NORTHWEST FLOW MAY BRING ISOLATED PRECIP TO OUR FAR NORTHEASTERN
ZONES...PRIMARILY MONDAY AND TUESDAY. IT WOULD SUPPORT ONLY LOW
END SLIGHT CHANCE POPS AT BEST. REDUCED POPS TO 10 PERCENT TOWARD
THE END OF THE EXTENDED PERIOD WITH THE WESTERN UPPER LEVEL RIDGE
MAKING A SLIGHT EASTWARD MOVE OVER THE ROCKY MOUNTAINS.MADE ONLY
MINOR ADJUSTMENT TO REFLECT THIS THINKING. BIGGEST CHANGE MADE WAS
TO LOWER POPS FOR FRIDAY NIGHT OVER OUR SOUTHERN ZONES...FOLLOWING
EXTENDED MODEL CONSENSUS AS THE STORM SYSTEM TEMPORARILY OPEN UP
TO DRY THINGS OUT A BIT BEFORE THE SYSTEM PUSH THE LAST OF THE
WIDESPREAD PRECIP THROUGH THE AREA SATURDAY AFTERNOON. BMICKELSON

PREVIOUS LONG TERM DISCUSSION...THE EXTENDED PERIOD WILL CONTINUE THE GENERAL
UPPER LEVEL FLOW PATTERN SHIFT THAT BEGINS IN THE LATER PART OF
THE SHORT TERM. THE MID CONTINENTAL TROUGH SHIFTS EAST AND PARKS
OVER HUDSON BAY TO BECOME A LONGWAVE TROUGH SPANNING THE NORTHERN
HALF OF CONUS BY THE END OF THE EXTENDED PERIOD. HIGH PRESSURE AND
HEAT WILL SETTLE OVER THE GREAT BASIN...NEVER MOVING EAST BEYOND
THE DIVIDE. THIS EVOLVING PATTERN WILL MAINTAIN NORTHWESTERLY FLOW
OVER MONTANA FOR INITIALLY COOLER THAN NORMAL TEMPERATURES THAT
THE ENSEMBLE SAYS WILL SLOWLY WARM TOWARDS NORMAL BY MID WEEK.
MODEL DIFFERENCES EARLY GIVE CONFIDENCE IN THE INITIAL PATTERN.
HOWEVER BY EARLY NEXT WEEK A DIFFERENCE DEVELOPS BETWEEN THE EC
AND THE GFS. THE EC DRIVES A LARGE SHORTWAVE AND COLD FRONT SOUTH
AROUND THE BACK SIDE OF THE CANADIAN LOW DURING THE MONDAY AND
MONDAY NIGHT TIME FRAME WHILE THE GFS KEEPS THE SHORT WAVE AND
STATIONARY FRONT MUCH MORE TO OUR NORTH. THE EC THEREFORE WILL BE
COOLER AND WETTER NEXT WEEK WHILE THE GFS WILL CONTINUE THE VERY
SLOW WARMING TREND.

FRIDAY NIGHT/SATURDAY...THE STACKED LOW STORM SYSTEM WILL BE
CENTERED OVER SOUTHERN MANITOBA. THE 00Z GFS PICKS UP AN ENERGETIC
SHORT WAVE/VORT MAX ROTATING AROUND THE LOW CENTER THAT DROPS INTO
MONTANA. THE 00Z EC ALSO PICKS UP THIS WAVE. OVERCAST AND RAIN
CONTINUE THE RELATIVELY COOL TEMPERATURES FROM FRIDAY. THE FAIRLY
STRONG SURFACE PRESSURE GRADIENT OF FRIDAY WILL CONTINUE THE
NORTHWESTERLY WINDS OVERNIGHT BEFORE RELAXING SLIGHTLY FOR
DIMINISHING WINDS SATURDAY.

SATURDAY NIGHT/SUNDAY...A SURFACE HIGH AND GENERAL WIDESPREAD
SUBSIDENCE WILL MINIMIZE ANY PRECIPITATION BUT KEEP TEMPERATURES
SLIGHTLY COOL. MINOR DIFFERENCES IN THE FLOW PATTERN EXIST BETWEEN
THE GFS AND EC. THE EC KEEPS THE STATIONARY BOUNDARY FARTHER WEST
THAN THE GFS WHICH WILL MAKE A DIFFERENCE WHEN THE NEXT SHORT WAVE
ROTATES SOUTH THROUGH THE CANADIAN PRAIRIE.

SUNDAY NIGHT AND BEYOND...WITH THE MORE WESTERLY POSITION OF THE
NEXT SHORT WAVE...THE 12Z EC BRINGS IN A COLD FRONT AND WIDESPREAD
RAIN. HOWEVER THE 00Z EC LOOKS MORE LIKE THE 00Z GFS. THE GFS ONLY
CLIPS THE NORTHEASTERN ZONES WITH THE SHORT WAVE AND IS LATER WITH
THE FRONT. SO THE MODELS ARE STILL ATTEMPTING TO SETTLE IN ON HOW
THE NEXT WAVE WILL ACT. WILL TRY TO STAY AWAY FROM THE 12Z EC
SOLUTION IN THE LATTER PART OF THE EXTENDED. THIS WILL RESULT IN
SLOWING DOWN THE WAVE. SCT

&&

.AVIATION...
VFR CONDITIONS WILL PREVAIL FOR ALL TAF SITES THROUGHOUT MOST OF
THE TAF CYCLE. GENERALLY BETWEEN 00Z AND 03Z...THUNDERSTORMS WILL
SPREAD THROUGH THE AREA FROM WEST TO EAST. KGDV WILL LIKELY NOT BE
AFFECTED BY THE STORMS AS MUCH AS THE OTHER TAF SITES. IF A
STRONGER STORM HAPPENS TO PASS DIRECTLY OVER KGGW...KOLF...OR KSDY
DURING THIS TIME...FLIGHT CONDITIONS MAY BRIEFLY WORSEN TO
MVFR/IFR. AMENDMENTS FOR THUNDERSTORMS MAY BE NECESSARY LATER THIS
AFTERNOON. BMICKELSON

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

WEATHER.GOV/GLASGOW

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GLASGOW MT
256 PM MDT WED AUG 11 2010

MTZ018>020-024>027-059>062-121200-
DANIELS-SHERIDAN-WESTERN ROOSEVELT-RICHLAND-DAWSON-PRAIRIE-WIBAUX-
NORTHERN PHILLIPS-SOUTHWEST PHILLIPS-NORTHERN VALLEY-
EASTERN ROOSEVELT-
256 PM MDT WED AUG 11 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT
STRONG TO SEVERE THUNDERSTORMS ARE A GOOD POSSIBILITY TONIGHT.
LARGE HAIL AND DAMAGING WINDS ARE TO BE THE MAIN THREATS FROM
THESE STORMS. ALSO EXPECT DANGEROUS CLOUD TO GROUND LIGHTNING.
THE ACTIVITY WILL GENERALLY MOVE IN FROM THE SOUTHWEST THIS
EVENING AND INTENSIFY.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

NO HAZARDOUS WEATHER IS EXPECTED.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

MTZ016-017-021>023-121200-
CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-
PETROLEUM-GARFIELD-MCCONE-
256 PM MDT WED AUG 11 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT
STRONG TO SEVERE THUNDERSTORMS ARE A GOOD POSSIBILITY TONIGHT.
LARGE HAIL AND DAMAGING WINDS ARE TO BE THE MAIN THREATS FROM
THESE STORMS. ALSO EXPECT DANGEROUS CLOUD TO GROUND LIGHTNING. THE
ACTIVITY WILL GENERALLY MOVE IN FROM THE SOUTHWEST THIS EVENING
AND INTENSIFY.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY
A COLD FRONT IS EXPECTED TO BE CROSSING THE AREA FRIDAY. LIGHT
WINDS DURING THE MORNING LOOK TO INCREASE WITH GUSTS TO AROUND 30
MPH MAKING THE WATERS OF FORT PECK LAKE ROUGH AND CHOPPY.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GLASGOW MT
452 PM MDT WED AUG 11 2010

MTZ061-112345-
VALLEY-
452 PM MDT WED AUG 11 2010

THE NATIONAL WEATHER SERVICE IN GLASGOW HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...
  NORTHERN VALLEY COUNTY IN NORTHEAST MONTANA...

UNTIL 545 PM MDT.

AT 448 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 15 MILES WEST OF OPHEIM..MOVING NORTHEAST AT 55
MPH.

HAIL UP TO THE SIZE OF NICKELS HAIL AND WIND GUSTS UP TO 50 MPH ARE
EXPECTED WITH THIS STORM.

LOCATIONS IN THE ADVISORY INCLUDE...
  RURAL AREAS OF NORTHERN VALLEY COUNTY...

THIS STORM MAY INTENSIFY...AND A SEVERE THUNDERSTORM WATCH IS IN
EFFECT FOR THIS AREA. BE CERTAIN TO MONITOR LOCAL RADIO AND TV
STATIONS...AS WELL AS LOCAL CABLE TV OUTLETS...FOR ADDITIONAL
INFORMATION AND POSSIBLE WARNINGS FROM THE NATIONAL WEATHER SERVICE.

LAT...LON 4900 10694 4900 10649 4878 10667 4877 10703
TIME...MOT...LOC 2252Z 207DEG 47KT 4898 10668

RSMITH
WEATHER.GOV/GLASGOW

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