Severe Thunderstorm Warning 149, NWS Glasgow, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
230 PM MDT THU AUG 11 2011

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SATURDAY...
THIS AFTERNOON THROUGH FRIDAY... LARGE SCALE PATTERN IS MAINLY
ZONAL FLOW THROUGHOUT THE SET OF PERIODS. A SHORTWAVE EMBEDDED IN
THE FLOW IS IMPACTING THE REGION THIS AFTERNOON AND SPARKING OFF A
FEW THUNDERSTORMS. SOME OF THESE COULD BECOME SEVERE NEAR THE
YELLOWSTONE VALLEY DUE TO CAPE VALUES ABOVE 1000 TO 1500 J/KG.
SHEAR VALUES ARE LACKING SO THUNDER THAT DOES DEVELOP NORTH OF THE
COLD FRONT OR YELLOWSTONE MAY BE RATHER STRATIFORM WITH MORE HEAVY
RAIN. SHOWERS AND THUNDERS WILL CONTINUE THROUGH THE NIGHT AND
EXIT TO THE EAST BY FRIDAY MORNING. FRIDAY SHOULD BE A CLEARING
DAY AS A RIDGE DEVELOPING OVER THE PACIFIC NORTHWEST BEGINS TO
GAIN DOMINANCE.

FRIDAY NIGHT THROUGH SATURDAY...RIDGE EXTENDING UP FROM THE DESERT
SOUTHWEST WILL REORIENT ITSELF ACROSS MONTANA AND INTO THE
SOUTHERN CANADIAN PRAIRIE. THIS WILL LEAD TO CLEARING SKIES AND DRY
CONDITIONS WITH TEMPERATURES BEGINNING THE WARM UP TO BACK TO NEAR
SEASONAL NORMS. GAH

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
ALTHOUGH THE MODELS DO NOT AGREE ON THE TIMING AND PLACEMENT OF
THE UPPER LEVEL FEATURES THEY DO HOWEVER INDICATE THAT EASTERN
MONTANA WILL REMAIN UNSETTLED IN THE LONG TERM FORECAST. THE UPPER RIDGE
ROOTED OVER THE WESTERN STATES WILL WEAKEN AND SHIFT EAST OVER
THE CENTRAL PLAINS AS A LONGWAVE TROUGH AND ASSOCIATED LOW
PRESSURE SYSTEM SWINGS THROUGH THE AREA. AS THE RIDGE WEAKENS THE
FLOW ALOFT WILL BECOME MORE SOUTHWESTERLY ORIENTATED. THE PROGRESSION OF THE
TROUGH WILL BE RELATIVELY SLOW WHICH WILL KEEP DIFFLUENT FLOW OVER
EASTERN MONTANA THROUGH LATE WEDNESDAY...THESE WILL ALLOW NEMONT
TO BECOME INCREASINGLY UNSTABLE BY MIDWEEK.

A SERIES OF SHORTWAVE DISTURBANCES ASSOCIATED WITH THE MENTIONED
UPPER LEVEL SYSTEM WILL FIRE ACROSS THE REGION AS THE UPPER LOW
SLIDES EASTWARD SUNDAY NIGHT THROUGH WEDNESDAY NIGHT. THESE WAVES OF
ENERGY WILL LIKELY TRIGGER CONVECTIVE ACTIVITY ACROSS EASTERN MONTANA...AND
GIVEN THAT THE TIMING AND PLACEMENT REMAINS UNCERTAIN...MOST OF
THE EXTENDED FORECAST REFLECT BROAD-BRUSHED CHANCES FOR SHOWERS
AND THUNDERSTORMS.

THURSDAY THROUGH FRIDAY MORNING...THE UPPER RIDGE WILL ATTEMPT TO
REBOUND BUT ANOTHER LONGWAVE TROUGH IS PUSHING ONSHORE THE WEST
COAST. THEREFORE NEARLY ZONAL FLOW WILL RESIDE OVER THE STATE.
MILD AND DRIER CONDITIONS CAN BE EXPECTED. AES

&&

.AVIATION...
A COLD FRONT PUSHING THROUGH THE STATE THIS AFTERNOON IS CAUSING
WINDS TO INCREASE AND SHIFT. ISOLATED THUNDERSTORMS DEVELOPING
ALONG AND BEHIND THE FRONT ARE PRODUCING STRONG GUSTY
WINDS...PERIODS OF HEAVY RAIN AND SMALL HAIL. THE INTENSITY AND
COVERAGE OF THUNDERSTORMS IS EXPECTED TO INCREASE TONIGHT...MAINLY
AFFECTING TERMINALS OLF...SDY AND GDV. LOOK FOR OVERALL VFR
CONDITIONS ACROSS NORTHEAST MONTANA...ANY AREA WITH THUNDERSTORMS
MOVING THROUGH COULD SEE PERIODS OF MVFR OR IFR CONDITIONS. AES

&&

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

&&

WEATHER.GOV/GLASGOW

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GLASGOW MT
216 PM MDT THU AUG 11 2011

MTZ016>027-059>062-121100-
CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-
DANIELS-SHERIDAN-WESTERN ROOSEVELT-PETROLEUM-GARFIELD-MCCONE-
RICHLAND-DAWSON-PRAIRIE-WIBAUX-NORTHERN PHILLIPS-
SOUTHWEST PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT-
216 PM MDT THU AUG 11 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

AN UPPER LEVEL DISTURBANCE IS EXPECTED TO MOVE ACROSS NORTHEAST
MONTANA THIS EVENING...PRODUCING SCATTERED SHOWERS AND THUNDERSTORMS.
SOME OF THE STRONGER STORMS OVER THE LOWER YELLOWSTONE RIVER
VALLEY AND NEAR THE NORTH DAKOTA BORDER MAY PRODUCE LARGE
HAIL...SOME GUSTY WINDS...AND CLOUD TO GROUND LIGHTNING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

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

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