Severe Thunderstorm Warning 39, NWS Glasgow, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
259 PM MDT WED JUN 16 2010

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH FRIDAY...

...A SIGNIFICANT THREAT FOR SEVERE WEATHER CONTINUES TO EXIST FOR
ALL OF NORTHEAST MONTANA THIS EVENING...

THIS EVENING A DEEPENING SURFACE LOW OVER SOUTHEAST MONTANA WILL
HELP SET THE STAGE FOR SEVERE THUNDERSTORMS OVER MUCH OF NORTHEAST
MONTANA. CLEARING THIS MORNING AND AFTERNOON ACROSS SOUTHEAST
MONTANA HAS ALLOWED TEMPERATURES TO ALREADY TO RISE INTO THE 80S.
AMPLE LOW MOISTURE TRANSPORT IN THE FORM OF SOUTHEAST WINDS OUT
OF THE DAKOTAS IS FURTHER MOISTENING THE AIRMASS OVER NORTHEAST MONTANA.
THE BIGGEST MONKEY WRENCH CONTINUES TO BE THE ABSENCE OF A STRONG
FEATURE TO ERODE THE STABLE LAYER IN THE ATMOSPHERE THAT IS
EFFECTIVELY CAPPING THE CONVECTION. THAT BEING
SAID...THUNDERSTORMS FORMING OVER THE NORTHERN WYOMING MOUNTAINS
SHOULD EFFECTIVELY ERODE THE CAP OR FEED OF THE ELEVATED
INSTABILITY AS THEY COME DOWN ONTO THE PLAINS. THESE WILL LIKELY
BE THE STORMS THAT PROVIDE SEVERE WEATHER OVER NORTHEAST MONTANA
THIS EVENING AND WILL NEED TO BE CLOSELY MONITORED.

FURTHER WEST...A SECOND MORE DEFINED FRONTAL BOUNDARY ON THE
BACKSIDE OF THE DEVELOPING LOW LIES ACROSS THE CENTRAL PART OF THE
STATE AND WILL BE A LARGE PLAYER IN INITIATING THUNDERSTORMS THIS
AFTERNOON ACROSS THE WEST LATER ON THIS EVENING.

PRECIPITABLE WATER VALUES ARE BETWEEN 1-1.5 INCHES ACROSS NORTHEAST
MONTANA...AND WHEN CONSIDERING ATMOSPHERIC TEMPERATURES IS VERY
MOIST. ANY STORMS THAT DEVELOP THIS EVENING INTO THURSDAY COULD
PRODUCE HEAVY RAIN...WHICH IN TURN COULD CAUSE FLASH FLOODING.
THUS WILL CONTINUE THE FLASH FLOOD WATCH THROUGH THURSDAY AFTERNOON.

THURSDAY THE LOW PRESSURE SYSTEM WILL BECOME VERTICALLY
STACKED...CENTERED OVER NORTHWEST NORTH DAKOTA. WRAP AROUND
PRECIPITATION WILL BE VERY WIDESPREAD...WITH SOME THUNDERSTORMS
POSSIBLE...MAINLY NEAR THE NORTH DAKOTA BORDER. WINDS LOOK TO BE
VERY STRONG AS COLD AIR ADVECTION AND A VERY TIGHT GRADIENT PAIR
UP ON THE BACK SIDE OF THE POTENT SURFACE LOW. READINGS OF
40-60 MPH ARE A POSSIBILITY ACROSS MUCH OF THE AREA...WILL
CONTINUE THE GOING WATCH FOR NOW GIVEN SEVERE WEATHER CONCERNS
THIS EVENING.

THURSDAY EVENING WINDS CONTINUE...BUT SHOULD SLOWLY TAPER OFF
THROUGH THE NIGHT. WITH THAT EXTENDED THE HIGH WIND WATCH AS HIGH WINDS
NOW LOOK TO LINGER THROUGH THE EARLY MORNING HOURS...ESPECIALLY
OVER HIGHER ELEVATION SITES SUCH AS THE BIG SHEEP MOUNTAINS.
PRECIPITATION WILL ALSO CONTINUE OVERNIGHT...BUT SHOULD DECREASE IN
INTENSITY FROM SOUTH TO NORTH THROUGH THE EVENING.

FRIDAY LIGHTER WRAPAROUND RAIN SHOWERS WILL CONTINUE...ESPECIALLY
NEAR THE CANADIAN BORDER AS THE LOW SLOWLY LIFTS INTO ONTARIO.
GUSTY NORTHWEST WINDS WILL CONTINUE BUT WILL BE BELOW HIGH WIND
CRITERIA. HOWEVER...A LAKE WIND ADVISORY LOOKS LIKE A SLAM DUNK
FOR FRIDAY. TEMPERATURES WILL BE WELL BELOW NORMALS IN THE WAKE OF
THE EXITING SYSTEM. GILCHRIST

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...
ANOTHER DIGGING AND STALLING UPPER TROUGH MOVES INTO THE INLAND
WESTERN STATES OVER THE WEEKEND...WHICH INDUCES WEAK UPPER RIDGING
OVER OUR AREA. THE RESULT WILL BE A GENERALLY DRY WEEKEND AND
TEMPS NEAR NORMAL. THEN THE UPPER TROUGH KICKS OUT NE TOWARD NE MT.
THIS INCREASES THE THREAT OF THUNDERSTORMS FOR SUNDAY NIGHT THRU
TUE. MOST MODELS HAVE BEEN INDICATING THIS...HOWEVER SEVERAL
MODEL RUNS HAVE ALSO BEEN SHOWING THAT THIS SYSTEM MAY REACH US IN
PIECES...WHICH WOULD MAKE TIMING THE PRECIP CHANCES TOUGHER AND
EXTEND THE UNSETTLED PERIOD LONGER. LATEST DGEX...CMC
GEM...NOGAPS...AND GFS ENSEMBLES ALL HAVE INDICATED THIS TO SOME
EXTENT. THIS IS DAY 7 THOUGH...SO WILL WAIT FOR BETTER MODEL
HANDLING OF THIS TO CHANGE POPS.

ONLY MODEST CHANGES IN THE THICKNESSES...SO TEMPS CONTINUE ON THE
PLEASANT AND MILD SIDE...WITH HIGHS MAINLY IN THE 70S...ABOUT
NORMAL FOR THIS TIME OF YEAR. SIMONSEN

PREVIOUS LONG TERM FRIDAY NIGHT THROUGH WEDNESDAY...THE STRONG
NORTHWEST WINDS ARE EXPECTED TO DIE DOWN BEFORE MIDNIGHT...AS THE
PRESSURE GRADIENT FROM THE STACK STORM SYSTEM RELAXES AS THE
SYSTEM MOVES TO THE NORTHEAST BY SATURDAY MORNING. THIS WILL BE A
RESULT OF AN UPPER LEVEL JET CORE MOVING OUT OF THE SOUTHWEST US
AD FORCING THE STACKED SYSTEM THROUGH THE BLOCKING RIDGE THAT HAD
SLOWED IT DOWN OVER THE NORTHERN PLAINS. AT THE SAME TIME ANOTHER
WEST COAST UPPER TROF WILL DEVELOP AND CONTROL THE FORECAST OVER
MONTANA FOR THE REST OF THE LONG TERM PERIOD.

SATURDAY MORNING ONCE THE SYSTEM HAS PASSED TEMPERATURES WILL
REMAIN SLIGHTLY COOLER THEN NORMAL WITH ZONAL/SW FLOW ACROSS
MONTANA. THE WARMER AIR WILL REMAIN SOUTH NEMONT FOR THE NEXT FEW
DAYS. ALSO BECAUSE OF THIS UPPER TROFFINESS OVER THE WEST COAST
UPPER LEVEL DISTURBANCES WILL BE EJECTED OUT OF THE BASE OF IT AND
ACROSS EASTERN MONTANA OVER THE NEXT SEVERAL DAYS. KEPT CLOSE TO
CLIMO POPS IN THE FORECAST AS THE SOUTHWEST FLOW AND DISTURBANCE
WILL LIKELY CREATE INSTABILITY AND DAYTIME CONVECTION OVER THE
MOUNTAINS OF CENTRAL MONTANA. SOME THESE STORMS MAY MOVE INTO
NEMONT EVERY AFTERNOON STARTING ON SATURDAY AND LASTING THROUGH
TUESDAY.

TUESDAY NIGHT AND BEYOND...DIFFERENCES BETWEEN THE GFS...GEM AND
ECMWF COME INTO PLAY TUESDAY NIGHT. THE ECMWF AND GEM ARE IN
BETTER AGREEMENT BUT THE GFS HAS A SHORT WAVE RIDGE OVER EASTERN
MONTANA. DECIDED TO LEAVE THE ZONES DRY AT THIS POINT AND WAIT FOR
MORE RESOLUTION OVER THE NEXT FEW MODELS RUNS. TEMPERATURES ARE
ALSO EXPECTED TO TREND TOWARDS NEAR NORMAL BY THE END OF THE LONG
TERM PERIOD. RSMITH

&&

.AVIATION...
WIDESPREAD SEVERE THUNDERSTORMS AREA EXPECTED TO DEVELOP LATE
THIS AFTERNOON AND EVENING...MOVING NE ACROSS THE AREA. LARGE HAIL
AND DAMAGING WIND GUSTS OVER 50 KT ARE POSSIBLE WITH THE
STORMS...AS WELL AS VISIBILITIES FALLING TO IFR 1-3 MILES IN HEAVY
SHOWERS. LATE TONIGHT AND THU...EXPECT WIDESPREAD IFR CE LINGS
BELOW 1K FT AGL ALONG WITH A STEADY RAIN FALLING HEAVY AT
TIMES...REDUCING VISIBILITIES DOWN TO 3-5 MILES. MOST HIGHER
ELEVATIONS THU WILL BE OBSCURED IN CLOUDS AND RAIN. VERY STRONG
WINDS WILL DEVELOP THROUGH MOST OF THE FORECAST AREA THU
AFTERNOON...INCLUDING ALL TAF SITES WHERE WINDS WILL BE WEST 25-40
KT ON THE AVERAGE. SOME AREAS OF NE MT THOUGH WILL SE GUSTS OVER 50
KT DURING THE AFTERNOON. SIMONSEN

&&

.HYDROLOGY...
A VERY MOIST ATMOSPHERE IN PLACE OVER NORTHEAST MONTANA TODAY INTO
THURSDAY WILL CREATE THE POTENTIAL FOR HEAVY RAIN FROM ANY
THUNDERSTORMS THAT DEVELOP. THIS RAINFALL WHEN COMBINED WITH
ALREADY SATURATED SOILS AND RUNNING STREAMS COULD ALLOW FLASH
FLOODING TO OCCUR. A FLASH FLOOD WATCH IS IN EFFECT FOR ALL OF
NORTHEAST MONTANA. PLEASE CONTINUE TO MONITOR THE LATEST FORECAST FOR
DETAILS. GILCHRIST

&&

.CLIMATE...
THE FIRST HALF OF JUNE WAS COOLER AND WETTER THAN NORMAL. THE
AVERAGE TEMPERATURE THROUGH THE 15TH WAS 59.1 DEGREES...WHICH IS
3.4 DEGREES BELOW NORMAL. RAINFALL THROUGH THE 15TH IS 1.93
INCHES...WHICH IS 0.82 INCHES ABOVE NORMAL. ALL HIGH TEMPERATURES
SO FAR THIS MONTH HAVE BEEN IN THE 60S AND 70S.. THERE HAVE BEEN
NO 80S FOR HIGHS HERE IN GLASGOW SINCE MAY 17TH-19TH. SIMONSEN

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR 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.

HIGH WIND WATCH FROM THURSDAY MORNING THROUGH LATE THURSDAY
NIGHT FOR CENTRAL AND SOUTHEAST PHILLIPS...CENTRAL AND SOUTHERN
VALLEY...WESTERN ROOSEVELT...PETROLEUM...GARFIELD...MCCONE...
RICHLAND...DAWSON...PRAIRIE...WIBAUX...NORTHERN PHILLIPS...
SOUTHWEST PHILLIPS...NORTHERN VALLEY.

&&

WEATHER.GOV/GLASGOW

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GLASGOW MT
244 PM MDT WED JUN 16 2010

MTZ016>027-059>062-172045-
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-
244 PM MDT WED JUN 16 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A STRONG STORM SYSTEM IS EXPECTED TO MOVE A VIGOROUS COLD FRONT
THROUGH EASTERN MONTANA LATE TONIGHT. THUNDERSTORMS ARE LIKELY
WITH AND AHEAD OF THE FRONT AND COULD BECOME SEVERE WITH LARGE
HAIL...DAMAGING WINDS...AND HEAVY RAINFALL.

A FLASH FLOOD WATCH IS IN EFFECT THROUGH THURSDAY AFTERNOON ALONG
AND BEHIND THE FRONT.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

A HIGH WIND WATCH FROM MIDDAY THURSDAY THROUGH LATE THURSDAY
NIGHT HAS BEEN ISSUED FOR STRONG NORTHWEST WINDS OF 30 TO 45
MPH...GUSTING TO 65 MPH BEHIND THE COLD FRONT. WINDS WILL THEN
SLOWLY TAPER OFF THROUGH FRIDAY MORNING AND AFTERNOON...ALTHOUGH A
LAKE WIND ADVISORY LOOKS LIKE A GOOD BET FOR FRIDAY.

.SPOTTER INFORMATION STATEMENT...

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

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