Hail in Montana, September 7, 2007

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
853 PM MDT FRI SEP 7 2007

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SUNDAY...
HAVE UPDATED FOR A SECOND TIME THIS EVENING TO BETTER REFLECT THE
HIGHER WIND THAT IS OCCURRING AND TO PUT A LAKE WIND ADVISORY FOR
FORT PECK LAKE. ADDITIONALLY HAVE ADDED IN MENTION OF ISOLATED
THUNDERSTORMS ACROSS THE SOUTHERN PORTION OF THE CWA AS THE
SHORTWAVE IS PACKING A BIT MORE PUNCH THAN EXPECTED WITH AN
UNSTABLE ENVIRONMENT. SMALL HAIL AND GUSTY WIND WILL LIKELY
ACCOMPANY THESE STORMS...AND ONE OR TWO COULD BECOME SEVERE WITH
LARGE HAIL BEING THE PRIMARY THREAT IN THIS COOL AND MOIST ATMOSPHERE.
OTHERWISE HAVE LEFT THE REMAINDER OF THE FORECAST ABOUT AS IT WAS
AS REMAINDER APPEARED TO BE IN GOOD SHAPE.

PREVIOUS DISCUSSION...
STRONG UPPER LEVEL SHORTWAVE IS CURRENTLY ENTERING SOUTHERN
ALBERTA. MEANWHILE...THERE IS A SURFACE LOW OVER WESTERN MONTANA
WITH SOME RAIN SHOWERS OVER SOUTHERN ALBERTA AND NORTH CENTRAL
MONTANA. THE SHORTWAVE IS EXPECTED TO TRACK OVER EASTERN MONTANA
LATE TONIGHT WITH THE SURFACE LOW MOVING EAST ALONG THE
MONTANA/WYOMING BORDER. THIS SYSTEM WILL BRING RAIN TO MOST OF THE
FORECAST AREA TONIGHT. WITH THE BEST LIFT AND OVERRUNNING
FORECASTED TO AFFECT AREAS NORTH OF THE MISSOURI RIVER...WILL
FORECAST THE HIGHEST CHANCE OF RAIN THERE...80%.

THIS SYSTEM WILL EXIT EASTERN MONTANA SATURDAY MORNING. COOL AND
SOMEWHAT UNSTABLE AIR WILL LINGER THROUGH THE DAY. WILL MAINTAIN A
CHANCE OF SHOWERS THROUGH THE DAY.

THE MAIN SHORTWAVE WITH THE NEXT SYSTEM ON SUNDAY IS EXPECTED TO
TRACK WELL SOUTH AND WEST OF THE FORECAST AREA. HOWEVER...AN UPPER
TROUGH AND WEAK COLD FRONT WILL COMBINE WITH SOME INSTABILITY TO BRING
A CHANCE OF SHOWERS TO NORTHEAST MONTANA. FORRESTER

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
UPPER AIR PATTERN HAS STRONG HIGH OVER THE EASTERN PACIFIC AND
GULF OF ALASKA...WHILE THERE IS A BROAD TROUGH OVER THE N ROCKIES
AND UPPER MIDWEST...AND A CLOSED LOW OVER HUDSON BAY. THIS KEEPS
NE MT IN A COOL NW FLOW MOST OF THE PERIOD. THE MAIN DISTURBANCE
IN THIS FLOW WILL BE A COLD FRONT AND UPPER TROUGH TO ARRIVE TUE
AFTERNOON AND EVE. MOISTURE LOOKS QUITE LIMITED BUT THIS WILL BE
ABOUT THE ONLY SIGNIFICANT CHANCE OF PRECIP DURING THE EXTENDED.
RECENT GFS RUNS HAVE BEEN SHOWING A CHILLY HIGH FROM N CANADA
MOVING INTO THE AREA BEHIND THIS SYSTEM WITH THICKNESSES DROPPING
TO 540 DM...AND 850 TEMPS TO 0C IN OUR N. NOT ALL MODELS LOOKING
THAT COLD THOUGH...SO THERE ARE JUST POSSIBILITIES FOR FREEZING
TEMPS TUE NIGHT AND WED NIGHT TO CONSIDER...AS SOME AREAS SHOULD EASILY
FALL TO THE 30S REGARDLESS.

MOST MODELS HAVE BEEN SHOWING THE UPPER RIDGE WEAKENS AND SHIFTS E
BRINGING WARMING TO OUR AREA BY FRIDAY. 12Z GFS GOES AGAINST THIS
THOUGH KEEPING NE MT IN COOL NW FLOW. ENSESMBLES DIFFER QUITE A
BIT TOO...SO WILL DISCOUNT 12Z GFS AND CONTINUE WITH THE REST OF
MODELS AND THE ONGOING FORECAST OF A MODEST WARMING TREND FOR
FRIDAY. SIMONSEN

PREVIOUS LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...OVERALL FAIRLY
TYPICAL WEATHER FOR EARLY-MID SEPTEMBER WITH TEMPERATURES DURING
THE EXTENDED PERIOD AVERAGING OUT CLOSE TO AVERAGE...WITH LITTLE
IN WAY OF SIGNIFICANT PRECIPITATION EXPECTED. MODELS ARE IN
REASONABLE AGREEMENT WITH THE OVERALL PATTERN...HOWEVER ARE FASTER
THAN LAST NIGHT WITH A COLD FRONT EARLY-MID WEEK.

SUN NIGHT & MONDAY...THE EXTENDED PERIOD STARTS OFF WITH GOOD MODEL
AGREEMENT.  A LARGE UPPER RIDGE WILL BE PARKED OFF THE PAC NW COAST
AND THE LOCAL AREA WILL BE IN A CYCLONIC FLOW WITH A SHORTWAVE
TROUGH PROGGED TO SWING ACROSS THE AREA SUNDAY NIGHT.  THIS MAY
TOUCH OFF A FEW SHOWERS SUNDAY NIGHT...ESPECIALLY ACROSS THE EASTERN
ZONES.  BY MONDAY THE MODELS ARE NOT IN THE BEST AGREEMENT ON
WHETHER THE TROUGH CONTINUES TO SLIDE EAST OR IF SOME OF THE UPPER
ENERGY HANGS BACK TO THE SOUTHWEST OF THE AREA. GIVEN THE TIME OF
YEAR WITH A MORE ACTIVE NORTHERN BRANCH OF THE JET WILL SIDE WITH
THE IDEA THAT THE TROUGH IS MORE PROGRESSIVE.

TUESDAY & WEDNESDAY...THE AREA REMAINS IN A NORTHWEST FLOW ALOFT
BETWEEN A STRONG RIDGE ACROSS THE PAC NW AND THE HUDSON BAY LOW.  A
DISTURBANCE DROPPING DOWN IN THE FLOW WILL PUSH A COLD FRONT ACROSS
THE AREA.  MODELS HAVE BEEN OFFERING UP BOTH DIFFERENT TIMING AND
STRENGTH WITH THIS FRONTAL PASSAGE.  YESTERDAY MANY MODELS WERE
BRINGING THE FRONT THROUGH ON WEDNESDAY...AND NOW MANY OF THE
MEDIUM RANGE MODELS AND ENSEMBLE MEMBERS ARE BRING THE FRONT
THROUGH TUESDAY OR TUESDAY EVENING. IN THE WAKE OF THE FRONT...A
COOL CANADIAN HIGH DROPS IN FROM THE NORTH. SOME UNCERTAINTY AS TO
WHETHER IT WILL BE TRULY AN ARCTIC HIGH OR HAVE MORE OF A NORTH
PACIFIC CONNECTION.

THURSDAY & FRIDAY...IT LOOKS LIKE THE HIGH SETTLES IN WEDNESDAY
NIGHT BEFORE SLIDING OFF THE EAST THURSDAY.  THE UPPER RIDGE IN THE
PAC NW LOOKS TO SLIDE IN FROM THE WEST LATE IN THE WEEK WITH DRY
AND MILDER WEATHER.  THERE IS THE POTENTIAL WEDNESDAY NIGHT THAT
IF THE SKY BECOMES CLEAR THAT THERE COULD BE SOME FREEZING
TEMPERATURES IN THE NORMAL COLD SPOTS ACROSS THE CWA. CB

&&

.AVIATION...
NUMEROUS SHOWERS TO AFFECT KGGW AND WOLF POINT THIS
EVENING...SPREADING TO KSDY AND KGDV LATE THIS EVENING AND
OVERNIGHT. A THUNDERSTORM REMAINS A POSIBILITY AT KGDV THIS
EVENING. CEILINGS WILL BE LOWERING TO AROUND 5K FT AGL LATER THIS
EVENING. A LOWER CLOUD LAYER IS LIKELY TO DEVELOP LATE TONIGHT AS
VISIBILITY IS ALSO REDUCED TO 5 MILES AT TIMES IN MODERATE
INTENSITY RAIN. THIS LOWER CLOUD LAYER WILL LIKELY BECOME A
WIDESPREAD BROKEN TO OVERCAST IFR CEILING BELOW 1K FT AGL BY
MORNING. EXPECT ALL HIGHER TERRAIN TO BECOME OBSCURED. RAIN WILL
TAPER OFF AND IFR CEILINGS WILL RAISE TO MVFR BY LATE MORNING.
SIMONSEN

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 3 AM MDT SATURDAY FOR FORT PECK LAKE.

&&

WEATHER.GOV/GLASGOW