Hail and Damaging Wind in Montana, May 20 to 21, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
238 PM MDT SUN MAY 20 2007

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH TUESDAY...
AFTERNOON WATER VAPOR IMAGERY REVEALS AN UPPER LOW ALONG JUST OFF
THE WASHINGTON COASTLINE WITH A PLUME OF MOISTURE STREAMING
NORTHEASTWARD ACROSS WESTERN MONTANA. PRIMARY SHORTWAVE TROUGH
IS FOUND ACROSS IDAHO AND THIS WILL BE THE MAIN TRIGGER FOR
ORGANIZED CONVECTION LATE TODAY/TONIGHT AS IT LIFTS ACROSS BIG SKY
COUNTRY.

AT THE SURFACE...A TROUGH IS FOUND RUNNING FROM NEAR PLENTYWOOD TO
MILES CITY WITH A FEW OUTFLOW BOUNDARIES NEARBY FROM MORNING
CONVECTION. A DEVELOPING SURFACE LOW HAS BEEN TAKING SHAPE WELL
SOUTH ACROSS THE MT/WY BORDER. DEWPOINTS HAVE MANAGED TO HOLD IN
THE LOW TO MID 50/S ALONG AND EAST OF THIS BOUNDARY THUS FAR WITH
LATEST GOES SOUNDER DATA REVEALING TWO AXES OF CAPES...ONE AHEAD
OF THE PRIMARY TROUGH NEAR WINNETT TO BOZEMAN AND THE OTHER ALONG
THE AFOREMENTIONED SURFACE TROUGH. MOST WIDESPREAD DEVELOPMENT
SHOULD OCCUR WITH THE WESTERN- MOST AXIS UNDERNEATH INCREASING
HEIGHT FALLS WHILE MORE ISOLATED CONVECTION SHOULD BE FOUND
FURTHER EAST GIVEN WEAKER UPPER SUPPORT. SEVERE POTENTIAL SHOULD
BE FOCUSED PRIMARILY ACROSS OUR EAST AND SOUTHEASTERN ZONES AND
LATEST LAPS AND MSAS PLOTS VERIFY WELL WITH THIS. EXPECT STORMS TO
INCREASE IN COVERAGE TONIGHT AHEAD OF THE MAIN SHORTWAVE.

PRECIPITATION SHOULD DIMINISH FROM WEST TO EAST EARLY MONDAY AS
BEST QG ASCENT SHIFTS NORTHEASTWARD. UPPER LOW/TROUGH THEN DIGS
TOWARDS THE CENTRAL ROCKIES WITH MAJORITY OF PRECIPITATION
EXPECTED SOUTH OF THE MISSOURI RIVER. POLAR AIR MASS FILTERS IN BY
MONDAY NIGHT...THOUGH CLOUDS SHOULD PREVENT LOWS FROM GETTING TOO
COLD. BROUGHT HIGHS ON TUESDAY DOWN SOME ACROSS SOUTHERN ZONES
WHERE CLOUD SHIELD AND STRATIFORM RAIN SHOULD GREATLY INHIBIT
INSOLATION. MCZ

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
MODELS ARE SUGGESTING COOLER CONDITIONS THROUGH THE PERIOD WITH
NIGHTTIME LOWS DIPPING INTO THE 30S ON SEVERAL NIGHTS. MADE SOME POP
ADDITIONS FOR THURSDAY NIGHT AND FRIDAY AS MODELS COMING INTO
AGREEMENT WITH A SYSTEM. TIMING ON WHEN IT LEAVES IS STILL UP IN THE
AIR...SO LEFT DRY FORECAST ALONE FRIDAY NIGHT. COOLED TEMPS A BIT
FOR SATURDAY OVER THE SOUTHERN ZONES WITH COOLER AIR ASSOCIATED WITH
CLOUDS/POSSIBLE PRECIP CHANCES TO OUR SOUTH. REST OF FORECAST LOOKS
GOOD. JAMBA

PREVIOUS DISCUSSION...
UNCERTAINLY CONTINUES INTO TUE NIGHT AND WED WITH MOVEMENT OF
CLOSED UPPER LOW THAT MODELS HAVE CONSISTENTLY BEEN THREATENING
OUR AREA FOR MANY RUNS...BUT OFTEN FARTHER S. WILL KEEP CHANCE
POPS CONFINED TO OUR SE CORNER AS THE LOW MOVES E OUT OF THE AREA.
A COOL AIRMASS CONTINUES OVER THE AREA THRU FRI UNDER A NW FLOW
ALOFT AND THICKNESSES IN THE 540S DM. EXPECT TO SEE PLENTIFUL LOWS
IN THE 30S WITH A THREAT OF FROST ANYWHERE FROM TUE NIGHT THRU FRI
NIGHT. NO SIGN OF A HARD FREEZE THOUGH.

IN WHAT IS ALMOST THE WETTEST TIME OF YEAR NOW...WOULD EXPECT
THERE TO BE A FEW SHOWERS IN COOL NW FLOW ALOFT...BUT STILL HARD
TO PICK OUR WHEN. MODELS HAVE BEEN SHOWING A SMALL COLD UPPER LOW
MOVING S FROM NW CANADA...BUT VARY GREATLY WHERE IT GOES. THIS
WOULD BE ABOUT THU OR THU NIGHT. NEED TO SEE A BETTER CONSISTENTLY
WITH ANOTHER MODEL RUN OR TWO BEFORE RAISING POPS BEYOND 10 PCT
NEIGHBORHOOD. MEANWHILE...ECMWF HAS ANOTHER TROUGH ABOUT FRI NIGHT
OR SAT AND DOESNT BUILD IN A WEAK RIDGE LIKE PREVIOUS RUNS AND
MODELS HAVE INDICATED FOR THE WEEKEND. SIMONSEN

&&

.AVIATION...
ANOTHER ROUND OF THUNDERSTORMS IS EXPECTED TO IMPACT THE AREA
TONIGHT. THESE WILL MOVE TO THE NORTHEAST WITH LOCALIZED IFR
CONDITIONS. ANY SEVERE CHANCES THIS EVENING APPEAR TO BEST IMPACT
SIDNEY AND GLENDIVE RATHER THAN GLASGOW AND WOLF POINT. LOW CLOUDS
ARE A POSSIBILITY EARLY SUNDAY. MONDAY...SCATTERED CLOUDS THAT
LIFT DURING THE DAY TO BETWEEN 4K AND 8K. WINDS SHOULD FEATURE A
LIGHT NORTHWEST BREEZE OF 10 TO 15 KTS. JAMBA

&&

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

&&

WEATHER.GOV/GLASGOW

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GLASGOW MT
841 PM MDT SUN MAY 20 2007

MTZ021>027-220245-
PETROLEUM-GARFIELD-MCCONE-RICHLAND-DAWSON-PRAIRIE-WIBAUX-
841 PM MDT SUN MAY 20 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MONTANA.

.DAY ONE...TONIGHT

A SEVERE THUNDERSTORM WATCH IS IN EFFECT UNTIL MIDNIGHT. LARGE
HAIL AND DAMAGING WINDS ARE POSSIBLE WITH SOME THUNDERSTORMS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

NO HAZARDOUS WEATHER EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

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