Damaging Wind in Montana, July 29, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
1009 AM MDT WED JUL 29 2009

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY...UPPER LOW SEEN ON
SATELLITE CHANNELS CENTERED OVER SE SK AND MOVING S. A SHORTWAVE
IS FARTHER UPSTREAM. MODELS SHOW THIS MOVING WEAKLY THRU OUR AREA
THIS AFTERNOON. LITTLE INDICATION OF A SURFACE FEATURE WITH THIS
THOUGH...AND 12Z KGGW SOUNDING WAS CAPPED AT 15K FT MSL. THIS
AIRMASS IS MOIST AND QUITE UNSTABLE THOUGH...SO SHOULD EASILY
PRODUCE SHOWERS AND A FEW THUNDERSTORMS TOO. WILL LOWER MORN POPS
THOUGH AS ONLY A FEW CELLS SEEN NOW ON RADAR. SIMONSEN

PREVIOUS SHORT TERM....FOR NORTHEAST
MONTANA...TODAY THROUGH FRIDAY...RAIN ASSOCIATED WITH TUESDAYS
COLD FRONT LINGERS OVER THE YELLOWSTONE VALLEY AT 09Z. THIS RAIN
WILL EXIT THE FORECAST AREA EARLY THIS MORNING. PATCHY FOG HAS
DEVELOPED OVERNIGHT OVER MANY PARTS OF THE AREA AND SHOULD LINGER
UNTIL A FEW HOURS AFTER SUNRISE THIS MORNING.

A SMALL UPPER LOW CURRENTLY CENTERED NORTHEAST OF REGINA
SASKATCHEWAN WILL MOVE SOUTH INTO NORTH DAKOTA THIS AFTERNOON. THIS
SMALL LOW IS CIRCULATING SOUTH AROUND A MUCH LARGE UPPER LOW THAT
IS OVER ONTARIO. THIS SYSTEM WILL MAINTAIN CYCLONIC FLOW ALOFT
OVER EASTERN MONTANA TODAY. WITH SOME INSTABILITY FROM DAYTIME
HEATING AND A FEW SHORTWAVES... THERE SHOULD BE A FEW SHOWERS AND
THUNDERSTORMS OVER THE AREA ESPECIALLY THIS AFTERNOON. NORTH WINDS
MAY APPROACH LAKE WIND ADVISORY CRITERIA BUT CONFIDENCE IS LACKING
IN SUSTAINED 20 MPH WINDS AT THIS POINT. WILL HOLD OFF ON ISSUING
AN ADVISORY AT THIS TIME. WITH COOL NORTHERLY FLOW
ALOFT...TEMPERATURES WILL REMAIN ABOUT 10 DEGREES BELOW NORMAL.

TONIGHT...LOOK FOR SOME CLEARING MAINLY AFTER SUNSET AS SMALL UPPER
LOW MOVES AWAY AND SURFACE HIGH PRESSURE MOVES IN. THE SURFACE
HIGH LINGERS INTO THURSDAY AFTERNOON AND WITH MORE
SUNSHINE...TEMPERATURES WILL BE SOMEWHAT WARMER THAN TODAY. A FEW
INSTABILITY SHOWERS AND THUNDERSTORMS ARE POSSIBLE IN THE
AFTERNOON. WILL MENTION A SLIGHT CHANCE FOR NOW.

THE NEXT SHORTWAVE ON NORTHWEST FLOW ALOFT WILL DROP SOUTH THROUGH
SASKATCHEWAN THURSDAY NIGHT AND MONTANA ON FRIDAY WITH A COLD
FRONT. MODELS HAVE DIFFERED FROM RUN TO RUN AS TO HOW MOIST OF A
FRONT THIS WILL BE. WILL MENTION A CHANCE OF SHOWERS AND
THUNDERSTORMS MAINLY ON FRIDAY FOR NOW.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...
UPPER LOW NORTH OF THE GREAT LAKES WILL CONTINUE TO USHER IN
COOLER WEATHER OVER THE EXTENDED PERIOD. WITH NORTHWEST FLOW THE AREA
WILL CONTINUE TO SEE COLD FRONTS MOVING THROUGH THE REGION EVERY
FEW DAYS. AFTER THE FIRST FRONTAL PASSAGE FRIDAY THE MODELS PART
WAYS WITH THE TIMING OF THE SECOND FRONT. THE ECMWF HAS THE FRONT
MOVING THROUGH DURING THE DAY ON SUNDAY. THE 00Z GFS WASHES OUT
THE FRONT AND BRINGS IT THOUGH MORE SUNDAY NIGHT. AS OF NOW WENT
WITH A BLEND THE 00Z GFS AND 12Z ECMWF SOLUTIONS AND LEFT A
GRADUALLY REDUCING CHANCE OF SHOWERS.

AFTER THIS FRONT MOVES THROUGH THE REGION EXPECT ANOTHER SHORT
WAVE TO PUSH THROUGH THE REGION MONDAY MORNING THROUGH THE MONDAY
EVENING TIME FRAME. THE ECMWF HAS THIS FEATURE AND CONTINUING TO
SHOW A CHANCE OF SHOWERS AND THUNDERSTORMS ON MONDAY IN THE WESTERN
ZONES. THE GFS HAS BACKED OFF OF THIS SHORTWAVE FEATURE FOR MONDAY
AND DRIED THIGHS OUT SOMEWHAT. THIS IS A DIFFERENT SOLUTION FROM
THE PREVIOUS GFS RUNS SO WILL LEAVE A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS IN THE FORECAST FOR MONDAY UNTIL THE MODELS CAN COME
TO SOME BETTER AGREEMENT. AFTER MONDAY THE UPPER TROFF STARTS TO
SHIFT TO THE EAST AND AN UPPER RIDGE BUILDS IN FROM THE WEST. THE
RESULT WILL BE WARMER TEMPERATURES CLOSER TO WHAT CLIMATOLOGICAL
NORMALS SHOULD BE FOR LATE JULY. THIS TRANSITION WILL BE GRADUAL
AND SEEMS AT THIS TIME TO BE WHAT IS REDUCING CONFIDENCE TO BELOW
AVERAGE/POOR IN THE LONG TERM ESPECIALLY PAST MONDAY NIGHT.
GHICKS/RSMITH

&&

.AVIATION...
VFR CONDITIONS ACROSS ALL TERMINALS WITH PARTLY TO MOSTLY CLOUDY
CONDITIONS DURING THE DAY. WITH DAYTIME HEATING AND A LITTLE
INSTABILITY ALONG WITH A PASSING UPPER LEVEL DISTURBANCE...SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS ARE POSSIBLE AT THE TERMINALS
THIS AFTERNOON. EXPECT THE LIGHT NORTH NORTHWEST WINDS TO INCREASE
UP TO 10 TO 20 KTS DURING THE AFTERNOON AND THEN TAPERING OFF
AFTER SUNSET. HICKS/RSMITH

&&

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

&&

WEATHER.GOV/GLASGOW