Area Forecast Discussion
Issued by NWS Glasgow, MT

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000
FXUS65 KGGW 050323
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
923 PM MDT MON MAY 4 2015

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH WEDNESDAY...
UPDATE...GOING FORECAST IS IN OVERALL GOOD SHAPE. BIGGEST CHANGE
WAS TO ADD MENTION OF SHOWERS AND THUNDERSTORMS ACROSS THE WEST
TONIGHT. MODELS ARE HINTING AT THE POTENTIAL FOR NOCTURNAL ELEVATED
CONVECTION TONIGHT...AND RADAR IS CONFIRMING THIS POTENTIAL WITH
STORMS DEVELOPING AFTER SUNSET. THUS UPDATED TO ADD LOW POPS AND
MENTION OF SHOWERS AND THUNDERSTORMS. THE REMAINDER OF THE
FORECAST IS UNCHANGED...WITH THE LAKE WIND ADVISORY EXPIRING AT 9
PM. GILCHRIST

PREVIOUS DISCUSSION...
...WET AND COOL TIMES AHEAD...

A CLOSED UPPER LOW OFF THE BRITISH COLUMBIA COAST WILL MOVE INTO THE
PACIFIC NW TUESDAY THEN ELONGATE WEDNESDAY. AN UPPER LOW OVER THE
DESERT SW WILL DRIFT NE AND EVENTUALLY SPREAD A RAINSHIELD OVER THE
EASTERN ZONES WEDNESDAY.

SURFACE LOW PRESSURE OVER THE ROCKIES WILL HELP TO PUMP MOISTURE
NORTH IN OUR DIRECTION OVER THE NEXT COUPLE OF DAYS WHILE ALSO
WARMING THINGS A BIT INTO TUESDAY. MARGINAL INSTABILITY MAY BE
ENOUGH TO TOUCH OFF A SHOWER/STORM OVER THE LITTLE ROCKIES INTO
TUESDAY OTHERWISE IT WILL BE BREEZY.

TUESDAY...THINGS WILL WARM QUICKLY AS 850 MB TEMPS HELP SOME PLACES
WARM TO NEAR 80. HOWEVER SW FLOW WILL HELP TRIGGER EVENING
THUNDERSTORMS OUT AHEAD OF A COLD FRONT OVER THE CENTRAL AND WESTERN
ZONES.

ON WEDNESDAY...THE COLD FRONT MEETS UP WITH THE UPPER LOW/S MOISTURE
AND BRINGS SHOWERS AND ISOLATED STORMS TO THE EASTERN ZONES. THE NAM
IS A BIT MORE AGGRESSIVE WITH FRONTAL LIFT WITH THE FRONT AND THUS
HAS BROUGHT OVER A HALF INCH OF QPF TO THE EASTERN ZONES WEDNESDAY
AFTERNOON. THIS LOOKS OK AS CUT-OFF SYSTEMS SOMETIMES DRIFT WEST OF
WHAT THE MODELS TRACK. RAINFALL SHOULD BE BENEFICIAL FOR THE MOST
PART. TFJ

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...
AFTERNOON UPDATE...LOOKS LIKE A COOLER EXTENDED PERIOD BUT THE
MODELS ARE NOT IN AGREEMENT WITH WHERE THE PRECIPITATION WILL BE
IN THE FRI-SUN TIME FRAME. SURFACE LOW MOVES ACROSS THE GREAT
BASIN WITH A STRONG COLD HIGH PRESSURE DOMINATING FROM CENTRAL SK
AND MB.  THE ONLY MODEL BRINGING WIDESPREAD PRECIP INTO OUR AREA
IS THE 00Z ECMWF WHILE THE OTHERS KEEP MOST OF THE MOISTURE TO OUR
SOUTHERN COUNTIES AND INTO THE BILLINGS CWA. THE ONLY CHANGES OF NOTE
TO THE EXTENDED WAS TO DRY THINGS OUT A LITTLE QUICKER ON THURSDAY
AND TO TWEAK THE POPS FOR THE WEEKEND SYSTEM. FRANSEN

THE UPPER TROUGH/LOW WILL DIG TOWARDS CALIFORNIA WEDNESDAY NIGHT
AND THURSDAY WHILE RIDGE REMAINS TO THE EAST. MEANWHILE...THIS
TROUGH IS EXPECTED TO SPLIT ON THURSDAY. THIS WILL KEEP SOUTHWEST
FLOW ALOFT OVER THE FORECAST AREA INTO THE WEEKEND.

MODEL DIFFERENCES ARE APPARENT IN THE TIMING AND TRACK OF THE
SHORTWAVES WITHIN THE SW FLOW ALOFT. FOR EXAMPLE...THE ECMWF IS
QUICKER THAN THE GFS IN MOVING WEDNESDAY`S SYSTEM TO THE EAST. THE
EC CURRENTLY MOVES THE SYSTEM TO THE EAST BY WEDNESDAY EVENING
WHILE THE GFS LINGERS WRAP AROUND RAIN OVER EASTERN MONTANA
THROUGH THURSDAY AFTERNOON. MEANWHILE...BOTH MODELS BRING A WAVE
INTO CENTRAL MONTANA ON THURSDAY WITH ENOUGH MOISTURE FOR A CHANCE
OF SHOWERS. WILL MAINTAIN CHANCES FOR SHOWERS WEDNESDAY NIGHT AND
THURSDAY AS SEE IF THE MODELS CAN SORT OUT THEIR DIFFERENCES IN
FUTURE RUNS.

SURFACE HIGH BUILDS INTO EASTERN MONTANA THURSDAY NIGHT WHILE A
SHORTWAVE RIDGE MOVES THROUGH THE AREA. EXPECT MAINLY DRY WEATHER
WITH A COOL NIGHT.

ON FRIDAY...NORTHERN BRANCH UPPER TROUGH DIGS INTO MONTANA AND AT
THIS POINT...THE MODELS KEEP IT OVER MONTANA FOR MOST OF THE
WEEKEND. THIS WILL CAUSE THE SOUTHERN BRANCH TROUGH/LOW TO STAY
SOUTH OF THE FORECAST AREA AS IT MOVES EAST OVER THE WEEKEND. IT
IS A CHANGE FROM LAST NIGHT`S MODEL RUNS THAT LIFTED THIS SOUTHERN
LOW OVER MONTANA DURING THE WEEKEND. FRIDAY STILL LOOKS DRY FOR
THE MOST PART AS IT LOOKS LIKE IT WILL BE FRIDAY NIGHT BEFORE THE
MOISTURE FROM THESE SYSTEMS REACHES NORTHEAST MONTANA. ECMWF IS
FASTER THAN THE GFS WITH MOVING THE SYSTEM THROUGH THE AREA.
EITHER WAY... IT LOOKS LIKE A COOL WEEKEND WITH CHANCES OF
SHOWERS. MAYBE COLD ENOUGH FOR SNOW SHOWERS AT TIMES.

FLOW ALOFT TURNS MORE ZONAL SUNDAY AND MONDAY BUT SHORTWAVES IN
THE FLOW ALOFT COULD CONTINUE TO BRING A FEW SHOWERS AT TIMES.
FORRESTER


&&

.AVIATION...
THIS EVENING DOPPLER RADAR IS PICKING UP SCATTERED RAIN SHOWERS
AND ISOLATED THUNDERSTORMS MOVING NORTHEAST IN THE COUNTIES WEST
OF KGGW. SOME OF THESE SHOWERS MAY REACH KGGW BEFORE THEY END PRIOR
TO MIDNIGHT.

OTHERWISE VFR CONDITIONS WILL PREVAIL TONIGHT...WITH CLEAR SKIES
OR A FEW MID TO HIGH CLOUDS.

AFTER 18Z TUE EXPECT AN INCREASE IN CLOUDS WITH AN APPROACHING
WEATHER SYSTEM THAT WILL ARRIVE AFTER 00Z.

SOUTHEAST WINDS WILL REMAIN STRONG THROUGH SUNSET TONIGHT IN THE
20 TO 30 KT RANGE AND DECREASE INTO THE 10 TO 20 KT RANGE
OVERNIGHT. EXPECT WINDS TO PICK UP AGAIN ON TUESDAY FROM THE
SOUTHEAST IN THE 15 TO 30 KT RANGE AFTER 15Z.

&&

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

&&

$$

WEATHER.GOV/GLASGOW





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