Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 052115
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
315 PM MDT TUE MAY 5 2015

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH THURSDAY...
BENEFICIAL RAIN EXPECTED FOR PARTS OF THE AREA MAINLY TO FALL
WEDNESDAY.

AN UPPER LOW OVER THE PACIFIC NW IS EXPECTED TO ELONGATE AND SPLIT.
ANOTHER UPPER LOW OVER THE SOUTHERN ROCKIES IS SENDING MOISTURE
INTO MONTANA THIS AFTERNOON. MODELS HAVE NOT BEEN VERY CONSISTENT
WITH DETAIL OVER THE NEXT 48 HOURS...SO DETAILS ON RAINFALL AMOUNTS
ARE NOT VERY CONFIDENT.

SURFACE TROUGH PROVIDING LIFT FOR SHOWERS AND THUNDERSTORMS TO
DEVELOP OVER FERGUS AND BLAINE COUNTIES THIS AFTERNOON THAT ARE
MOVING NORTH-NORTHEAST. SOME GUSTY WINDS MAY ACCOMPANY THE STORMS
THROUGH 9 PM FOR THE WESTERN ZONES. THESE EVENING SHOWERS SHOULD BE
ENOUGH TO STABILIZE THINGS IN THE AREA AND DIMINISH THE CHANCES FOR
PRECIPITATION LATER IN THE NIGHT.

WEDNESDAY...THE MODELS THEN PUSH MOISTURE EAST WITH THE GFS FASTEST
AND ECMWF SLOWEST. WENT THE MIDDLE ROAD AND NAM ALSO HAD THIS
SIMILAR SPEED. EASTERN ZONES WILL HAVE THE BEST SHOT FOR RAIN
ESPECIALLY IN THE AFTERNOON WITH AMOUNTS TOPPING A QUARTER INCH
(0.25") IN MOST PLACES.

WEDNESDAY NIGHT...THINGS CONTINUE TO PROGRESS EAST WITH LEFTOVER
LIGHT SHOWERS CONFINED TO AREAS NEAR THE NORTH DAKOTA BORDER.
AGAIN...THE GFS IS FASTEST AND ECMWF SLOWEST.

THURSDAY...SURFACE HIGH PRESSURE RIDGES INTO THE AREA ALLOWING FOR
SOME SUNSHINE. BUT WITH A COOL AIRMASS IN PLACE...TEMPERATURES ARE
ONLY EXPECTED TO TOP OUT IN THE 50S MOST PLACES. TFJ


.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY...

WITH RELATIVELY GOOD MODEL AGREEMENT IN THE EARLIER PORTION OF
THE EXTENDED FORECAST PERIOD...FELT IT WAS WARRANTED TO ADJUST AND
UPDATE THE FORECAST FOCUSING MAINLY ON THE POPS AND WEATHER
GRIDS.

THURSDAY NIGHT THROUGH SUNDAY NIGHT...THE GENERAL SYNOPTIC
PATTERN IN THE EXTENDED PERIOD WILL EVOLVE RATHER SLOWLY WITH NE
MONTANA UNDER THE INFLUENCE OF THE NORTHERN STREAM TROUGH OVER
CENTRAL CANADA BATTLING THE WEAK SOUTHERN STREAM RIDGE OVER THE
CENTRAL US STATES. CONDITIONS SEEM FAVORABLE TO ALLOW FOR
ACCUMULATING RAIN OVER OUR SOUTHERN ZONES FRIDAY NIGHT THROUGH
SATURDAY NIGHT.

AFTER SUNDAY NIGHT...THE MODELS BECOME VERY MUDDLED AND CONFUSED
WITH NO RHYME...REASON...OR CONSENSUS TO BE SEEN TO START NEXT
WEEK. CHOSE TO LEAN MORE TOWARD A MODEL BLEND WITH CLIMO FOR THIS
LATTER PERIOD OF THE EXTENDED. BMICKELSON

PREVIOUS LONG TERM DISCUSSION...THE EXTENDED FORECAST PERIOD
BEGINS THURSDAY EVENING WITH NORTHEAST MONTANA BETWEEN A SPLIT
TROUGH PATTERN. THE SOUTHERN WAVE WILL BE A CLOSED LOW SPINNING
OVER CENTRAL CALIFORNIA AND A LONG-WAVE TROUGH CENTERED OVER
NORTHERN SASKATCHEWAN AND MANITOBA. LOCALLY CONDITIONS WILL BE DRY
OVERNIGHT. THEN BY FRIDAY EVENING THE SOUTHERN LOW WILL HAVE MOVED
INTO THE SOUTHWEST DESERT WHILE THE NORTHERN WAVE BEGINS TO
DEVELOP A TROUGH EXTENSION REACHING SOUTH OVER MONTANA. THIS
NORTHERN LOW WILL BEGIN TO PUSH COOLER TEMPERATURES SOUTH INTO OUR
AREA FOR THE WEEKEND. A WEAK FRONT COULD PRODUCE SOME SHOWER
ACTIVITY THROUGH THE WEEKEND. HOWEVER MOST OF THE ENERGY AND QPF
WILL REMAIN SOUTH TIED UP WITH THE SOUTHERN TROUGH. 850MB
TEMPERATURES WILL HOVER NEAR 0C WHILE 700MB TEMPERATURES TREND
CLOSE TO -10C. SO EXPECT HIGHS IN THE 50S AND LOWS IN THE 30S.

EARLY NEXT WEEK THE SOUTHERN TROUGH RETROGRADES AND MOVES TO THE
NORTHWEST TO KEEP THOSE COOL TEMPERATURES GOING WITH ISOLATED
SHOWERS. THE PATTERN BECOME LESS CERTAIN AFTER THE WEEKEND...BUT
THE WARMER AIR WILL HAVE A HARD TIME REACHING NORTH INTO THE
REGION. SO OVERALL...EXPECT BELOW NORMAL TO NEAR NORMAL
TEMPERATURES INTO MID-WEEK. SCT


&&

.AVIATION...

VFR CONDITIONS WILL PREVAIL THROUGHOUT MOST OF THE TAF CYCLE WITH
RAIN SHOWERS AND NEAR MVFR CONDITIONS POSSIBLE
OVERNIGHT...INCLUDING A FEW THUNDERSTORMS THIS EVENING WEST...THEN
AGAIN WEDNESDAY AFTERNOON EAST. IF A STORM HAPPENS TO PASS
DIRECTLY OVER A TAF SITE...MVFR TO BRIEF IFR CONDITIONS MAY BE
POSSIBLE. BMICKELSON


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 9 PM MDT THIS EVENING FOR FORT PECK
LAKE FOR CENTRAL AND SOUTHEAST PHILLIPS...CENTRAL AND SOUTHERN
VALLEY...GARFIELD...MCCONE...PETROLEUM.

&&

$$

WEATHER.GOV/GLASGOW





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