Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 021533
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
933 AM MDT WED SEP 2 2015

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH FRIDAY...
UPDATE...
THE INHERITED FORECAST IS WELL ON TRACK. NEAR TERM WINDS WERE
REFRESHED USING THE LATEST HIGH RESOLUTION MODEL
BLENDS...OTHERWISE FEW CHANGES FOR NOW. MALIAWCO

PREVIOUS DISCUSSION...

SOUTHWEST FLOW WILL PREVAIL OVER NORTHEAST MONTANA THE NEXT FEW
DAYS AS AN UPPER TROUGH/LOW DIGS SOUTH FROM BRITISH COLUMBIA INTO
THE PACIFIC NORTHWEST.

THE SW FLOW ALOFT WILL INITIALLY BRING HOT AND DRY AIR INTO THE
FORECAST AREA TODAY. MOST AREAS WILL HAVE HIGHS WELL INTO THE 90S
WITH A FEW AREAS IN THE SOUTHEAST APPROACHING 100 DEGREES. A LOW
PRESSURE SYSTEM WILL MOVE ACROSS ALBERTA AND SASKATCHEWAN THIS
AFTERNOON AND EVENING. THE SYSTEM WILL BRING A COLD FRONT THROUGH
NORTHEAST MONTANA IN THE LATE AFTERNOON AND EARLY EVENING. WITH
LIMITED MOISTURE...MOST AREAS WILL HAVE A DRY FRONTAL PASSAGE.

THE FRONT BECOMES QUASI-STATIONARY IN THE WESTERN DAKOTAS TONIGHT.
WITH MOISTURE STAYING TO THE WEST...MOST AREAS WILL REMAIN DRY
OVERNIGHT.

THE COLD FRONT WILL BE SLOW TO MOVE EAST ON THURSDAY WHICH WILL
RESULT IN A TEMPERATURE GRADIENT ACROSS EASTERN MONTANA WITH HIGHS
IN THE 70S WEST AND 80S EAST. MOISTURE AND SHORTWAVES REMAIN TO
THE WEST WHICH WILL KEEP THE WEATHER DRY OVER THE FORECAST AREA.

THE UPPER TROUGH WILL DIG SOUTH TO CALIFORNIA AND NEVADA THURSDAY
NIGHT AND FRIDAY. A SHORTWAVE TROUGH WILL MOVE NORTHEAST ALONG THE
MONTANA/DAKOTAS BORDER THURSDAY NIGHT AND FRIDAY. MODELS ARE
TIMING THE MOISTURE WITH THIS WAVE AT DIFFERENT TIMES FOR
NORTHEAST MONTANA. WILL BROADBRUSH A CHANCE OF SHOWERS AND
THUNDERSTORMS FOR NOW. FORRESTER


.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...

SYNOPTIC SET UP... LONG RANGE BEGINS WITH A SMALL DIFFERENCE IN
MODELS WHICH IS QUICKLY EVOLVING APART IN MODELS. AREAS OF
SIMILARITY RESIDE ON THE HOT HIGH PRESSURE OVER THE FOUR CORNERS
WITH A RIDGE RUNNING INTO THE DAKOTAS AND ONTARIO. A LARGE COLD
TROUGH RUNS FROM NORTHERN ALBERTA THROUGH SOUTHERN BRITISH
COLUMBIA AND THEN CHANGES ITS BASE PLACEMENT DEPENDING ON MODEL.
GEM AND GFS DROP THE BASE OF THE TROUGH OVER NORTHERN CALIFORNIA
WHILE THE EC AND DGEX PLACE THE LOW FARTHER NORTH OVER THE
PACIFIC NORTHWEST.

FRIDAY NIGHT THROUGH SUNDAY NIGHT... DIFFERENCES BETWEEN THE
MODEL SETS IN THE BASE OF THE TROUGH TO THE WEST ARE SUBTLE AT
THIS RANGE BUT LEAD TO DOWNRIGHT CHAOS UPSTREAM IN SOUTHWEST FLOW
LOCATED OVER NORTHEAST MONTANA. DIFFERENCES IN MODEL QPF BASED ON
PLACEMENT OF THE DOWNSTREAM JETS VARY FROM A QUARTER INCH TO 4
INCHES OVER 60 HOURS. CURRENTLY THE BULK OF THE PRECIPITATION
LOOKS TO FALL OVER SATURDAY NIGHT AND SUNDAY WHEN THE BASE OF THE
SYNOPTIC TROUGH ITSELF MOVES THROUGH AND A TROWAL MAY/OR MAY NOT
SET UP BEHIND IT. A CLOSED LOW WILL ALSO FORM AT THE SURFACE
SOMEWHERE BETWEEN SOUTHERN MONTANA AND SOUTHERN SASKATCHEWAN.
THIS WIDE SPREAD OF RANGE MEANS THAT SURFACE WIND DIRECTIONS AND
SPEEDS ARE VERY MUCH SUBJECT TO CHANGE OVER THE NEXT FEW FORECAST
CYCLES. REGARDLESS OF THESE PLACEMENT PROBLEMS COOLER CONDITIONS
WITH AT LEAST LIMITED EXTENDED RAIN IS ANTICIPATED DURING THESE
PERIODS. CONFIDENCE IS BELOW AVERAGE.

MONDAY ONWARD... AS THE BASE OF THE TROUGH EXITS THE AREA COOL
ZONAL FLOW WILL TAKE OVER. EXPECT CONDITIONS TO REMAIN DRY WITH A
SLIGHT WARMING TREND. GAH



&&

.AVIATION...

A LEE SIDE SURFACE TROUGH SLIDES INTO NORTHEAST MONTANA
TODAY...FOLLOWED CLOSELY BY A COLD FRONT.

SOUTHERLY WINDS WILL RELAX AND BECOME VARIABLE LATER TODAY. THEN
AS THE SURFACE TROUGH MOVES INTO THE DAKOTAS...WIND BEHIND THE
TROUGH WILL STRENGTHEN AND BECOME NORTHERLY TONIGHT AND THURSDAY.

THE MAIN EFFECT OF THE COLD FRONT WILL BE TO INCREASE SKY COVER
TODAY THROUGH THURSDAY. THE PATTERN WILL REMAIN DRY.

SCT


&&

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

&&

$$

WEATHER.GOV/GLASGOW


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