Area Forecast Discussion
Issued by NWS Glasgow, MT

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000
FXUS65 KGGW 231620 AAA
AFDGGW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
920 AM MST SUN NOV 23 2014

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH TUESDAY...

THE UPPER AND LOWER TROUGHS HAVE MOVED OFF TO THE EAST THIS
MORNING. THE EFFECT HAS BEEN TO DIMINISH WIND AND SNOWFALL OVER
THE WESTERN COUNTIES. SO FOR THE UPDATE WILL DROP VALLEY...
GARFIELD AND PHILLIPS COUNTIES FROM THE WINTER ADVISORY.
ELSEWHERE...BEGINNING WITH VALLEY AND GARFIELD COUNTIES...LIGHT
SNOW IS STILL FALLING AND WIND REMAINS STRONG. THOSE SITES THAT
MEASURE VISIBILITY SHOW SNOW AND BLOWING SNOW STILL AFFECTING
EASTERN COUNTIES. SO WILL LET THEM CONTINUE FOR NOW. ANOTHER EDIT
WAS TO DROP MAXIMUM TEMPERATURES A BIT BASED ON CAA FROM THE
NORTHEAST. SCT

PREVIOUS DISCUSSION...
SURFACE LOW OVER SOUTHEAST SASKATCHEWAN WITH TIGHT GRADIENT AND
COLD AIR ADVECTION OVER NORTHEAST MONTANA PRODUCING VERY STRONG
WINDS OVER THE REGION THIS MORNING. SOME BANDS OF LIGHT SNOW ARE
ALSO BEGINNING TO WRAP INTO THE NORTHEAST FOR THE POTENTIAL FOR
BLOWING SNOW TO INCREASE. WILL THUS CONTINUE THE BLOWING SNOW
ADVISORY ALONG WITH THE LAKE WIND ADVISORY.

SYSTEM MOVES QUICKLY EAST TODAY WITH SNOWFALL ENDING BY LATE
AFTERNOON. TOTAL ACCUMULATION IS EXPECTED TO BE AROUND AN INCH OR
LESS. NEXT UPPER WAVE DROPS THROUGH THE NORTHERN ROCKIES TONIGHT
SENDING AN IMPULSE ALONG THE BOUNDARY OVER CENTRAL MONTANA. AS THE
BOUNDARY FLEXES EAST COULD SEE A LITTLE LIGHT SNOW OVER THE
SOUTHWEST ZONES TONIGHT INTO MONDAY MORNING.

A WEAK CHINOOK PUSHES THE BOUNDARY EASTWARD MONDAY NIGHT BEFORE
ANOTHER CLIPPER DROPS OUT OF ALBERTA. A LITTLE SNOW IS POSSIBLE AS
THE SYSTEM CROSSES NORTHEAST MONTANA ON TUESDAY. EBERT

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
HUDSON BAY LOW WILL ESTABLISH ITSELF BY TUESDAY AND WILL ALLOW
SEVERAL SUB-TROUGHS TO JOG DOWN FROM THE NORTHERN PRAIRIE
PROVINCES AND PINWHEEL AROUND IT. TO THE WEST A LARGE RIDGE HAS
DEVELOPED OVER THE NORTHEAST PACIFIC AND ALLOWS ITS INFLUENCE TO
BE FELT OVER THE COAST OF CALIFORNIA...THE PACIFIC NORTHWEST...
AND BRITISH COLUMBIA. NORTHEAST MONTANA WILL BE CAUGHT BETWEEN THE
INFLUENCE OF THESE TWO FEATURES THROUGHOUT THE LONG RANGE. SEVERAL
MESO-TROUGHS WILL PASS THROUGH THE AREA AND ALLOW THE ARCTIC
BOUNDARY TO WAFFLE BACK AND FORTH ACROSS THE CWA. TIMING OF THE
BOUNDARY WILL BE ALMOST IMPOSSIBLE AS RELATIVE MEASURE OF
PREDICTABILITY IS NEAR ZERO THROUGHOUT THE LONG RANGE AND STANDARD
DEVIATION OF THE 500 MB HEIGHT ENSEMBLE IS REACHING 80 TO 100
METERS AT TIMES. EVEN AMONG MULTI MODEL MEMBERS CONSISTENCY IS
POOR IN ALL BUT THE LARGEST OF FEATURES.

THIS BEING SAID...THERE DOES LOOK TO BE SUFFICIENT ENOUGH MOISTURE
IN AN ATMOSPHERIC RIVER OVERRUNNING THE FRONTAL BOUNDARY TUESDAY
NIGHT THROUGH ROUGHLY THURSDAY TO OVERSPREAD A WIDE AREA AND GRAZE
AT LEAST A PART OF THE CWA. OVERRUNNING EVENTS OF THESE KINDS CAN
BE TRICKY AND PRESENT VARIOUS PRECIPITATION TYPE CHALLENGES.
SO...WHILE THE DOMINANT PRECIPITATION TYPE WILL LIKELY BE
SNOW...RAIN AND FREEZING RAIN CAN NOT RULED OUT YET AND WILL NEED
TO BE FURTHER INVESTIGATED DURING LATER SHIFTS. GAH

&&

.AVIATION...
LOW CEILINGS DOWN TO 1500 FT WITH REDUCED VISIBILITY DOWN TO A
MILE OR LESS WILL PREVAIL OVER MUCH OF THE AREA THROUGH NOON
TODAY AS AN AREA OF LIGHT SNOW SHOWERS WITH NORTHWEST WINDS OF 20
KTS GRADUALLY MOVES EASTWARD. SNOW SHOULD DECLINE AND FLIGHT
CATEGORY IMPROVE FROM WEST TO EAST AFTER NOON TODAY AS STORM
SYSTEM MOVES EASTWARD. SNOW IS INTERMITTENT WITH PERIODS OF GOOD
VISIBILITY AND IMPROVED CEILINGS. WINDS HAVE BEEN GUSTING TO AT 30
TO 40 KTS AND WILL REMAIN ELEVATED UNTIL LATER THIS AFTERNOON.
MARTIN


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 5 PM MST THIS AFTERNOON FOR FORT PECK
LAKE FOR CENTRAL AND SOUTHEAST PHILLIPS...CENTRAL AND SOUTHERN
VALLEY...GARFIELD...MCCONE...PETROLEUM.

WINTER WEATHER ADVISORY UNTIL 2 PM MST THIS AFTERNOON FOR
DANIELS...DAWSON...EASTERN ROOSEVELT...MCCONE...PRAIRIE...
RICHLAND...SHERIDAN...WESTERN ROOSEVELT...WIBAUX.

&&

$$

WEATHER.GOV/GLASGOW





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