Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 010349
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
849 PM MST SAT FEB 28 2015

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH MONDAY...

UPDATE...
TEMPERATURE READINGS DROPPING QUICKLY IN THE NORTHEAST CORNER
THEREFORE AN ADJUSTMENT LOWER WAS REQUIRED IN THAT AREA. CLOUDS
WILL CONTINUE TO SPREAD OVER THE REGION FROM THE NORTHWEST TO THE
SOUTHEAST. UPSTREAM SNOW SHOWERS WERE NOTED AT MOST LOCATIONS WILL
KEEP THE POPS AS IS FOR TONIGHT AND OVERNIGHT. OTHERWISE NO OTHER
CHANGES WERE NEEDED AT THIS TIME.         PROTON


PREVIOUS DISCUSSION...
A COLD NORTHWESTERLY FLOW ALOFT WILL CONTINUE OVER
NORTHEAST MONTANA THROUGH THE SHORT TERM. AN UPPER LEVEL
DISTURBANCE IN THIS FLOW WILL BRING INCREASING POTENTIAL FOR LIGHT
SNOWFALL FROM NORTH TO SOUTH ACROSS THE AREA TONIGHT. DO NOT
EXPECT MUCH IN THE WAY OF ACCUMULATIONS WITH THIS FEATURE...BUT
CONFIDENCE IS GOOD IN SOME LIGHT SNOWFALL. THUS TRENDED UP POPS
TOWARD SCATTERED CATEGORY...ESPECIALLY OVER MORE UPSLOPE PRONE
AREA SUCH AS THE OPHEIM AREA AND THE BIG SHEEP MOUNTAINS.

SUNDAY EXPECT A FEW LINGERING LIGHT SNOW SHOWERS THROUGH THE
DAY...BUT OVERALL DECREASING POTENTIAL AS THE DAY WEARS ON. AGAIN
MORE FAVORED AREAS FOR SNOW SHOWERS WILL BE UPSLOPE PRONE AREAS
SUCH AS THE BIG SHEEP MOUNTAINS AND THE HIGHER TERRAIN OF SOUTHERN
WIBAUX COUNTY.

SUNDAY NIGHT WEAK RIDING BETWEEN SYSTEMS WILL MAKE FOR DRY
CONDITIONS. SKIES WILL PARTIALLY CLEAR...MAKING FOR GOOD
RADIATIONAL COOLING AND A RETURN TO BELOW NORMAL TEMPERATURES. GILCHRIST


.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
ON MONDAY AND MONDAY NIGHT AN ENERGIZED TROUGH LOOKS TO SWING
ACROSS THE NORTHERN HIGH PLAINS...BUT 12Z GUIDANCE CONTINUES TO
SUPPORT THE IDEA OF HAVING THE BETTER DYNAMICS AND MORE ABUNDANT
MOISTURE TO THE SOUTH AND WEST OF THE CWA. NEVERTHELESS...THE
TROUGH MAY PROVIDE ENOUGH DYNAMIC FORCING FOR ASCENT TO PRODUCE
SOME LIGHT SNOW FOR A TIME ACROSS THE REGION AND SO WILL MAINTAIN
SLIGHT CHANCE TO CHANCE POPS FOR MONDAY AND MONDAY NIGHT.

THE MAIN STORY FOR TUESDAY INTO WEDNESDAY WILL BE AN ARCTIC AIR
MASS THAT SETTLES IN WHILE THE TROUGH SLIDES EAST. THE CORE OF THE
ARCTIC HIGH MAY PASS EAST OF THE AREA AND INTO THE DAKOTAS...BUT
THE 12Z ECMWF STILL PAINTS 850MB TEMPERATURES IN THE -20C TO -25C
RANGE NEAR THE CANADIAN BORDER AND ALONG THE NORTH DAKOTA BORDER
FOR TUESDAY AFTERNOON INTO TUESDAY NIGHT. THIS WILL MEAN THAT
HIGHS ON TUESDAY WILL ABSOLUTELY STRUGGLE TO GET OUT OF THE SINGLE
DIGITS. TUESDAY NIGHT IS MORE COMPLICATED. WHILE THIS IS WHEN THE
COLDEST 850MB TEMPERATURES WILL BE OVERHEAD...IT IS STILL UNCLEAR
AS TO THE PRECISE TIMING OF CLEARING. AS SUCH CLOUD COVER
FORECASTS WILL NEED CLOSE ASSESSMENT OVER THE NEXT COUPLE OF DAYS.
FASTER CLEARING WOULD MEAN MORE EFFICIENT RADIATIONAL COOLING
WHILE SLOWER CLEARING WOULD MEAN A SOMEWHAT MILDER NIGHT. TIGHT
PRESSURE GRADIENT WILL MAKE FOR BLUSTERY WINDS AS WELL WHICH WHILE
MAY SERVE TO KEEP THE BOUNDARY LAYER MIXED...COULD PRODUCE
BITING...EVEN DANGEROUS WIND CHILLS. LACK OF SNOW COVER WILL ALSO
LIMIT HOW COLD IT GETS BUT WITH ALL THESE FACTORS
CONSIDERED...CAN EASILY SEE LOWS WELL BELOW ZERO AND A WIND CHILL
ADVISORY SEEMS ALL BUT CERTAIN AT THIS POINT.

MODELS SHOW 850MB TEMPERATURES MODERATING IN THE WESTERN ZONES BY
WEDNESDAY...BUT TAKING A LITTLE LONGER IN THE EASTERN ZONES. AS
SUCH...NOT CONVINCED THAT WEDNESDAY WILL BE MUCH WARMER THAN
TUESDAY...ESPECIALLY WHERE MIXING IS LIMITED. THE GOOD NEWS IS
MODELS ARE SUGGESTIVE OF A LARGE UPPER RIDGE BECOMING ESTABLISHED
OVER THE WESTERN CONUS BY THE END OF THE WEEK WHICH SHOULD RESULT
IN SUBSTANTIALLY WARMER TEMPERATURES. MALIAWCO


PREVIOUS LONG TERM DISCUSSION...
SYNOPTIC SET UP... LONG RANGE BEGINS WITH WITH A COLD CORE TROUGH
RUNNING FROM THE NORTHWEST TERRITORIES THROUGH THE CANADIAN
PRAIRIES AND MONTANA AND DAKOTA HIGH PLAINS. THIS TROUGH BECOMES
PROGRESSIVELY WARMER OVER THE ROCKIES AND RUNS DOWN INTO THE
DESERT SOUTHWEST. A LARGE RIDGE IS PRESENT OVER THE NORTHEAST
PACIFIC AND RUNS FROM OFF THE COAST OF CALIFORNIA TO THE ALASKAN
PANHANDLE. NORTHERN FLOW RESIDES BETWEEN THESE TWO LARGE FEATURES
AND RUNS FROM BRITISH COLUMBIA TO THE PACIFIC NORTHWEST.

MONDAY NIGHT THROUGH TUESDAY NIGHT... VERY BEGINNING OF THESE
PERIODS STARTS WITH A COLD BLAST AND SUBSEQUENT ISOLATED TO
SCATTERED SNOW SHOWERS MONDAY NIGHT. THE COLD SHOULD HANG IN
THROUGH AT LEAST TUESDAY NIGHT WITH DRY HIGH SURFACE PRESSURE
DURING THE LAST 24 HOURS.

WEDNESDAY THROUGH THURSDAY NIGHT... THESE PERIODS WILL BE MARKED
BY DRY AND WARMING TEMPERATURES. FLOW WILL BECOME NORTHERN TO
NORTHWESTERN AS THE PACIFIC RIDGE SETTLES IN OVER THE WESTERN HALF
OF THE CONUS. EXPECT SOME DOWN-SLOPE WINDS DURING THIS TIME AS WEAK
CHINOOKS BEGIN TO AFFECT THE AREA. CONFIDENCE TO THIS POINT IS
ABOVE AVERAGE.

FRIDAY ONWARD... BULK OF THE WESTERN CONUS RIDGE WILL REMAIN IN PLACE
DURING THIS TIME. HOWEVER THE PERIPHERIES SUCH AS MONTANA MAY BE
JUST CLOSE ENOUGH TO THE EDGE OF THE NORTHWEST FLOW TO RECEIVE
SOME MOISTURE AND A SLIGHT COOL DOWN FROM A HINTED BACK DOOR FRONT
FRIDAY AND FRIDAY NIGHT. THIS EFFECT DISAPPEARS VERY QUICKLY AS
THE MAJORITY OF SOLUTIONS WARM MONTANA UP EVEN MORE LEADING INTO
SATURDAY ONWARD. CONFIDENCE AT THIS POINT IS AVERAGE. GAH


&&

.AVIATION...
FLIGHT CATEGORY: MVFR TO VFR. TEMPORARY IFR POSSIBLE.

SYNOPSIS: A WEAK WAVE WILL MOVE IN FROM THE NORTHWEST AND BRING
LOWERING CLOUDS WITH ISOLATED TO SCATTERED SNOW SHOWERS. MAIN
IMPACTS SHOULD BE BETWEEN 06 TO 18Z. AFTERWARD SKIES SHOULD BEGIN
TO CLEAR FROM WEST TO EAST DURING THE AFTERNOON WITH PRIMARY VFR.

CIGS: SCT-BKN LOW LEVEL CLOUDS INTO MVFR AFTER 09Z. CLOUDS WILL
DROP BELOW 2 KFT MAKING FUEL LOADING COMMON FOR ALL TERMINALS OTHER
THAN KGGW THROUGH 18Z.

VSBY: LIGHT SNOW SHOWERS WILL BRING VSBY RESTRICTIONS FROM 06Z TO
18Z. SNOW WILL COMMONLY REDUCE VSBY TO 5 TO 6 SM AS IT PASSES.
HEAVIER BANDS WILL TEMPORARILY BRING VSBY DOWN TO 2 TO 3 SM AS IS
EVIDENT UPSTREAM IN SWIFT CURRENT.

WINDS: WEST-NORTHWEST 5-15KTS.

GAH


&&

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

&&

$$

WEATHER.GOV/GLASGOW




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