Area Forecast Discussion
Issued by NWS Glasgow, MT

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000
FXUS65 KGGW 282103
AFDGGW

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

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SUNDAY
NIGHT...

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 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: HIGH MVFR TO VFR.

SYNOPSIS: PARTIAL CLEARING IS EXPECTED THIS EVENING BEFORE
ANOTHER DISTURBANCE SLIDES OUT OF CANADA...BRINGING LOWER CIGS AND
POTENTIAL FOR SNOW SHOWERS TONIGHT INTO SUNDAY MORNING.

CIGS: SCT-BKN MID LEVEL CLOUDS THIS EVENING...ANOTHER ROUND OF LOW
VFR/HIGH MVFR CIGS EXPECTED TONIGHT INTO SUNDAY.

VSBY: MAINLY UNRESTRICTED. POSSIBLE MVFR WITH LIGHT SNOW SHOWERS
EARLY THIS AFTERNOON AND AGAIN TONIGHT INTO SUNDAY.

WINDS: WEST-NORTHWEST 5-15KTS.

GILCHRIST

&&

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

&&

$$

WEATHER.GOV/GLASGOW








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