Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 020253
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
853 PM MDT WED APR 1 2015

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH FRIDAY...
REMOVED FIRE WEATHER HIGHLIGHTS WITH LATEST UPDATE. CLOUDS HAVE
HELD AT BAY A BIT MORE THAN EXPECTED SO LOWERED SKY A BIT AND
LOWERED POPS BUT KEPT THE INCREASING TREND. REST OF FORECAST
LOOKED GOOD. TFJ

543 PM UPDATE...WIND STRENGTH HAS DIMINISHED TO THE POINT THAT
THE HIGH WIND WARNING FOR SOUTHWEST PHILLIPS COUNTY HAS BEEN
CANCELLED. WIND IS EXPECTED TO REMAIN ELEVATED ALL NIGHT AS THE
SURFACE LOW AND THE WRAP-AROUND PRECIPITATION MOVE INTO THE AREA
LATER TONIGHT. RELATIVE HUMIDITIES HAVE RISEN ABOVE CRITICAL
VALUES IN SOME AREAS OF THE RED FLAG. THEREFORE CANCELLED THE RED
FLAG FOR ZONES 134 AND 135 EARLY.

PREVIOUS DISCUSSION...
THE CANADIAN STACKED STORM SYSTEM THAT SENT A COLD FRONT THROUGH
THE REGION TODAY MOVES EAST INTO MANITOBA TONIGHT. THIS WILL BRING
SOME WRAP-AROUND MOISTURE INTO NORTHERN PORTIONS OF NORTHEAST
MONTANA TONIGHT AND THURSDAY MORNING. THE SYSTEM ALSO PRODUCED A
STRONG SURFACE GRADIENT FOR STRONG NORTHWEST WINDS. WINDS ALOFT
WILL LINE UP WITH THE SURFACE WINDS AND EFFICIENT MIXING WILL
MAINTAIN THE STRONGER GUSTS. SINCE THE SURFACE LOW ROTATES
PARTIALLY BACK INTO THE AREA...WINDS WILL REMAIN STRONG TONIGHT
THROUGH THURSDAY. THUS THE NPW FOR FORT PECK LAKE WILL CONTINUE
OVERNIGHT. CAA WILL DRIVE TEMPERATURES SLIGHTLY BELOW NORMAL.

TWO HEADLINE PRODUCTS BASED ON THE WIND STRENGTH...HIGH WIND
WARNING FOR SW PHILLIPS CO AND THE RED FLAG WARNING...WILL
CONTINUE THROUGH 03Z THIS EVENING. THE OTHER IS THE NPW FOR FORT
PECK LAKE WHICH GOES UNTIL 00Z FRIDAY.

AN ARCTIC LOW MOVES OVER HUDSON BAY THURSDAY NIGHT AND FRIDAY.
THIS WILL SEND THE STATIONARY BOUNDARY FURTHER SOUTH TO KEEP
TEMPERATURES COOLER THAN OF LATE...BUT ACTUALLY CLOSE TO NORMAL.
WITH AN UPPER RIDGE GROWING MORE AMPLIFIED OUT IN THE FAR
WEST...EXPECT NORTHWEST FLOW ALOFT. WEAK DISTURBANCES IN THAT FLOW
WILL ELEVATE THE CHANCE FOR ISOLATED RAIN OF SNOW SHOWERS. QPF
AMOUNTS WILL REMAIN LOW. SCT

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

GIVEN THE RELATIVE BETTER THAN AVERAGE MODEL AGREEMENT REGARDING
PRECIPITATION AMOUNTS...TIMING...AND PLACEMENT IN THE EXTENDED
FORECAST...FELT IT WAS WARRANTED TO UPDATE THOSE GRIDS THROUGH
EARLY TUESDAY MORNING.

THIS NEXT OPPORTUNITY TO IMPROVE THE EXTENDED FORECAST IS
REGARDING A LARGE STORM SYSTEM FROM THE GULF OF ALASKA AND THE
CANADIAN WEST COAST WHICH WILL MOVE ON SHORE OVER THE PACIFIC
NORTHWEST AND SPREAD OVER THE ROCKY MOUNTAINS WITH MULTIPLE UPPER-
LEVEL LOW CENTERS AND LOBES PINWHEELING THROUGH THE FLOW. MODEL 850
MB TEMPERATURES ALSO DROP A COLD AIR MASS OVER NE MONTANA THEN.
MODEL SURFACE TEMPERATURES ARE TRENDING LOWER. PARAMETERS TO ALLOW
SNOWFALL TO REACH THE GROUND ARE ALSO SUPPORTIVE. GFS FORCING FOR
ASCENT SHOWS THE STRONGEST SIGNATURE FOR LIFT I HAVE SEEN IN A
WHILE. MODEL ENSEMBLE SPREAD ALSO POINTS TO SLIGHTLY BETTER MODEL
CONSENSUS. ALL OF THESE SIGNS POINT TO A PERIOD OF TIME OF
GREATEST IMPACT GENERALLY FROM SUNDAY NIGHT THROUGH TUESDAY
MORNING. GRANTED...MODEL SOLUTIONS CAN SHIFT AROUND AND FLIP FLOP
ON US...BUT FELT COMFORTABLE ENOUGH TO RAISE POPS AND BEGIN
SHOWING SNOW ACCUMULATIONS. BMICKELSON

PREVIOUS LONG TERM DISCUSSION...THE LATEST 00Z GUIDANCE BRINGS IN
A SHORTWAVE UPPER RIDGE ACROSS CENTRAL MONTANA LEADING NORTHWEST
FLOW ALOFT AND A WEAK EMBEDDED SHORTWAVE THROUGH THE CWA FRIDAY
NIGHT INTO SATURDAY. THIS WILL PROVIDE ENOUGH DYNAMIC FORCING FOR
ASCENT TO MENTION SLIGHT CHANCE POPS FOR PORTIONS OF THE REGION. A
SOMEWHAT MORE VIGOROUS SHORTWAVE LOOKS TO FLATTEN THE RIDGE AS IT
TRANSLATES EAST ON SATURDAY NIGHT WHICH WILL BRING A MORE
WIDESPREAD SLIGHT CHANCE OF RAIN SHOWERS TO THE REGION...WITH SOME
SNOW POTENTIALLY MIXING IN NEAR THE CANADIAN BORDERS. GROUND
TEMPERATURES MAY BE TOO WARM TO GET CONCERNED ABOUT
ACCUMULATIONS...THOUGH AN ISOLATED COATING IS CERTAINLY POSSIBLE.

ANOTHER RIDGE IS EXPECTED TO QUICKLY BUILD INTO THE NORTHERN HIGH
PLAINS ON SUNDAY IN THIS RATHER PROGRESSIVE WEATHER PATTERN WHICH
WILL HELP TO BRING DRY CONDITIONS TO THE AREA. AS THE RIDGE AXIS
EXITS THE CWA INTO THE DAKOTAS ON SUNDAY NIGHT THE FLOW ALOFT
ORIENTS SOUTHWEST AND A NEW SHORTWAVE WILL APPROACH...POTENTIALLY
BRINGING THE NEXT ROUND OF RAIN AND/OR MIXED PRECIPITATION. THE
OVERALL SOUTHWEST FLOW/TROUGH PATTERN MAY MAINTAIN UNSETTLED
WEATHER CONDITIONS ACROSS THE REGION THROUGH THE MIDWEEK THOUGH
TIMING AND PLACEMENT UNCERTAINTIES WITH REGARD TO PRECIPITATION
CHANCES BEGIN TO INCREASE AT THIS POINT IN THE FORECAST PERIOD DUE
TO PROGRESSIVE NATURE OF THIS PATTERN. THEREFORE TRENDED POPS
TOWARD CLIMO THROUGH ABOUT MIDWEEK WITH COOL TEMPERATURES COMPARED
WITH WHAT HAVE BEEN RECENTLY OBSERVED.

BEYOND THE MIDDLE OF NEXT WEEK BROAD AGREEMENT EXISTS BETWEEN THE
00Z ECMWF/GFS ON HAVING A LARGE UPPER RIDGE BUILDING INTO THE
WESTERN CONUS. DID HAVE ENOUGH CONFIDENCE AS A RESULT TO INTRODUCE
A DRY FORECAST WITH THE START OF A WARMING TREND. MALIAWCO


&&

.AVIATION...
VFR CONDITIONS WILL RULE THE NIGHT WHILE THE POTENTIAL FOR AN
ISOLATED SHOWER CONTINUES. STEADIER SHOWERS MAY AFFECT THE
TERMINALS THURSDAY MORNING AND MAY BE ACCOMPANIED BY MVFR CIGS.
OTHERWISE WEST WINDS SUSTAINED OF 15 TO 30 KTS WITH GUSTS TO 35
KTS WILL DIMINISH SOME OVERNIGHT TO 10 TO 20 KTS WITH GUSTS TO 25
KTS. MALIAWCO


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 6 PM MDT THURSDAY FOR FORT PECK LAKE
FOR CENTRAL AND SOUTHEAST PHILLIPS...CENTRAL AND SOUTHERN
VALLEY...GARFIELD...MCCONE...PETROLEUM.

&&

$$

WEATHER.GOV/GLASGOW





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