High Wind in Montana, November 17 to 18, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
930 PM MST MON NOV 16 2015

...UPDATE AVIATION SECTION
.DISCUSSION...
THE ACTIVE PATTERN IS STILL ON TARGET. WINDS HAVE NOT YET STARTED
ALONG THE ROCKYS, GUSTS HAVE REACHED 54 MPH AT DEEP CREEK, AND 37
MPH AT TWO MEDICINE. DID MAKE SOME TWEAKS TO THE TEMPERATURES AS
SOME VALUES WERE ALREADY AT OR BELOW FORECAST MINS. ONCE THE WINDS
PICK UP...THEY WILL START RISING AGAIN.  DB

&&

.AVIATION...
UPDATED 0430Z.

VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH TUESDAY MORNING.
GUSTY WEST-SOUTHWESTERLY SURFACE WINDS ARE EXPECTED TO DEVELOP AT
ALL TERMINALS, EXCEPT KBZN, DURING THE PREDAWN HOURS OF TUESDAY AND
THEN PERSIST THROUGHOUT THE DAY ON TUESDAY. WINDS SHOULD BE
STRONGEST DURING THE AFTERNOON HOURS AND EVEN PICK UP AND GUST AT
KBZN AFTER 18/00Z. DB

&&

.PREV DISCUSSION...
/ISSUED 550 PM MST MON NOV 16 2015/

TONIGHT THROUGH WEDNESDAY...A VERY ACTIVE PATTERN IS EXPECTED OVER
THE COMING DAYS AS A STRONG UPPER LEVEL JET CURRENTLY OVER THE
PACIFIC PUSHES INLAND TO THE ROCKY MOUNTAINS. ABUNDANT MOISTURE
WILL BRING WIDESPREAD SNOW TO THE MOUNTAINS NEAR THE CONTINENTAL
DIVIDE FROM LATE TONIGHT THROUGH WEDNESDAY. SCATTERED SHOWERS WILL
ALSO MOVE OFF THE ROCKY MOUNTAIN FRONT AND OVER THE PLAINS TUESDAY
NIGHT AND WEDNESDAY. HOWEVER, THE MAIN IMPACT IN THE SHORT TERM
PERIOD WILL BE VERY STRONG WINDS ACROSS A LARGE PORTION OF THE
FORECAST AREA. HIGH WIND WARNINGS HAVE BEEN ISSUED FOR THE ROCKY
MOUNTAIN FRONT, FOR ALL OF CENTRAL AND NORTH CENTRAL MONTANA AND
NORTHERN PORTIONS OF SOUTHWEST MONTANA. MODEL RUNS HAVE BEEN
CONSISTENTLY SHOWING THE WINDS AT MOUNTAIN TOP LEVEL AND ABOVE
COULD BE AS STRONG AS 90 KNOTS. SURFACE PRESSURE GRADIENTS ALONG
THE ROCKY MOUNTAIN FRONT WILL ALSO BE EXTREMELY STRONG. AM
EXPECTING TOP WIND GUSTS ALONG THE ROCKY MOUNTAIN FRONT TO HIT 100
MPH WITH 70 MPH WIND GUSTS LIKELY OVER THE PLAINS. THERE IS ALSO A
RISK THAT WINDS COULD EXCEED THESE LEVELS. THE STRONG DOWNSLOPE
WINDS AND SHORTWAVE RIDGING ALOFT WILL ALLOW HIGH TEMPERATURES TO
RISE BACK ABOVE SEASONAL AVERAGES ON TUESDAY BUT THEY WILL DIP
BACK DOWN INTO THE 30S AGAIN ON WEDNESDAY AS THE NEXT COLD FRONT
SWEEPS THROUGH THE REGION. MPJ

WEDNESDAY NIGHT THROUGH MONDAY...CHILLY AND BREEZY CONDITIONS WILL
START THIS FORECAST PERIOD AS OUR REGION WILL BE UNDER NORTHWEST
FLOW ALOFT BEHIND THE WEATHER SYSTEM THAT PUSHES THROUGH THE STATE
LATE TUES-EARLY WED. POCKETS OF MOISTURE TRAVERSING THE FLOW WILL
PRODUCE SCATTERED AREAS OF LIGHT SNOW SHOWERS, MAINLY ALONG AND WEST
OF A LINE FROM CUT BANK TO BOZEMAN THROUGH THURS MORNING.  SNOW WILL
BECOME MORE WIDESPREAD INTO THURS EVE AS ANOTHER SHORTWAVE TROF AND
BROAD MOISTURE PLUME DROP INTO MT FROM ALBERTA. WITH THURS HIGH
TEMPS ONLY IN THE LOW 30S ACROSS THE CENTRAL AND HILINE COUNTIES,
SNOW MAY BEGIN TO ACCUMULATE THERE BY LATE AFTN, BUT WARMER TEMPS IN
SOUTHWEST MT WILL LIMIT ACCUMULATION UNTIL LATER THURS EVENING.  THE
SNOW CONTINUES UNTIL AROUND MIDDAY FRI WHEN THE SHORTWAVE EXITS
EASTWARD. PROJECTED SNOWFALL TOTALS ARE 1 TO 3 INCHES FOR THE PLAINS
AND VALLEYS AND 3 TO 6 INCHES IN THE MTNS.  FORECAST MODELS ARE IN
GENERAL AGREEMENT THAT WE'LL REMAIN UNDER NORTHWEST FLOW THRU SUN
AFTN WITH SOME ISOLATED SNOW SHOWERS, MAINLY OVER THE CENTRAL AND
SOUTHWEST MTN RANGES. FROM SUN EVE THROUGH MONDAY MODEL SOLUTIONS
BECOME SO WILDLY DISPARATE THAT FINDING A COMPROMISE BETWEEN THE
LARGE HIGH PRESSURE RIDGE AND SLIGHTLY WARMER, DRY CONDITIONS OF THE
GFS AND AN EQUALLY LARGE, WET AND COLDER UPPER-LEVEL TROF OF THE
ECMWF WAS ALMOST USELESS.  GIVEN THAT THE ECMWF'S SOLUTION WAS ALSO
A SIGNIFICANT DEPARTURE FROM ITS OWN PREVIOUS RUNS, THE CURRENT
FORECAST LEANS CONSIDERABLY CLOSER TO THE GFS, MODIFIED WITH THE
ADDITION OF SLIGHT CHANCE PROBABILITIES OF PRECIP FROM GREAT FALLS
SOUTHWARD TO THE MT/ID BORDER TO BETTER BLEND WITH NEIGHBORING
FORECAST OFFICE OUTLOOKS. WARANAUSKAS

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  28  50  30  36 /   0  10  40  30
CTB  26  51  26  33 /  10  10  50  30
HLN  27  47  31  40 /  20  20  40  30
BZN  16  42  29  38 /  10  10  30  30
WEY   9  25  20  27 /  20  30  50  50
DLN  16  39  25  33 /  20  20  30  30
HVR  24  53  30  37 /   0  10  40  30
LWT  22  51  29  32 /  10  10  30  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING FROM 11 AM TUESDAY TO 5 PM MST WEDNESDAY FOR
MTZ010>014-044>047-049>054.

HIGH WIND WARNING FROM 5 AM TUESDAY TO 11 AM MST WEDNESDAY FOR
MTZ009-048.

&&

WEATHER.GOV/GREATFALLS