Winter Weather Advisory 21, NWS Great Falls, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1028 PM MST SUN NOV 1 2015

UPDATED AVIATION DISCUSSION

.UPDATE...WINDS CONTINUE TO GRADUALLY DIMINISH ACROSS THE
FORECAST AREA THIS EVENING. STILL ISOLATED/SCATTERED SHOWERS
EXPECTED TO MOVE ACROSS PORTIONS OF THE STATE OVERNIGHT BUT
GENERALLY QUIET WEATHER SHOULD PREVAIL FOR MOST LOCATIONS. MADE
ONLY MINOR POP CHANGES TO STAY IN COORDINATION WITH SURROUNDING
OFFICES. REMAINDER OF THE FORECAST IS IN GOOD SHAPE AND NO FURTHER
UPDATES ARE ANTICIPATED. MPJ

&&

.AVIATION... UPDATED 0528Z.

FLOW ALOFT GRADUALLY SHIFTS FROM WEST TO SOUTHWEST AND DECREASES
LATE TONIGHT THROUGH MONDAY AS AN UPPER LEVEL TROUGH MOVES INLAND. A
FEW SHOWERS ARE POSSIBLE NEAR THE KHLN AND KBZN TERMINALS TONIGHT AS
BAND OF MOISTURE IN UPPER FLOW SHIFTS SOUTH EXITING BY 10Z. SURFACE
WINDS WILL CONTINUE TO DECREASE TONIGHT, BECOMING LIGHT AND VARIABLE
FOR A PERIOD MONDAY BEFORE BECOMING EASTERLY MONDAY EVENING AS LOW
PRESSURE DEVELOPS TO THE SOUTH. CLOUD-COVER WILL DECREASE TONIGHT
THROUGH MONDAY MORNING BEFORE INCREASING AGAIN FROM THE SOUTH LATE
MONDAY. VFR CONDITIONS WILL PREVAIL THROUGH MONDAY AFTERNOON WITH
LOCAL MVFR AND MTN OBSCURATION DEVELOPING MONDAY EVENING FROM KBZN
SOUTH AS PRECIPITATION DEVELOPS. HOENISCH

&&

.PREV DISCUSSION...
/ISSUED 445 PM MST SUN NOV 1 2015/
THIS AFTERNOON THROUGH WEDNESDAY EVENING...ZONAL FLOW PATTERN ALOFT
KEEPING BREEZY TO GUSTY WINDS ACROSS THE REGION TODAY.  HIGH WIND
WARNING ALONG THE ROCKY MTN FRONT HAS BEEN EXTENDED UNTIL 5PM TO
ACCOUNT FOR STRONG WINDS CONTINUING THERE FOR A FEW MORE HOURS.
WINDS SHOULD DECREASE IN ALL AREAS THIS EVENING/TONIGHT AS SURFACE
PRESSURE GRADIENT WEAKENS AND CORE OF JET STREAM SAGS SOUTHWARD.

FORECAST STILL ON TRACK FOR DEEP UPPER-LEVEL TROF, CURRENTLY
EXTENDING FROM CENTRAL BRITISH COLUMBIA INTO THE NORTHEAST PACIFIC
OCEAN, TO SPLIT INTO TWO PARTS, WITH THE NORTHERN SECTION CONTINUING
ACROSS SOUTHERN CANADA WHILE THE LARGER SOUTHERN PORTION TRACES A
BROAD ARC THROUGH WA/OR AND INTO CA/NV BY LATE MON AFTN. LEADING
EDGE OF MOISTURE WITH THIS SYSTEM WILL GENERATE SCATTERED VALLEY
RAIN/MTN SNOW SHOWERS ALONG THE ROCKY MTN FRONT AND THE SOUTHWEST
MTN RANGES WHILE REST OF REGION REMAINS DRY THROUGH THE DAYTIME
HOURS ON MON. A SURFACE COLD FRONT ASSOCIATED WITH THE NORTHERN TROF
SECTION WILL PUSH INTO MONTANA FROM ALBERTA MON NIGHT, BRINGING
COLDER TEMPS JUST AS THE PRIMARY MOISTURE AND ENERGY OF THE SOUTHERN
PIECE OF THE TROF LIFTS NORTHEAST THROUGH THE GREAT BASIN AND INTO
THE NORTHERN ROCKIES. FORECAST MODELS HAVE BEEN VERY CONSISTENT IN
DEVELOPING WIDESPREAD PRECIPITATION WITH THE PRIMARY MOISTURE PLUME
WITH THE HEAVIEST AMOUNTS MON NIGHT THROUGH TUESDAY NIGHT FROM
GALLATIN/MADISON COUNTIES NE THROUGH SOUTHERN FERGUS COUNTY WITH
LESSER AMOUNTS ALONG AND W OF I-15 AND ALONG/NORTH OF LINE FROM
GREAT FALLS TO HAVRE. ACCUMULATING SNOW (2-4 INCHES IN THE VALLEYS
AND 4-1 INCHES IN THE MTNS) IS LIKELY IN THE MADISON-TO-FERGUS SWATH
BUT LESS SO THE FURTHER NORTH YOU GO. SNOW FOR THE CENTRAL AND
HILINE COUNTIES WILL DEPEND A LOT ON THE TRACK OF A SECOND SURGE OF
MOISTURE THAT ARRIVES TUES AFTN/EVE, WITH A CHANCE THAT LOCATIONS
FROM GREAT FALLS NORTHWARD MAY SEE LITTLE, IF ANY, ACCUMULATION.
THE ENTIRE SYSTEM STILL LOOKS TO EXIT OUR REGION ON WEDNESDAY WITH
SNOW TAPERING OFF FROM WEST-TO-EAST DURING THE DAY.
WARANAUSKAS

WEDNESDAY THROUGH SUNDAY...MODELS REMAIN IN DECENT AGREEMENT
CONCERNING THE EXIT OF THE TROUGH RESPONSIBLE FOR THE WIDESPREAD
PRECIPITATION EVENT THAT MAINLY OCCURS ON TUESDAY. SOME RESIDUAL
MOISTURE WILL EXIST WEDNESDAY MORNING...BUT BY THE AFTERNOON HOURS
MOST OF THE SHOWER ACTIVITY SHOULD DECREASE AS A BRIEF DRYING TREND
DEVELOPS WEDNESDAY EVENING. MODELS ARE SUGGESTING A SERIES OF
SHORTWAVE TROUGHS THAT COULD MOVE ACROSS THE AREA AT VARIOUS TIMES
THROUGH THE REMAINDER OF THE WORK WEEK. THIS WILL RESULT IN COOLER
AND POTENTIALLY WETTER CONDITIONS THAN SEASONAL AVERAGES. HAVE KEPT
POPS UP DUE TO THIS POTENTIAL HOWEVER THIS BROAD BRUSH SOLUTION IS
MORE DUE TO A LACK OF CONFIDENCE IN THE VARIOUS MODEL SOLUTIONS
RATHER THAN A PERCEIVED CONFIDENCE IN A PARTICULAR MODEL. BY
SATURDAY A RIDGE OF HIGH PRESSURE IS EXPECTED TO MOVE INTO THE AREA
AND TEMPERATURES WILL BEGIN TO WARM BACK TOWARD SEASONAL VALUES.
THIS WARMING IS EXPECTED TO BE SHORT LIVED AS THE NEXT ROUND OF
MOISTURE AND COOLER TEMPERATURES IS EXPECTED BY MOST OPERATIONAL
MODELS TO IMPACT THE AREA LATE SUNDAY. SUK

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  31  46  28  40 /  10  10  50  80
CTB  28  47  23  41 /  10  10  30  20
HLN  35  47  31  37 /  30  20  70  70
BZN  33  46  30  34 /  20  40  90  90
WEY  28  37  25  34 /  40  80  80  80
DLN  33  45  29  34 /  20  30  80  60
HVR  30  50  26  42 /  10  10  20  40
LWT  32  47  29  35 /  10  20  80  90

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

WEATHER.GOV/GREATFALLS