312
FXUS65 KGGW 152109
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
209 PM MST SUN DEC 15 2024
DISCUSSION
KEY MESSAGES:
- MULTIPLE DISTURBANCES ARE FORECAST FOR MONDAY NIGHT INTO
TUESDAY, AND WEDNESDAY EVENING INTO THURSDAY. LIGHT SNOW IS
EXPECTED WITH THE FIRST DISTURBANCE.
- EXPECT OVERALL SEASONABLE TEMPERATURES THIS WEEK, WITH A
SIGNIFICANT GRADIENT FROM WINNETT TO PLENTYWOOD.
WEATHER PATTERN OVERVIEW:
A SHORT TIME PERIOD OF DRYING IS EXPECTED WITH A SHORTWAVE RIDGE
MOVING ON MONDAY, FOLLOWED BY ANOTHER DISTURBANCE MONDAY NIGHT
INTO TUESDAY. CONFIDENCE IS LOW FOR SNOW ACCUMULATION ACROSS THE
NORTHERN AND EASTERN ZONES PARTICULARLY, SINCE THERE IS NOT MODEL
AGREEMENT ON THE STRONGEST FORCING PLACEMENT. GENERALLY HIGHER
AMOUNTS ARE EXPECTED CLOSER TO CENTRAL MONTANA, SOUTH AND WEST OF
FORT PECK LAKE WHERE THE CHANCE OF EXCEEDING 2" IS AROUND 20
PERCENT AT THIS TIME.
ALTHOUGH THERE IS LOW CONFIDENCE ON TIMING AND LOCATION OF
PRECIPITATION, THERE APPEARS TO BE ANOTHER SHORTWAVE TROUGH THAT
WILL MOVE THROUGH FAIRLY ZONAL FLOW WEDNESDAY EVENING INTO
THURSDAY. DETERMINISTIC MODEL SOUNDINGS FROM THE GFS AND ECMWF
INDICATE A STRONG LOW LEVEL INVERSION WILL BE PRESENT AT THE ONSET
OF THE EVENT, THE SPEED AT WHICH THIS INVERSION ERODES, AND
THEREFORE PRECIPITATION TYPE WILL BE CRITICAL. BY THE WEEKEND,
ENSEMBLES HAVE INCREASING AGREEMENT FOR AN UPPER LEVEL RIDGE
MOVING INTO THE AREA TO BRING SOLIDLY WARMER AND DRIER THAN NORMAL
CONDITIONS.
FORECAST CONFIDENCE & DEVIATIONS:
NO NOTABLE DEVIATIONS WERE MADE TO THE BASE FORECAST. THERE
REMAINS MODERATE CONFIDENCE ON LIGHT SNOW ACCUMULATION OCCURRING MONDAY
NIGHT INTO TUESDAY, WITH LOW CONFIDENCE ON PRECIPITATION AMOUNT
AND TYPE FOR THE WEDNESDAY EVENING INTO THURSDAY SYSTEM.
AVIATION
LAST UPDATED: 2100Z
FLIGHT CAT RANGE: VFR TO IFR.
DISCUSSION: DRY CONDITIONS WILL PREVAIL OVER THE CYCLE AS A WINTRY
MIX TAPERS OFF FOR KSDY AND KGDV THIS AFTERNOON. AFTER 03Z, A DECK
OF MVFR CEILINGS PUSHES BACK SOUTHWEST TOWARD THE TAF SITES,
MAINLY IMPACTING KOLF AND KSDY. THERE IS MODERATE CONFIDENCE FOR A
BRIEF PERIOD OF IFR CEILINGS WITH THIS.
WIND: NORTHWEST AT 15-25 KNOTS WITH GUSTS UP TO 35 KNOTS,
DECREASING TO 10-15 KNOTS AFTER 12Z.
GGW WATCHES/WARNINGS/ADVISORIES
NONE.
WEATHER.GOV/GLASGOW
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