Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
832 FXUS65 KGGW 150759 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 159 AM MDT Sun Sep 15 2024 .DISCUSSION... KEY MESSAGES: 1) Warm temperatures will continue through Tuesday. 2) Showers and thunderstorms chances start on Monday. 3) Cooler temperatures move in Tuesday night with widespread rain that continues through Wednesday night. WEATHER PATTERN OVERVIEW: Eastern Montana will be in a shortwave ridge in SW flow aloft today which will bring warm and dry weather. Meanwhile, ensembles continue to show the Pacific trough deepening across the west with divergent upper flow over Montana by Monday. Given 1000 to 2000 J/KG CAPE with 20-30 kts of shear and precipitable water values around an inch or slightly higher across the CWA, expect support the chance for multicellular thunderstorms Monday afternoon and evening. An isolated strong storm is possible with gusty winds and small hail given the instability present, but with modest shear unable to sustain the updrafts, do not expect widespread severe weather concerns at this time. The trough moves east on Tuesday and brings and upper low across Montana Tuesday night and Wednesday with cool and wet weather over the region. The NBM 48 hour probability of 1 inch of rain is now 60 to 70 percent across Phillips County between Tuesday and Wednesday night and drop quickly south and east of there. Closer to the MT/ND Border, probability of an inch of rain is only around 10 percent while the probability of 0.25 inch of rain is 40 to 60 percent. Dry slotting is expected at times along the MT/ND border which will result in lower rainfall amounts. While the upper low moves north Wednesday night, varying degrees of upper trough remains over the area into next weekend with chances of showers at times. FORECAST CONFIDENCE & DEVIATIONS: High confidence exists on warm and dry weather today. Medium confidence exists on thunderstorms Monday given the modest setup. Confidence for rain is high west and low to medium east for Tuesday and Wednesday with decent support for cooler and wetter weather unfolding. Consensus continues to show for widespread rain in the west but there remains uncertainties in the coverage and amount of precipitation due to dry slotting at times, especially for eastern areas. Have opted to keep the forecast in line with NBM overall for now, which handles the big picture well. && .AVIATION... Last Updated: 0800Z Discussion: VFR conditions will continue today and tonight. High clouds will be over parts of the area this morning before clearing this afternoon. More high clouds will move into the area tonight. Winds: Variable early 10 knots or less become SE 5 to 10 knots this afternoon east to NE 5 to 15 knots tonight. && .GGW WATCHES/WARNINGS/ADVISORIES... None. && $$ weather.gov/glasgow