Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
805 FXUS65 KGGW 080601 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 1201 AM MDT Fri May 8 2026 .KEY MESSAGES... - The next chance for isolated showers and perhaps a lone thunderstorm is across the west this afternoon. - Above normal temps, low relative humidity, strong northwest winds, and pre-greenup fuels has lead to a Red Flag Warning being issued across the east this afternoon. - A slightly wetter system arrives tonight into Saturday in the southwest with up to a tenth of an inch possible over Petroleum, SW Phillips, and SW Garfield counties. && .DISCUSSION... WEATHER PATTERN OVERVIEW: Currently a low pressure system lies over the Hudson Bay while a ridge runs up the western North American coast from California to British Columbia. Northeast Montana is in between these two features under northwest flow aloft. A weak shortwave will work its way through the flow pattern and drag some afternoon showers and an isolated thunderstorm or two through central and western parts of the area on Friday afternoon. There is a better chance of the activity being mostly showers in the northeast and thunderstorms in the southwest based on the surface equivalent potential temperature forecast in the HRRR, NAMNEST, and HRWFV3. There does not appear to be sufficient CAPE values in the northeast based on these models. Pressure gradient force will strengthen up just prior to a cold front moving through in the evening. This will allow for low relative humidity and moderate to high northwest winds. Looking at GOES NDVI most areas across the east are around or below 20-30% greenness and throwing that into the mix justifies the Red Flag Warning that is in effect for fire weather zones 120 and 122 from noon Friday through 8 PM Friday. A few relative humidity values dropped to 10 percent on Thursday, so we expect something similar on Friday in the east. Saturday: With the cold front moving through the previous night a zone of lift will be associated with the post frontal disturbance across central Montana for about 24 hours. This will have some impact across the southwest including Petroleum, SW Phillips, and SW Garfield counties. Precipitation accumulation ranges from a few hundredths up to around a tenth of an inch in the southwest, with isolated higher amounts up to two tenths in the higher terrain. Sunday through the work week: Ridge to the west moves across the region, flatten, and then rebounds in the west by Wednesday. The latest GFS ensemble suggests backbuilding of a trough over North Dakota on Monday into Tuesday, but there is high uncertainty on whether or not substantial precipitation chances will reach northeast Montana at that time. FORECAST CONFIDENCE & DEVIATIONS: Main NBM deviation was to hourly PoPs through Friday afternoon by raising them to 20 to 50 percent. Also dropped the relative humidity in fire weather zones 120 and 122 for Friday afternoon. There is moderate confidence in thunderstorms occurring in the southwest, and low confidence in the northeast part of the area occurring this afternoon. There is HIGH confidence of critical fire weather conditions occurring on Friday afternoon for fire weather zones 120 and 122. There is MODERATE confidence in rain showers up to a tenth of an inch across Petroleum, SW Phillips, and SW Garfield counties Friday night into Saturday, with low confidence on these locations receiving two tenths of an inch of precipitation. && .AVIATION... LAST UPDATED: 0630Z FLIGHT CAT RANGE: VFR DISCUSSION: Mainly mid to high clouds are expected from now through late morning before a chance of showers and isolated thunderstorms move through between 18Z Friday and 02Z Saturday. There is low to moderate (20 to 40 percent) confidence of MVFR conditions occurring in this time period. WIND: Northwest at 6 to 13 knots through 10Z, becoming light and variable, increasing to 10 to 20 knots after 18Z, becoming northeast at 8 to 16 knots after 02Z Saturday. && .GGW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from noon to 8 PM MDT Friday for Dawson/McCone/Prairie/Richland/Wibaux Counties-Fort Peck Reservation and Daniels/Roosevelt/Sheridan Counties. && $$ weather.gov/glasgow