Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
473 FXUS65 KGGW 291957 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 157 PM MDT Sun Sep 29 2024 .DISCUSSION... KEY MESSAGES: 1) Record heat is likely today with widespread highs in the 90s. 2) Gusty northwest winds and low humidity this afternoon through Monday has prompted a Red Flag Warning and Lake Wind Advisory. 3) Gusty winds near 58 mph over Sheridan and eastern Roosevelt counties have justified a High Wind Watch for Monday. 4) Monday will be much cooler, with dry conditions and more seasonable temperatures for the rest of the week. WEATHER PATTERN OVERVIEW: Record warmth takes hold today with a strong upper level ridge and temperatures aloft more typical of July. A cold front arrives this evening bringing a significant cooldown to near normal levels for the rest of the week. It will come through dry or any isolated showers will have difficulty reaching the ground as measurable rain. The winds will be sustained through Monday afternoon, with gusts up to 55 mph. Once the winds calm down significantly late Monday night and skies remain mostly clear, there is widespread frost potential with some typically colder valleys dropping below the freezing mark for the first time this season. Ensembles show the dry pattern continuing through the week with little in the way of disturbances passing through. FORECAST CONFIDENCE & DEVIATIONS: High confidence exists for the dry pattern and temperature changes for the next several days. The only departures from the base forecast were to make slight adjustments upward for winds and downward for humidity through Monday. Used a 50/50 blend of NBM/NBM90 for wind and windgust during that time. This targeted this extreme event for heat and cold frontal passage with enhanced focus on fire weather headlines, as observations this past week have been consistently drier/windier than the NBM. Staring at NBM probabilities grids for wind gusts greater than 55 mph in GFE pushed out an 80% chance of reaching it sometime within the whole 24 hour period across Sheridan and eastern Roosevelt counties. Used DESI to sus out a 20%-30% chance for any given hour of 58 mph from 7AM to 3PM to be more focused. Rolling a 20% chance 8 times over for each hour during that whole time span comes out to roughly a 84% chance for a severe gust over-all during that whole time span. Therefore, have place a high wind watch out at roughly this time span in case the Plentywood AWOS or any site south or east of it gets hit. Despite all this, a 20% chance for any given hour still feels low. So, will allow the evening and overnight crew another look to decide whether to upgrade it to a warning or cancel it while still getting the word out. /GAH && .AVIATION... LAST UPDATED: 1930Z FLIGHT CAT: MVFR - VFR DISCUSSION: SKC to FEW mid-level clouds are expected in the afternoon. A cold front this evening brings a period of SCT to BKN clouds near MVFR hieght from 06-13Z tonight along KGGW and KOLF. There is some uncertainty as to whether there will be enough low clouds to generate a MVFR ceiling at these locations. Afterward, VFR conditions will prevail through Monday afternoon into the overnight hours. WIND: W at 10 to 20 kts through the afternoon. Veering to the northwest and increasing to 25 - 30 kts, gusting 40, after the cold front passes through this evening. These strong winds will last through the night and into Monday afternoon. Some calming is expected Monday evening after sundown. GAH && .GGW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 7 PM MDT Monday for Dawson/McCone/Prairie/Richland/Wibaux Counties-Fort Peck Reservation and Daniels/Roosevelt/Sheridan Counties-Northern Valley and Northern Phillips Counties-Southern Petroleum and Southern Garfield Counties-The Lower Missouri River Breaks including the Charles M Russell National Wildlife Refuge. Lake Wind Advisory until 8 PM MDT Monday for Central and Southeast Phillips-Central and Southern Valley-Garfield-McCone- Petroleum. High Wind Watch from late tonight through Monday afternoon for Eastern Roosevelt-Sheridan. Red Flag Warning until 3 AM MDT Monday for The Little Rockies. && $$ weather.gov/glasgow