Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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708 FXUS65 KTFX 081020 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 420 AM MDT Wed May 8 2024 .SYNOPSIS... Rain and snow will decrease somewhat today over North Central Montana, but warming air from the northeast may help some scattered showers and thunderstorms to develop east of Interstate 15. Precipitation will continue off and on over and near the Central Montana mountains and into Southwest Montana. Winds will continue to be gusty into the overnight period as well. Overall, high pressure aloft will help decrease precipitation tonight into Thursday, bringing a warming and drying period for Friday through the weekend. && .DISCUSSION... Key Points: - Main adjustment was to add Rocky Mountain Front plains and Meagher County valleys to Winter Weather Advisory - Precipitation will continue through today then decrease overnight into Thursday - High pressure aloft will bring a warmer and drier period starting this Friday Today through Thursday... Widespread rain and snow is starting to decrease somewhat from the northeast early this morning. However, evaporative / dynamic cooling from the heavier precipitation has caused snow levels to fall to the surface on the plains adjacent to the Rocky Mountain Front, on the north facing slopes of the Central Montana mountains, and into the valleys of Meagher County. Additional accumulating snow of mostly 2 to 5 inches with the persistent gusty northerly winds will continue difficult driving conditions across these areas this morning, so have expanded the Winter Weather Advisory to include all of these areas. The northerly winds are showing signs of decreasing, but gusts mostly in the 40 to 50 mph range continue across the area, so will leave the High Wind Warning in effect until 6 am today. Otherwise, warmer low- to mid- level air is being advected into the area in a northeast flow aloft between the low pressure trough exiting the area to the southeast and a building high pressure ridge to the northwest. This has resulted in a rising of the snow level over Blaine, Hill, Chouteau, and northern Fergus Counties. This warming should help weakly destabilize the airmass there this afternoon, bringing the threat for some weak thunderstorms. However, the moisture will continue to move over the area, keeping the threat for additional measurable snowfall in the mountains, so will allow the Winter Warnings and Advisories continue there into this evening. Overall, precipitation and wind should decrease from the northwest overnight into Thursday as the high pressure ridge continues building into Montana. This should also help warm temperatures back closer to normal on Thursday. Friday through next Wednesday... Ensemble guidance in good agreement with having the Pacific high pressure ridge remaining the dominant weather feature for this period. Temperatures are forecast to warm back above normal on Friday and up to 15 degrees above normal for the weekend. Much of the period should remain mostly dry, but a disturbance riding over the ridge may bring a few showers and thunderstorms on Sunday. A shortwave trough is then forecast to gradually break down the ridge Tuesday into Wednesday, helping to cool temperatures a bit and bring an increasing chance for showers and thunderstorms. -Coulston && .AVIATION... 1219 AM MDT Wednesday May 8 2024 (08/06Z TAF Period) Widespread rain, mountain snow, and associated MVFR/IFR/LIFR conditions over North-central and portions of Southwest MT will continue through at least 08/18Z before gradually diminishing/improving later Wednesday afternoon and evening. The rain has begun to change over to snow for the North-central terminals along the MT highway 200 corridor and along the Rocky Mountain Front. These areas will continue to see snow through 08/15Z and then will switch back to rain. Strong gusty north to northwesterly winds over the plains will slowly diminish through 08/12Z. Expect widespread mountain obscuration for much of the period as well as turbulence and instances of low level wind shear through at least 08/12Z. - RCG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .HYDROLOGY... The recent heavy rainfall running out of the Bears Paw Mountains has caused minor low-land flooding across Blaine, Hill, Chouteau, and Fergus Counties, so a Flood Advisory remains in effect through Thursday morning. This rainfall will also cause area rivers and creeks to rise, including Beaver Creek, Clear Creek, Peoples Creek, and Lodge Creek. In fact, the forecast for Clear Creek has already risen above Moderate Flood Stage as of 3 am; therefore, a Flood Warning has been issued for that point until further notice. -Coulston && .PRELIMINARY POINT TEMPS/POPS... GTF 44 38 57 35 / 100 80 30 0 CTB 43 33 60 33 / 100 20 10 0 HLN 45 40 58 37 / 100 70 20 0 BZN 44 33 55 31 / 100 80 40 10 WYS 45 30 53 25 / 80 40 20 0 DLN 47 36 57 34 / 90 50 10 0 HVR 57 41 65 38 / 80 50 20 0 LWT 41 34 50 32 / 100 90 60 10 && .TFX WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 6 AM MDT early this morning for Cascade County below 5000ft-Eastern Glacier, Western Toole, and Central Pondera-Eastern Pondera and Eastern Teton-Eastern Toole and Liberty-Fergus County below 4500ft-Hill County-Judith Basin County and Judith Gap-Snowy and Judith Mountains-Western and Central Chouteau County. Winter Storm Warning until midnight MDT tonight for Big Belt, Bridger and Castle Mountains-East Glacier Park Region-Gallatin and Madison County Mountains and Centennial Mountains-Snowy and Judith Mountains-Southern Rocky Mountain Front. Winter Weather Advisory until noon MDT today for Cascade County below 5000ft-Eastern Glacier, Western Toole, and Central Pondera- Eastern Pondera and Eastern Teton-Fergus County below 4500ft- Gates of the Mountains-Judith Basin County and Judith Gap- Meagher County Valleys-Northern High Plains-Southern High Plains. Winter Weather Advisory until 6 AM MDT early this morning for Bears Paw Mountains and Southern Blaine-Eastern Toole and Liberty. Blizzard Warning until midnight MDT tonight for Little Belt and Highwood Mountains. Winter Weather Advisory until midnight MDT tonight for Elkhorn and Boulder Mountains-Upper Blackfoot and MacDonald Pass. Flood highlights in effect for portions of North Central MT. && $$ http://www.weather.gov/greatfalls