Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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811 FXUS65 KTFX 120158 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 758 PM MDT Sat May 11 2024 Updated forecast and hydrology sections .SYNOPSIS... The ongoing warm weekend will continue into Monday. Showers and a few thunderstorms will develop along the Hi-Line tonight, with additional afternoon and evening showers and thunderstorms likely across the plains Sunday and Monday. A cooler and more unsettled pattern will arrive for mid-week. && .UPDATE... Current forecast is on track. No forecast updates planned for this evening. An upper level ridge is building over the Pacific Northwest, resulting in a northwesterly flow aloft over Central Montana. A weak upper level disturbance is sliding southeastward in this flow aloft. A few showers/isolated thunderstorms could slide into the Havre/Harlem areas, mostly after Midnight. Instability is low, so the chances for any lightning are also low. Additionally, this disturbance is not very strong, so most locations will receive less than 0.10 inches of precipitation if it does rain. Overnight low temperatures look on track. Note, there will be some increased cloud cover over North Central MT overnight as this upper level disturbance moves through. Even though I am not expecting overcast skies, the cloud cover could limit viewing of the Aurora at times tonight. (It will not be as clear as last night for most areas.) Brusda && .AVIATION... 12/00Z TAF Period Note: The NWS Great Falls Weather Forecast Office manages the following TAFs: KCTB, KHVR, KGTF, KLWT, KHLN, KBZN, KEKS and KWYS. For most of this TAF period, our eastern most airfields, KHVR and KLWT, operate under VFR conditions; however, from 12/09Z to 12/12Z, the KHVR TAF degrades into the MVFR range, while KLWT falls into MVFR conditions during the last hour of this TAF period. In both cases, MVFR conditions are due to low visibility in light rain showers and mist. All other airfields remain VFR for the duration of this TAF period. Periods of mountain obscuration are forecast, especially, for the mountains of north central and central Montana. This evening, a few thunderstorms may develop and move across the region. Areas of showery precipitation and virga are forecast. Portions of north central and central Montana reach high temperatures favoring density altitude issues. Generally, winds remain light and variable; however, winds gusting to 35KT across The Northern Rocky Mountain Front are forecast develop tomorrow during the late morning/early afternoon hours, and to continue into the evening hours. - Fogleman Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .HYDROLOGY... Clear Creek continues to slowly fall. The creek is expected to fall below flood stage overnight tonight. Thus the flood warning for this creek will likely be cancelled later tonight. The flood watch continues for the Bears Paw Mountains. However, no new flood impacts were reported today. If that trend continues overnight, the flood watch could be cancelled early. The flood watch continues for the mountain ranges of Central Montana. No new flood impacts were reported today. This is good news, as this means the runoff is coming off slowly or the runoff is soaking into the ground. In either case, if this trend continues, this flood watch could also be cancelled early. Brusda && .PREV DISCUSSION... /ISSUED 300 PM MDT Sat May 11 2024/ Through Monday... Upper level ridging, with axis over the west coast, is slowly building eastward. With ridge axis off to the west, flow aloft is out of the northwest. A weak wave diving southeastward through this flow will result in showers and a couple thunderstorms tonight, mainly across eastern portions of the Hi-Line. This activity moves east of the area by 7AM Sunday. Additional instability will develop across Central and North-central Montana Sunday, resulting in a round of isolated afternoon and evening showers and thunderstorms. Concerns with thunderstorms that form will be for gusty winds, given relatively deep mixing and inverted-V soundings. Expect more of the same on Monday, though the opportunity for showers and perhaps a thunderstorm or two will spread further southwest into Southwest Montana. Additionally, breezy westerly winds look to develop over the plains as a passing wave moves overhead. -AM Tuesday through next Saturday... Expect periods of rainfall to continue through the day on Tuesday as moisture continues to work into the area from the north and west. For the most part, precipitation will be rainfall except at the highest elevations even as cooler air from Canada pours into the region behind a surface cold front that will work in with the rain. Beyond Tuesday, a ridge will develop to our southwest, but with a northwesterly flow aloft in place, expect near to perhaps a bit cooler than average temperatures, with opportunities for showers. Ludwig/AM && .PRELIMINARY POINT TEMPS/POPS... GTF 48 78 49 76 / 20 20 10 20 CTB 47 78 49 73 / 20 20 0 20 HLN 50 80 51 77 / 0 10 0 20 BZN 43 76 46 73 / 0 0 10 50 WYS 35 69 37 65 / 10 10 10 60 DLN 42 76 46 73 / 0 0 10 30 HVR 48 76 49 80 / 50 10 30 30 LWT 45 70 46 71 / 20 30 20 30 && .TFX WATCHES/WARNINGS/ADVISORIES... Flood highlights are in effect for portions of the CWA. && $$ http://www.weather.gov/greatfalls