Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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573 FXUS65 KTFX 301119 RRA AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 515 AM MDT Tue Apr 30 2024 Updated Aviation Discussion .SYNOPSIS... A slow moving Pacific storm system will bring breezy to windy conditions, below average temperatures and periods of rain and snow through much of this week with more widespread precipitation and periods of wintry conditions across portions of north- central and central Montana Wednesday through Thursday. Temperatures moderate some heading towards the weekend, but the typically active spring weather pattern will persist for the foreseeable future. && .DISCUSSION... Satellite imagery this morning reveals a complex upper level low taking shape over SW Canada with several notable shortwaves pivoting around it, including a stronger wave approaching the Pacific NW and weaker waves lifting out of the Northern Rockies and MT along the International Border. While we spend most of today in between these disturbances, cold/unstable westerly flow aloft and the arrival of additional moisture ahead of the disturbance moving into the Pacific NW will support the development of showers this afternoon, across the western and southwest MT mountains. Areas near Glacier NP will also see an increase in snow showers this afternoon as one of the embedded disturbances within the larger scale low moves east along the MT/AB border. Otherwise, breezy to windy and cooler conditions will be noticeable with afternoon temperatures around 10 degrees below seasonal averages and westerly winds with gusts 30-40 mph. Highest winds speeds today will be near the Rocky Mtn Front and central MT mountain ranges where a few gusts may exceed 45 mph, particularly for a period late this morning through mid-day with the passage of an embedded wind maximum. The larger scale closed upper level low moves east of the Rockies tonight with its circulation shifting slowly across MT/AB/SK through Thursday. Models are in general agreement and continue to trend somewhat slower with the arrival of more widespread precipitation circulating into the forecast area. Widespread precipitation develops across southern AB/SK in association with a TROWAL (trough of warm air aloft) and shifts southwest into areas along the east side of Glacier NP by Wednesday morning. Colder air aloft wraps into the circulation Wednesday with widespread precipitation expanding south and east across much of north- central MT by Wednesday afternoon with moist/cyclonic NW flow now forecast to linger across the area through at least Thursday afternoon. This has shifted the more impactful period of winter precipitation for portions of central MT to late Wednesday through Thursday, though precipitation amounts have not changed significantly. Winter storm warnings and advisories for The Glacier NP/Rocky Mtn Front vicinity begin at midnight tonight with areas near the AB border being initially impacted tonight before precipitation spreads south on Wednesday. Winter weather advisories were added for the Big Belt/Bridger and Snowy mountain ranges beginning Wednesday afternoon with the Winter Storm Watch for the Little Belts continuing while these highlights were extended through Thursday afternoon. There is some potential for additional winter weather highlights across portions of central MT adjacent to the Little Belts but considerable uncertainty exists at these lower elevations due to marginal temperatures with melting and compaction likely to limit accumulation and impacts to roads. Still, the later onset of precipitation towards Wednesday night and Thursday could allow for some overnight accumulation and minor winter weather impacts to the Thursday morning commute that will need to be watched. Models continue to delay the exit of troughing from the area through Friday though the bulk of the widespread precipitation should be ending Thursday night. A brief period of ridging is possible early this weekend before the next round of troughing arrives late this weekend into early next week with models suggesting temperatures remaining closer to seasonal averages for this period. Hoenisch && .AVIATION... 515 AM MDT Tue Apr 30 2024 (30/12Z TAF Period) A somewhat moist and unstable westerly flow aloft persists across the region today. Scattered showers exist near KHVR early this morning with scattered shower development expected this afternoon across much of southwest Montana. Mainly VFR conditions prevail with some brief MVFR and mountain obscuration possible near early morning and afternoon shower activity. Westerly surface winds with gusts 25- 35 kts develop at most terminals late this morning and continue through this afternoon before diminishing this evening. Hoenisch Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 51 31 47 32 / 20 30 70 80 CTB 47 31 43 32 / 50 50 80 80 HLN 51 31 50 36 / 30 10 60 60 BZN 49 24 48 29 / 40 40 40 40 WYS 42 20 40 19 / 60 70 60 30 DLN 47 24 45 28 / 30 30 30 20 HVR 54 32 50 33 / 30 40 70 70 LWT 48 27 46 28 / 10 10 60 60 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning from midnight tonight to noon MDT Thursday for East Glacier Park Region. Winter Weather Advisory from midnight tonight to noon MDT Thursday for Northern High Plains-Southern Rocky Mountain Front. Winter Storm Watch from Wednesday morning through Thursday afternoon for Little Belt and Highwood Mountains. Winter Weather Advisory from noon Wednesday to 6 PM MDT Thursday for Big Belt, Bridger and Castle Mountains-Snowy and Judith Mountains. && $$ http://www.weather.gov/greatfalls