Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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071 FXUS65 KTFX 190611 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1210 AM MDT Wed Jun 19 2024 Aviation Section Updated .SYNOPSIS... Although the remainder of the week will largely be unsettled, temperatures will be on the warming trend. Mostly dry and warm conditions this weekend will trend cooler early next week as breezy westerly winds develop. && .UPDATE... Showers and thunderstorms over Central/North-central MT are now starting to diminish as diurnal heating wanes, but lighter shower activity will linger through midnight or so. Lapse rates are still sufficient for a few more storms over the southwest, especially for locations south of I90. Light winds and abundant surface moisture will create favorable conditions for patchy fog development later tonight into early Wednesday, particularly for areas that undergo partial clearing and have received rainfall today; however, broad troughing aloft is expected to maintain at scattered cloudiness and should ultimately reduced the overall coverage. Pops and temperatures were matched per current trends with the remainder of the forecast remaining on track. - RCG && .AVIATION... 19/06Z TAF Period Showers with an isolated lightning strike are diminishing across the region. With calm winds, some clearing skies, and low level moisture from rain earlier today, there is a chance for some fog to roll in early this morning (in TAFs for KBZN, KWYS, KGTF, KTCB, and KHVR). Model data suggests that fog can have the capability of producing IFR conditions at KCTB/KGTF (30-40% chance for KGTF to have LIFR ceilings if fog develops). Trends in fog will continue to be monitored overnight. Other than fog, VFR conditions prevail through the TAF period. There`s a 10-20% of some isolated showers/few thunderstorms across Central/North Central MT Wednesday afternoon. However, chances were too low to include them in this round of TAFs, but may be added to future TAFs if probabilities uptrend slightly. -Wilson Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 247 PM MDT Tue Jun 18 2024/ Through Friday... Strong upper level ridging across the eastern CONUS will allow for upper level troughing to persist across the western CONUS this week. Embedded waves within this troughing will bring the best chances for mainly afternoon and evening showers and thunderstorms this afternoon and Friday afternoon, but will be around Wednesday and Thursday as well. Temperatures will be on a warming trend this week, though overnight lows tonight will largely be in the 30`s F, with elevated valleys dropping into the 20`s. Temperatures tonight will challenge record lows for the date in many locations. One thing to keep an eye on will be for an opportunity for more organized thunderstorms Friday afternoon. If the present timing holds, the combination of the passing shortwave, ample instability, and sufficient shear will result in a respectable environment for stronger storms. Saturday into next week... Flow across the eastern CONUS finally becomes more zonal, allowing systems to begin tracking eastward again. As troughing from this work-week shifts eastward, another will begin moving eastward across the northern Pacific, setting up near the Canadian coastline by Friday night. This will result in a brief period of upper level ridging across the northern Rockies. Dry conditions are forecast Saturday through at least early Sunday, with temperatures Sunday climbing to the warmest of the forecast period. The next round of troughing will begin building in by Sunday afternoon. There is a fair bit of uncertainty at this range with respect to timing and depth/strength of this troughing, which leads to decreased confidence on potential impacts. A more benign scenario would result in just a period of breezy westerly winds in the afternoon Sunday, primarily across the plains, while a more impactful scenario would bring showers and perhaps a few thunderstorms as well later in the day. As of now the more benign scenario is favored, but trends will need to be monitored for timing changes with this system. Regardless, temperatures trend closer to normal for Monday, with breezy winds looking to continue over the plains into early next week. Small opportunities for showers and thunderstorms will be around early next week, but specifics are murky at this point. -AM && .PRELIMINARY POINT TEMPS/POPS... GTF 37 67 41 75 / 70 20 0 10 CTB 33 64 38 73 / 40 30 0 20 HLN 40 72 45 80 / 40 20 0 10 BZN 33 69 39 77 / 50 0 0 10 WYS 26 63 33 72 / 20 0 0 10 DLN 32 67 38 73 / 50 0 0 0 HVR 40 70 44 79 / 80 30 10 20 LWT 34 65 41 71 / 40 50 0 20 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls