Sunrise 5:47 AM   Sunset 9:01 PM Moonrise 3:10 PM   Moonset 2:48 AM

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FXUS65 KTFX 190238 AFDTFX

Area Forecast Discussion National Weather Service Great Falls MT 838 PM MDT Sat May 18 2024

UPDATE

An upper level trough encompasses much of SW Canada extending into the NW US with somewhat moist and unstable westerly flow across the Northern Rockies and MT leading to the development of widely scattered showers earlier today. These showers will continue to decrease through the rest of this evening as the atmosphere stabilizes. The next disturbance moving through the upper level trough will arrive in western MT later tonight with an area of more widespread precipitation developing over western portions of central MT early Sunday morning. Incoming model guidance supports this area of precipitation as more of a frontogenetic feature (focused band of rain/mountain snow) that propagates east across central MT from roughly Helena to Lewistown Sunday morning before precipitation becomes more showery Sunday afternoon. Hoenisch

SYNOPSIS
Light rain showers will affect the Cut Bank and Havre areas overnight tonight, while rain and snow showers become more widespread on Sunday across Central and Southwest MT. Expect showers early in the week, with a better chance for widespread rain and mountain snow by the middle of the work week. Overall, temperatures will generally be below normal across the area through the upcoming week.

AVIATION
19/00Z TAF Period

Area remains under a somewhat moist/unstable westerly flow aloft with widely scattered showers tracking east across the northern tier of the state while more isolated activity exists elsewhere early this evening. These showers may affect KCTB and KHVR through 04z with a brief period lower VFR (>3000ft) ceilings and some very isolated lightning cannot be ruled out as well. Otherwise, VFR conditions prevail through most of tonight, but mid-level clouds increase with some increase in showers across portions of central and southwest MT later tonight. A weather disturbance embedded within the westerly flow moves into the region Sunday morning with showers becoming more widespread across central and southwest MT.
While VFR conditions generally prevail, periods of MVFR conditions and more widespread mountain obscuration can be expected on Sunday.
Surface winds decrease across much of the area tonight with a return to west/northwesterly winds at most terminals by Sunday afternoon.
Hoenisch

Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information.

PREV DISCUSSION
/ISSUED 555 PM MDT Sat May 18 2024/ Tonight through Sunday...Scattered light rain showers will affect the Hi-line area tonight, with a rumble of thunder also possible.
On Sunday, the precipitation becomes a bit more widespread over Central and Southwest MT. Snow levels will fall to about 3500 feet on Sunday morning. Any snow accumulations will be in the mountain, mostly above 7000 feet. Since most areas will receive less than 2 inches of snow, and the snowfall will occur during the day, no winter highlights are planned for at this time. Afternoon temperatures will continue the cooling trend on Sunday as well.

Monday and Tuesday...An upper level trof will be trying to develop over MT early next week. This will result in unsettled conditions and the chances for light showers to continue Mon/Tue.
Temperatures will warm a touch each day Mon/Tue.

Wednesday through Saturday...There is the potential for another spring storm to affect a good portion of the CWA next Wed/Thu.
Some forecast models prog over 1 inch of QPF over the Southern Rocky Mountain Front and Central Montana during this period.
However, the latest NBM only has a 20 percent chance of 1 inch of rainfall in these areas. It does look like it will be cold enough for snow as well, mostly above 6500 feet. Snow accumulations could approach 10 inches or snow near the peaks, and a winter highlight might be needed for portions of the CWA As we go into Memorial Day weekend next weekend, there is some uncertainty of how widespread the precipitation will be, but it is looking likely that showers will be affecting portions of the CWA next weekend.
Brusda

PRELIMINARY POINT TEMPS/POPS
GTF 40 56 35 59 / 20 80 40 60 CTB 32 55 34 57 / 10 80 30 60 HLN 42 58 37 61 / 50 60 20 60 BZN 36 54 33 57 / 10 70 30 70 WYS 35 53 26 50 / 20 40 20 60 DLN 35 53 32 55 / 10 40 20 50 HVR 38 60 38 60 / 20 70 20 40 LWT 37 52 32 54 / 30 80 30 60

TFX WATCHES/WARNINGS/ADVISORIES
None.

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