textproduct: Great Falls

KEY MESSAGES

- Isolated showers and thunderstorms through the remainder of the day today.

- Dry and mild Thursday and much of Friday ahead of a cold front arriving Friday evening.

- Gusty winds and perhaps a few thunderstorms accompany the cold front Friday evening ahead of a cooler weekend.

DISCUSSION

- Meteorological Overview:

An upper level wave within a building upper level ridge is departing eastward early this afternoon. Lingering moisture and daytime heating will result in isolated showers and thunderstorms this afternoon and early evening, mainly near terrain. The overall magnitude of instability is low however, which limits any concerns for a stronger thunderstorm today.

A more anti-cyclonic flow develops into Thursday, which will suppress any shower or thunderstorm activity ahead of an approaching upper level trough that moves overhead Friday. Gusty southerly to southwesterly winds look to develop just ahead of the passage of the trough and associated cold front Friday. A gusty wind shift looks to accompany the front, with a few thunderstorms developing along it acting to locally amplify wind gusts. Most areas look to see winds at least briefly subside after frontal passage Friday night, though along the Rocky Mountain Front and adjacent plains strong cross barrier flow and ridgetop stability will keep gusty winds going through the night into Saturday.

As daytime mixing ensues Saturday, gusty winds become more common again, particularly across the plains given respectable mid level flow continuing across the region. Another trough looks to move onshore across the west late weekend into early next week, though confidence in its progression and whether or not there is an additional reinforcing trough remains low. The main takeaway for Sunday into early next week will be for near to slightly below average temperatures, with low-end probabilities for precipitation. -AM

- Forecast Confidence & Scenarios:

The main source of uncertainty which will help determine how impactful Friday afternoon and evening will be is related to timing of the cold front. Most guidance has settled on late afternoon and early evening, which would be the most favorable timing for convective enhancement of wind gusts near any shower or thunderstorm that develops. Should this trend much later, the risk for convective enhancement would diminish somewhat.

That said, cooler air moving in near the surface will still result in a favorable mountain wave setup near the Rocky Mountain Front and adjacent plains, which will result in a stretch of gusty winds into Saturday. The most favored timeframe for a strong wind gust is Friday evening into early Friday night, which is when cross barrier flow is strongest. The probability for a 58+ mph gust around Cut Bank is roughly 50-60%. Given this is still a bit more than 48 hours away, no High Wind Watches are being considered at this time. -AM

AVIATION

23/18Z TAF Period.

Generally mild and dry with VFR conditions prevailing across the region. Any areas of lingering mid-level clouds will clear out during the afternoon hours today. Otherwise, cloud cover through midday tomorrow is expected to be limited to areas of high clouds. ESH

PRELIMINARY POINT TEMPS/POPS

GTF 51 84 57 87 / 0 0 0 0 CTB 47 78 50 81 / 0 0 0 0 HLN 47 81 49 84 / 0 0 0 0 BZN 45 78 46 81 / 0 0 0 0 WYS 31 70 34 69 / 0 0 0 0 DLN 43 77 44 78 / 0 0 0 0 HVR 48 83 57 89 / 0 0 0 0 LWT 50 81 54 84 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.