textproduct: Great Falls

KEY MESSAGES

- Another cool and cloudy day today with isolated rain or snow showers.

- A hard freeze is likely tonight as skies clear with light winds by Wednesday morning.

- Warmer temperatures Wednesday through the weekend with chances for showers and a few thunderstorms, mainly Thursday and Saturday.

DISCUSSION

- Meteorological Overview:

Today through Thursday...Cyclonic, northwest flow aloft will help to maintain scattered shower and isolated thunderstorm chances across Southwest through North Central Montana through the evening hours tonight, especially over the higher terrain and in northerly upslope areas. High temperatures today will once again be well below normal, with most locations running 10 to 15 degrees below normal. Transient ridging begins to slide east over the Northern Rockies during the overnight hours, with surface high pressure drifting south and east towards the Central Rockies. Light winds and clearing skies over this timeframe (tonight) will allow temperatures to cool efficiently, with most locations falling into the low to mid-20s, with the exception of the cold prone valleys of Southwest Montana where the teens will be possible. Overall dry conditions with moderating temperatures are expected on Wednesday as the transient ridge axis moves overhead; however, precipitation chance will be on the increase Wednesday night as a fast moving shortwave dives southeast from British Columbia and over the Northern Rockies through the day on Thursday. This shortwave will support numerous showers and scattered thunderstorms across Southwest through North Central Montana during the day on Thursday.

Friday through next Tuesday...Ensemble clusters are in good agreement with upper level ridging over the Eastern Pacific shifting east and over the Northern Rockies through the day on Friday before a fast moving shortwave dives southeast from the Pacific Northwest/British Columbia and flattens the ridge over the Northern Rockies (Friday night through the day on Saturday). Upper level ridging quickly builds back in over the Eastern Pacific from Saturday night and through the day on Sunday, with this ridge continuing to build east over the Northern Rockies and amplifying further through the first half of the upcoming work week. This pattern will promote moderating temperatures on Friday following Thursday's cool and wet conditions, but this moderation will be short-lived as temperatures cool back to near or slightly below normal on Saturday. Along with the cool down on Saturday another opportunity for widespread precipitation will be possible, especially across Southwest and Central Montana. Temperatures warm well above normal then for the second half of the weekend and beginning of the upcoming work week. - Moldan

- Forecast Confidence & Scenarios:

A hard freeze (min temps 28F or less) is expected (>80% probability) at most locations across north-central and southwest MT tonight. This is within the typical climatological window for our area but those with more sensitive vegetation may need to take protective steps. A few daily temperatures records may also be challenged tonight with forecast minimum temps at or below daily records at Great Falls (26F in 2020), Havre (24F in 1967) and Lewistown (21F in 1942). Hoenisch

AVIATION

05/06Z TAF Period

Northerly flow aloft with embedded moisture will maintain broken mid level clouds with areas of mountain obscuration through Tuesday afternoon with clearing from north to south Tuesday evening. A few showers are possible through Tuesday afternoon, mainly near the mountains with a 20-30% chance for brief MVFR conditions at some central and SW MT terminals. Northerly surface winds persist with a few gusts in excess of 20kts through N-S oriented SW MT valleys and during the Tuesday afternoon period elsewhere. Hoenisch

PRELIMINARY POINT TEMPS/POPS

GTF 49 25 69 48 / 20 10 0 20 CTB 49 22 70 45 / 20 0 0 10 HLN 49 26 69 47 / 10 10 0 20 BZN 48 21 64 39 / 20 10 0 10 WYS 44 16 56 31 / 10 10 0 10 DLN 50 22 65 41 / 10 10 10 0 HVR 50 21 66 39 / 10 0 0 10 LWT 44 20 59 40 / 20 10 0 10

TFX WATCHES/WARNINGS/ADVISORIES

None.