textproduct: Great Falls

KEY MESSAGES

- Near average today and Thursday with a few pop up showers and thunderstorms. - Warmer on Saturday ahead of a cold front, with a few stronger thunderstorms possible in the afternoon. - Another return to average expected early next week, but warmth returns by midweek.

DISCUSSION

- Meteorological Overview:

Northwesterly flow aloft will prevail through the remainder of the work week, resulting in some cooler and unsettled weather through Friday. Afternoon showers and thunderstorms are expected to be commonplace today and Thursday, and while some gusty winds and small hail are possible, severe weather is not expected either afternoon thanks to a lack of organization in the storms. Friday will be a bit of a warmer and drier afternoon as a weak transient upper level ridge moves overhead, with the warmest air found in the Southwestern Montana valleys where some mid to upper 80s are possible.

A cold front will cross the area on Saturday, which will result in a cooler day across the Southwest portion of Montana as showers and thunderstorms arrive there early, but temperatures will rise to the low 80s across the plains ahead of the front, provided it does not cross the area earlier than expected. However, as the cold front approaches the plains, showers and thunderstorms are likely to develop and may become a bit more organized, and may become capable of producing some more organized gusty winds and/or hail.

Behind this cold front, temperatures will once again fall for a few days early next week as northwesterly flow aloft persists, which will once again bring the possibility of pop up afternoon showers and thunderstorms. Upper level ridging looks to return again for the middle of next week, which will bring warmer air back into the Treasure State.

- Forecast Confidence & Scenarios:

Showers and thunderstorms today and Thursday: Overall, showers and thunderstorms over the next 48 hours should remain generally beneficial. However, a few of the stronger thunderstorms may be able to produce some small hail and gusty winds, as temperatures aloft are sufficiently cool to allow for some small hail growth and there is just enough of a dry mixed layer at the surface to promote some modestly gusty outflows to around 40 to maybe 50 mph or so on the high end.

Saturday Thunderstorms: A cold front moving through the northwestern US on Saturday will bring a round of more organized showers and thunderstorms to the area as it pushes through. While a widespread severe outbreak is not expected at this time, the presence of a forcing mechanism (the front), modest instability, and modest shear profiles indicate there is some potential for the storms to be a bit better organized than those of today and tomorrow. Given this, I cant rule out the possibility of a stronger storm or two that would be able to produce some borderline severe wind or hail (58 mph gusts or 1 inch diameter hail) ahead of the front. The other possibility is that, instead of hail, a few of the storms could produce some heavier downpours, which could produce some minor flooding concerns. Ludwig

AVIATION

17/18Z TAF Period

Scattered showers/thunderstorms will affect the northern/central portions of the CWA through the period. Most storms will be short lived. Expect a mid level ceiling across much of the CWA through the period. Mountains/passes will be obscured at times by passing showers/thunderstorms. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 46 70 45 75 / 20 40 0 0 CTB 44 65 41 71 / 50 50 10 0 HLN 48 77 47 81 / 20 0 0 0 BZN 44 79 44 82 / 0 0 0 0 WYS 34 75 37 81 / 0 0 0 0 DLN 42 80 45 85 / 0 0 0 0 HVR 44 70 42 74 / 20 70 0 0 LWT 41 66 40 72 / 20 60 10 0

TFX WATCHES/WARNINGS/ADVISORIES

None.