textproduct: Great Falls

KEY MESSAGES

- Patchy fog and light rain showers this morning over North Central MT.

- Showers and thunderstorms arrive on Thursday afternoon over Southwest MT and spread northward into Central MT Thursday evening.

- Some storms could be strong Thursday and Friday.

- Drier and mild conditions develop by Sunday.

DISCUSSION

- Meteorological Overview: An upper level disturbance is moving eastward across southern Canada this morning. Thus some light rain showers are affecting areas along the Highway 2 corridor from east of Shelby to Harlem. These showers should exit the area by 9 AM or so. Patchy fog has also developed over North Central MT as well this morning. This fog should burn off by mid morning as well.

On Thursday, the next upper level trof approaches from the west. A southwest flow over Central MT develops, resulting in an unstable airmass by Thu afternoon. Expect several rounds of showers/thunderstorms over Southwest/Central MT from Thursday evening through Fri. Some storms could be on the strong side. The precipitation will be a bit slow to exit, with showers continuing into Saturday.

For Sunday and Monday, and upper level ridge builds over the CWA, resulting in drier and mild conditions.

For next Tue/Wed...the forecast models are struggling on a solution, as both models differ from one another.

- Forecast Confidence & Scenarios: The main concern for the thunderstorms Thu night and Friday will be how strong will the thunderstorms be. Some storms could produce strong wind gusts and hail. Instability of CAPE could exceed 1500 j/kg around Helena on Friday. Additionally, the airmass will remain unstable Thu night for thunderstorms to likely continue much of Thursday night.

For next Tue...both the GFS/EC models continue to have opposite solutions, with one model warm/dry...the other model cold/wet. Thus confidence is low at this time for next Tue. Brusda

AVIATION

16/12Z TAF Period

Morning showers/patchy fog will diminish over North Central MT by mid morning. Generally quiet conditions expected this afternoon. Some low level wind shear possible around Bozeman late this evening, otherwise the next chance for showers/thunderstorms develops on Thu morning over Southwest MT. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 63 42 73 49 / 0 0 0 20 CTB 59 39 68 46 / 20 0 0 20 HLN 68 44 79 51 / 0 0 0 60 BZN 71 40 78 47 / 0 0 10 30 WYS 74 35 72 38 / 0 20 60 70 DLN 73 41 77 45 / 0 0 30 40 HVR 66 41 77 47 / 10 0 0 20 LWT 64 41 77 49 / 0 0 0 10

TFX WATCHES/WARNINGS/ADVISORIES

None.