textproduct: Great Falls

KEY MESSAGES

- Near to above average temperatures this weekend cool to below average early next week.

- Isolated showers and thunderstorms primarily in the afternoon and evening this weekend with a winder coverage early next week.

DISCUSSION

- Meteorological Overview:

The upper level ridge extending north into MT will gradually weaken and collapse southward today as a blocking upper level ridge amplifies offshore of the Pacific NW through early next week. A northwesterly flow aloft develops across the region today and turns more northerly early next week as the offshore ridge amplifies while troughing deepens and expands westward to our NE across central Canada.

A subtle weather disturbance moving across southern AB/SK is pushing a weak surface cold front south across the area today with the primary impact being a shift to northerly surface winds and slight increase in dewpoints (20s to 30s). While the influx of low level moisture is limited, it will support the increased risk for shower and isolated thunderstorm development this weekend with a focus across north-cental MT later this afternoon into this evening and more across southwest MT on Sunday. Temperatures cool only slightly and remain above seasonal averages through the weekend.

Energy moving around the deepening trough across Canada early next week will bring more noticeable cooling, to near or slightly below seasonal averages Monday and Tuesday, as a cooler airmass slides south from Canada. The risk for showers and isolated thunderstorms also increases as additional moisture arrives under a slightly cyclonic northerly flow aloft. The upper level pattern de-amplifies mid to late next week with temperatures returning to near and above seasonal averages. The presence of moisture or embedded weather disturbances later next week remains less certain. Hoenisch

- Forecast Confidence & Scenarios:

Confidence in the coverage and location of showers and isolated thunderstorms this weekend is lower than average with both moisture being a limiting factor as well as only weak instability (CAPE 200- 500j/Kg), which may also be hindered by mid to high level cloud- cover. Despite this, some high resolution model guidance continues to point at areas near Glacier county and the Rocky Mtn front for convective development this afternoon with cells tracking southeast across nroth-central and central MT this evening. The risk for lightning is as high as 10-20% across these areas late today and tonight, shifting to southwest MT on Sunday. Hoenisch

AVIATION

02/06Z TAF Period.

VFR conditions continue to prevail over the 0206/0312 TAF period due to the presence of upper level ridging moving southeast over the Northern Rockies. A weak cold front moves south from Canada Saturday morning, lowering CIGS and increasing chances for showers, mainly to the plains terminals of Central and North Central Montana beyond 18z Saturday. The terminals in Southwest Montana will see chances for showers increase after 20z. - Dzomba

PRELIMINARY POINT TEMPS/POPS

GTF 67 42 73 43 / 0 20 0 20 CTB 64 37 72 41 / 20 30 0 10 HLN 70 43 73 44 / 10 10 10 10 BZN 71 39 70 40 / 0 10 20 10 WYS 62 30 63 30 / 10 10 20 10 DLN 71 41 70 40 / 0 0 10 10 HVR 67 39 76 41 / 10 10 0 20 LWT 64 40 68 39 / 10 30 10 20

TFX WATCHES/WARNINGS/ADVISORIES

None.