textproduct: Glasgow

KEY MESSAGES

- Gusty winds tonight through potentially Saturday afternoon. Peak wind gusts are expected to reach 40 MPH Friday afternoon.

- Daily high temperatures to drop into the mid to high 60s Saturday through the outlook.

- Possible rain showers between late Sunday afternoon and late Monday morning south of the Missouri River and east of Fort Peck Lake.

DISCUSSION

SYNOPTIC SETUP: An upper-level ridge over the central United States and an Eastern-Pacific trough over the PNW and British Columbia are acting to create SW flow aloft over Montana.

TODAY: The ridge will begin exiting eastward ahead of the trough, which will dig over eastern Montana by tomorrow morning. Embedded within the overall trough is a smaller shortwave that will propagate NE from over Wyoming to western Montana over the course of tomorrow afternoon. The shortwave's enhanced pressure gradient will lend itself to producing gusty SE winds. Peak wind gusts are expected to reach 35 MPH tomorrow afternoon.

TONIGHT INTO SATURDAY: The embedded shortwave will continue propagating eastward as the main trough digs over western Montana and the front passes by early Saturday morning. Frontal passage will cause winds to veer W-NW and daily high temperatures to drop into the mid to high 60s. It is uncertain whether wind gusts will remain elevated overnight behind the front. Regardless, gusts will die down by late Saturday afternoon. A Lake Wind Advisory has been issued, valid from 8AM Friday until 9AM Saturday.

SUNDAY THROUGH MONDAY: The trough axis will exit to the NE, leaving SW flow aloft over Montana in it's wake. Low-level moisture moving through this flow coupled with isolated pockets of vorticity may generate rain showers between late Sunday afternoon and late Monday morning south of the Missouri River and east of Fort Peck Lake. An isolated thunderstorm or two may be possible during this time, particularly in the southeast most portion of the CWA. Currently, the bulk of QPF is anticipated over the Yellowstone Valley, but confidence is low as the track appears to be shifting SE and totals are decreasing quickly between the last few forecasts.

MONDAY NIGHT ONWARD: Forecast in general looks to become semi-zonal as SW flow aloft flattens. However, ensembles are in disagreement between minor ridging and troughing, which is reducing confidence in the forecast from Tuesday night onward.

FORECAST CONFIDENCE & DEVIATIONS:

Winds for the next 24 hours are anticipated to be higher than current model guidance indicates. The NBM 90th percentile has manually been given more weight in the forecast.

DON

AVIATION

LAST UPDATED: 0700Z

FLIGHT CAT RANGE: VFR

DISCUSSION: Fog is not expected to occur tonight. Expect between SKC and FEW, with mid- to high-level clouds across the region through the morning. SCT to BKN mid-level cloud decks will likely develop in the afternoon.

LLWS: There is a small chance (10-30%) for low-level wind shear across the region from 06-14Z due to a developing low-level jet. Confidence is not high enought to include LLWS in the TAFs directly.

SFC WIND: SE at 05 to 15 kt increasing to 12 to 18 kt with gusts to 28 kt by tomorrow morning and to 15 to 20 kt with gusts to 25 kt by tomorrow afternoon.

GGW WATCHES/WARNINGS/ADVISORIES

Lake Wind Advisory from 8 AM this morning to 9 AM MDT Saturday for Central and Southeast Phillips-Central and Southern Valley- Garfield-McCone-Petroleum.