textproduct: Glasgow

KEY MESSAGES

- Winter Weather Advisory in effect from 6 PM tonight to noon Monday for northern Phillips and northern Valley Counties. A Winter Weather Advisory remains in effect until noon Monday for southwestern Phillips County.

- Our area is forecast to receive 0.5" to 1.0" of total precipitation with lower amounts in Wibaux County. Snow accumulations are confined to Northern and Southwestern Phillips and Northern Valley Counties.

DISCUSSION

A positively-tilted longwave trough continues to dig southward into the Pacific NW. Ample moisture is advecting from the Pacific into our region via SW mid-level flow aloft. This system is already causing impacts upstream, such as heavy snowfall across many roadways across Billings and Great Falls. Here in Glasgow, we are observing rainfall, but the timing of transition from rain to snow is uncertain, lowering confidence in snowfall amounts. It looks to be transitioning earlier than previously forecasted, which may heighten anticipated snow totals. The rain to snow switch will likely occur at the surface this evening. This shift could occur earlier depending on the strength of the surface trough, which may cause more intense surface cooling.

Forecast QPF totals from this system continue to trend higher compared to previous model guidance. Much of our region may see as much as half an inch to an inch of total precipitation, with lower amounts in Wibaux County. Much of the already fallen precipitation has been rain, which will then mix with and change to snow this evening, resulting in accumulating snow remaining confined to northern Valley and northern, southwestern Phillips counties.

Warm ground temperatures, exceeding 40 degrees, will prevent snowfall from sticking to the ground, preventing significant accumulation, with the exception of the Little Rockies and higher elevations along the Canadian border. As a result, a Winter Weather Advisory remains in effect for southwestern Phillips County for up to 6 inches of snowfall, with higher amounts possible depending on elevation. Another Winter Weather Advisory has been issued for northern Phillips and northern Valley Counties, beginning 6 PM tonight through noon Monday.

Temperatures for Sunday and Monday will be much cooler than the seasonally typical due to cold polar air lingering along the backside of the cold front. Beyond Monday, temperatures should gradually warm up as an upper-level cut-off low develops over the Four Corners region and advects warmer air into the CWA.

FORECAST CONFIDENCE & DEVIATIONS:

Confidence in below average temperatures through Monday is high, but decreases as the week progresses, becoming low by Friday. Precipitation chances later in the week depend on the track of the low pressure system over the Four Corners.

Model agreement deteriorates drastically beyond Wednesday; confidence remains low for weather conditions mid-week onward. The GEFS and EPS do not concur about the ejection of the cut-off low. It could eject through the northerly jet or continue meandering over the Four Corners.

Confidence is low regarding QPF, as each model run it has trending higher than the last. Localized areas may receive more than forecast.

FIN

AVIATION

LAST UPDATED: 2009Z

FLIGHT CAT RANGE: IFR conditions through the TAF cycle.

Discussion: IFR conditions are expected as ceilings continue to stay static across the areas this afternoon. Cigs are overcast at 1100 ft. An AIRMET over stations details cigs below 1000 ft, with patchy fog and misty conditions reducing visibility below 3 statute miles. The AIRMET is valid until 03Z tonight. Expect cigs to lower from 900 ft down to 200-900 ft across all terminals, with the exception of KGGW, as ceilings there lower to a minimum of 900 ft, accompanied by rain, snow, and windy conditions at 17Z.

Winds: Gusty northeast winds are expected to veer northwest. Expect gusts through 01Z up to 21 kts at KGGW and KOLF. From 03Z onward, expect high winds, gusting up to 18 kts intermittenly between 05Z and 07Z at KSDY. Winds will weaken from 15 kts to 5 kts throughout the forecast period. No LLWS is expected.

FIN

GGW WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory from 6 PM this evening to noon MDT Monday for Northern Phillips-Northern Valley.

Winter Weather Advisory until noon MDT Monday for Southwest Phillips.