textproduct: Great Falls

KEY MESSAGES

- Light snow in Blaine county early this morning.

- Mild temperatures across Central and Southwest Montana valleys persist through the middle of the week, with the plains joining in on the milder temperatures on Sunday.

- Light precipitation along the ID border Sunday night into Monday.

- There is still quite a bit of uncertainty with respect to precipitation toward the middle of next week.

DISCUSSION

- Meteorological Overview:

A weak upper level wave rushing southeastward from southern AB toward the Dakotas within a northwesterly flow aloft will send a weak cold front southward over the plains through the remainder of the night. Some light snow looks to develop mainly for areas in northern Blaine county through the early morning. There will be an opportunity for some very light snow in other areas where the cold front moves through, but any snow would be minimal (Less than a half an inch). Meanwhile across the valleys of Central and Southwest Montana temperatures remain on the mild side today, as the front looks to get hung up in the Little Belts/adjacent ranges.

A drier northwesterly flow aloft moves in late today, but it looks to arrive a bit too late for any modification of the cooler airmass over the plains this afternoon. That warmup for these areas looks to arrive Sunday as drier flow aloft continues, especially over North- central Montana. The only blemish Sunday through Tuesday looks to be for an upper trough over CA/NV ever so slightly swiping Southwest Montana along the ID border with some very light precipitation. That said, this is low probability at this time and is highly dependent on a more northerly track of the aforementioned upper level disturbance heading into early next week.

Looking toward Wednesday upper level troughing moves in across the west. At least light precipitation is favored Wednesday into Thursday, with at least slight cooling of temperatures. Wednesday onwards is discussed a bit further in the Confidence section. -AM

- Forecast Confidence & Scenarios:

Wednesday Onward:

Ensembles/cluster guidance are essentially unanimous that upper level troughing will exist across the west. Confidence quickly wanes however diving into specifics, as there are numerous potential outcomes. To keep things on the brief side, the more potent scenario (Would favor more precipitation), which keeps the troughing more intact and further north is favored in approximately 40% of ensemble members. Conversely, the combined probability of a weaker trough or one that splits (Resulting in less precipitation for most areas) is approximately 60%.

Confidence wanes in the forecast even more behind this system heading toward the weekend. Warmer and drier scenarios are nearly equal probability to cooler/wetter ones to close out the week. We will need to build confidence in the evolution of the system Wednesday into Thursday before confidence toward next weekend increases. -AM

AVIATION

28/06Z TAF Period

A Canadian cold front will move south through the plains tonight into Saturday morning before becoming nearly stationary near the central island ranges during g the afternoon hours. There will be a northerly wind shift, increased MVFR clouds, and even some areas of light snow behind the front. Partial clearing of skies then looks to occur between 28/20 and 29/00Z. Farther south, strong west to northwesterly flow aloft will cause instances of mountain wave turbulence and low level wind shear for locations along the Continental Divide and over southwest MT. The winds aloft will continue to decrease through 28/15Z as will their associated wind shear and turbulence impacts. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 33 18 55 26 / 10 0 0 0 CTB 28 11 51 24 / 0 0 0 0 HLN 48 26 54 30 / 0 0 0 0 BZN 54 26 58 30 / 0 0 0 10 WYS 39 18 43 27 / 0 10 30 50 DLN 53 30 55 33 / 0 0 10 10 HVR 28 11 45 22 / 20 0 0 0 LWT 34 19 52 27 / 10 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 11 AM MST this morning for Bears Paw Mountains and Southern Blaine-Northern Blaine County.