textproduct: Great Falls

KEY MESSAGES

- Today and Friday it will be dry with mountain snow and isolated lower-elevation rain/snow returning for the weekend.

- Temperatures will remain well-above seasonal averages through Monday.

- Another system will bring more widespread precipitation and cooler temperatures Tuesday through Thursday.

DISCUSSION

- Meteorological Overview:

Today the upper-level ridge begins to build back in over North- central, Central, and Southwestern Montana. This will keep warm (well-above seasonal averages) and mostly dry weather across the area on Thursday. Due to an increasing pressure gradient along the Rocky Mountain Front and plains west of I-15 it will be windy Thursday evening into Friday morning. On Friday the upper-level ridge remains over North-central, Central, and Southwestern Montana. This will keep warm (well-above seasonal averages) and dry temperatures for the area. On Saturday the upper-level ridge begins to flatten with an upper-level shortwave moving over the area. Then southwest flow aloft begins to develop Saturday afternoon/evening. This will bring mountain snow to North-central, Central, and Southwestern Montana. On Saturday isolated lower-elevevation locations will with see a rain/snow mix. On Saturday temperatures will be well-above seasonal averages. On Sunday the upper-level ridge with southwest flow aloft remains over North-central, Central, and Southwestern Montana. This will continue to allow Pacific moisture to stream into the area and bring mountain snow with isolated lower-elevations seeing a rain/snow mix. On Sunday temperatures will remain well-above seasonal averages.

On Monday an upper-level trough begins to make its way towards Montana. This will bring strong winds to north-south orientated valleys of Southwestern Montana. On Monday snow will linger in the mountains of North-central, Central, and Southwestern Montana. On Monday due to southwest flow aloft it will be well-above seasonal averages for temperatures. Tuesday through Wednesday an upper- level trough will move over North-central, Central, and Southwestern Montana. This will bring widespread snowfall and cooler temperatures to the area for Tuesday and Wednesday. -IG

- Forecast Confidence & Scenarios:

Thursday night into Friday morning there is greater than an 80% chance for wind gusts of 55 mph or greater along the Rocky Mountain Front. For snow Saturday through Monday there is greater than a 50% chance for 4 inches of snow or greater across the Mountain of North- central Montana.

For the midweek system the timing and track of the upper-level system keep changing and exhibit little if any run-to-run consistency. This results in there being high uncertainty in snowfall amounts and how cold temperatures will get. -IG

AVIATION

12/06Z TAF Period

Overall, VFR conditions will prevail over much of the CWA through the period. The exception will be the West Yellowstone area, where light snow will be possible until morning. Otherwise, clouds will be on the increase over North Central MT during the morning hours, with light snow possible over the Northern Rockies by Thursday evening. Mountains/passes will be obscured at times over the Northern Rockies and in the West Yellowstone area. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 48 22 52 32 / 0 0 0 0 CTB 48 23 50 28 / 0 0 0 0 HLN 43 21 47 25 / 0 0 0 0 BZN 44 19 46 21 / 0 0 0 0 WYS 34 17 38 16 / 70 20 0 0 DLN 47 21 47 22 / 0 0 0 0 HVR 47 20 49 27 / 0 0 0 0 LWT 42 15 47 26 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.