textproduct: Great Falls

KEY MESSAGES

- Precipitation largely subside this evening.

- Two cold nights ahead, with lows in the 20s for many areas.

- Slowly trending warmer through the week, with a few rounds of precipitation at times.

DISCUSSION

- Meteorological Overview: The core of the upper level troughing is beginning to track east of the region this afternoon, resulting in a northerly flow aloft. Northerly/northwesterly upslope precipitation continues this afternoon, with additional precipitation developing in the form of showers, mainly across Southwest MT and vicinity.

Loss of daytime heating and upslope flow will allow for precipitation to come to an end this evening. Lighter northerly flow aloft continues into tonight though, which will allow for quite a cold night across the region. Most locations look to fall into the 20s, with a few cold prone locations dipping into the teens. Some patchy fog cannot be ruled out tonight, though coverage will depend on where most precipitation falls through the remainder of the day today.

Cool air aloft persists into Monday, which will combine with daytime heating to result in a mix of rain and snow showers across the region. Slightly warmer air aloft begins to move in Monday night, though lingering cooler air at the surface will result in another cold night before temperatures trend closer to average during the day Tuesday. A few afternoon showers will be around Tuesday, but overall coverage of the showers is questionable at this time.

Several disturbances pass across the region within a northwest flow aloft Wednesday onward, which will allow for a couple stretches of precipitation. Temperatures over this timeframe slowly trend warmer, though this trend will be briefly interrupted by the showery conditions at times. -AM

- Forecast Confidence & Scenarios:

Cold temperatures tonight and Monday night:

The probability for an overnight low below 32F is nearly 100% in all areas tonight. That probability isn't quite as high for Monday night, but is at or greater than 50% in the overwhelming majority of areas.

Precipitation Wednesday:

A sharper trough looks to pass across the region Wednesday into Wednesday night. This trough looks cool enough to result in some mountain snow, but most precipitation looks to fall as rain. Areas along the Rocky Mountian Front and across Central Montana terrain have a roughly 30% probability for 0.25" liquid from this system. -AM

AVIATION

17/18Z TAF Period

VFR conditions will prevail at the KBZN, KEKS, and KWYS terminals during this TAF Period. At the KBZN and KEKS terminals between 17/18Z and 18/02Z there is a 15 - 20% chance for rain and snow showers and thunderstorms. A the KHLN terminal there is a 30 - 40% chance for rain and snow showers and a 15 - 20% chance for thunder between 17/18Z and 17/24Z. At the KGTF and KCTB terminals there is a 15 - 40% chance for rain and snow showers between 18/00Z and 18/06Z. At the KLWT terminal during the majority of this TAF Period there is at least a 15 - 40% for rain and snow showers. Any thunderstorms will produce gusty, erratic winds and frequent lightning. At any sites that clear there is a very low chance for patchy fog to form which is too low to include in any TAF at this time. During the majority of this TAF Period there will be mountain obscuration across North-central, Central, and Southwestern Montana. -IG

PRELIMINARY POINT TEMPS/POPS

GTF 28 53 30 65 / 40 10 0 10 CTB 24 54 30 63 / 20 10 10 20 HLN 31 56 32 65 / 20 10 0 0 BZN 25 51 25 61 / 20 20 10 0 WYS 21 44 18 54 / 10 10 10 0 DLN 25 51 26 60 / 20 10 0 0 HVR 27 55 28 68 / 40 10 0 0 LWT 27 47 25 60 / 60 30 10 10

TFX WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until midnight MDT tonight for Big Belt, Bridger and Castle Mountains-East Glacier Park Region-Elkhorn and Boulder Mountains-Little Belt and Highwood Mountains- Southern Rocky Mountain Front-Upper Blackfoot and MacDonald Pass.