textproduct: Great Falls

KEY MESSAGES

- Periods of dense fog and even some isolated instances of icing over elevated surfaces will continue through Sunday, most widespread over central and north-central Montana.

- Precipitation becomes more widespread by Sunday, with accumulating snow most prevalent over the higher terrain of southwest Montana Sunday night into Monday morning.

- Temperatures trend closer to average next week.

..Periods of dense fog through Sunday

Low level easterly flow will continue to maintain low stratus and mostly nighttime patchy/areas of fog through Sunday. Central and north-central areas will see the most widespread instances of dense fog below a half mile, namely plains locations along the Rocky Mountain Front and on the north side of the central island ranges. Some of the colder/higher southwest valleys will also see patchy dense fog, especially those along the MT/ID/WY borders. Impacts will mostly be directly related from the reduced visibility, but freezing drizzle may cause some slippery spots to develop on area roadways, particularly the more susceptible bridges and elevated surfaces.

...Light mountain snow and lower elevation rain, snow, and some mixed precipitation Sunday through Monday morning...

The main trough moves through Sunday through early Monday and brings a wave of widespread precipitation to much of the forecast area. Aside from some light snow along the Continental Divide and perhaps some spotty freezing drizzle over the plains west of I15 and over the higher southwest valleys, most of the precipitation will be falling in the form of rain until Sunday night. The overall pattern and NBM probabilities favor the Madison and Gallatin ranges for the best chance (60 to 80%) for snowfall amounts in excess of 3 inches. Lighter snows, generally up to a couple inches, look to fall along the Continental Divide and the central island ranges. The colder air is still not looking to be optimally aligned with the moisture for lower elevation snows, but will monitor the Gallatin valley where there is around a 30 to 40% chance for a couple inches of snow on the south/eastern fringes of the valley Monday morning. - RCG

AVIATION

31/12Z TAF Period

Low level easterly flow combined with a moist southwesterly flow aloft will bring periods of IFR/LIFR conditions and mountain obscuration from low stratus, patchy fog, and spotty light showers through around 31/21Z and then again after 01/00Z. The worst and most widespread degraded conditions will be over central and north- central MT, especially for the plains along the Rocky Mountain Front and north of the central island ranges. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 49 34 44 34 / 10 10 80 90 CTB 49 29 46 29 / 10 0 60 50 HLN 50 34 43 33 / 20 20 80 90 BZN 47 32 42 31 / 40 20 80 100 WYS 44 29 41 26 / 90 70 90 90 DLN 47 36 41 33 / 70 60 100 90 HVR 45 29 47 30 / 20 10 30 80 LWT 46 32 50 30 / 40 10 30 100

TFX WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 11 AM MDT this morning for Eastern Glacier, Western Toole, and Central Pondera-Fergus County below 4500ft-Judith Basin County and Judith Gap-Northern High Plains- Southern High Plains.