textproduct: Great Falls

KEY MESSAGES

- Areas of dense fog continue this morning for the Milk River Valley in Hill and Blaine County.

- Light showers will affect Southwestern Montana on Saturday.

- It will be warm (above seasonal averages) and mostly dry through Monday with a cooldown and more widespread precipitation expected on Tuesday.

DISCUSSION

/Issued 259 AM MST Sat Nov 14 2026/

- Meteorological Overview:

The upper ridge axis over the CONUS Central Plains will continue to propagate eastward with strong southerly flow over Montana transitioning to Southwesterly flow over the next 12 to 24 hours. With support from a broad negatively tilted trough extending from the PNW through Western CONUS, a weak upper-level disturbance will perturbate through the flow bringing generally light showery precipitation over Southwest MT this morning. Due to surface warming and ABL mixing, WBZ heights will stay around 3000 FT so snow will be contained to the mountain ranges. There is a stable layer over the Northern regions of the state with weak easterly flow keeping low-level fog producing moisture trapped along the Milk River Valley until this afternoon when diurnal boundary layer mixing occurs.

For Sunday, warm and dry conditions will persist with Southwesterly flow aloft maintaining warm air advection to keep temperatures in the 50s and 60s. With the approaching Pacific trough, pressure gradient winds will increase over Southwest MT with gusts up to 40 mph expected within the valley downslope regions Sunday morning into the afternoon.

Beginning Monday night, the Pacific system will kick a strong upper-level shortwave trough out over western CONUS bringing deep ascending moisture and instability over Montana into Wednesday and fueling cyclogenesis over the Yellowstone area. This low pressure system will deepen and move eastward across the Continental Divide pulling colder Canadian air south into the region and creating widespread snow across the CWA by Tuesday night. Moisture laden Southwesterly flow aloft with cold northerly advection will provide healthy snow growth zone profiles over much of the state. Most likely placement for a weak deformation zone to develop will be Northwest of the low over Western and Central MT. - Akins

- Forecast Confidence & Scenarios:

The persistence of fog this morning is high for the Havre and Milk River Valley areas however current REFS guidance is about 40% probability for the fog extending westward to Shelby and Cut Bank. For the upcoming winter event Tuesday, ensembles are signaling a potential weak deformation zone for moderate snowfall setting up approximately over Helena and Great Falls. ECMWF and GFS show similar mesoscale band placement within the broader pattern however intensity, exact location, and duration still diverge. Most snowfall estimates for lower elevation areas are 1-4 inches over the Monday night to Wednesday timeframe. Next run will bring event time within most short-medium range ensemble members for higher fidelity scenario creation. - Akins

AVIATION

14/12Z TAF Period

Main aviation concern this morning is the persistence of fog along the Hi-line and Milk River vicinity including KHVR with some potential for fog extending as far west as Shelby and KCTB before dissipating by 18z. Otherwise, mid-high level cloud-cover streaming north into the region continues to thicken with scattered/light precipitation initially confined to southwest MT expanding northward this afternoon. Expect some increase in mountain obscuration as mainly VFR cloud ceilings lower at times across central and SW this afternoon. An embedded weak frontal boundary moves east across the area this afternoon, bringing a shift to breezy west winds at most terminals with winds diminishing and clouds decreasing from west to east this evening. Hoenisch

PRELIMINARY POINT TEMPS/POPS

GTF 61 37 57 38 / 0 10 0 0 CTB 56 31 54 35 / 0 0 0 0 HLN 55 32 55 32 / 30 10 0 0 BZN 56 30 53 30 / 10 20 0 0 WYS 42 25 41 22 / 40 20 0 0 DLN 50 31 49 30 / 40 10 0 0 HVR 59 32 59 33 / 0 0 0 0 LWT 63 35 57 37 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 11 AM MST this morning for Hill County- Northern Blaine County.