textproduct: Great Falls

KEY MESSAGES

- Rain continues to slowly exit Central MT throughout the morning.

- Dry conditions and warm temperatures settle in for most of the week.

- Unsettled weather and a cool down in temperatures possible next weekend.

DISCUSSION

/Issued 501 AM MDT Sun Sep 20 2026/

- Meteorological Overview:

The vertically stacked low pressure system will continue to slide eastwards throughout the day. With it will also pull the precipitation over Central MT. However, expect light rain to continue over Central MT through at least the morning hours. Isolated showers may linger in eastern Fergus County through Sunday afternoon. As this storm system exits, high pressure moves into the region, creating low level stability. The calm conditions with breaking in the clouds overnight tonight will bring the potential for fog to develop mainly in Southwest MT this morning. Similar conditions set up Monday morning, with the potential for fog development to shift into North-Central MT as well.

A drier weather pattern sets up for most of the week as the current storm system moves east and another shortwave slides south of Montana across the Great Basin. As this shortwave slides across the Great Basin region, areas near the MT/ID border might get clipped with a few rain showers late Tuesday night. For the second half of the week, southwest flow dominates as the next incoming trough builds off of the western U.S. coast. Above normal temperatures are expected through Friday.

Ensembles hint at this upper-level trough moving through next weekend, bringing back chances for precipitation. This trough also pushes temperatures down closer to normal, and may lower snow levels to the higher mountain peaks. -Wilson

- Forecast Confidence & Scenarios:

There still remains some uncertainty in fog development across the Southwest MT valleys this morning. The main uncertainty is forecast soundings also showing low stratus also developing, which could prohibit fog potential. The best chances for fog development will be in the higher Southwest MT valleys. There's a 10-20% chance for fog development this morning. Monday morning, hi-res guidance shows greater probabilities, with a 30-60% chance for fog with less than a mile of visibility along US Highway 2 from Havre to Cut Bank. -Wilson

AVIATION

20/18Z TAF Period

Scattered to broken MVFR/low-VFR conditions will prevail through 00z Monday along and east of a KWYS, to KLWT, to KHVR line; with increasing CIGS thereafter. The potential for fog development then becomes the next concern, most notably over the plains terminals of KHVR and KCTB where MVFR/low-VFR VIS is expected to develop between 10-14z Monday. Additional fog development is possible across Southwest Montana during this timeframe; however, confidence was not high enough to prevail at this time. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 73 46 79 48 / 0 0 0 0 CTB 73 44 76 45 / 0 0 0 0 HLN 72 44 76 46 / 0 0 0 0 BZN 66 39 73 41 / 10 0 0 0 WYS 62 26 69 29 / 10 0 0 0 DLN 67 38 72 40 / 0 0 0 0 HVR 73 45 78 47 / 10 0 0 0 LWT 65 43 74 46 / 30 10 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.