textproduct: Great Falls

KEY MESSAGES

- Hot, dry, and breezy conditions will generally prevail today with isolated to scattered shower and thunderstorm activity mostly confined to the higher terrain of far southwest MT.

- A cold front will bring northerly breezes, a brief cooldown, and mostly dry conditions aside from a few stray showers or storms.

- Summer heat builds again and daily rounds of storms return heading towards the middle of the week.

DISCUSSION

/Issued 344 AM MDT Sun Jul 19 2026/

A mid- level trough will continue to move eastward through the Canadian prairies will bring increased westerly flow aloft over the Northern Rockies today. Deep layer mixing will help transfer the stronger 30 to 40 kt H700/H500 flow to the surface for breezy to windy conditons today, especially along the Rocky Mountain Front and the plains. In addition to the dry westerly breezes, ridging aloft, currently centered over the Great Basin, will continue to maintain hot temperatures. Although fuels are not quite dry enough for widespread fire weather concerns, a day like today will accelerate the curing process.

The drier westerly flow aloft will also slow down shower and thunderstorm activity, but ML CAPE will generally be running between 500 and 800 J/kg over the southwest. With little forcing available, widely scattered showers and storms will mostly be confined to far southwestern areas along the MT/ID/WY borders. If outflow boundaries or other lifting mechanisms become strong enough to erode the 20 to 50 J/kg of inhibition, then widely scattered storms may develop over much of the southwest and even central areas southeast of a Helena to Lewistown line; however, the chances for this occurring are running less than 20% at this time. Any storm that does develop will be capable of strong, gusty winds, hail, and downpours in addition to cloud to ground lightning.

Another trough running along the Canadian border will send a Canadian surface front through the forecast area and will bring a northerly wind shift and a brief cooldown tonight into Monday. There will also be variable clouds and perhaps an isolated shower or storm. Ridging aloft strengthens and brings a return to hot conditions heading towards the middle of the week. Passing shortwaves interacting with rich monsoon moisture will also increase daily shower and thunderstorm activity, along with severe weather and localized flooding concerns. Southwesterly flow aloft becomes more established over the Northern Rockies by next weekend. This will do little to cool temperatures, but will bring drier air in and increase winds for elevated fire weather concerns depending on the mid-week rainfall quality. - RCG

AVIATION

19/12Z TAF Period

Increased westerly flow aloft and deep diurnal mixing will bring breezy to windy conditions today, especially along the Rocky Mountain Front and the plains. Shower and thunderstorm activity will mostly be confined to far southwestern areas along the MT/ID/WY borders with generally less than a 20% chance for a shower or storm over central and southwestern areas southeast of a KHLN to KLWT line. General VFR flight categories will prevail, but there will be some elevated smoke streaming in from the west and northwest that will decrease slantwise visibility upon ascent/descent. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 93 57 84 60 / 0 0 0 0 CTB 85 56 80 57 / 0 0 0 0 HLN 93 57 87 61 / 20 0 0 0 BZN 93 57 91 58 / 20 10 0 0 WYS 87 49 91 50 / 40 20 20 30 DLN 90 55 88 55 / 20 10 10 10 HVR 93 58 87 58 / 0 0 0 0 LWT 89 55 82 54 / 20 10 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.