textproduct: Great Falls

KEY MESSAGES

- Dangerously hot temperatures continue through today.

- Heat lessens slightly Monday through Thursday, but temperatures still remain warm and in the 90s.

DISCUSSION

- Meteorological Overview:

Upper level ridging will dominate over the Northern Rockies throughout the entire period; however, with the ridge axis being orientated just to the east and over the Northern High Plains, which would place Southwest through North Central Montana beneath overall southwest flow aloft, isolated showers and thunderstorms can't be ruled out from the afternoon through evening hours on any given day. This is especially true considering the fact that monsoonal moisture will continue to lift north and east within the ridge over the timeframe, with subtle waves providing additional forcing occasionaly. High temperatures will remain well above normal through the day today, with temperatures only cooling several degrees from Monday through Thursday but still remaining above normal. By Friday strong warm air advection and increasing 1000-500mb thicknesses will help to push temperatures back near the century mark across most lower elevations, with these hot temperatures persisting into the upcoming work week. - Moldan

- Forecast Confidence & Scenarios:

Heat Advisories and Extreme Heat Warnings through this Evening...

Hot temperatures will linger across much of Southwest through North Central Montana through the day today, with eastern areas of Central and North Central Montana (areas along and east of a Havre to Lewistown line) seeing a warm start to the day as temperatures only fall into the low 70s early this morning. Increasing wildfire smoke from regional wildfires will continue overspreading the Northern Rockies through the day as the upper level flow remains out of the southwest, with the thickest smoke expected to be over Central and North Central Montana. Should this smoke be thicker than currently expected then it is possible that high temperatures along and north of the Montana Hwy 200 corridor could be some 5 to 10 degrees too warm for the day on Sunday. Should temperatures be inhibited from warming to the current forecasted highs then an earlier ending to the current suite of Heat Advisories or Extreme Heat Warnings would be warranted.

Return of Extreme Temperatures by Friday...

While temperatures will remain hot through the upcoming work week, latest climate anomaly indicators are suggesting the potential for another unusual period of hot temperatures beginning on Friday and extending into the upcoming weekend; most notably across Southwest Montana. NBM5.0 probabilities for high temperatures of 100 degrees or warmer range from a 20-60% chance along and north of the I-90 corridor on Friday for lower elevations, with probabilities increasing to a 40-80% chance on Saturday for these same locations. The fact that the climate anomaly indicators are suggesting another unusual period of hot temperatures is remarkable considering that July 30 through August 1st is the climatological peak for average high temperatures across Southwest through North Central Montana. - Moldan

AVIATION

26/06Z TAF Period

Other than passing cirrus clouds, mostly clear skies will be persistent through the TAF period across North-Central MT. There is a low chance for isolated showers to linger overnight across Southwest MT. Another round of isolated showers and thunderstorms to develop Sunday afternoon and evening for areas mainly along and south of I-90. Gusty winds will be possible with thunderstorms. Breezy synoptic winds develop along the North- Central MT plains Sunday afternoon. Smoke aloft can cause slantwise visibility issues through the TAF period. -Wilson

PRELIMINARY POINT TEMPS/POPS

GTF 97 60 95 59 / 0 0 0 0 CTB 88 54 89 55 / 0 0 0 0 HLN 95 60 94 60 / 0 0 0 0 BZN 95 59 95 58 / 30 20 10 20 WYS 86 52 86 49 / 30 20 20 0 DLN 92 56 91 55 / 20 10 0 0 HVR 98 59 97 59 / 0 0 0 0 LWT 94 58 92 58 / 0 10 0 10

TFX WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 9 PM MDT this evening for Beaverhead and Western Madison below 6000ft-Canyon Ferry Area-Cascade County below 5000ft-Eastern Glacier, Western Toole, and Central Pondera- Eastern Pondera and Eastern Teton-Eastern Toole and Liberty- Gallatin Valley-Gates of the Mountains-Helena Valley-Hill County- Judith Basin County and Judith Gap-Madison River Valley-Meagher County Valleys-Missouri Headwaters-Northern Blaine County- Western and Central Chouteau County.

Extreme Heat Warning until 9 PM MDT this evening for Bears Paw Mountains and Southern Blaine-Fergus County below 4500ft.