textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Rapidly building heat will bring widespread temperatures in the 70s and 80s this weekend. Temperatures may reach near 90 degrees by Tuesday.

- Dangerously cold water is the primary hazard. River temperatures in the 40s and 50s can trigger immediate cold-water shock.

A strong high-pressure system is building over the region. We have high confidence that dry and unusually warm weather will last through at least the middle of next week. Tuesday and Wednesday remain on track to be the hottest two days of the season so far. Current forecasts show temperatures nearing 90 degreesthere is a 25% chance for Tuesday and a 40% chance for Wednesday in the Missoula and Bitterroot valleys. The valleys of the Lower Clark Fork and the Kootenai are likely to see similar probabilities, with a 70% chance for the lower Idaho river valleys. These temperatures would approach daily record highs for many locations.

Despite the summer-like air, local rivers and streams remain extremely dangerous. Waterways are running fast and high due to peak mountain snowmelt. Debris and hazards may be hidden just under the waters surface. Water temperatures between 40 and 50 degrees can paralyze muscles and trigger an immediate, uncontrollable gasp for air (cold-water shock) within minutes, even for experienced swimmers. Anyone recreating near the water is urged to wear a life jacket and stay back from slippery, unstable banks.

Forecast confidence decreases by Thursday as the high-pressure system begins to weaken. There is currently a 50% chance of a shift toward cooler weather and a more unsettled pattern (increased clouds and rain) by Thursday. However, 20% of long- range forecast models suggest the high-pressure ridge may hold until the end of the week. In that case, near-record warmth would continue.

AVIATION

Clear skies and good visibility (VFR) will continue across the Northern Rockies through the forecast period. Expect typical afternoon winds from the west to gust between 10 and 20 knots, though Kalispell (GPI) will see more southerly winds due to the Flathead Lake breeze. Winds will become light and variable overnight.

MSO WATCHES/WARNINGS/ADVISORIES

MT...None. ID...None.