textproduct: Glasgow

KEY MESSAGES

- Warm temperatures above normal and mostly clear skies into Friday.

- Friday will be monitored for any Fire Wx concerns as a ridge breaks down. - Overcast skies, possible precipitation, and much colder temperatures this weekend and into Monday.

DISCUSSION

Synoptic Setup: Forecast begins with relatively zonal to NW flow from Montana through the PCNW and across SW Canada. To the S, hot high pressure sits over the desert southwest with a ridge building into the Intermountain West. Farther West a highly amplified trough sit south of the Aleutian Islands.

Today through Thursday night: Zonal to NW flow remains relatively intact with temps remaining 5 to 15 degrees above normal with relatively dry conditions. There is a small chance during this time that any fires out west could begin to pool smoke across the area, but HRRR and RAP Smoke models suggest nothing more than light haze. Meanwhile, the Intermountain West ridge will drift east and the crest will start to bump up against MT while the Aleutian trough behind it will begin slamming up against the PCNW coast.

Friday: Ridge crest will move across eastern Montana raising highs to 10 to 20 degrees above normal with highs into the 70s and 80s. There is a chance that some chinook winds could begin to dry out the atmosphere a bit more than normal as well here leading to possible fire weather concerns. This ridge will also be monitored for breakdown timing. Meanwhile, the PCNW trough will smash into the large ridge and begin digging S into the lower Intermountain west and southern California instead.

Friday night into Monday: Newly minted SW flow regime will drag a cold front across Montana Friday night and lead to pacific moisture streaming into the region. By Saturday to Saturday night rains showers will begin to form as highs drop into the 40s and 50s by Sunday or nearly 20 degrees below normal. Expect a strong wind behind this frontal passage Saturday. Temps dropping low are suggesting that snow may be possible overnight Sunday night but totals will be less than an inch if it snows at all. Also, warm ground should melt off all of it. No accumulation would be expected. Cooler, wetter periods holds through about Monday before beginning to clear out. However, forecasts beyond Saturday do become in question as ensemble data moves out of phase with each other. In addition, the ridge to the east appears to become persistent and blocks any progress in the flow which may mean the cooler and wetter air could hold on if the trough is delayed its exit to the east.

FORECAST CONFIDENCE & DEVIATIONS: - No changes from NBM.

- There is moderate to low confidence (30-50%) in frontal timing Friday night. This could easily shift up to 12 hours in future forecasts.

- There is high confidence (70-90%) in warm temperatures through Friday and cooler temps for Sunday/Monday.

- There is moderate to high confidence (50-80%) in any precip occuring Saturday night through Monday morning.

AVIATION

LAST UPDATED: 0400Z

FLIGHT CAT RANGE: VFR

DISCUSSION: FEW/SCT mid-to-high clouds over the next 24 hours.

WINDS: W and light through mid-morning. Veering NW by late morning and then back to W again in the afternoon. Becoming light and variable tonight.

/GAH

GGW WATCHES/WARNINGS/ADVISORIES

None.