Weather Lookup

Discussion

Key messages:

- valley rain and mountain snow sunday into monday morning, focused along and south of i-90. Northwest montana stays mostly dry.

- high pressure bringing stable conditions and valley fog next week.

- potential return to unsettled pattern with chances for mountain snow by next weekend (nov. 7-8).

A broad low pressure system continues to spin along the pacific northwest coast this morning, with southerly flow transporting atmospheric moisture and cloud cover across the northern rockies. Shower activity has been observed across lemhi county, id into southwest montana (along the divide) this morning and that trend will continue through the evening. Most locations along and north of the i-90 will stay dry this evening.

Heading into sunday, the low pressure system will push south and east, moving towards the four corners region. Forecast guidance has trended this low further south over the last few days and forecast precipitation and mountain snow amounts have decreased since the last forecast cycle. Nonetheless, widespread precipitation will develop along and south of i-90 sunday, with the highest precipitation totals focused along the divide and in lemhi county, id. Valley areas will generally see less than 0.10 inches, with up to 0.50 inches in the mountains.

As discussed previously, snow levels will be around 7000 feet during the day sunday, but lower to 5000 feet sunday evening. This will bring minor snow accumulations to lost trail pass, georgetown lake, homestake pass, and passes along the divide in lemhi county (i.E. Lemhi pass), where lows by monday morning will be near freezing. Impacts will primarily be slushy accumulations at these locations.

High pressure builds by monday morning, but fog and low clouds could again be impactful, especially areas that received rain the day before: west-central and southwest montana, parts of central idaho, and lemhi county.

Chances for fog or low clouds continue tuesday and wednesday mornings, while daytime temperatures climb to slightly above- average readings. The pattern becomes progressively more unsettled by the end of the week. Late week mountain snowfall will depend on how much moisture and dynamical energy can break off from a longwave trough over the northeast pacific and move onshore, similar to what we have been experiencing lately.

Aviation

Stratus continues to linger across the valleys of the northern rockies. Some improvement will occur where sunshine is able to diminish the low clouds from the top and showers will create some mixing and stratus lifts but other areas will simply remain shocked in at least through tonight. Showers will pass through lemhi county and southwest montana this afternoon and evening with more widespread precipitation by early sunday morning, generally from i-90 southward.