textproduct: Great Falls

KEY MESSAGES

-Mountain snow of 1-3" confined to the highest peaks of the Rocky Mountain Front with no expected pass impacts.

-Additional rounds of showers through Sunday bringing rain and gusty winds with any storms that are able to develop Sunday evening.

-Widespread gusty winds Sunday and Monday with High Wind Watch out for the Madison River Valley.

DISCUSSION

A weak upper-level ridge briefly builds in through Today, bringing cool and mostly dry conditions across the region. On Sunday, the main closed upper-level we have been tracking over the past several days continues to correct slower and further northwest. As a result, QPF continues to drop and temperatures have gradually moderated as the signal grows for strong southwesterly winds Sunday and Monday area wide. Sunday remains the primary day for precipitation and impacts, with shower activity largely focused along the Hi-line and Rocky Mountain Front closest to the low. Further south, an embedded shortwave looking to primarily impact north-central Montana Sunday evening into early Monday morning. Despite limited instability, decent low-level lapse rates and mid-level forcing will support the potential for a few weakly convective showers. Model soundings show the classic inverted-v profiled, which combined with 40-50kt 700mb winds, will allow showers to transfer stronger winds down to the surface. While the severe threat is low, localized strong winds gusts remain a possibility with any of the stronger showers or "storms".

On Monday, the low exits but low level winds remain elevated. Mid-week, models are showing a healthy signal for another upper- level low pressure to try and swing through the forecast area. Uncertainty in regards to timing and strength is high but worth keeping an eye on as it could bring additional chances of precipitation or at least unsettled weather. Beyond mid-week, our pattern remains locked in place with ridging anchored over the South-Central Plains bringing multiple opportunities for weak shortwaves to move through the regional flow. Additionally, models are hinting at a stronger trough to attempted to push into the Pacific Northwest before becoming a cut-off low introducing additional uncertainty into the extended forecast.

- Forecast Confidence & Scenarios:

Confidence is high that winter weather impacts will be negligible. Snowfall of 1-3" remains strictly confined to high mountain peaks along the RMF with no impacts to road surface or passes. If the low pressure continues its trend of NW, QPF amounts will continue to slip as we lose the forcing needed for more widespread precipitation.

Confidence is moderate, but growing, in regards to elevated surface winds Sunday into Monday. The new orientation and track of the upper-low will increase surface winds across the area, bringing widespread gusts over 30kt especially in the Plains and Southwest flow aligned valleys in Southwest Montana. Madison River Valley looks particularly favorable for winds gusting upwards of 55kts thus the placement of the High Wind Watch.

Confidence in the general forecast past mid-week remains low. Questions in regards to upper-level pattern remain aplenty with a wide array of potential from a cut-off low plaguing the region to continued rounds of swift moving shortwaves. In the instance the cut-off scenario takes place, generally expect prolonged period of unsettled weather and cooler temperatures with increased cloud cover. On the flip side, if the wave remains open than well see much of the same with the current pattern. Quick moving shortwaves bringing new rounds of weather to watch and temperatures much more seasonal.

-JR

AVIATION

12/12Z TAF Period.

Expect passing clouds across the CWA through the period. Ceilings will be just above IFR conditions for most areas, mostly this morning. Humidity is near 100 percent in many areas this morning, but cloud cover is preventing fog development. That being said, some patchy fog can't be ruled out before 15z today. A few sprinkles/light showers are possible today, but any rainfall impacts should be minor. Mountains/passes will be obscured through at least this afternoon. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 58 41 64 45 / 10 0 30 80 CTB 52 37 54 39 / 20 0 50 50 HLN 65 42 69 43 / 0 0 40 40 BZN 71 40 75 37 / 0 0 0 40 WYS 72 37 67 26 / 0 10 0 10 DLN 74 39 73 35 / 0 0 0 0 HVR 60 36 66 43 / 10 0 10 80 LWT 59 37 68 41 / 10 10 0 70

TFX WATCHES/WARNINGS/ADVISORIES

High Wind Watch from Sunday afternoon through Sunday evening for Madison River Valley.

Fire Weather Watch for portions of Southwest MT on Sunday.