textproduct: Great Falls

KEY MESSAGES

- Much cooler today across the region behind a cold front. A few showers cannot be ruled out today over the plains and adjacent areas.

- Temperatures already begin to trend warmer Tuesday, and will do so through the end of the week.

- Next round of heat looks to peak Friday, with fire weather concerns also returning in some areas that day.

DISCUSSION

- Meteorological Overview:

An upper level disturbance tracking across the region through the day today will result in quite a cool day behind a cold front moving through as of publishing this discussion. Upper level support will yield a few showers through the day today, mainly north of the I-90 corridor. Overall precipitation amounts with any shower that forms looks to be not much more than a few hundreths.

By tomorrow another upper level ridge begins to work in from the west. That said, a cyclonic northwesterly flow aloft over the Northern Rockies will act to temper the warming trend, at least for a day or two before the ridge fully moves overhead toward the latter half of the week. After today the region looks dry as the upper level ridge slowly builds in.

Friday looks to be the hottest day at this time, with breezy winds over much of the region by mid-afternoon. Should this scenario unfold, concerns for fire weather conditions would be increase.

Confidence in specifics wanes into next weekend, though there does look to be some form of zonal flow aloft in place. The uncertainty lies in whether there will be any embedded waves capable of producing additional stretches of gusty winds or precipitation should they be strong enough. -AM

- Forecast Confidence & Scenarios:

Largest source of uncertainty for this forecast will be just how breezy and dry it will be on Friday across many areas. Ensemble average 700 mb flow is on the order of 15 kts or so. Given the expected deep mixing on Friday, these winds should not struggle to mix to the surface. Should this mid level flow trend stronger, closer to the current 75th percentile (20-25 kts), there would be increased concern for at least elevated fire weather Friday. -AM

AVIATION

03/06Z TAF Period

VFR conditions will prevail across all terminals during this TAF Period outside of the KCTB, KHVR, KHLN, KLWT, and KGTF terminals. At the KHVR and KCTB terminals smoke will periodically reduce visibility to at least MVFR-levels for the first fews hours of this TAF period before it moves southward. At the KGTF terminal smoke will reduce visibility to MVFR levels for next few hours. At the KLWT and KHLN terminals smoke will briefly reduce visibility to MVFR levels at the beginning of this TAF Period. A cold front is sliding south from Canada during the beginning of this TAF Period and will shift winds from westerly to more northerly. It will be windy across all terminals during the beginning of this TAF Period. At the KGTF, KHVR, and KCTB terminals MVFR-level ceilings will occur for a few hours around 03/12Z. At the KLWT terminal during the majority of this TAF Period there is a 15% or greater chance for a light rain shower. Across most of the TAF sites smoke from wildfires will reduce slantwise visibility during this TAF Period. -IG

For KGTF: Winds shift to northwesterly between now and 09Z associated with a surface cold front and remain northwesterly through this forecast period. Between 09Z and 15Z there is an 80% chance for a 15 kt crosswind. Before 09Z and after 16Z there is a 10% chance for a 15 kt crosswind. Increased humidity in the 0C to -10C layer will result in at least brief/minor icing concerns by early Monday morning. -IG

FIRE WEATHER

Remaining concerns through the day today will include a cold front progressing southward over the plains as of writing this discussion early this morning, resulting in a gusty wind shift to a more northerly direction through the morning. A persistent breezy northwest wind along and east of US-87 will result in elevated fire weather conditions through the early evening. -AM

PRELIMINARY POINT TEMPS/POPS

GTF 70 47 78 49 / 20 0 0 0 CTB 66 42 74 46 / 20 0 0 0 HLN 72 47 79 48 / 20 10 0 0 BZN 72 43 78 46 / 20 0 0 0 WYS 71 33 75 35 / 0 0 0 0 DLN 72 43 76 45 / 0 0 0 0 HVR 70 43 79 48 / 20 10 0 0 LWT 64 42 73 46 / 40 10 0 0

TFX WATCHES/WARNINGS/ADVISORIES

Red Flag Warning until 3 AM MDT early this morning for Central and Eastern Lewis and Clark National Forest Areas-Chouteau and Fergus Counties-Eastern Glacier/Toole/Central/Eastern Pondera/Liberty-Helena and Townsend Ranger Districts of the Helena National Forest-Hill and Blaine Counties-Lewis and Clark National Forest Rocky Mountain District-Rocky Mountain Front- Lincoln Ranger District of the Helena National Forest.