textproduct: Great Falls

KEY MESSAGES

- Gusting winds along the Rocky Mountain Front through the upcoming week, with the strongest winds expected from Friday afternoon through Saturday morning.

- Predominately dry conditions over the next week outside of some periods of light, mountain snow.

- Temperatures warm well above normal to end the work week and through the weekend.

DISCUSSION

- Meteorological Overview:

A weak shortwave embedded within northwest flow aloft will move over the Northern Rockies through the overnight hours tonight. While this disturbance is largely deprived of moisture in the low levels, mainly being realized as an increase in mid-level cloud cover, a few light snow showers can't be ruled out in the northerly upslope regions of Central Montana and across the Island Ranges. Snow accumulations across these areas will generally be less than 1/4", but a few areas could see upwards of 1" of snow. Otherwise upper level ridging builds in over the Western CONUS beyond Wednesday, with weak shortwaves diving southeast over the ridge axis. This ridge will promote relatively dry conditions otherwise, with the exception of some light mountains snow showers as the aforementioned waves dive southeast over the region. Temperatures will warm progressively through the remainder of the work week and weekend beneath the ridge, with highs reaching the mid-40s to low 50s by Friday before rising further into the 50s to near 60 degrees over the weekend. - Moldan

- Forecast Confidence & Scenarios:

Gusty Winds along the Rocky Mountain Front through the Weekend...

A prolonged period of strong and gusty southwest to west winds, predominately driven by a moderate to at times strong pressure gradient, will occur along the Rocky Mountain Front through the work week and upcoming weekend. NBM probabilities for wind gusts in excess of 55 mph for any given day generally range from a 30% to 50% chance along and west of the US Hwy 89 corridor north of the MT Hwy 44 Jct. Of these days the most noteworthy event with respect to the potential for high winds appears to be from Friday afternoon/evening through Saturday morning when H700 cross barrier flow increases to between 40-60kts. At this time climate anomaly indicators such as the NAEFS and ECMWF EFIs do not suggest any anomalous values with this respect to this event. - Moldan

Mild Temperatures from Wednesday thru next Sunday...

Ensembles continue to favor well above average temperatures over the Northern Rockies during the second half of this week. With ridging aloft expected to be the dominant weather feature, the NAEFS analysis still highlights H500 heights running between 1 and 2 standard deviations above climatology. Additionally, gusty southwesterly surface winds will promote additional warming in the form of downsloping. This should equate to temperatures running as high as 20 degrees above average at times. The primary uncertainty will be the weak troughs undercutting the ridge that may prevent afternoon highs from realizing their maximum potential on some days. Either way, expect a significant warm up compared to this past weekend. Some impacts from this warm up may include the potential for ice jams on area rivers during the thaw process and grasslands losing the limited moisture from the recent light snowfall. - RCG

AVIATION

26/18Z TAF Period

An upper level disturbance embedded within northwest flow aloft will move over the Northern Rockies through the overnight hours tonight, with the primary impact to terminals across Southwest through North Central Montana being scattered to broken mid-level clouds. While this disturbance is largely moisture deprived in the low levels a few snow showers can't be ruled out over/near the KGTF and KHLN between mainly 00-09z Tuesday. Otherwise VFR conditions will prevail with mountains becoming obscured beyond 00z Tuesday. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 28 44 27 46 / 20 10 0 0 CTB 19 41 23 44 / 10 0 0 0 HLN 24 40 23 40 / 20 10 0 10 BZN 15 34 19 37 / 10 0 0 10 WYS -1 24 2 27 / 0 0 0 20 DLN 15 39 19 39 / 10 0 0 0 HVR 10 26 11 29 / 10 10 0 0 LWT 18 39 21 42 / 10 10 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.