textproduct: Great Falls

KEY MESSAGES

- Breezy at times Wednesday afternoon with stronger winds possible around any thunderstorm that develops.

- Cooler and wetter conditions continue on Thursday with another chance for afternoon thunderstorms.

- More seasonable temperatures Friday and Saturday before cooling off again Sunday and Monday.

DISCUSSION

- Meteorological Overview:

Breezy conditions are expected on Wednesday across portions of Central Montana but to a lesser extent than what was observed on Tuesday. Northwesterly flow will remain in place through Thursday bringing daily chances for afternoon showers and thunderstorms.

On Friday, upper-level ridging starts to build bringing a day of warmer and drier conditions to the region. Saturday into Sunday the ridge flattens a bit with allows for a brief period of precipitation before building back over the western CONUS through at least the middle of next week.

- Forecast Confidence & Scenarios:

Gusts up to 35 mph are possible Wednesday afternoon, especially along the Hi-Line and Central Montana east of a line between Inverness and Geyser. Afternoon instability is enough that isolated thunderstorms are possible across the Northern Plains. With DCAPE values in the 400-800 J/kg range, strong wind gusts are possible with any thunderstorm that develops. The overall severe threat is quite low but it is definitely within the range of possibilities for a couple thunderstorms to turn severe on Wednesday afternoon, particularly when it comes to severe wind gusts.

On Thursday, the models are a little split on the potential. The NAM and RDPS are relatively more robust in SFC CAPE. Whereas the GFS and HRRR seem a little less convinced. The main uncertainty is how a potential shortwave might behave as it dips down out of Alberta. Currently both the GFS and Euro have it missing us whereas the NAM has it clipping the northeastern portion of our CWA. The placement and track of this shortwave will be the main thing to watch as it will directly play into how the thunderstorm potential will play out. -thor

AVIATION

17/06Z TAF Period

VFR conditions are expected to prevail through the period. Northwesterly winds will be gusty at times across North-Central and Central Montana through Wednesday afternoon, although gusts are generally expected to remain below 35kts. The only exception would be around any thunderstorm activity that develops after 17/20Z which may produce locally stronger winds as well as brief periods of MVFR/IFR conditions. -thor

PRELIMINARY POINT TEMPS/POPS

GTF 69 46 73 47 / 20 30 10 0 CTB 66 43 68 44 / 30 30 20 10 HLN 75 47 79 49 / 10 10 0 0 BZN 75 43 78 45 / 0 0 0 0 WYS 73 34 76 38 / 0 0 0 0 DLN 76 42 80 46 / 0 0 0 0 HVR 68 43 71 44 / 30 20 30 10 LWT 65 40 68 41 / 20 20 40 0

TFX WATCHES/WARNINGS/ADVISORIES

None.