textproduct: Great Falls

KEY MESSAGES

- Dry and above normal temperatures prevail through Tuesday.

- A spring storm to affect the CWA once again Wed into Thu.

- It turns much cooler by Thursday, with below normal temperatures continuing into next weekend.

DISCUSSION

- Meteorological Overview: An upper level ridge of high pressure will gradually build over the northern Rockies between now and Tuesday. This will result in warmer temperatures each day from now through Tuesday, with Tuesday being the warmest day. A few record high temperatures will be possible on Tue, with many areas of North Central MT having high temperatures in the 80s.

Wed thru Fri...The next spring storm arrives on Wed. The arrival time will be critical in determining how strong/severe any thunderstorm activity will be. The upper level dynamics will be supportive of strong storms, with the main question being how much daytime heating will we get before the storms arrive. The upper level trof moves from southern Idaho into Central MT by Thu morning, as colder air warps around the developing surface low that also develops near Central MT. This could result in areas of heavy rain/snow over Central MT from Wed night into Thu, with the heaviest precipitation ending Thu night.

Fri through next Sat...the upper level low that will be over Central MT on Thu is now progged to just drift/stall as it moves northeast into southern Canada. The upper level low will be close enough resulting in an unstable northwesterly flow aloft over the CWA, which will allow for daily chances for light rain/snow showers over the CWA, along with much below normal temperatures for Fri/Sat.

- Forecast Confidence & Scenarios:

There continues to be up to a 90 percent chance that record high temperatures will be possible on Tuesday.

There is up to a 20 percent chance that most lower elevation locations could get 2 inches of snowfall Thu into Fri.

For the Kings Hill, Glacier Park, Tobacco Root and Big Sky area, there is a 70 percent chance snow accumulations could exceed 8 inches from Wed night into Fri. Thus winter statements are looking more likely for mountain areas by early next week.

Additionally, some forecast models have significantly increased the total precipitation and surface winds with this spring storm, resulting in over 10 inches of snowfall at lower elevations between Great Falls and Lewistown and over 3 inches of liquid precipitation. In terms of winds, some models have a north wind over 55 mph over much of North Central MT. Overall the probability of this occurring is on the low side, there is about a 10 percent chance right now that this system could end up being a significant spring storm.

AVIATION

18/18Z TAF Period

VFR conditions will prevail through the period. Other than some passing high clouds, no aviation impacts are expected at this time. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 30 68 39 75 / 0 0 0 0 CTB 25 67 36 73 / 0 0 0 0 HLN 31 69 40 75 / 0 0 0 0 BZN 25 67 35 74 / 0 0 0 0 WYS 15 57 24 64 / 0 0 0 0 DLN 27 66 36 72 / 0 0 0 0 HVR 28 69 38 74 / 0 0 0 0 LWT 28 65 40 71 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.