textproduct: Great Falls

KEY MESSAGES

- Widely scattered showers and thunderstorms this afternoon across southwest Montana and eastern portions of central MT.

- Dry and warm conditions for Independence Day.

- Afternoon showers and thunderstorms possible again Sunday with a more widespread thunderstorm risk Monday and Monday night.

DISCUSSION

- Meteorological Overview:

Broad troughing across western Canada and upper level ridging centered south of the region maintains a general west to southwest flow across the Northern Rockies and MT into next week. Temperatures remain warm as upper level ridging to the south gradually exerts a greater influence across area with the warmest temperatures likely to occur next Tuesday/Wednesday.

A weak shortwave trough moving east across the area today along with afternoon heating/destabilization has led to thunderstorm development early this afternoon across Judith Basin and Fergus counties. Additional isolated to widely scattered showers and thunderstorms are likely to develop across southwest MT later this afternoon before the shortwave moves east of the region this evening.

Warming aloft on Saturday will lead to more stable conditions with little to no risk for shower/thunderstorm development and overall warm but somewhat breezy afternoon conditions for the Independence Day holiday. A somewhat stronger shortwave associated with troughing across BC moves through the region Sunday bringing a return to afternoon shower/thunderstorm development followed by some slight cooling on Monday, mainly for north-central MT, as a cooler airmass slides south from AB. A shortwave disturbance moving around the building SW US upper ridge moves through the region Monday/Monday night bringing a more widespread risk for thunderstorms. A deeper surge of moisture accompanies the wave on Monday which may support a risk for locally heavy rain and the potential more organized/strong thunderstorms.

- Forecast Confidence & Scenarios:

Thunderstorms through the rest of this afternoon will be limited to areas along/south of a line from Helena to Lewistown. Higher CAPE and surface dewpoints exist across Fergus county early this afternoon which will support a risk for a few stronger storms there before drier/more stable air moves east later this afternoon. Across southwest MT there is less low level moisture available with dewpoints mainly in the 40s leading to a lower coverage of storms with areas near the ID/WY border last to see the drying this evening. Hoenisch

AVIATION

03/18Z TAF Period

Expect VFR conditions along with light winds to prevail across North Central and Southwestern Montana over the next 24 hours. A few isolated SHRA/TSRA are expected to develop across the higher terrain of SW MT this afternoon, but impacts to airports are uncertain at this time. Ludwig/thor

PRELIMINARY POINT TEMPS/POPS

GTF 52 86 55 85 / 0 0 0 0 CTB 50 80 50 80 / 0 0 0 0 HLN 53 85 56 86 / 10 0 0 20 BZN 49 85 54 87 / 10 0 0 10 WYS 40 80 43 84 / 20 0 0 0 DLN 48 84 51 86 / 20 0 0 20 HVR 53 86 56 86 / 0 0 0 0 LWT 49 84 52 83 / 10 0 0 10

TFX WATCHES/WARNINGS/ADVISORIES

None.