textproduct: Great Falls

KEY MESSAGES

- It will warm up through Monday with a brief cooldown on Tuesday before it warms up to end the work week.

- Showers and thunderstorms will linger through early next week with Tuesday having the most widespread showers and thunderstorms.

DISCUSSION

- Meteorological Overview:

This morning there is upper-level zonal flow over North-central, Central, and Southwestern Montana which will build into an upper- level ridge with southwest flow aloft by this afternoon. This will keep monsoonal moisture around but allow temperatures to warm up several degrees compared to yesterday but still be slightly below seasonal averages. This afternoon and evening there will be another round of showers and thunderstorms primarily confined to Southwestern Montana. On Sunday the upper-level ridge with southwest flow aloft remains over North-central, Central, and Southwestern Montana. This will allow temperatures to warm up a few more degrees to be around seasonal averages. An upper-level shortwave will move through the flow and bring isolated showers and thunderstorms to North-central, Central, and Southwestern Montana Sunday afternoon/evening.

On Monday the upper-level ridge with southwest flow aloft remains over North-central, Central, and Southwestern Montana. By Monday evening the upper-level ridge begins to break down. This will bring breezy conditions to the area with isolated showers and thunderstorms Monday afternoon and evening. Temperatures will remain near seasonal averages on Monday. On Tuesday there will be zonal flow (west - east) over North-central, Central, and Southwestern Montana. This will allow temperatures to cool down to below seasonal averages with breezy conditions due to modestly strong low and mid-level winds. There will also be showers and thunderstorms across North-central, Central, and Southwestern Montana on Tuesday. On Wednesday and Thursday an upper-level ridge begins to build back in across North-central, Central, and Southwestern Montana. On Wednesday and Thursday temperatures will warm back up to around seasonal averages. On Wednesday and Thursday it will be mostly dry across the area. On Friday the upper-level ridge is over North-central, Central, and Southwestern Montana. This will bring hot and dry weather to the area. -IG

- Forecast Confidence & Scenarios:

In any areas where skies clear this morning there is a moderate chance for fog to form.

Today there is a 30% chance for showers and thunderstorms in Central and Southwestern Montana. On Sunday there is a 20 - 30% chance for thunderstorms across North-central, Central, and Southwestern Montana. On Monday there is a 15 - 30% chance for thunderstorms across North-central, Central, and Southwestern Montana. On Tuesday there is a 30 - 40% chance for thunderstorms across most of North- central, Central, and Southwestern Montana.

Today there is a 20 - 50% chance for a quarter inch of rain or greater across most of Southwestern Montana. As a result there is too low of a risk to consider any potential flash flooding on burn scars today. -IG

AVIATION

15/06Z TAF Period

A few lingering showers near the ID border may impact KWYS through 09z. Otherwise, main aviation concerns through the overnight period will be low clouds persisting across much of north- central MT, maintaining MVFR to occasional IFR ceilings with some potential for fog development, mainly near the KCTB terminal. Lower clouds look to dissipate late Saturday morning across north- central MT with shower and thunderstorms development Saturday afternoon primarily focused across southwest through central MT.

For KGTF: MVFR to occasional IFR low clouds persist through Saturday morning with most of the cloud layer occurring below the freezing level (10-15kft MSL), keeping the risk for icing minimal. Lower cloud ceilings look to mix out between 17-19z with VFR conditions following through the afternoon. The risk for showers or a thunderstorm in the vicinity increases after 02z Sun. Surface winds are expected to be 10kts or less and somewhat variable through Saturday morning before becoming predominantly northeast Saturday afternoon and evening with minimal cross-wind concerns. Hoenisch

PRELIMINARY POINT TEMPS/POPS

GTF 77 51 83 52 / 0 20 20 20 CTB 71 46 77 47 / 0 0 10 10 HLN 78 50 82 53 / 20 50 10 20 BZN 77 47 79 48 / 20 40 10 30 WYS 72 34 75 35 / 50 50 20 10 DLN 74 44 77 46 / 50 40 10 30 HVR 76 49 84 50 / 0 0 10 20 LWT 73 48 79 49 / 30 40 30 20

TFX WATCHES/WARNINGS/ADVISORIES

None.