textproduct: Great Falls

KEY MESSAGES

- Daily chances for afternoon and evening showers and thunderstorms through at least Saturday. - Some strong to severe thunderstorms are possible Thursday with locally gusty winds, hail and intense rainfall.

- Seasonable temperatures today warm back to afternoon temperatures in the 90s by early this weekend.

DISCUSSION

/Issued Issued by National Weather Service Missoula MT/

A broad mid-upper level ridge remains in place over much of the US. The ridge center expands/shifts westward some by the weekend as as and upper level trough in the eastern Pacific lifts northward along its periphery into BC. A south to southwesterly mid-level flow around the ridge maintains a stream of anomalous atmospheric moisture from the SW US across the Northern Rockies into the upcoming weekend with some indications of the deeper moisture being shunted east by Sun/Mon as an upper level system moving through western Canada temporarily flattens the northern periphery of the ridge.

Today will be the coolest (but still seasonably warm) of recent and upcoming days with considerable cloud-cover streaming across the region and even some patchy fog early this morning across mainly north-central MT. Convection will be somewhat inhibited today by the more extensive cloud-cover and lack of any larger scale forcing, but a few widely scattered showers and thunderstorms may still develop from terrain heating this afternoon. The upper level trough lifting toward BC tomorrow will provide some larger scale lift for a more widespread coverage of showers and thunderstorms Thursday afternoon/evening. The increased flow aloft will provide enough shear to support some strong to severe thunderstorms late Thursday with isolated strong winds and hail, while the deep moisture still in place will bring a risk locally intense rainfall with some some storms. At this point models are not focusing on any particular area for heaviest rainfall but coverage of thunderstorms is likely to be greatest across central and southwest MT vs areas to the north.

A daily risk for showers and thunderstorms continues through at least Saturday with lower confidence in the coverage or intensity of storms with less forcing available. Temperatures also warm back up as the ridge nudges westward by the end of the week with widespread maximum temperatures in the 90s likely again by Friday and Saturday. Hoenisch

AVIATION

15/12Z TAF Period

Some patchy low clouds and possibly some fog are evident on satellite imagery across parts of nort-central MT and will have some potential to move into some TAF sites through 15z with KLWT most liey to have MVFR/IFR ceilings while confidence is much lower elsewhere. Variable mid-high level cloud-cover will continue to stream north/northeast across the region otherwise today with a few light showers possible at southwest MT terminals later this morning. Confidence in thunderstorm coverage this afternoon is low but cannot be ruled out at most TAF sites. Hoenisch

PRELIMINARY POINT TEMPS/POPS

GTF 83 59 88 60 / 30 10 20 30 CTB 80 57 84 59 / 30 30 20 20 HLN 86 62 90 63 / 40 20 30 50 BZN 86 57 90 59 / 70 30 20 20 WYS 83 49 87 50 / 40 40 30 20 DLN 85 55 89 57 / 50 20 20 20 HVR 82 59 89 61 / 50 20 0 20 LWT 77 54 84 56 / 60 30 30 40

TFX WATCHES/WARNINGS/ADVISORIES

None.