Marine Weather and Tide Forecast for Park City, MT

DISCUSSION
Today through Thursday Night...

Satellite imagery shows WNW flow aloft with an upper level jet to our south from OR to southwest WY. There is a weak shortwave moving thru south central MT, which with steep mid level lapse rates is producing showers over/near the Beartooth Absarokas as of 0730z. As this wave tracks to the ESE the rain and mountain snow showers will do likewise thru the remainder of the night...likely staying to the south of Billings. There are also a couple of showers dropping thru eastern Powder River along an axis of low level frontogenesis, and these should exit southeast MT over the next couple hours. Light easterly winds persist in our far east and in this area there is still a risk of localized fog from now thru ~14z.

Once the south central MT wave exits to the east, we will undergo gradual height rises associated with a low amplitude ridge to our west. With this in mind, shower potential will be lower today and anchored mainly over our southern mountains. Low level frontogenesis will again be a potential axis of showers and weak t-storms this afternoon from Miles City to Broadus eastward.
Elsewhere, it will be drier with mixed/breezy downslope winds (gusts 20-30 mph). Look for high temps in the mid 50s to mid 60s, again coolest near the Dakotas border.

Flat ridging will bring a period of dry weather tonight thru midday Thursday. Boundary layer in our far east looks to remain moist enough for another risk of fog late tonight thru early Thursday east of Forsyth and Broadus.

Surface winds turn easterly Thursday and the ridging should push temps to the mid 60s to lower 70s (the warmest day for about a week). Next Pacific shortwave will introduce height falls and a chance of convection by afternoon in the west. Showers w/ embedded weak t-storms are likely from west to east with the trof passage Thursday night. There will be a bit of plains moisture return ahead of this wave, but the flow is too progressive to allow enough moisture/instability for any risk of strong storms. Current HRRR shows sbcapes of 200-400 j/kg. Regarding precip, though there remains a fair amount of model uncertainty, most areas should see 0.15" or less. The probability of exceeding 0.20" is 35-45% in our NW and NE, to less than 10% in Sheridan County.

JKL

Friday through Tuesday...

Potential for showers and weak t-storms will continue each day Friday through Sunday, as another trof moves slowly thru the region. Ascent generally looks to remain weak and the precip will be more diurnally driven than not, but there is model uncertainty regarding the depth of the trof. As a result, there is considerable ensemble spread in QPF during this time. A higher amplitude trof would obviously be wetter, but this won't be rain- maker of the magnitude of the past few days. The probability of exceeding 0.50" from Friday to early Sunday ranges from about 10% in the north to 45% in the south. Sheridan has a 20% chance of reaching an inch of precip. Upslope areas in our south should pick up greatest amounts as flow turns northwesterly by Saturday (which seems to be the wettest and coolest day). Temps will cool back to the 60s Friday and Saturday. Snow levels in the high country look to set up around 9kft, so keep this in mind if you are planning to head for the mountains over Memorial Day weekend.

There is growing confidence for a building ridge early next week, which would bring warmer & drier weather. A potential fly in the ointment is if the ridge axis stays to our west and cyclonic northerly flow remains over the northern plains...a set up which would keep "cooler" easterly winds for southeast MT and northern WY. For now, look for near 70F in the west Sunday, followed by mid 60s to mid 70s Monday, and 70s to lower 80s Tuesday. Cannot completely rule out some mainly diurnal mountain showers on these days. The warmer temps will also increase high elevation snow melt again, but our rivers are currently in good shape and can take some water.

JKL

AVIATION

There is a risk of fog & stratus (30% chance) near the Dakotas border (affecting KBHK-K97M) from now through ~14z this morning.
The remainder of the area will see VFR, but an early morning disturbance is bringing scattered rain and mountain snow showers to southern areas...so expect mountain obscurations and perhaps local MVFR near the foothills. VFR will otherwise prevail today and tonight with only isolated afternoon and evening showers. KMLS & KBHK could see an isolated TS nearby (<20% chance) between 21-06Z. Late tonight, localized fog is possible again in far southeast east of Rosebud County. JKL

PRELIMINARY POINT TEMP/POPS

Tdy Thu Fri Sat Sun Mon Tue ------------------------------------------------------- BIL 064 041/071 046/069 046/063 046/070 046/075 050/080 1/U 02/W 53/W 36/T 22/T 01/U 12/T LVM 061 036/065 040/067 043/062 041/071 045/077 048/079 1/B 06/T 65/W 46/T 21/U 12/T 23/T HDN 064 039/071 046/069 046/064 044/068 044/074 048/080 1/U 01/B 63/W 46/T 33/T 11/U 12/W MLS 064 038/070 048/067 045/064 045/066 044/072 047/078 2/T 10/U 84/W 35/T 33/T 11/U 11/U 4BQ 062 038/068 046/069 046/061 045/063 043/069 046/076 1/U 10/U 62/T 46/T 44/T 11/U 11/U BHK 056 032/064 043/061 041/059 042/061 040/066 042/071 2/T 10/U 74/W 34/T 44/T 11/U 11/U SHR 061 035/070 042/069 044/060 041/064 041/071 044/077 3/W 11/B 43/T 58/T 44/T 12/T 12/T

BYZ WATCHES/WARNINGS/ADVISORIES
MT...None.
WY...None.