Marine Weather and Tide Forecast for Bozeman, MT

DISCUSSION
Today through Friday...

Satellite imagery shows flat ridging over the region, with some high clouds already spreading in from the west ahead of a trof over the PacNW. Skies have cleared over most of the forecast area and temps have responded. As of 2am it is 30F at Judith Gap and Harlowton, mid 30s at Roundup and upper 30s at many other sheltered locations. Expect some early morning frost in the notoriously colder spots. The main issue in the immediate short term is fog potential in our east. Though it hasn't happened yet, the clear skies, light east winds and dewpt depressions of 1-3F suggest fog remains a good bet over our east (i.e. Miles City, Baker & Ekalaka). The HRRR hints at fog development by ~10z and this seems reasonable.

Most of today will be dry and warmer with temps reaching the mid 60s to lower 70s, along with developing east winds. Beginning around 21z we will start to see convection develop in our west as aforementioned PacNW trof moves into the northern Rockies.
Although bulk shear will increase, we are looking at less than 500 j/kg of sbcape (there isn't much time for pre-frontal moisture return), so expect the convection to remain benign. Look for a west to east moving area of showers tonight with the trof passage.
Greatest pcpn amounts (0.30" or less) should be produced in our NW where forcing will be greatest, and in our NE-E per LLJ and higher pwats.

Shortwave exits to our NE by early Friday and this should be followed by a period of mostly dry wx under subsidence, with post-frontal stabilization. Expect at least a few showers to wrap back southward behind the trof by Friday afternoon. The potential for lightning on Friday is low (<10% chance). Temps tomorrow will be a bit cooler w/ highs in the 60s most places.

JKL

Friday Night through Wednesday...

Trof passage will likely bring showers to the region Friday night through Saturday, but tonight's model runs have overwhelmingly become flatter/weaker with this system. Our pcpn forecast has thus trended down. Latest NBM probabilities for 0.50" are 5-10% in the north to 35-45% from Sheridan to Alzada. NW flow upslope areas should be favored. The chance of an inch or more of precip is down to 15-20% at Sheridan, 10% from Pryor to Lame Deer and Ekalaka, and less than 10% further north. This system remains something to watch, especially with regard to outdoor activities over Memorial Day weekend, but it does not appear to be a significant precip maker. Snow levels will be around 9kft, so heads up to anyone planning to head to the mountains this weekend.

Cyclonic northerly flow will keep shower potential going on Sunday, mainly across our east and and during the peak heating hours. Temps Saturday and Sunday will be seasonable (upper 50s and 60s).

Confidence is high for ridging and above normal heights Monday through Wednesday, as a deep low anomaly settles over the Gulf of AK. This will bring warmer and drier weather, no doubt of that, but there are details to be worked out. We may remain under cyclonic northerly flow and backdooring east winds Monday & Tuesday...keeping the warmup somewhat gradual. There is also the possibility of a weak shortwave or two undercutting the ridge and bringing at least a low chance of diurnal showers and thunderstorms. For now, look for temps to warm to the 70s and eventually lower 80s by midweek, with a slight chance of showers and thunderstorms each day. Given high confidence of above normal heights and weak flow aloft, this does not look like a severe weather scenario. Also, the warmer temps will promote high elevation snow melt and this will be something to monitor.

JKL

AVIATION

Localized fog will impact southeast MT thru ~15Z this morning, with reduced visibility possible (30% chance) at KMLS, KBHK & K97M. Otherwise, VFR will prevail today with winds becoming easterly (gusts under 25 knots). By mid to late afternoon, expect scattered showers and a few thunderstorms to develop over the west. Showers and isolated embedded thunderstorms will track west to east across the area tonight, exiting the east by daybreak Friday. Look for local MVFR in this shower activity, and occasional mountain obscurations. JKL

PRELIMINARY POINT TEMP/POPS

Tdy Fri Sat Sun Mon Tue Wed ------------------------------------------------------- BIL 070 046/068 046/066 047/069 046/073 050/076 051/079 2/T 52/W 26/T 32/T 01/U 12/T 22/T LVM 065 039/067 042/065 042/070 044/075 047/076 047/077 4/T 63/W 36/T 21/U 01/U 23/T 22/T HDN 072 045/068 045/065 046/068 045/073 047/076 049/080 0/B 52/W 26/T 44/T 11/U 12/W 22/T MLS 070 047/065 044/066 046/066 045/069 046/074 049/079 0/U 73/W 25/W 44/T 11/U 01/U 21/U 4BQ 068 045/067 046/061 048/061 044/065 046/071 049/075 0/U 62/W 26/T 45/T 21/B 01/U 21/B BHK 065 042/055 041/059 043/059 040/062 042/068 044/072 0/U 64/W 24/W 45/T 21/B 01/B 21/U SHR 069 041/067 043/061 043/064 041/070 043/073 046/076 1/B 42/W 28/T 56/T 12/T 13/T 22/T

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