Marine Weather and Tide Forecast for Bozeman, MT

8pm UPDATE
Overall the forecast remains on track. While showers will linger across the CWA into the morning, the steady rain will be confined to far eastern Montana, especially near and NE of Baker, MT where they could pick up another 0.5" in the next 12-24 hours.

Gusty winds will slowly taper off for the western 2/3 of the CWA overnight. For far eastern Montana, the pressure gradient around the occluded SFC low will tighten up overnight, however, due to the slight nocturnal inversion and ascent ahead of a vort max, wind gusts will remain below 50 mph though the night. Even though there wil be precip falling, the rainfall rate will likely not be enough to mix the stronger winds down to the sfc. A very brief window exists just after daybreak for the potential for some wind gusts near 60mph. As 850mb winds will be around 50kts at this time and this region will be on the backside of the aforementioned vort max, some of these winds could mix down between 6-9am before the low moves eastward. Opted to not issue any wind highlights due to the very narrow window and low confidence. WMR

DISCUSSION

Through Saturday Night...

Strong low pressure system over the Dakotas will continue to influence our eastern CWA through Friday morning. Winds will increase tonight over the MT/Dk border area with gusts 45-55 mph expected, possibly a little higher, thanks to a tightening pressure gradient associated with a deepening surface low over the eastern portion of the Dakotas. However, with upper vertical motion over the area, we think winds will remain under our high wind hi-light criteria. The trough axis will swing around through eastern Montana as well tonight bringing rainfall across our eastern border counties. So a wet/windy ride for our eastern border tonight into early Friday. In the meantime, numerous convective showers will prevail across our west and southern sections through this afternoon, winding down after sunset as instability wanes. Some rumbles of thunder are possible, but CAPE is generally low (100-300 J/kg), so strong thunderstorms are not anticipated.

A weak flat upper ridge builds in from the west on Friday as the Dakota upper low slowly slides east. So look for lingering light rain along the eastern border Friday to decrease. Pacific moisture in the westerly mid level flow will move into our west and bring an increasing chance of showers (iso/sct) and isolated thunder by late Friday, especially across our SW mountains (Beartooths/Absarokas). As mid level winds back ot the SW Friday night and 500 mb heights rise a bit, precipitation should die off.

Saturday/Saturday night...Split upper trough (northern branch over British Columbia coast, southern branch into Nevada) will develop to our west with southwest flow bringing some moisture and perturbations back across our western CWA with some isolated showers spreading east as well Saturday night. Again, some thunder is possible, but CAPE remains under 500 J/kg and forcing is weak, so no strong thunderstorms are anticipated.

Look for overnight lows to generally range from upper 30s to mid 40s the next few nights. We may approach the freezing mark along portions of Fallon and Carter Counties Friday night where a brief light frost cannot be ruled out locally (25% chance of dipping below 32F). Daytime highs will be in the 60s at most locations Friday with some 50s still near the Dakota border. Highs on Saturday will be in the 60s to near 70 degrees.

As for impact precipitation...At this time, the forecast for Baker, MT has around an additional 0.70 inches of rain for Baker through Friday morning, but there is still a 25 percent chance that they could see over an inch of rain from this whole event.
Luckily, soils are drier in this region at this time, so any rain that falls should not be to much of a problem, even if the high end amounts occur. BT

Sunday through Wednesday...

Ensembles show the next low moving into the Pacific NW coast early Sunday. Low level easterly flow will aid in beneficial precipitation for the region through Monday night. Uncertainty still remains of the exact track of the low and exact precip amounts. There is a 40-60% chance of at least an inch of precip across the region. With instability present Sunday evening, a few thunderstorms are possible with heavy rainfall being a concern given above average atmospheric moisture and low level easterly flow. Heavy rainfall potential will also lead to concern for continued rises on small streams especially with the recent precip. As for mountain snowfall, snow levels will begin around 8-9,000 ft Sunday evening, dropping to around 7,000 ft Monday morning. There is about a 30-40% chance of at least a foot of snowfall in the Beartooth/Absarokas Sunday through Monday night.
Additionally, a tight pressure gradient over eastern MT Sunday will allow for breezy winds over SE MT. Some ensembles are depicting lower heights with some energy moving to the north of us late Tuesday into Wednesday, bringing low to moderate precip chances.

High temperatures will be in the 50s and 60s Sunday, cooling to the 50s for Monday with 50s/60s for the remainder of the period.
TS

AVIATION

00z TAF Discussion...Flight conditions will be primarily VFR across the area tonight into Friday. However, portions of SE Montana including, KBHK and KMLS, will see MVFR to occasional IFR conditions at times as a disturbance in the Dakotas continues to back into these areas. Scattered showers further west across central and western areas will diminish significantly as the sun sets, though isolated patches of convection can't be ruled out through the night. Local MVFR conditions can be expected near any shower activity. In the early morning hours patchy stratus/fog can't be ruled out in the western foothills. Elsewhere northwest winds should limit fog/low stratus potential with many areas seeing gusts in the 20 to 35kt range tonight into tomorrow. Low level wind shear is possible where surface inversions get strong enough, mainly in low lying locations though did add a mention for KBIL. Chambers

PRELIMINARY POINT TEMP/POPS

Fri Sat Sun Mon Tue Wed Thu ----------------------------------------------------------- BIL 044/063 044/067 048/065 045/053 043/063 044/067 045/072 32/W 34/T 28/W 98/W 55/W 54/T 23/W LVM 038/061 039/064 044/056 038/053 039/062 039/066 040/069 32/W 44/T 5+/W 97/W 45/W 54/T 23/T HDN 044/063 043/068 049/070 045/053 042/062 042/067 043/073 32/W 23/W 28/W 99/W 66/W 54/T 33/W MLS 047/062 040/067 047/065 043/052 042/059 042/067 044/072 66/W 12/W 36/W 99/W 75/W 44/W 32/W 4BQ 045/058 039/066 046/066 043/050 042/056 042/064 043/070 54/W 21/B 36/W 99/W 75/W 44/W 22/W BHK 038/054 033/063 039/056 038/051 038/058 039/064 040/069 88/W 20/B 35/W 89/W 75/W 33/W 32/W SHR 040/060 038/067 044/069 040/050 038/058 037/064 038/071 32/W 23/T 28/W 99/W 66/W 55/T 23/T

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