Marine Weather and Tide Forecast for Mount Shasta, CA

FXUS66 KMFR 282102 AFDMFR

Area Forecast Discussion National Weather Service Medford OR 102 PM PST Sat Feb 28 2026

DISCUSSION
A warm front lifting northward across SW Oregon is producing weak isentropic lift and generating some light rain along it early this afternoon. Snow levels are way up there -- around 8000-9000 feet. Rainfall has been generally light, with amounts ranging from a few hundredths to around 0.20 of an inch in areas that have had rain. A few spots along the SW Oregon coast and western Siskiyou County have had up to 0.25 of an inch.

Meanwhile, a cut off low is spinning about 600 miles to the WSW of Brookings currently. Satellite imagery shows the warm front well across SW Oregon, with a warm sector to the south across NorCal.
Lightning has been observed in the warm sector across NW California, primarily in Trinity, Humboldt and Mendocino counties, though also recently as of around noon, Shasta County and Plumas County. The warm sector will continue to advance north- northeastward this afternoon into this evening and a mid-level shortwave disturbance will move through. This will result in some healthy showers developing across our NorCal counties (Siskiyou/Modoc). Model guidance continues to peg this area as having the highest probability of lightning (25-40%) through this evening, but there is a slight chance (15-25%) all the way up to around the Rogue-Umpqua Divide in southern Oregon (including Grants Pass/Medford/Ashland) and also over south-central Oregon east of the Cascades as these showers move off to the east- northeast. CAMs show MUCAPE of about 250-500 J/KG, which is sufficient for lightning, isolated gusty winds and brief downpours and we can't rule out some small hail either. But, parameters don't look impressive enough to be too concerned about severe weather.

The convective acitivity is being supported by a 100-kt upper level jet, which will move off to the east of the area tonight.
While instability won't go away completely, thunder chances should diminish after 06Z (10pm). With the low offshore, we'll remain in diffluent flow aloft, so PoPs will remain high (50-90%) with coverage of shower activity highest during Sunday afternoon/evening. There is just enough instability for a slight chance of thunderstorms then too (15-20%), mainly from NorCal up the Cascades (western Klamath County) and over the west side (mainly inland from the coast).

The core of the closed low will move onshore Sunday night, then open up into a trough as it heads into the Great Basin on Monday.
PoPs and coverage of showers should diminish during this time period with most areas inland from the coast drying out Monday afternoon/evening. We should note that there won't be much of an air mass change as this low moves onshore, but snow levels lower to around 6000-6500 feet. Shortwave upper ridging moves in Monday night into Tuesday morning and the drier period will persist through Tuesday for inland areas. Rain chances increase along the coast Tuesday as the next upper trough approaches the PacNW, but even there, rain could hold off until the night. Temperatures remain mild for early March with highs in the upper 50s/low 60s west of the Cascades and 55-60F over the East Side.

WNW flow aloft will bring a fairly sharp upper trough through the area Tuesday night into Wednesday. Expect a period of light to moderate precipitation to accompany the cold front (all areas - 70-100% chance) with the focus along the coast and into the Cascades. Snow levels will drop during this event, down to 4000-5000 feet by Wednesday evening, but this will still keep most winter impacts confined to the higher terrain and Cascade passes.
There is a high 24-hr probability of 4 inches of snow or greater (85% chance) at Crater Lake National Park through Wednesday night, but the probability diminishes to 40% at Lake of the Woods on Highway 140. Snowfall rates on Highway 62 south of Crater Lake, but also on Highway 230 and 138 arounf Diamond Lake could reach 1 inch per hour briefly early Wednesday morning. Snow amounts are shown to be 3-7 inches above 5000 feet in the Cascades (north of Howard Prairie) with higher amounts to 10 inches above 5500 feet.
Snow amounts farther south in the Siskiyous only look to be an inc or so. Behind the front, showers probably diminish by Wednesday evening for the Rogue Valley (and southeast of the Cascades), but onshore flow keeps them going along the coast, to around the Rogue-Umpqua Divide and over to the Cascades. Back side energy could still bring low chances (15-30%) of showers on Thursday across NW sections, with dry weather elsewhere.

Late next week, recent guidance is showing more solutions favoring amplification of an upper ridge offshore, which would direct the best jet-related action to our north. Many ensemble solutions also show the ridge "flopping over" into the PacNW Friday/Saturday, which would keep things largely dry. We've given it a broad-brush for now given the uncertainty with the highest PoPs remaining along the coast and into the Cascades, but lower PoPs (and little to no precip) indicated south and east of the Cascades. There is really no indication of any big precip producers on the horizon.
-Spilde
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