Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
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908 FXUS66 KMFR 290404 AFDMFR Area Forecast Discussion National Weather Service Medford OR 904 PM PDT Sun Apr 28 2024 .DISCUSSION...The forecast is on track for this evening. Radar indicates some light showers over Douglas County as well as over the Cascades and around Mount Shasta. Overnight temperatures will remain above freezing for areas west of the Cascades tonight. A cold front will bring precipitation to west side areas starting on Monday morning, with some showers possible over northern Klamath and Lake counties as well. Snowfall will be limited to Cascades peaks with amounts looking to remain below advisory thresholds. While substantial road accumulation is not currently expected, snow showers can still lower visibility or locally slick conditions. Extra caution is advised for anyone traveling over the Cascades through the day Monday. Please see the previous discussion for more details about the short- and long-term forecasts. -TAD && .AVIATION...29/00Z TAFs...A front will move onshore late tonight into Monday morning. Rain and MVFR ceilings along the coast will press inland and reach as far south and east as the Cascades/Siskiyous, where snow levels will be low enough to cause terrain obscurations/limited visibility. Breezy southwest winds along the coast shift to northwest Monday morning. Expect the lower conditions to improve to VFR in most areas Monday afternoon, though some terrain obscuration and showers could linger near the Cascades. -Spilde/Smith && .MARINE...Updated 800 PM Sunday, April 28, 2024...Weak high pressure southwest of the waters will result in light to moderate west winds and moderate seas this evening. A front will move through the waters early Monday morning with stronger west winds and low end small craft advisory conditions into Tuesday morning. A low with some high and steep swells will then move into the waters Tuesday afternoon and evening. A thermal trough is anticipated to build briefly Wednesday into Wednesday night with northerly winds increasing south of Cape Blanco. Calm seas and weak winds are likely Thursday into Friday. -DW && .PREV DISCUSSION... /Issued 442 PM PDT Sun Apr 28 2024/ SHORT TERM...Tonight 4/28 through Monday night 4/29...Satellite imagery is showing some cloud cover across portions of southern Oregon and northern California with radar showing some light showers in northern Douglas County moving into Lane County. Expect a relatively benign rest of the afternoon and evening. Then, the next front swings into the Pacific Northwest late tonight into early Monday morning and brings the next dose of precipitation with it. Snow levels will be lower around 3500 feet or so, but precipitation amounts will largely be light with the heavies amounts being focused in the Cascades north of highway 140. Still, snowfall amounts are expected relatively light with the highest amounts of 2 to 5 inches possible for Crater Lake, Diamond Lake, and Willamette Pass. Meanwhile, Siskiyou Summit on I-5 might see a dusting of snow with highway 97 east of the Cascades seeing less than an inch possible. Cloud cover will linger and will heavily influence temperatures. This will keep afternoon high temperatures low, and could allow for overnight lows to stay moderately warmer. Despite clearing skies, we`re not expecting a freeze tonight for the Illinois Valley (15 percent chance or less). However with the next cold front coming through, the chances of a freeze Monday night into Tuesday morning increase to 60 percent, but cloud cover may inhibit freezing temperatures. Have issued a freeze watch for Monday for portions of the Illinois Valley. Please see the NPWMFR for more details. -Schaaf LONG TERM...Tuesday through Sunday, April 30 - May 5, 2024... A cool spring weather pattern will continue into Tuesday as WNW flow aloft brings yet another upper air disturbance into the PacNW from the Gulf of Alaska. Some cold/frosty spots are possible in the morning in the valleys west of the Cascades, primarily south of the Umpqua Divide. As the upper trough moves across northern Oregon, gusty breezes will develop Tuesday afternoon, especially east of the Cascades. We`ll remain on the southern fringes of this system, with highest PoPs (for showers) across the north. There is a fairly high probability of precipitation (50-80% chance) from the coast to Douglas County and over to the Cascades north of Crater Lake. Amounts appear to be on the light side again, generally 0.10-0.20 for the Coos Coast Ranges and along the Lane/Douglas county border with maybe a couple of inches of snow above 4500 feet north of Crater Lake. South of the Umpqua Divide, precip chances diminish quickly to below 20% Tuesday, though an isolated shower/sprinkles cannot be ruled out. The upper trough will exit to the east Tuesday night into Wednesday, so precip chances drop to almost nil. Another cold night is expected, so frost/freeze potential will again be in play for the west side valleys. The potential for frost (lows 33- 36F) is highest (50-80% chance) for a few hours in the typically colder locations (Illinois/Applegate Valley/Grants Pass areas) with freezing conditions (<=32F) possible (20-30% chance) in the Illinois Valley as well. Heights rise on Wednesday as the upper trough continues to shift to the east, resulting in at least partial sunshine with a dry and slightly milder afternoon (high temps back closer to seasonal normals). However, yet another upper trough coming out of the Gulf of Alaska Wednesday night will skim by to our north on Thursday. As has been the case for the last 3 days, models are showing most of the precip with this system staying well to our north, but a 20-30% chance of showers persists for areas along the coast and across northern Douglas County. Modest warming will continue with highs in the upper 60s to low 70s west of the Cascades and generally in the mid 60s over the East Side. Uncertainty increases late next week into the weekend. The majority of models/ensembles show at least brief upper ridging again on Friday with approximately another 5 degrees of warming (compared to Thursday). Then, guidance is showing a potentially more substantial trough moving in Friday night into next weekend with higher PoPs and lower temps, but confidence in the specifics of timing/strength right now remains low. -Spilde && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Freeze Watch from late Monday night through Tuesday morning for ORZ024. CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory from 5 PM Monday to 11 PM PDT Tuesday for PZZ356-376. Small Craft Advisory from 5 AM Monday to 11 PM PDT Tuesday for PZZ350-370. && $$