Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
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264 FXUS66 KMFR 240028 CCA AFDMFR Area Forecast Discussion National Weather Service Medford OR 428 PM PST Sat Nov 23 2024 .DISCUSSION...An upper low off the southern British Columbia coastline continues to bring unsettled weather to the area. The upper low is forecast to shift slowly south along the Pacific Northwest coastline...bringing rounds of steady precipitation mixed with showers through at least the first part of next week. The first round of steady precipitation will begin impacting southern Siskiyou county Sunday morning...impacting the west side by Sunday afternoon. The activity will spread east through the day. Another round of precipitation spreads from west to east early Monday morning into the afternoon hours. Snowfall along the southern Siskiyou passes will be the biggest impact of the storm...and a Winter Storm Warning was issued to account for this hazard. Please see the warning for additional information. Scattered showers linger through much of Tuesday before the upper low moves southeast into northern California allowing for upper level ridging to set up over the area Wednesday into Thanksgiving. Unfortunately with high pressure building over the area...there is the possibility of dense fog over the valley locations...so warm days aren`t expected. One thing we do have confidence in regarding this pattern change mid next week...dry weather through at least the holiday weekend. In fact...only 1 ensemble member...so about 3% of the models...are showing any precipitation from Saturday through the following Tuesday after Thanksgiving. -Riley && .AVIATION...24/00Z TAFS...A weak short wave disturbance east of the Cascades this evening will push eastward out of the area overnight. As a result, isolated to scattered showers early this evening will gradually diminish and end late this evening/overnight. Residual VFR ceilings (local MVFR and higher terrain obscured) should also gradually break up. This presents a tricky forecast with fog potential given all the recent moisture of the past few days. With enough clearing and winds decoupling from the boundary layer, fog seems likely in some wet side valleys, including the Rogue, Illinois, Umpqua and other coastal valleys. However, some of these places keep the cloud deck most of the night (Roseburg) and guidance indicates VFR prevailing. We have gone with LIFR fog in the Medford TAF toward Sunday morning since clearing is expected there this evening which would maximize radiational cooling and the potential for fog later tonight. We`ve left it out of Roseburg for now, but will re-evaluate this evening. Meanwhile, another front will be approaching the coast from the Pacific and this will bring the potential for low level wind speed shear to North Bend, Roseburg and Medford overnight or Sunday morning. Wind speeds 1500-2000 feet above the ground are 25-30kt greater than surface winds (light just below the inversion). So, we`ve included this in the TAFs for those terminals. The front will bring light rain and MVFR ceilings beginning late Sunday morning to the coast, spreading inland during the afternoon. Breezy to gusty S- SE winds are possible Sunday afternoon in the Shasta Valley, southern Rogue Valleys and over the East Side. -Spilde && .MARINE...200 PM PST Saturday, November 23, 2024...Gusty south winds will continue today, with seas remaining high and steep. Another front will approach the area this evening, bringing south gales and very steep wind driven seas tonight through Sunday. Conditions remain unsettled the upper level low finally moves eastwards between Monday and Tuesday. High pressure builds for the remainder of the week with relatively low seas. -Smith && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...Winter Storm Warning from 10 AM Sunday to 4 AM PST Tuesday for CAZ082. PACIFIC COASTAL WATERS...Small Craft Advisory until 10 PM PST this evening for PZZ350-356-370-376. Gale Warning from 10 PM this evening to 7 PM PST Sunday for PZZ350-356-370-376. && $$