Area Forecast Discussion
Issued by NWS Medford, OR

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688 FXUS66 KMFR 241145 AFDMFR Area Forecast Discussion National Weather Service Medford OR 445 AM PDT Mon Jun 24 2024 .DISCUSSION...
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Updated Aviation Section...
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&& .AVIATION...
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(24/12Z TAFs)...VFR conditions continue across northern California and southern Oregon tonight. A marine push has brought a stratus layer near the Coos and Douglas counties line. Northerly winds could push these clouds into the southern Umpqua Valley, but is not expected over Roseburg. Other areas will remain VFR through the TAF period with elevated afternoon winds, especially at the coast. There is a 40-50% probability for MVFR ceilings at the coast tomorrow morning, so have added that to TAFs. -TAD/Hermansen
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&& .PREV DISCUSSION...
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/Issued 333 AM PDT Mon Jun 24 2024/ DISCUSSION...Satellite imagery this morning is showing some low clouds in the Coquille Valley, and patchy fog along the coast, but other than that, skies are clear. Dry weather will persist today with lots of sunshine. High temperatures in the upper 80s east of the Cascades to the low to mid 90s across NorCal will be about 5-10F above normal. Over the west side, highs will be around 90F or so in the Rogue/Illinois valleys, but in the low to mid 80s near Roseburg. Coastal locations will have highs in the upper 60s/low 70s. Expect breezes to pick up again for most areas mid- late this afternoon and evening before subsiding around sunset. Mid-level SW flow will increase tonight and Tuesday ahead of an upper trough offshore, but with a dry air mass in place, we aren`t expecting any precipitation. It will turn breezy again Tuesday afternoon/evening, even gusty at times over portions of the east side. Over there, SW winds peak at 15-25 mph with gusts to 35 mph. Please see the fire weather section below for more details on that. Tuesday will be the hottest day, especially for the west side valleys where temps will peak in the low to mid 90s for Medford/Ashland/Grants Pass and up around 90F in Roseburg. Models are showing some mid and high level moisture arriving from the south that will graze areas south and east of the Cascades later Tuesday pm/night and into Wed am. So, some cirrus or altocumulus are possible then, but model precipitation probabilities remain 10% or less. It isn`t out of the question there could be some returns on radar over there, but given the dry air mass below, it`s likely to be virga and not reach the ground. It should be noted that instability is lacking since this moisture is arriving primarily Tuesday night, so thunder probabilities are also very low (10% or less). The upper trough offshore will move closer on Wednesday and mid- level flow will continue to increase with another dry cold front passing through. This will bring the potential for strong, gusty WSW winds east of the Cascades during the afternoon/evening (shifting to NW) with gusty NW breezes just about everywhere else. Local in-house guidance is showing peak wind gusts of 35-45 mph in NE California and over the east side deserts with gusts of 20-30 mph for most other locations. Temperatures will be lower by at least 10F Wednesday west of the Cascades and by 5F or so over the east side. Moisture remains limited with this system, but another strong marine push could induce some light rain/drizzle or mist along the coast and mountains of Douglas County. The cool upper trough will swing onshore into the PacNW Wednesday night into Thursday. The best precip chances are to our north, but there remains a low probability (<20%) of showers across northern Douglas County. Thursday is probably the coolest day for most inland areas with highs only in the upper 70s/low 80s for the west side valleys and in the 70s to near 80F east of the Cascades and over NE California. Warm, dry weather is expected Friday and Saturday with the next trough/mostly dry frontal system expected to arrive on Sunday. -Spilde MARINE...Updated 215 AM Monday, June 24, 2024...The thermal trough continues today, and steep seas will persist for much of the waters south of Cape Blanco into this evening, with very steep and hazardous seas south of Pistol River. The approach of another front then disrupts the pattern with improving conditions tonight into early Thursday. The front is expected to provide a deep layer of low clouds and a slight chance of showers Wednesday night. A return of the thermal trough pattern is expected Thursday into at least Friday night, with steep seas possible south of Cape Blanco. -DW/Hermansen FIRE WEATHER...Conditions yesterday east of the Cascades and, in particular, Modoc County, were certainly within the realm of "critical" in terms of fire weather with gusty winds and very low humidity during the afternoon/early evening. Some of the more prone RAWS stations in Modoc County (Timber Mtn, Devil`s Garden) and also east of the Cascades (Summit, Coffee Pot) reported wind gusts of 30-35 mph with afternoon RH values down in the 10-15% range. Today, it will be very dry again with breezes picking up in the afternoon. Despite similar low afternoon MinRHs, we don`t think it will be quite as breezy as yesterday. So, while fire risk is elevated, we`ll have no headlines. However, as an upper trough offshore approaches on Tuesday, mid- level flow increases modestly. That, combined with an already very dry air mass will lead to critical fire weather conditions again in the afternoon/early evening. We got word from our local fuels experts that fire danger is increasing to high for areas from the east slopes of the Cascades eastward. As such, we have issued a Fire Weather Watch for strong, gusty SW winds of 15-25 mph with gusts to 35 mph for portions of the Fremont/Winema NF and Modoc NF in FWZs 624/285. Criteria are a bit higher in FWZ 625 (Deserts), so no headline there. It will also be quite breezy with low humidity in portions of the Shasta Valley, but we don`t expect it to meet the 6-hour duration criteria there. By Wednesday, the upper trough offshore will move closer and mid- level flow will increase more substantially. This will be the windiest day of the next several. We expect another period of stronger, gusty WSW winds (15-30 mph, gusts 40-45 mph) in combination with low humidity (around 15%) during the afternoon/evening, especially east of the Cascades. For most of the rest of the area, guidance is showing a drop in temperature and an increase in humidity to help mitigate this threat, but areas farther east are more susceptible. We`ll see if further headlines are necessary. Right now, thunder probabilities remain very low (10% or less), grazing the SE portion of the area. -Spilde
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&& .MFR WATCHES/WARNINGS/ADVISORIES... OR...Fire Weather Watch from Tuesday afternoon through Tuesday evening for ORZ624. CA...Fire Weather Watch from Tuesday afternoon through Tuesday evening for CAZ285. PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT this evening for PZZ356-376. Hazardous Seas Warning until 11 PM PDT this evening for PZZ356- 376. && $$