Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
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565 FXUS66 KMFR 110410 AFDMFR Area Forecast Discussion National Weather Service Medford OR 910 PM PDT Wed Jul 10 2024 .DISCUSSION...An update was issued earlier this evening to extend both the Excessive Heat Warning for western and central Siskiyou County /PDXNPWMFR/, and the Heat Advisory for areas east of the Cascades through Saturday evening. Also, the Excessive Heat Warning for Jackson, Josephine, and eastern Curry counties was downgraded to a Heat Advisory, in effect also through Saturday evening. The slight cooling for Thursday, a few degrees across most inland sites, should hold steady for the remainder of this week. Then, another very slight nudge lower in temperatures early next week looks to hold steady through the middle of next week. Overall, not as extreme as what occurred last weekend into early this week, but still well above normal and well justifying the continuation of the headlines. The 18Z model data supports the forecast of a few cumulus buildups over eastern Modoc County on Friday, in advance of a slight (10-15%) chance of thunderstorms over northern California and east of the Cascades during Saturday afternoon and evening and again Sunday afternoon and evening. At the coast, night and morning low clouds are expected to be prevalent from Cape Blanco northward, with gradual erosion of the clouds during the day-time hours. The Brookings temperature forecast is a challenge with a north to weakly northeast direction of the low level flow which should bring above normal temperatures into Saturday. && .AVIATION...11/00Z TAFS...Along the coast and just offshore, satellite image shows marine stratus from about Bandon north, and just to the west of the North Bend airport. The marine stratus should return at North Bend by 2z. Visibility could also drop later tonight to 4 miles or even less at North Bend. South of Cape Blanco, marine stratus should remain offshore beyond 5 nm from shore int tonight, the exception will be south of Gold Beach where marine stratus with IFR ceilings could return late this evening. Inland, west of the Cascades, VFR conditions will continue through the TAF period with gusty breezes into early this evening, and again Thursday afternoon. The exception will be MVFR visibility in the vicinity of the Salt Creek and Shelly Fires, and in Medford tonight as the smoke from the Salt Creek Fire could drift into the airfield. East of the Cascades, VFR conditions will continue through the TAF period. However, smoke from the Salt Creek fire could get transported into the area resulting in visibility lowering to 5 miles. -Petrucelli && .MARINE...Updated 200 PM Wednesday, July 10, 2024...A thermal trough will strengthen through Thursday resulting in stronger north winds and increasingly hazardous seas. Small Craft Advisory conditions with moderate north winds and steep wind-driven seas are expected through this afternoon for areas south of Cape Blanco, with Small Craft Advisory conditions spreading into the northern waters this evening as north winds and seas increase which will last through Thursday. Meanwhile, gales and very steep, hazardous seas develop this evening from Gold Beach south. Moderate to strong north winds and steep to very steep seas continue Friday. Then, winds and seas are expected to gradually lower Saturday and Sunday. -Petrucelli && .PREV DISCUSSION... /Issued 447 PM PDT Wed Jul 10 2024/ .DISCUSSION... Temperatures are trending lower compared to what we`ve seen the last few days. This relatively cooler trend will continue for most of our Oregon zones through the remainder of the week. However, the NWS HeatRisk algorithm remains in the major category for parts of Siskiyou County around the Shasta Valley as high temperatures are still about 20 degrees warmer than normal for this time of year. In addition, low temperatures will be around the mid 60`s to upper 60`s in sections of northern California. A push of cooler air or a cold front will move into the forecast area around Friday. BUFR soundings show steep lapse rates up to 10 C/km up to 600 mb ahead of the front. This will result in some gusty conditions east of the Cascades with wind gusts up to 35 mph or perhaps even higher if we do indeed mix that deep. Heading into the weekend, a closed low will approach from the south, which will introduce a risk of thunderstorms across our forecast area. The highest risk areas will be east of the Cascades in Lake and Klamath counties. We also considered adding sections of western Siskiyou County in the risk area, although many of the upper level soundings didn`t show enough CAPE. Some of the soundings did show a small surge of moisture at the mid levels on the other hand. The storm threat will persist into Sunday as an upper level wave moves through into the forecast area. However, the threat of lightning significantly decreases Sunday night as the wave moves eastwards. -Smith && .FIRE WEATHER...Issued 300 PM Wednesday July 10, 2024... ..Near critical fire weather conditions possible through at least this weekend... Hot, breezy, low humidities, and occasional unstable afternoon conditions will persist through this weekend, and this will lead to near critical fire weather conditions. Additionally, we have a chance for thunderstorms this weekend, mainly across the eastside. Wind speeds are not too impressive this week, but they certainly will be on the breezy side around 10-20 mph, with speeds becoming more of a concern for Red Flag conditions by Friday over the eastside and parts of Siskiyou County. Single digit RH values are also forecast this week during the afternoon hours across the eastside and some isolated westside valleys like Northern California. These factors, on top of this prolonged drying stretch will result in elevated to critical fire weather conditions nearly every day this week. This afternoon and tomorrow afternoon may fall just short of actually reaching those critical thresholds due to the wind. While no official warnings are out now, it will be very borderline today and tomorrow afternoon for fire weather conditions, so the threat is there even if we aren`t hitting "criteria". Conditions worsen as the week progresses, and we will likely see Red Flag Warnings coming to fruition as early as Friday. For the thunderstorm potential, it should be noted that the trend stay the same from yesterday for both Saturday and Sunday. We were seeing slight increases early in the week, but those trends have flatlined. A lot will depend on how a ridge of high pressure sets up over the Four Corners region as this will direct monsoonal moisture northward. There is about a 10-20 percent chance for isolated thunderstorms both Saturday and Sunday. -Guerrero && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Excessive Heat Warning until 9 PM PDT this evening for ORZ024- 026. Heat Advisory until 9 PM PDT Saturday for ORZ024-026-029>031. CA...Excessive Heat Warning until 9 PM PDT this evening for CAZ080>082. Heat Advisory until 9 PM PDT Saturday for CAZ083>085. PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT Friday for PZZ350-356-370. Gale Warning until 8 PM PDT Friday for PZZ356-376. Small Craft Advisory until 11 AM PDT Thursday for PZZ376. && $$