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Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
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615 FXUS66 KMFR 111200 AFDMFR Area Forecast Discussion National Weather Service Medford OR 500 AM PDT Sun Aug 11 2024 ...Updated Aviation Section... .AVIATION (12Z TAFs)... A marine layer is causing IFR/LIFR conditions along/near the coast, and this is expected to last through the morning hours before some relief this afternoon. Another night of IFR to MVFR is likely to return tonight for the coast. Otherwise, inland TAF sites will be under mostly clear skies with smoke impacts still a concern for visibilities today. Breezy afternoon conditions are also expected before speeds relax after sunset. -Guerrero && .PREV DISCUSSION... /Issued 320 AM PDT Sun Aug 11 2024/ DISCUSSION...The forecast area is sandwiched between a weak upper low near 38N/133W and an upstream upper trough moving into northwest Washington state, with a weak west to southwest flow. Much like the last few nights/early mornings, the latest satellite image shows marine stratus along the coast and inland into the coastal river valleys and Coquille Basin. The inland push of the marine stratus has been slow but steady and could move into portions of the Umpqua Basin towards daybreak. Elsewhere skies are clear. Dry weather will continue today with the marine stratus away from the coast gradually burning off during the morning. Meanwhile the marine stratus is expected to persist at the coast and just offshore through the day. Also the exception to the dry weather will be patchy drizzle along the south coast, including Brookings this morning. Weak instability exist over the northern Cascades this afternoon, but mid level moisture and trigger is lacking. This in addition to the extent of the smoke will put a cap on the amount of instability, therefore were not expecting thunderstorms. However, we`ll see cumulus build ups in the afternoon. Not much change in the pattern is expected through next week. The general consensus among the operational models, ensemble members and clusters all point to weak troughing over the area. This will result in cooler afternoon temperatures that will be near normal for this time of the year for the interior. Monday, the weak upper trough that is currently offshore will move inland and it will become negatively tilted by Monday afternoon. This along with increasing instability could set the table for Isolated thunderstorms east of the Cascades Monday afternoon into Monday evening. The wildcard in terms of thunderstorm coverage or lack thereof will be the extent of the smoke. If the smoke remain extensive, it will put a cap or even result in less instability resulting in a couple of isolated storms or nothing at all. Weak troughing remains over the area for the rest of the week with dry conditions. the one exception could be Thursday. The models are in pretty good agreement showing an upper trough moving through the area Thursday afternoon which could provide enough trigger to kick off isolated thunderstorms Thursday afternoon and evening. Afternoon temperatures during this time will be slightly below normal. Next weekend, the clusters suggest the upper trough will deepen some with the center of the upper trough over the PAC NW. The ensemble means show some variation with the center of the upper low/trough with the ECMWF mean showing the upper trough over the area while the GFS mean has it centered slightly to the west. The operational models are in similar agreement showing a rather strong upper low for this time of the year centered over the PAC NW. Afternoon temperatures for the interior are likely to end up below normal (6-8 degrees) for this time of the year. -Petrucelli AVIATION (06Z TAFs)...A marine layer will continue IFR conditions at the coast and coastal valleys, both north of Cape Blanco and south of Gold Beach overnight, including at North Bend (KOTH) and Brookings (BOK). This is expected to persist through around 18Z Sunday morning, then develop again early Sunday evening, around 03Z. Meantime, inland TAF sites are expected to remain mostly VFR. Wildfire smoke is thickest, with MVFR visibility likely, from eastern Douglas County into northern Klamath County, and in southwest Siskiyou County. Elsewhere, smoke could still cause minor visibility restrictions. Otherwise, typical afternoon and evening breezes are expected with clear skies. -DW MARINE...Updated 200 AM Sunday, August 11, 2024...Wind speeds will peak this afternoon combined with steep seas which will result in conditions hazardous to small craft through this evening. The probability for wind gusts of 34 knots or greater south of Cape Blanco is roughly 40-60% where we have the current Small Craft Advisory. These speeds will remain breezy/gusty until sunset before slowly decreasing overnight. Thereafter, winds and seas will both ease through at least the middle of the week. -Guerrero FIRE WEATHER...Issued 200 AM Sunday August 10, 2024...The forecast period will trend cooler through next weekend with increasing onshore flow. The increased onshore flow will result in good overnight recoveries for the coast, coastal valleys, Coquille and Umpqua Basin, including the complex of fires in central and eastern Douglas County. Weak upper troughing is expected today with cooler afternoon temperatures. There`s good agreement instability is marginal at best, with little or no trigger, and dryer at the mid levels. In addition, the extent of the smoke east of the Cascades will also likely inhibit the formation of storms, therefore the threat for thunderstorms are next to zero. The most likely scenario will be cumulus build ups in the afternoon over the Cascades and higher terrain east of the Cascades and northern Cal. Monday, an upper trough that is currently offshore will move inland as it gets picked up by a deepening upstream upper trough in northwest Washington, the upper trough is expected to become negatively tilted and this in combination with increasing instability, mid level moisture and trigger could result in isolated thunderstorms east of the Cascades Monday afternoon into Monday evening. However, if the smoke remains extensive east of the Cascades, it could put a cap or event result in less instability, thus resulting in no thunderstorms. Weak troughing remains over the area for the rest of the week with dry conditions. the one exception could be Thursday. The models are in pretty good agreement showing an upper trough moving through the area Thursday afternoon which could provide enough trigger to kick off isolated thunderstorms Thursday afternoon and evening. Afternoon temperatures during this time will be slightly below normal. Also higher afternoon relative humidities are expected with fairly good overnight recoveries, even for the eastside and northern California. We`ll still have to deal with gusty breezes in the afternoon and early evening hours, but with higher humidities in the afternoons, were not expecting critical conditions. Next weekend is still shaping up to be cool with higher relative humidities in the afternoons along with good overnight recoveries as an upper trough settles near or over the forecast area. -Petrucelli && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 2 AM PDT Monday for PZZ356-376. && $$