Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
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642 FXUS66 KMFR 041731 AFDMFR Area Forecast Discussion National Weather Service Medford OR 1031 AM PDT Thu Jul 4 2024 .Updated Aviation Discussion. .AVIATION...04/18Z TAFS...VFR conditions will continue through the TAF period with gusty north winds north of Cape Blanco, including North Bend this afternoon into this evening, and breezy afternoon and early evening winds at Roseburg. There`s some evidence supporting localized low clouds in portions of the Coquille Basin late tonight and portions of the coast, including North Bend late tonight resulting in IFR ceilings, but confidence is not high enough to include this in the TAF. Meanwhile, smoke from the Shelly Fire in western Siskiyou county could result in visibilities dropping below 6 miles this afternoon, and smoke could settle into the valleys tonight, locally lowering ceilings and visibility. -Petrucelli && .DISCUSSION...Satellite imagery is showing some stratus quickly dissipating along the Coquille Basin, and persisting offshore. Meanwhile, smoke from the Shelly Fire can be seen moving east along Sawyers Bar Highway indicative of a strong high pressure system. Meanwhile, observations are starting to show the winds relaxing a little bit, but remaining easterly along the coast range. We have allowed the current Red Flag warning in the Kalmiopsis to expire, but we will continue to see very dry humidities. The question will be whether the winds will become typically breezy this weekend and so we will be evaluating further potential for additional red flag products. In addition, temperatures will be very hot today for most inland locations. It is worth noting that the low temperature at the Brookings airport was 75 degrees, and current observations in the Chetco basin are already showing temperatures in the mid 80s. Guidance is suggesting another day of temperatures pushing into the mid to upper 90s before the winds come from the ocean giving a quick cooldown. Have issued a heat advisory to account for this. Interestingly this is confined to largely the Chetco Basin as there is a Brookings Agrimet station showing temperatures in the upper 50s with weak winds coming from the ocean. This suggests that Crescent City may be a good place to go to escape the heat today. -Schaaf && .MARINE...Updated 830 AM Thursday, July 4, 2024...Winds and seas will gradually improve later today as the thermal trough pushes inland and expands northward. North to northeast winds will ease some at this time, but seas and winds will remain hazardous to small craft with hazardous warning level seas lingering through this evening for the outer waters south of Cape Blanco. Conditions improve further on Friday as winds continue to weaken, but seas will remain steep due to fresh swell and ongoing wind waves. A period of improved conditions is expected over the weekend with sub-advisory conditions likely for at least the inner waters on Saturday, and possibly all the waters on Sunday. Strong high pressure aloft will disrupt the thermal trough pattern, keeping winds in the 10 to 15 knot range. Swell will be low and seas will remain dominated by fresh swell. The thermal trough rebounds early next, and hazardous conditions are likely to return at that time. -Schaaf/BR-y && .PREV DISCUSSION... /Issued 432 AM PDT Thu Jul 4 2024/ DISCUSSION...As stated in the previous AFD, here is information on a fire in southwest Siskiyou County--A wildfire [is] growing within the Marble Mountains southwest of Shelly Lake near the PCT in south west Siskiyou County. Siskiyou County Emergency management is requesting hikers along the PCT to be aware of and avoid this fire. Overnight satellite shows the hot spot in this area of the new fire with stratus riding along the central Oregon coast. The lower cloud deck is starting to reach parts of Coos County this morning, including Charleston. There are clear skies elsewhere and this will continue today. A ridge is present off the coast and will be moving inland towards southern Oregon the next few days. This will bring the warmest temperatures of the week to the area. The Chetco effect will be present this afternoon with highs in the mid-90s near Brookings. On average, highs will be 5-15 degrees above normal this afternoon. This translates to 90s with triple digits in more valley locations west of the Cascades as the heat expands to more west side locations including the Illinois Valley and Umpqua Basin. Winds will overall be lighter, so please plan accordingly with these temperatures in mind before going out to the fireworks. The heat will be the worst Friday and Saturday. The probability of reaching highs of 110 degrees in Medford is near 70-80% Friday and Saturday afternoons. There is also a ~35% probability to reach 115 Saturday in Medford. For reference, 115 is the hottest high on record for Medford. There will also be a factor of low temperatures west side only falling to the low to mid-60s Friday and into the weekend. With this in mind, it is crucial that precautions are taken to prepare and deal with the heat. With the heat concerns for the coming days, an Excessive Heat Warning and Heat Advisory exists for most locations (with an emphasis on valleys) this morning through Monday evening. Early next week the ridge will move farther east and temperatures will fall from the weekend peak, although it will still be warm with highs in the triple digits for the Rogue and Illinois valleys. - Hermansen FIRE WEATHER...Updated 300 AM Thursday, July 4, 2024... ..Near critical fire weather conditions possible in the afternoons and evenings through the weekend for much of southern Oregon and northern California... ..RED FLAG WARNING REMAINS IN EFFECT UNTIL 8 AM PDT THIS MORNING FOR EAST WIND WITH POOR OVERNIGHT RH RECOVERY FOR FIRE WEATHER ZONES 619 AND 620... Fire weather concerns will remain elevated through the weekend. A strong thermal trough remains along the coast this morning. This is resulting in moderate to poor RH recoveries for the upper slopes and ridges, along with gusty northeast winds of 15-25 mph with gusts 30 to 40 mph. Critical fire weather conditions are occurring for portions of FWZ 619 and 620 and a Red Flag Warning remains in effect until 8 AM this morning. The pattern will transition today as the thermal trough expands northward and northeast flow weakens. Strong high pressure aloft will move over the region today and linger overhead through the weekend. Very hot temperatures (100-110 degrees) and very low (low teens/single digit) daytime humidities are expected during this time away from the immediate coast. Recoveries will improve some along the coast, but will remain in the moderate to poor range across the area through the weekend. Afternoon breezes will be slightly weaker than normal today and then fairly typical for Friday. With the heat and very dry conditions, however, even typically breezy afternoon conditions could result in dangerous weather that is favorable for the rapid spread of fire. Near critical conditions are possible for West Side Valleys for the remainder of the week. We`re keeping an eye on a disturbance expected to move into the region from California on Saturday and Sunday. While the atmosphere will be too dry for thunderstorms, this may enhance the afternoon breezes on those afternoons. This combined with very low daytime humidities in the low teens and single digits could lead to some widespread critical fire weather conditions this weekend, including the Rogue/Applegate Valleys, the Cascades, western and central Siskiyou County and portions of the East Side. We`ll continue to monitor this development and evaluate the need for any products in upcoming shifts. /BR-y && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Excessive Heat Warning until 9 PM PDT Monday for ORZ023>026. Heat Advisory until 9 PM PDT Monday for ORZ022-029>031. CA...Excessive Heat Warning until 9 PM PDT Monday for CAZ080-081. Heat Advisory until 9 PM PDT Monday for CAZ084-085. PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT Friday for PZZ350-356-370-376. Hazardous Seas Warning until 11 AM PDT this morning for PZZ356- 370-376. && $$