FXUS66 KMFR 281559 AFDMFR Area Forecast Discussion National Weather Service Medford OR 859 AM PDT Wed Jul 28 2021 .SHORT TERM...The forecast remains on track with the main concerns for the next few days centered around heat and thunderstorms. The high pressure ridge over the area will strengthen through Friday resulting in a significant warm up. Very hot temperatures are expected for inland areas west of the Cascades Thursday and Friday with warm overnight lows. The hottest day is expected Friday with high temperatures peaking 10 to 15 degrees above normal across inland. Very hot temperatures with relatively warm overnight lows will result in elevated heat risk. An excessive heat warning has been issued for inland areas west of the Cascades for Thursday and Friday. Thunderstorms are also forecast due to southerly moisture continuing to move up into the area. Moisture and instability is limited today and expect a slightly chance for showers and thunderstorms mainly over northeast portions of the area in the Southern Oregon Cascades, northern Klamath and northern Lake Counties. Thursday, the moisture and instability will increase, and expect isolated to scattered thunderstorms from the Cascades eastward and Siskiyous southward. Additionally, there will be a slight chance for thunderstorms west of the Cascades in southwest Oregon, including in eastern Josephine, Jackson and eastern Douglas Counties. The slight chance for thunderstorms continues on Friday for similar areas. For additional details on the thunderstorm forecast, please see the previous discussion below. && .AVIATION...For the 28/12Z TAF Cycle... Along the coast, LIFR ceilings have built in this morning with some high clouds move in overhead. Into valleys east of the Cascades, some lower ceilings and LIFR visibilities have developed over Klamath Falls and sections of the Klamath Basin. Look for these low ceilings to persist a few hours past sunrise this morning before the clouds burn off. Elsewhere, VFR will prevail today. There is also a low chance of thunderstorms near Crescent and Chemult later this afternoon. If storms do form, low ceiling and visibilities can be expected under storms. By tonight, the lower LIFR ceilings will move back into the coast over North Bend and some of the valleys near the coast. -Smith && .PREV DISCUSSION... /Issued 500 AM PDT Wed Jul 28 2021/ DISCUSSION...28/00Z NAM/GFS/EC in. There are still lots of clouds streaming from south to north over the Medford forecast area this morning, but little in the way of precipitation. Skies are now clearing from the south. The KMFR 28/00z sounding showed record precipitable water of 1.44 inches Tuesday afternoon. Klamath Falls set a new daily rainfall record with 0.37", breaking the old record of 0.33" set in 1947, while Mt Shasta City tied their daily rainfall record with 0.20" set in 2020. A long wave trough is west of southeast Alaska and a strong long wave ridge is over the central U.S. Both of these features will retrograde slowly through the remainder of the week. Southerly flow aloft will continue to bring monsoonal moisture into the area, but the heat will also return as the ridge builds into the area from the east. It will be very hot inland Wednesday through Friday. The hottest day looks to be Friday with inland west side highs around 15 degrees above normal. Cloud cover will keep the east side cooler with forecast highs around 10 degrees above normal. An Excessive Heat Watch is currently in effect. See NPWMFR for details. As far as thunderstorms go, there will be enough moisture for isolated afternoon and evening thunderstorms every day during this interval, mostly from the Cascades east. Thursday looks to be the biggest day for convection, when coverage will likely be scattered over the Cascades and northern Klamath county. Steering flow will be southeasterly this day, and this may advect some thunderstorms and moisture to the west side. At this time it looks like most, if not all, of the west side thunderstorm activity will be from the Siskiyous south. Saturday and Sunday will be significantly cooler due to increased cloud cover with inland highs around 5 degrees above normal over the inland west side and slipping below normal over the east side. Currently only isolated afternoon and evening thunderstorms are forecast for these days, but the models indicate that a short wave may enhance activity Saturday. Temperatures Monday through Wednesday will look similar to the Sunday values. Afternoon and evening thunderstorms remain in the forecast Monday from around the Cascades east. Steering flow will turn southeasterly again Monday, and this could push some of those thunderstorm into the west side valleys. There are no thunderstorms currently in the forecast Tuesday and Wednesday, but this may change, as the medium-range models indicate that, while it will be more stable during this interval, there is some lingering instablity and some moisture to work with, maybe enough to support some isolated activity. FIRE WEATHER...Updated 200 AM Wednesday 28 July 2021...It will heat up Wednesday afternoon and afternoon humidities will drop quite a bit compared to Tuesday. The heating will create unstable conditions, and there will be a slight chance of thunderstorms, mainly across northern and eastern parts of the area and from the Cascades east. Deep southerly flow will continue to advect monsoonal moisture into the area through Monday. It will be quite hot Wednesday through Friday over the inland areas, especially the west side, with the hottest day on Friday. Model guidance is showing enhanced instability on Thursday afternoon/evening focused near the Cascades north of Howard Prairie and near and just north of Crater Lake/Chemult/Crescent areas. Some (but not all) models show a decent short wave moving north- northwestward from Reno/Tahoe region Wednesday night and reaching that area at peak heating Thursday afternoon and evening. Enough mid- level moisture is present to support scattered thunderstorms there. Therefore, a Fire Weather Watch remains in effect for abundant lightning on dry fuels for FWZs 617 (Toketee Falls eastward), 623 (north of Howard Prairie) and 624 (north and west of a line from Chiloquin to Silver Lake). This does NOT currently include the Bootleg or Jack fires. See RFWMFR for details. Isolated afternoon and evening thunderstorms, mostly east of the Cascades, will persist through Monday. Saturday will bear watching, as a passing short wave may enhance thunderstorm activity that day. The steering flow will become southeasterly Monday, and this may push some thunderstorms into the west side valleys. There are no thunderstorms currently in the forecast Tuesday and Wednesday, but this may change, as the medium-range models indicate that, while it will be more stable during this interval, there is some lingering instablity and some moisture to work with, maybe enough to support some isolated activity. && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Red Flag Warning from 2 PM to 11 PM PDT Thursday for ORZ617-623-624. Excessive Heat Warning from 11 AM Thursday to 11 PM PDT Friday for ORZ023-024-026. CA...Excessive Heat Warning from 11 AM Thursday to 11 PM PDT Friday for CAZ080>082. Pacific Coastal Waters...Small Craft Advisory from 11 AM to 11 PM PDT Thursday for PZZ356-376. $$ CC/CC/CC