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Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
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183 FXUS66 KMFR 130552 AFDMFR Area Forecast Discussion National Weather Service Medford OR 1052 PM PDT Mon Aug 12 2024 .DISCUSSION...An update to the forecast is not necessary this evening. A few thunderstorms earlier this evening produced around 8 lightning strikes east of the Cascades. It was breezy and warm today, but temperatures were generally a few to several degrees below normal, which was a few to several degrees cooler than yesterday. A trough dominated upper level pattern will continue this episode of breezy afternoons with slightly cooler than normal conditions with night and morning low clouds for the coast and coastal valleys. A stable air mass will be in place on Tuesday, and likely during the early part of next week. In between, Wednesday through Saturday, there will be some modest/very slight possibilities of showers and thunderstorms with the highest probabilities, around 10-15%, for Klamath and Lake counties on Thursday afternoon/evening, and then closer to the Cascades (central and eastern Siskiyou, eastern Jackson, eastern Douglas, and Klamath counties) on Saturday. && .AVIATION...13/06Z TAFS...Marine stratus along the coast will be the main concern this evening along with some ceilings in the Cascades. Overall, MVFR ceilings seem most likely, although periods of IFR ceilings remain possible along the coast tonight based on the latest satellite data. Smoke from the fires seems to have settled in northern Lake and Klamath Counties based on air quality data, so IFR visibilities are likely in those areas. Otherwise, some isolated showers are possible overnight east of the Cascades. Smoke will continue to impact the same locations as mentioned above on Tuesday with VFR ceilings spread across other locations in the forecast area. -Smith && .MARINE...Updated 130 PM Monday, August 12, 2024... High pressure is weakening in the Pacific. Benign wave conditions will persist through most of the week with no thermal trough condition. A weak northerly short period swell will glide through the waters this week. && .FIRE WEATHER...Issued 200 PM Monday August 12, 2024...Temperatures will trend cooler through next week with increasing onshore flow, improving humidities, and breezy afternoon winds as upper level troughing settles in and remains over the Pacific Northwest. Another relatively strong marine push is expected tonight into tomorrow, with extensive stratus and fog decks west of the Cascades that may even push into the Rogue Valley by daybreak Monday. Afternoon breezes could be gusty as well in the afternoon, but not as strong as Monday afternoon. Despite these winds, rising humidities should keep us well outside of any critical thresholds. With the shortwave passing just south and eats of the area this afternoon and tonight, some instability is expected to develop this afternoon. Instability is marginal at best, and mid level moisture is lacking, therefore the threat for thunderstorms is low. The most likely scenario will be cumulus build ups over the Cascades, higher terrain east of the Cascades, and in northern California, and one or two of these could develop into a mature storm. While the threat for thunderstorms is low, the threat for strong outflow winds is very high and will be a concern for any ongoing or new fires. Note that outflow winds could initialize from the more robust cumulus fields as well, although the resulting winds would not be as strong. Then, with the trough remaining overhead through the week, we can not completely rule out additional afternoon convection, particularly Wednesday and especially Thursday afternoons and evenings as additional shortwaves pass through the region. Again, we only expect isolated storms should any develop, and confidence is pretty low across the board, especially given that wildfire smoke has a tendency to suppress convective development. Models are showing the potential for a much stronger, broader trough arriving and setting up over or very near the area late this week into this weekend. This will maintain our cooler temperatures and higher humidities, and may also produce more widespread chances for showers and thunderstorms Friday into Saturday. While wetting rains are very unlikely, we will keep a close eye on how the system develops, as cooler temperatures, higher humidities, and even a small amount of rain will be very welcome to fire concerns. -BPN && .PREV DISCUSSION... /Issued 230 PM PDT Mon Aug 12 2024/ DISCUSSION...An upper trough over the Pacific Northwest brought cooler temperatures to the area...with most locations currently running between 5 and 10 degrees cooler compared to yesterday at this time. Cumulus clouds are developing in eastern Siskiyou and Klamath counties as well as Lake county...all locations where the short term models are indicating the possibility of showers/thunderstorms. According to the short term models...showers and the possibility (around 15% chance) of thunderstorms increases between 00z and 03z. Any activity that does develop is expected to move northeast out of the area by 09z tonight. As far as smoke goes...the greatest impact for smoke will be over Lake...Klamath...eastern Douglas...and northern Jackson counties through at least Wednesday. An air quality advisory was issued by the Oregon Department of Environmental Quality. Please see https://oregonsmoke.org for more information. We will continue to be in a trough pattern through the week...with temperatures below normal...and a slight chance of thunderstorms/showers most days through Thursday. The one day we may have a break in the action will be Tuesday. The best chance for showers and thunderstorms will be generally along the east side. There is still quite a bit of uncertainty in the extended forecast as far as timing of precipitation...but we do know that we will stay in this cooler weather pattern through the forecast. CCR && .MFR WATCHES/WARNINGS/ADVISORIES... OR...None. CA...None. PACIFIC COASTAL WATERS...None. && $$