Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
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487 FXUS66 KMFR 090420 AFDMFR Area Forecast Discussion National Weather Service Medford OR 920 PM PDT Sat Jun 8 2024 .UPDATE...An update has been issued to fine tune the probability of showers and thunderstorms overnight into Sunday evening. && .DISCUSSION...Instability was sufficient this afternoon and evening to produce scattered showers and thunderstorms, mainly east of the Cascades. This activity was in advance of a Pacific trough. The trough will track inland overnight and across the area on Sunday into Sunday evening. This will continue a slight chance to chance of showers and slight chance of thunderstorms into Sunday afternoon. Though the set up will not be identical, similar weather to this afternoon is expected during Sunday afternoon with the focus of activity shifted slightly eastward into far eastern Siskiyou, eastern Klamath, and Lake, and Modoc counties. By 8 PM Sunday evening, the trough axis is expected to be at the eastern edge of our area, with further shower and thunderstorm activity to occur east of Lake County. Also, the arrival of the trough will bring an influx of coastal clouds tonight through Sunday, into Monday morning. The outlook is still for a seasonable, stable air mass beginning Monday with inland temperatures similar to those of today during Monday through Thursday. Weak instability may nudge into Modoc County by Thursday afternoon, then a trough is likely to bring a seasonable frontal passage north of our area with a cool down to near normal temperatures inland for the end of the week. && .AVIATION...09/00Z TAFs... Thunderstorm activity will remain active into the early evening along and east of the Cascades as the atmosphere destabalizes. These storms haven`t produce that strong of wind gusts with a few observation sites reporting gusts up to 20 knots. Hail remains the main threat. The thunderstorm threat will persist overnight east of the Cascades and in the central Cascades as the upper level wave approaches the Oregon coast. Some models also show a bulk of moisture around 7000 to 9000 feet above sea level, which could aid in initiating convection overnight. Right now the threat of overnight thunderstorms remains low, although these events are sometimes underdone in the models. Other than storms, lower ceilings will build into the coast overnight. Surface pressure begins to build gradually as the upper level wave pushes inland around sunrise. IFR ceilings are most likely, although periods of LIFR ceilings also remain possible early Sunday. -Smith && .MARINE...Updated 200 PM Saturday, June 8, 2024...Gusty north winds will bring steep seas to areas south of Ophir and a few miles away this evening. Then, a moderate west swell moves in tonight through Sunday. During this time, the thermal trough will restrengthen, bringing increasing north winds and steep to very steep seas Sunday into early next week, especially south of Cape Blanco. Conditions will at least remain hazardous to small craft south of Cape Blanco through midweek. Conditions could worsen again around Thursday as the thermal trough builds strength. -Smith && .PREV DISCUSSION... /Issued 247 PM PDT Sat Jun 8 2024/ DISCUSSION... Short Term...Rest of Today through Monday Night...A trough will approach the coast this afternoon and evening, move onshore tonight, and pass over southern Oregon and far northern California tomorrow. This trough is responsible for the cooler temperatures today, and it will also be the lifting mechanism the atmosphere needs to tap into some relatively significant instability in the low to mid levels, while also providing enough shear to enhance thunderstorm chances. A few convective cells have already formed today, and activity is expected to intensify and become more widespread through the afternoon, mainly along and east of the Cascades and in northern California. Some of these storms could be strong; while severe storms are not expected, they are not out of the question, with around a 5 percent chance for any given storm to produce strong winds and/or large hail. Elevated instability is expected to continue through tonight and into Sunday afternoon as the trough passes onshore. Convective activity is therefore expected to continue all the way into Sunday afternoon as well, although over time it will be concentrated more to the east, ahead of the trough axis. Ridging returns Sunday night into Monday, along with a reintensifying thermal trough along the coast. This will dry things out and bring an end to thunderstorm chances, and it will also allow temperatures to bump back up, reaching about 10 degrees above normal for this time of year as we head into the extended period. -BPN LONG TERM...Tuesday 6/11 through Saturday 6/15...The extended forecast begins with zonal flow (west to east) at the middle levels of the atmosphere. While weak disturbances will pass largely to the north of the area, expect dry weather to continue across southern Oregon and northern California through the extended period. However, temperatures will be much slightly above normal with highs in the upper 80s to low 90s east of the Cascades and lower 80s to upper 70s east of the Cascades. The coast will be cooler with temperatures in the 60s. Then, for the weekend, the general flow pattern will turn to become more unsettled as a low pressure system approaches the Pacific Northwest. The general front ahead of the low will be relatively weak and precipitation is not expected that far south. However, some precipitation in showers will be possible within the low itself. Ensembles do show some timing differences, but the general thought is that temperatures will be even cooler over the weekend, winds will be breezy, and that a slight showers will be possible largely north of the Douglas/Lane County Border. However, this could change as the details of this system become more clear. Have gone with the National Blend of Models for this forecast package. -Schaaf && .MFR WATCHES/WARNINGS/ADVISORIES... OR...None. CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 11 AM PDT Monday for PZZ356-376. Hazardous Seas Warning from 5 AM Sunday to 11 AM PDT Monday for PZZ356-376. && $$