Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
751 FXUS66 KMFR 070530 AFDMFR Area Forecast Discussion National Weather Service Medford OR 1030 PM PDT Thu Jun 6 2024 .UPDATE...Updated aviation section for 06z TAFs. && SHORT TERM...An upper level ridge is in place and hot temperatures were observed across inland areas today with highs in the upper 80s to upper 90s. A record high temperature of 95 was set for Mount Shasta City. Along the coast, temperatures were generally mild (except for locally warmer conditions across southern coastal Curry County) with some breezy/gusty afternoon winds. Meanwhile, mid level moisture and instability associated with a weak upper level disturbance brought some isolated thunderstorms to northern California and portions of Lake County. Two strong thunderstorms were observed earlier this evening in south- central and southeast Siskiyou County, where radar indicated a potential for severe hail. Moderate CAPE, instability and an upper level jet aloft provided extra instability and lift for these storms. With the onset of sunset, storms have weakened but isolated thunderstorms persist across central/eastern Modoc and southern/eastern Lake counties. Models continue to support these storms diminishing late this evening. This pattern will remain in place on Friday, with hot temperatures impacting all inland areas and isolated thunderstorms expected again across portions of northern California and from the Southern Oregon Cascades east as a weak shortwaves moves across the area. High temperatures across inland valleys on Friday are expected to be 2 to 6 degrees hotter than today and record to near-record highs are possible for Klamath Falls, Alturas and Mount Shasta City. Chances for thunderstorms (15-20%) will be highest from the Cascades east and into western Siskiyou Counties on Friday. Storm activity is expected to be isolated Friday afternoon and evening. Also, models are showing lesser chances for severe thunderstorms compared to today and no severe activity is expected on Friday. Moderate CAPE and instability may be present across portion of the east side, especially in Lake county, which may allow for a few locally stronger storms. On Saturday, the upper level ridge will shift east slightly as an upper trough approaches from the west. This will result in daytime temperatures trending slightly less hot. There will be continued slight chances for thunderstorms (across northern California and form the Cascades east) as moisture moves into the area from the southwest and combines with daytime instability. LONG TERM...Sunday morning through Friday. We`ll start off the extended forecast with an upper level wave pushing into the forecast area Sunday morning. Models are anticipating plenty of cloud cover in the morning with modest upper level divergence ahead of the wave. With modest synoptic lift, thunderstorms still remain in the forecast on Sunday east of the Cascades. The NBM probability of thunder is showing values around 30 to 35 percent within any point east of the Cascades and in Modoc County for Sunday afternoon and evening. Deterministic models show about 1000 j/kg of convective available potential energy with 20 to 30 knots of shear out of the south. These values are pretty good for generic thunderstorms, although the widespread aforementioned cloud cover could seriously impact available potential energy for any storms. In any case, some thunderstorm activity seems likely around our CWA on Sunday. The trough axis eventually swings by with deeper moist west flow pushing into the forecast area. This will result in temperatures trending lower, although still above the seasonal normals(1991-2020) for this time of year. This warmer than normal trend can be seen in the ensemble forecasts, and we have pretty high confidence in warmer than normal for much of next week. The 700 mb temperature around 9000 feet is in the 90th to 97.5th percentile for much of next week according to the GEFS. Other than that, nothing stands out in the extended forecast for much of next week as the PoP forecast is between 0 and 5%. The exception is around Day 7 as half of the ensemble members anticipate the next trough to hit the Pacific Northwest. However, the other half are expecting a ridge to still stay in control. One can note that the PoP forecast does increase slightly Thursday night into Friday with the more significant increase north of Douglas County. -Smith AVIATION...07/06Z TAFs...VFR conditions will prevail across northern California and southern Oregon tonight. The exception is at North Bend and elsewhere along the coast, where stratus caused IFR/LIFR ceilings and vis last night, and is expected to do the same again tonight based on a persistence forecast. This runs against some model output and is causing a low confidence forecast for the lower conditions along the coast. Gusty north winds expected along the Oregon coast and over Roseburg Friday afternoon. Thunderstorms are also expected again on Friday, in much the same areas of south and Southeast Siskiyou County, and east across Modoc and Lake Counties. Northeastern Klamath County may also observe an isolated thunderstorm tomorrow. -Miles MARINE...Updated 830 PM Thursday, June 6, 2024...A thermal trough will continue to produce gusty north winds and steep wind-driven seas across the area coastal waters, with very steep and hazardous seas south of Cape Blanco. Winds will decrease overnight and into Friday morning. Even as winds decrease, very steep seas will continue south of Cape Blanco into late Friday morning. Steep seas will remain in all waters into late Friday night. Please see MWWMFR to see more detailed areas of expected hazards as well as timing for current Small Craft Advisories and Hazardous Seas Warnings. Seas will be calm through Saturday, although westerly swell will start to increase during the day and a thermal trough will return late Saturday night. Steep seas are expected to return to all waters Sunday and continue into early next week as the thermal trough strengthens. -BPN/Miles PREV DISCUSSION... /Issued 300 PM PDT Thu Jun 6 2024/ DISCUSSION...A weak upper trough is moving slowly into SW Oregon which is the triggering mechanism for mainly slight (10-20%) chances over the east side this afternoon and tonight. The exception is along the Warners and in far southeast Lake county where there is a narrow region of 30-50% chances aligned closest to the area of convection currently ongoing and developing from parts of Washoe and Harney Counties. Storms are not expected to be of great impact. After tonight we move into Friday with concerns of very warm high temperatures and another round of slight chance (15-20%) thunderstorms over the east. The NBM has been fairly consistent with advertising temperatures 3 to 7 degrees warmer than today west of the Cascades, well into the 90s for the western valleys and near 90 over the east. These are departing from normals by +15 to +20 degrees, so a fairly unusual warm spring day. Near-record or record highs will be monitored at Klamath Falls (91/1996), Alturas (93/1996) and Mount Shasta City (92/2015). Current records are shown. The heat risk with this period only reaches 2 in the warmest locales as overnight low temperatures will be fairly cool and relieving generally in the 50s. Friday`s storms should be slightly more numerous and extending further west into the Cascades versus today with a more significant trough approaching. The deep upper low digs into the PacNW by Saturday cooling temperatures by 3-8 degrees. Stavish && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT Saturday for PZZ350-356-370-376. Hazardous Seas Warning until 11 AM PDT Friday for PZZ356-376. && $$