Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
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124 FXUS66 KMFR 171143 AFDMFR Area Forecast Discussion National Weather Service Medford OR 443 AM PDT Tue Sep 17 2024 ...New Aviation Section... .AVIATION (12Z TAFs)... Between systems, the terminals will undergo some changes today as another front pushes into the region, bringing widespread rainfall to the region. Low to mid level clouds will be abundant today/tonight, so expecting many hours with MVFR conditions or close to MVFR for mainly ceilings. Medford might actually see some clearing this morning in between systems, but expecting that to change once the front moves inland. Along/near the coast (KOTH), IFR/LIFR conditions may develop tonight as the low levels remain very saturated when rainfall ends, so expecting conditions to deteriorate overnight for both ceilings and visibilities. -Guerrero && .PREV DISCUSSION... /Issued 254 AM PDT Tue Sep 17 2024/ DISCUSSION...A deep upper trough carved out over the western United States will continue to bring cooler than normal weather to SW Oregon and northern California today. One upper low is ejecting to the ENE across Nevada early this morning, while another trough coming southward from the coast of British Columbia will form another closed low off the PacNW coast by this evening. Wrap-around moisture on the back side of the low to the east will continue to bring some showers to the east side (especially Warner Mtns eastward) this morning, but a few isolated showers could be observed as far west as the Cascades. These should end though later this morning and this afternoon as the upstream trough boots the low toward western Wyoming. Most of the area will be dry at least for a few hours today since we`ll be smack dab in between systems. But, more showers will develop as the offshore closed low meanders southward along the PacNW coast. Some of these showers could reach the Oregon coastline around lunchtime, but are more likely this afternoon. Inland valleys probably remain dry into the afternoon, but we expect the showers to overspread most of the west side later this afternoon and evening. Highest likelihood for measurable rainfall here in the Rogue Valley will be between 5 and 10 pm this evening. Models have decreased QPF a bit with this system with the focus for amounts of 0.25-0.50 of an inch along the immediate coast. Inland valleys west of the Cascades should receive 0.10-0.25 of an inch while most areas east of the Cascades will range from nothing to 0.10 of an inch. Hi- res guidance is showing a small area of increased QPF near Mount Shasta/Medicine Lake region into NW Modoc near Lava Beds National Monument beginning late this evening. Amounts there could be 0.10-0.25 of an inch. Model instability does not favor thunder over inland areas today/tonight, though isolated thunderstorms are possible nearest the cold core upper low over the nearshore marine waters. Shower chances will diminish from NW to SE across the area overnight into Wednesday morning, though could linger in portions of NorCal Wednesday. After some low clouds and patchy fog in southern Oregon Wednesday, many areas will turn out partly sunny with a slightly milder afternoon, though still a bit below normal for afternoon high temperatures. The closed low will shift inland across south-central California Wednesday night into Thursday and move into southern Nevada/NW Arizona by Friday. This should be far enough away to keep shower chances to our south, but we can`t completely rule out a stray showers in SE Modoc Thursday. Otherwise, we`ll begin a warming/ drying trend for all areas with temperatures getting back closer to normal (80-85F west side valleys and 75-80F over east side populated areas). This pattern will persist into the weekend with mostly flat ridging. Models do show a weak trough moving by to the north over the weekend (Sat night/Sun AM), but precipitation chances are low (less than 25%) and only exist north of the Rogue- Umpqua divide. There isn`t too much to get excited about in the extended forecast (Monday and beyond) either with the main storm track still decidedly to the north. This should favor drier than normal conditions and temperatures near or maybe even a bit above normal. -Spilde AVIATION...17/06Z TAFS...Cloud cover remains over much of northern California and southern Oregon due to a lingering low pressure system to the south. Little shower activity remains on radar, with MVFR and IFR ceilings remaining over areas east of the Cascades and VFR ceilings over other inland areas. Marine stratus is at MVFR levels as well for areas north of Cape Blanco, with IFR levels possible but not strongly expected. Another low pressure system will move south over the Pacific through the day Tuesday, with precipitation mostly falling west of the Cascades. Thunderstorms are possible over the ocean but have single digit chances over land. Showers may locally lower visibility and ceilings as well as obscure elevated terrain through Tuesday and possibly into early Wednesday morning. -TAD MARINE...Updated 245 AM PDT Tuesday, September 17, 2024... Winds will shift to the south ahead of an incoming front today. This will allow for winds and seas to remain relatively light today/tonight. The front will also bring widespread rain (today/tonight) with a slight chance (15-30 percent) for thunderstorms (mainly tonight) over the waters. Any thunderstorms that develop will have the potential for strong, erratic gusty winds (40-50mph). Moderate to occasionally strong north winds and steep seas will develop Wednesday as a thermal trough develops, with Small Craft Advisory conditions expected through the rest of the week. There is some indication that a Hazardous Seas Warning maybe needed middle/late this week. There is also some wiggle room in the extent of the possible Small Craft Advisory later this week. All that said, will wait on issuance at this time to nail down coverage on possible warning level conditions that may accompany the Small Craft Advisory. -Guerrero && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT early this morning for PZZ350-356-370-376. Hazardous Seas Warning until 5 AM PDT early this morning for PZZ356-376. && $$