FXUS66 KMFR 022355 AFDMFR Area Forecast Discussion National Weather Service Medford OR 454 PM PDT Fri May 2 2025 .DISCUSSION (Today through Thursday)... Overview: Today will be the most impactful day of the forecast, and will be noted by a chance of thunderstorms. Strong storms could develop today with lightning, small hail (<1.00"), and gusty winds (45-55 mph) as the main threats. These threats are currently highest along and near the Cascades and to the east, which includes northern California and south central Oregon. Outside of thunderstorm chances, it will be a breezy this afternoon as the front passes through the region. In fact, it will likely be breezy through the weekend. Cooler (below normal) high temperatures will be noted through the weekend with another warm up next week. At this time, not seeing a great deal of confidence for another round of precipitation as next week looks mostly dry but Wednesday could be the earliest day. Further Details: Current satellite imagery shows an area of cumulus developing along and near the Cascades and to the east as daytime heating helps lift parcels. 12Z forecast soundings indicated convective temperatures would be around the mid 60s early this afternoon, and these temps are being realized across eastern observation sites. Expecting cumulus to continue to develop and eventually turn into thunderstorms across these areas. Not expecting development on the westside until the front arrives late this afternoon/early evening. MUCAPE values are still progged to be around 200-700 J/kg with DCAPE values around 1000-1200 J/kg on some of the higher ends. If these DCAPE values are realized through evaporative cooling processes, we could see severe wind gusts (60+mph), but in order for that to happen we need an updraft to maintain. Given bulk shear (0-6km) values around 20-45 knots, this is certainly possible today if everything phases together. Upper level support is lagging today, and this could end up being the biggest influencer with regards to lack of updraft maintenance. This means severe weather chances are around 5 to 15 percent today, but general thunderstorms are more likely around 20-40 percent today/tonight. If a thunderstorm can maintain long enough for precipitation to overcome the updraft, we could certainly see wind gusts of 45-55 mph and in a couple isolated spots as high as 60+ mph. There is at least some evidence for a rogue thunderstorm or two overnight, but this is a very low chance scenario around 10-20 percent. By sunset, we will likely lose much of the instability in the atmosphere, but if somehow a storm can manage to maintain or develop tonight, we will have to watch for strong gusty winds as dry air near the surface could lead to this potential. Again, this is a low chance, but its not a zero chance. We wouldn't necessarily need a thunderstorm for these strong gusts, as a 50+ mph gusts are possible without lightning. This hazard could have the most potential impact over the Rogue Valley due to population density alone. West of the Rogue Valley we are very unlikely to see any of these threats. At this time, river gauges and river forecasts are not suggesting any flooding, but the Sprague River near Beatty will approach and stay under Minor flood stage, so this is worthy of monitoring. Generally not expecting many areas to receive over half an inch of rainfall, but areas along and near the Cascades would have the best chance through 24 to 36 hour totals ending Saturday night. Of course, if a thunderstorm maintains or trains over an area we could see higher convective rainfall rates. If this occurs upstream of the Sprague River, we may need to reevaluate the river forecast and response to increased rainfall. -Guerrero && .AVIATION...03/00Z TAFs...A frontal system will move onshore tonight. Scattered showers and isolated thunderstorms are developing late this afternoon from the Trinity Mtns in norCal and also Modoc County, but also from around Highway 97 eastward in Oregon. While most of the time will be VFR, showers will be capable of locally lowering ceilings and visibilities as well as obscuring elevated terrain wherever they occur. The main threat from any of the stronger cells in those locations this evening will be gusty outflow winds. Alturas briefly observed a wind gust to 45 mph earlier. West of the Cascades, thunderstorms are unlikely (less than 10% probability). However, we do expect clouds to lower and thicken overnight to MVFR (higher terrain obscured) with some light rain developing as well. This will stick around until mid-late morning with clouds breaking up and precip becoming more showery Saturday afternoon. Expect some breezy conditons again Saturday afternoon. There is still a slight chance (15-25%) of thunderstorms in the SE portions of the area (Modoc/Lake counties) Saturday afternoon. -Spilde && .MARINE...02/18Z TAFs...MVFR and IFR ceilings remain along the Oregon coast this morning, with periods of LIFR visibilities being observed at North Bend. An approaching front should bring more consistent MVFR ceilings along the coast, although North Bend does have periods of IFR ceilings forecast for this evening. MVFR ceilings will be possible for inland areas as well as the front moves eastward through the day. There are slight (10-20%) thunderstorm chances for areas east of the Cascades this afternoon and evening, with those chances returning to single digits by early Saturday morning. Showers will be capable of locally lowering ceilings and visibilities as well as obscuring elevated terrain wherever they occur. Areas west of the Cascades should start to see more stable conditions by Saturday afternoon, while showers look to continue east of the Cascades into the next TAF period. -TAD && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory from 11 PM this evening to 11 PM PDT Sunday for PZZ350-356-370-376. Hazardous Seas Warning from 11 PM Saturday to 11 PM PDT Sunday for PZZ356-376. && $$