801 FXUS66 KMFR 200553 AFDMFR Area Forecast Discussion National Weather Service Medford OR 1053 PM PDT Sat Jul 19 2025 .UPDATE...Updated Aviation Discussion. && .AVIATION...20/06Z TAFs...Areas of IFR and local LIFR will spread along the coast tonight through Sunday morning, mainly for areas from Cape Blanco northward and Brooking southward. These low ceilings are expected to develop around 08-10z, with improving conditions around 18-20z. For inland areas, expect VFR areawide. Gusty winds are expected in the late afternoon and early evening for area TAF sites. Areas of haze and smoke from wildfires will reduce visibilities in western Siskiyou County. && .PREV DISCUSSION... /Issued 255 PM PDT Sat Jul 19 2025/ DISCUSSION...(Today through Friday)... Overview: Items of interest include the cooler temperatures albeit near normal through most of the forecast (Monday is below normal), continued dry/breezy conditions, and thunderstorm chances next week. Perhaps the most noteworthy item is the fact we could have an active week starting Monday with several days of thunderstorms potentially. At this time, if we had to choose one day, Thursday looks like the highest potential for strong to severe thunderstorms. That said, each day Mon-Thurs (and to some degree Friday) could have thunderstorms. Further Details: The overall pattern--more or less--can be summed up as a trough over the Pacific Northwest through the next several days. By Monday, we will see this influence our weather by bringing thunderstorm chances across the region. There is some evidence of thunderstorms potentially Monday morning, but this may be just showers until daytime heating kicks into gear. The trough holds on through Tuesday and while the "official" forecast doesn`t convey thunderstorms on Tuesday, there is at least some small potential there that the NBM hasn`t quite grabbed onto yet. This is likely due to outliers and weighting functions, but as high resolution data comes in, we may have a clearer picture. By Tuesday night, the trough over the PacNW will transitions east, and a cut-off low will form over the Pacific roughly off the coast of San Fransisco. This will meander around this location through roughly Friday afternoon before getting absorb into the mean flow. As this cut-off low forms, it will spread PVA across the area and this pattern would be conducive for thunderstorms as we reach peak heating each afternoon Wed/Thurs; however, at this time Wednesday has no mention of thunderstorms but that could change. Thursday is shaping up to see more thunderstorm activity than as of recently where we have seen mostly isolated storms. Thursday could be more scattered to perhaps widespread. That being said, split flow patterns and cut-off lows can be tricky, especially this far out. Ensemble members are showing the potential for CAPE to reach values near 1000 J/kg with ample bulk shear (0- 6km) around 25 to 40 knots. Moisture advection will be ample with very high theta-e values advecting into the region as well. This setup could bring strong to severe storms across the region with abundant lightning. We will have to see what happens when new data comes in, especially the HiRes data. This being several days out and a cut-off low situation, we could see changes to the orientation of the trough which would affect moisture pull and timing/coverage of convection. Stay tuned as we continue to monitor next week for potentially active weather over several days. -Guerrero MARINE...Updated 100 PM PDT Saturday, July 19, 2025...A weak thermal trough along the coast will maintain gusty north winds south of Cape Blanco through tomorrow morning. This will result in low end advisory level winds and steep seas south of Port Orford. Winds weaken tomorrow afternoon as an upper level trough settles over the region and disrupts the thermal trough pattern. Thereafter, relatively light winds and seas are expected through much of next week. FIRE WEATHER...Updated 230 PM PDT Saturday, July 19, 2025... Humidities are trending higher compared to 24 hours ago and that has lowered the fire weather threat west of the Cascades. The hot dry windy index has also trended lower compared to 24 hours ago. However, it will remain rather breezy with wind gusts still pushing that 25mph to 30 mph mark, which is already occuring around Summer Lake and the Summit RAWS east of the Cascades. RHs will continue to trend higher across the area and that will keep any fire weather threat to just Modoc County and their typical windy and breezy summer time weather. MOS Guidance hints at sustained 10 to 20 with gusts to 30 mph with RH in the lower teens around Alturas and the Devils Graveyard RAWS. That is pretty darn close to red flag criteria with the gusty winds. We`ll continue to headline the fire weather conditions in that zone into Sunday. The big topic will be the thunderstorm forecast and that is covered in more detail in the discussion above. -Smith && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 11 AM PDT Sunday for PZZ356-376. && $$