####018007784#### FXUS66 KMFR 170417 AFDMFR Area Forecast Discussion National Weather Service Medford OR 917 PM PDT Fri May 16 2025 .UPDATE...Updated Aviation Discussion. && .AVIATION...17/00Z TAFs...A front is moving inland tonight bringing rain, mountain obscurations and MVFR and areas of IFR conditions. Along the coast, expect a mix of MVFR and IFR conditions with areas of LIFR through tonight, transitioning to MVFR Saturday morning. Inland, rain MVFR will spread inland around 05-11z and persist through Saturday morning. MVFR conditions will be widespread across much of southern Oregon along with local IFR and widespread mountain obscurations. Across northern California, expect a mix of VFR and MVFR conditions tonight through Saturday morning. Isolated to scattered thunderstorms embedded with rain showers are expected tonight through Saturday afternoon across Lake County and Modoc County, including Lakeview and Alturas. This risk will reach a peak tonight and early Saturday morning, but continue into the afternoon. Chances for thunderstorms (15-20%) are also expected tonight into Saturday across Douglas County, for the Southern Oregon Cascades and northern and eastern Klamath County. Ceilings will gradually lift to VFR Saturday afternoon, but expect areas of MVFR to linger in heavier showers. Showers decrease in coverage Saturday evening, becoming limited to the coast, Umpqua and Cascades, where some areas of MVFR conditions may persist. && .PREV DISCUSSION... /Issued 811 PM PDT Fri May 16 2025/ DISCUSSION...A fairly vigorous upper trough offshore supported by a 150-kt jet will sharpen as upper level energy dives ESE into northern California overnight into Saturday morning. Showers will break out along the coast later this evening, but the best forcing is over the East Side where showers likely develop quickly between 1-3 am. This is a bit unique to have a sharpening upper trough to swing through in the middle of the night and also to have enough instability present east of the Cascades (about 300-500 J/KG) to support convection. As such, we expect isolated to scattered thunderstorms to develop within the band of showers that gets going (mainly east of Klamath Falls). Best shot for thunder (20-30%) is in Modoc and up into portions of Lake County overnight into Saturday morning. We don't expect severe weather, but some of the stronger cells could contain gusty winds and, of course, cloud to ground lightning. The main axis of instability shifts to the east during Saturday morning, but the cold pool aloft will move in, so we'll maintain scattered showers, most numerous near and north of the Umqpua Divide, over the Cascades and from around Winter Rim eastward over the East Side. There is also a risk of thunder in portions of Douglas County Saturday in any of the heavier showers, but isolated (15-20% chance) at best. For the Rogue Valley, showers will be more hit-or-miss. Some areas may have brief downpours, while others miss out all together. Locally breezy conditions develop too Saturday, especially east of the Cascades in the afternoon where non-thunderstorm wind gusts could be 30-40 mph. Overall, expect a cooler than normal day with highs generally in the 60-65F range for the west side and 55-60F east of the Cascades. Shower coverage diminishes Saturday afternoon/evening as warmer air aloft moves in, though some do linger near the Cascades due to moist onshore flow. -Spilde MARINE...Updated 800 PM Friday, May 16, 2025...Rain showers with light to moderate winds and increasing west seas are expected tonight through Sunday morning. Another frontal system will move into the area on Monday with winds veering from south to northwest. Northerly winds will increase on Tuesday from the brief development of a thermal trough near shore. Meantime, building seas on Tuesday may possibly becoming high and steep with the combination of the higher wind waves and a building west-northwest swell at 13 seconds. Conditions are likely to improve slightly on Wednesday. PREV DISCUSSION... /Issued 253 PM PDT Fri May 16 2025/ DISCUSSION...Cloud cover is rebuilding this afternoon ahead of an approaching upper trough. The first impacts from this approaching system will be thunderstorm chances developing east of the Cascades late tonight into early Saturday morning. The best chances (10-15%) will be across Modoc and southern Lake counties, with lesser chances (5-10%) covering eastern Klamath and northern Lake counties. Any thunderstorms that develop are likely to be isolated and remain below severe thresholds. Thunderstorm chances increase to 15-20% across Lake and Modoc counties on Saturday afternoon before decreasing through Saturday evening and night. Other areas are expected to see at least light showers at some point between Saturday morning and Sunday afternoon. Overall amounts will be unimpactful. Coos County, the Cascades, areas around and east of Lakeside, and the Warner Mountains are expected to see between 0.25 and 0.50 inches of rainfall. Occasional snow showers are possible over the Cascades early Sunday morning, but accumulation is not expected. The Umpqua Valley may see 0.10 inches of rainfall, and other areas will have rainfall measured in the hundreths. Temperatures will cool through the weekend as the trough moves over the area. Seasonal temperatures under zonal flow aloft look to continue through the week. A couple of weak disturbances may briefly affect conditions for certain locations. On Monday, a weak front could bring some clouds to Coos and eastern Douglas counties. Brief showers are possible over these areas on Monday morning and afternoon, but amounts will be one or two hundreths at most. On Wednesday or Thursday, a weak disturbance could bring gusty winds and isolated showers to the northernmost border of the CWA. Deterministic guidance for both the ECMWF and the GFS show some upper instability passing over the area, with some variation in timing and structure. Individual ensemble members for both the GFS and ECMWF are split on showing the disturbance or not, and those that show it do so with some variation in timing and location. Zonal flow continues on Friday, with some uncertainty for the weekend. While both models show some amount of upper level ridging, the strength and position of the ridge vary. The general expectation seems to be additional warming on Saturday and Sunday, but little overall consensus on how warm next weekend will be. NBM probabilistic guidance echos this uncertainty, with daytime highs forecast to be from seasonal temperatures to 10 degrees above on next Sunday. -TAD MARINE....Updated 200 PM Friday, May 16, 2025...A trough will produce light showers with moderate winds and moderate swell dominated seas tonight through Sunday morning. Northwest winds will be strongest Saturday evening south of Brookings. Another seasonable system will follow on Monday with winds veering from south to northwest. Northerly winds will increase on Tuesday from the brief development of a thermal trough near shore. Meantime, building seas on Tuesday may possibly becoming high and steep with the combination of the higher wind waves and a building west-northwest swell at 13 seconds. Conditions are likely to improve slightly on Wednesday. -DW && .MFR WATCHES/WARNINGS/ADVISORIES... OR...None. CA...None. PACIFIC COASTAL WATERS...None. && $$ ####018008315#### FXUS63 KOAX 170418 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1118 PM CDT Fri May 16 2025 .KEY MESSAGES... - Widely scattered showers continue this afternoon, mainly over northeast Nebraska (20-60% chance). Showers end early this evening. - High Wind Warning and Wind Advisory remain in effect for the forecast area until 9 pm tonight. Expect northwest 30 to 40 mph winds with gusts up to 60 mph at times before subsiding late tonight. - Breezy winds linger early Saturday before subsiding by the afternoon with pleasant conditions expected. Several chances for showers and storms return Sunday night through Wednesday, potentially with heavy rain and severe weather. && .DISCUSSION... Issued at 323 PM CDT Fri May 16 2025 .SHORT TERM.../Today through Saturday Night/ 1930z 500 mb RAP objective analysis shows the closed upper level low located right over Minnesota. Two vorticity lobes are noted within the flow: one associated with the main closed low over Minnesota extending southwestward toward Nebraska, and the secondary lobe across Kansas associated with a weak wave. This wave provided some forcing to generate widely scattered showers this morning over our far south with a few mPING reports of rain. This activity has largely pushed east into central Iowa this afternoon, but we are starting to see more widely scattered showers across northeast Nebraska associated with the vorticity lobe from Minnesota and the cyclonic wrap around flow. These showers will eventually dissipate as we head into the early evening hours. PoPs are currently at 20 to 60%, with the highest chances in far northeast Nebraska. The main concern today continues to be the strong environmental winds. RAP sfc analysis shows an impressive 987 mb low associated with the upper level disturbance based over west central Minnesota, with a tight pressure gradient extending southwestward into a large portion of the South Dakota, Iowa, and Nebraska area. 850 mb upper air analysis shows a strong jet associated with the closed low feature, with the strongest winds (50-55 kts) seen over northeast Nebraska and slightly lower speeds (35-45) observed over the rest of eastern Nebraska/western Iowa. BUFKIT soundings show growth of the mixed layer anywhere from 850-700 mb across northeast Nebraska, while areas farther south where some gaps in cloud cover are present show a deeper mixed layer up to 650 mb in the late afternoon hours. This will allow us to tap into the strong winds/jet aloft with anywhere from 35-45 kts of momentum transfer occurring at the surface. The tapping into this stronger sink of momentum coupled with the tight pressure gradient will result in widespread sustained northwest winds of 30 to 40 mph with gusts anywhere from 50 to 60 mph. So, have continued the midshift's High Wind Warning over northeast Nebraska and Wind Advisory for the rest of the CWA through 9 pm tonight. Localized visibility reductions due to blowing dust remain possible, as do localized power outages and tree damage. The scattered showers across the north may help drive some of the aforementioned momentum downward as well. Winds will somewhat relax late this evening into Saturday morning, but could still see some breezy northwest winds of 15 to 25 mph, particularly over northeast Nebraska. Did lower highs from NBM guidance today to account for northwest winds and cloud cover hindering daytime heating. Highs today will be in the mid 50s north to mid 70s south. Lows tonight will be in the 40s. Saturday will see the sfc low over Minnesota continue eastward toward the Ontario/Great Lakes area, with sfc ridging moving in behind the low. This will result in winds slowly relaxing during the day with dry conditions expected. Highs will be in the upper 60s to mid 70s with a few clouds. Lows Saturday night will be in the low to mid 40s. .LONG TERM.../Sunday through Thursday/ Flow aloft at 500 mb becomes southwesterly on Sunday as the longwave trough over the Four Corners area ejects northeastward. The wave will induce cyclogenesis, with a sfc low developing over the eastern Colorado area and resultant warm front extending eastward somewhere over the Kansas/Nebraska vicinity. Forcing for ascent increases by Sunday evening as the mid level wave approaches the Central/Northern Plains. Dew points in the low to mid 60s also arrive within the warm sector aided by 1000-850 mb moisture transport from the Gulf. With CAPE anywhere from a few hundred to thousand J/kg and 0-6 km bulk shear around 50-60 kts, these ingredients will support severe weather across portions of the Central/Northern Plains Sunday evening, with the Storm Prediction Center highlighting mainly south of Interstate 80 in a slight risk of severe weather, while an enhanced risk is seen just south of the border into Kansas. One of the big questions that remains is where the baroclinic zone/warm front will end up at. This will be extremely important in determining where the better moisture and instability will be. GEFS and Euro based ensembles still show considerable uncertainty in the location of the sfc low center. Regardless of where the severe threat ends up happening, we will still see some scattered showers and thunderstorms, as the NBM currently has a 70 to 90% chance of PoPs Sunday evening through early Monday morning. Sfc low will continue to track to the northeast Monday, but still seeing several discrepancies on where the sfc low and its associated baroclinic zones/fronts will set up. Again, this will have important implications on where we could see severe weather this day, but the Storm Prediction Center currently highlights portions of the forecast area in a 15% risk for severe weather. NBM currently has a 70-90% chance of scattered showers and storms areawide Monday night lingering into Tuesday. PoPs decrease on Wednesday as the system finally exits the area with dry conditions anticipated per NBM guidance on Thursday. With several chances for showers and storms to start the work week, this certainly leads to some concern regarding flooding potential. Admittedly, what leads to some uncertainty regarding flood potential is our current drought conditions. The majority of eastern Nebraska is in a moderate to severe drought, while southwest Iowa is abnormally dry to in a moderate drought. While there is still some uncertainty with these upcoming waves/disturbances regarding timing and location, do see at times deterministic PWATs up to 1.5 inches across our far south and into southwest Iowa. With warm cloud depths between 3,500 to 4,000 meters, these ingredients indicate efficient rainfall production could occur. Ensemble members of the GEFS, Euro, and Canadian show the best PWAT values (anywhere from 1.2 to 1.7 inches) arriving sometime early Monday morning through about early Tuesday morning. Again, lots of uncertainty exists at this point in the extended forecast as the evolution of the upper level features will influence how the sfc low tracks and where its baroclinic zones set up. We recommend you continue to stay tuned to the forecast for the latest updates regarding the severe and heavy rainfall potential for the Sunday through early Wednesday systems. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1115 PM CDT Fri May 16 2025 A few MVFR cigs linger in the far northern reaches of the forecast area, but otherwise low VFR cigs persist elsewhere. Cigs might lower a bit overnight and push an increasing number of observations into the MVFR category before improvements after sunrise Saturday. Breezy northwesterly winds continue to slow tonight and will continue that trend over the next 20 hours. They'll gain and easterly component by Saturday evening. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Castillo AVIATION...Nicolaisen