Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
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780 FXUS66 KMFR 140552 AFDMFR Area Forecast Discussion National Weather Service Medford OR 1052 PM PDT Sat Jul 13 2024 Updated AVIATION Section .DISCUSSION...Satellite imagery is showing clouds across much of the East Side and in northern California as well. Radar is confirming some showers across portions of the East Side with a few lightning strikes. Also of note is the Shelley Fire is very visible via satellite and RADAR, particularly in the aloft slices of the RADAR imagery. This suggests that the unstable nature of the Atmosphere that is causing the showers and thunderstorm chances has caught the Shelley fire and allowing for some extreme plume-dominated growth. This is confirmed by the incident meteorologists on the fire who we are working with in order to keep firefighters abreast of the weather in order to keep them safe. In other news, temperatures will not be as hot tomorrow; albeit still a few degrees above normal. Therefore we allowed the Excessive Heat Warning and Heat Advisory to expire at 9pm. A red flag warning for lightning on dry vegetation will continue overnight into tomorrow through 11pm as this unstable airmass will allow for dry thunderstorms to be possible overnight. Tomorrow still seems on track to be our big thunderstorm day; so will continue to monitor the forecast. For more information about the forecast, please read the previous discussion below. -Schaaf && .AVIATION...14/06Z TAFS...Isolated lightning in NE Siskiyou, Modoc and into SE Lake counties earlier this evening has ended. There`s still a slight risk of lightning overnight in those same areas as moisture and elevated instability continue to push northward, but dry weather persists west of the Cascades even if some higher level clouds move in. Despite the higher cloud cover, VFR prevails over most of the CWA. However, IFR/LIFR marine stratus/fog continue to impact the coast north of Cape Blanco and also south of Pistol River. These lower conditions will persist through about 17-18Z on Sunday before clearing back to the beaches. North winds pick up in North Bend again Sunday afternoon (up to 25kt). Expect stratus/fog to return to the same coastal areas again Sunday evening, probably around 00z at North Bend. Expect another round of isolated to scattered storms Sunday afternoon/evening with a larger coverage area from western Siskiyou County northward up to the Siskiyou Mtns, southern Cascades (south of Crater Lake) and then over to the east side again. Most activity should remain east of the west side valleys, though can`t rule out a stray storm in southern Rogue Valley near Ashland or up at Mt A. Smoke from the Shelly fire in western Siskiyou County could bring visibility reductions in the immediate vicinity of the fire with MVFR visibility 15-25 miles away, especially to the NE (toward Montague) as S-SW winds carry the main plume in that direction. -Spilde && .MARINE...Updated 830 PM Saturday, July 13, 2024...We have cancelled the gale warning. Observations are showing weaker winds compared to yesterday at this time and we expect further weakening of the thermal trough tonight through Monday. Even so, conditions will remain hazardous due to a continuation of moderate north winds and steep to very steep seas, dominated by wind waves. We have issued a hazardous seas warning to account for the very steep wind seas from around Gold Beach southward and beyond about 10 NM from shore (southern half of PZZ376). Models are showing a slight coastward push to around 8 NM for seas near 10 feet between Gold Beach and Port Orford Sunday afternoon, but it`s a small area and not representative of the entire zone. Even so, a small craft advisory remains in effect for the southern inner zone (PZZ356) for gusty north winds and steep seas. The same is true for areas north of Cape Blanco, where north winds and seas will produce conditions hazardous to small craft. Eventually, though, winds and seas are expected to gradually subside Tuesday into Thursday. -Spilde && .PREV DISCUSSION... /Issued 545 PM PDT Sat Jul 13 2024/ DISCUSSION...Satellite is creating a beautiful picture with the stratus banking the coast. Some stratus was reaching into the Coquille Basin this morning, but that has been burning off, albeit stubbornly. Inland, cumulus is starting to creep up into Modoc, Lake and Siskiyou counties. The Shelly Fire is the main smoke producer in the area today, with most of the smoke staying in Siskiyou County with haze across more areas in Southern Oregon and Modoc County. Highs this afternoon will be in the 90s or low 100s widespread besides the coast. It will also be the last day in the forecast for record watching. The record high for Alturas is 102 from 2014 with a forecast of 101 and Mount Shasta has a record of 99 from 2021 with a forecast of 103. This afternoon is also the last afternoon where a Heat Advisory will be in effect for Jackson and Josephine counties with an Excessive Heat Warning for most of Siskiyou County. Overall, temperatures will be near 5-10 degrees above normal the next few days, which will mean temperatures will still range from 50s and 60s in the mornings to 90s/low 100s in the afternoons inland. The trend of warmer than normal conditions will continue through the rest of the week. Please still take precautions when having to be out in the heat this next week. The main smoke concerns lie in Siskiyou County with the Shelly Fire while haze is present in other parts of Southern ORegon and Northern California. Into tomorrow morning the smoke will come across southerly flow which will move lower concentrations to Jackson, Klamath and Lake counties. The cumulus that is building is indicating that there is more moisture in the air. This afternoon there is a 15-20% chance for lightning from central Siskiyou County east into Modoc County and in portions of southern Klamath and Lake counties. A 5-15% chance for lightning continues tonight that includes Callahan, Lakeview and Alturas. Tomorrow is looking more favorable for lightning with a 15- 30% chance with a line from western Siskiyou County and up into eastern Jackson County and Crescent that continues eastward. Dry conditions are favored to return Wednesday. From Thursday through the weekend, the probability for reaching 100 degrees in Medford lowers to 25-45% while highs and lows are forecast to be 5- 10 degrees above normal. -Hermansen AVIATION...14/00Z TAFS...VFR prevails over most of the CWA, but marine stratus (IFR/LIFR) has already moved into North Bend and will remain there (and along the rest of the coast north of Cape Blanco) the remainder of the night through about 17-18Z on Sunday. Fog/low clouds will also return to Brookings overnight into Sunday morning. Gusty north winds (up to 25kt) in North Bend will ease this evening, but develop again as conditions break to VFR Sunday morning/afternoon. Expect stratus/fog to return to the same coastal areas again Sunday evening. Meanwhile, isolated thunderstorms are developing in NE California and pushing into south-central Oregon this evening. These storms are very high-based, so little or no precipitation is reaching the ground. However, gusty outflows (40-45kt) are possible along with cloud to ground lightning. These are primarily in Siskiyou and Modoc counties, but also portions of southeastern Klamath and southern Lake counties. Coverage of storms should diminish tonight, though may not go away completely. Expect another round of isolated to scattered storms Sunday afternoon/evening with a larger coverage area from western Siskiyou County northward up to the Siskiyou Mtns, southern Cascades (south of Crater Lake) and then over to the east side again. Smoke from the Shelly fire in western Siskiyou County could bring visibility reductions in the immediate vicinity of the fire with MVFR visibility 15-25 miles away, especially to the NE (toward Montague) as SW winds carry the main plume in that direction. -Spilde FIRE WEATHER... ...RED FLAG WARNING IN EFFECT UNTIL 8 PM THIS EVENING FOR STRONG GUSTY WIND AND LOW RH FOR NORTHERN FIRE WEATHER ZONES 624 AND 625... ..RED FLAG WARNING IN EFFECT UNTIL 11 PM PDT SUNDAY FOR LIGHTNING ON DRY FUELS FOR FIRE WEATHER ZONES 284...285..624 AND 625... ..RED FLAG WARNING IN EFFECT FROM 2 AM TO 11 PM PDT SUNDAY FOR LIGHTNING ON DRY FUELS FOR FIRE WEATHER ZONES 280...281...282... AND 621... ..FIRE WEATHER WATCH IN EFFECT FROM SUNDAY EVENING THROUGH MONDAY EVENING FOR LIGHTNING ON DRY FUELS FOR FIRE WEATHER ZONES 280...281...282...284...285...624 AND 625... Hot, breezy, low humidities, and unstable afternoon conditions will persist through this weekend. The focus of today`s efforts was to fine tune the thunderstorm forecast for this weekend and to glean any details for the Monday/Tuesday timeframe as well. Strong high pressure will linger over the Great Basin region into next week and a weak low pressure will move northward just offshore of the California coast. This is a pretty classic thunderstorm pattern for this area as the flow turns more southerly and moist unstable air moves into the region. For today, we expect isolated thunderstorms to be focused over our southeastern zones (284, 285, southern 624 and 625) and this is covered by the current Red Flag Warning (RFW). Storms are already moving into Modoc County this afternoon, so the forecast remains on track for today. Meanwhile, the RFW for FWZs 624 and 625 is actually a combination of critical concerns. Gusty southwest winds have shifted northward today and humidities will remain very low across the northern portions of those zones. So north of a line from roughly Chiloquin to Paisley, we expect critical fire weather conditions due to gusty winds and low RH, while south of there the concern is due to lightning on dry fuels. Though confidence is higher for isolated coverage vs scattered, any lightning in the area right now should be highly efficient fire starters thanks to the recent prolonged stretch of very hot and very dry conditions. Additionally, any storms that develop today into tonight will be high based and have very little to no precipitation with them. As we head into tonight and Sunday, the potential for thunderstorms shifts westward. It`s not out of the question we see some isolated, elevated convection continue Saturday night into Sunday morning, but Sunday afternoon and evening looks like the day for the most coverage of storms as the mid-level moisture field shifts westward. Have upgraded the Fire Weather Watch for FWZ 624, 625, 284, 285, 280 to a Red Flag Warning and have also added FWZs 281, 282 and 621 to the warning. Additionally, to cover the potential for isolated dry thunderstorms for the overnight period, have basically just stretched out the current Red Flag Warning to continue overnight tonight through late Sunday evening. The exception being FWZs 280/281/282/621 where that Red Flag starts at 2 am tonight and carries through late Sunday evening. Storms should trend wetter on Sunday, but will still be a mix of dry and wet storms, with lightning strikes outside of precipitation cores a real possibility and cause for concern. The focus of today`s efforts has largely been on the weekend setup, but it looks like we`ll maintain at least isolated thunderstorm chances Monday into Tuesday. There is some uncertainty due to model differences regarding where these chances are focused, which could include west of the Cascades or even nocturnal thunderstorms at some point. We`ve gone ahead and issued a Fire Weather Watch for late Sunday night through Monday evening where confidence is highest for the continued thunderstorm threat, and this includes FWZs 280/281/282/284/285/624/625. We`ll have to monitor model trends closely as each day passes, but we`ll be in a thunderstorm pattern through Tuesday, and subtle shifts in model trends could lead to big changes in the forecast. /BR-y && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Red Flag Warning from 2 AM to 11 PM PDT Sunday for ORZ621. Red Flag Warning until 11 PM PDT Sunday for ORZ624-625. Fire Weather Watch from Sunday evening through Monday evening for ORZ624-625. CA...Red Flag Warning from 2 AM to 11 PM PDT Sunday for CAZ280>282. Fire Weather Watch from Sunday evening through Monday evening for CAZ280>282. Red Flag Warning until 11 PM PDT Sunday for CAZ284-285. Fire Weather Watch from Sunday evening through Monday evening for CAZ284-285. PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT Monday for PZZ356-370-376. Small Craft Advisory until 8 PM PDT Sunday for PZZ350. Hazardous Seas Warning until 8 PM PDT Sunday for PZZ376. && $$