####018007599#### FXUS66 KLOX 160320 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 820 PM PDT Thu May 15 2025 .SYNOPSIS...15/706 PM. A cooling trend is expected Friday through the weekend with some morning drizzle possible Saturday. Much warmer temperatures are expected next week, especially inland as high pressure builds over the region. && .SHORT TERM (THU-SUN)...15/819 PM. ***UPDATE*** Onshore gradients combined with a coastal eddy and a weak trough aloft should help to create a deeper and more widespread marine layer tonight. Low clouds are expected to develop for most coastal areas, most widespread across the Santa Barbara portion of the Central Coast and the LA Basin, extending inland to the adjacent coastal valleys. Low cloud coverage for the Ventura Coast and especially the Santa Barbara South Coast is less certain, but believe that the western portion of the Oxnard Plain and the Eastern SBA South Coast will see low clouds later tonight into early Friday. Gusty west to northwest winds continue this evening over portions of the area, but weaker than on previous days and well below Advisory level. The windiest areas continue to be SW Santa Barbara County and the interior sections, including the Antelope Valley and interior San Luis Obispo County. High temperatures on Friday are expected to lower a few degrees, anywhere from 2 to 6 degrees cooler for the valleys with little change for the coast and deserts. Coastal low clouds and fog should clear by late morning, with clear to partly cloudy skies in the afternoon. ***From Previous Discussion*** Gradients are starting to trend onshore today as the last in a series of mostly weak troughs moves through the West Coast, peaking locally on Saturday. Temperatures today ended up being quite a bit warmer across the interior, but little changed near the coast. As that trough advances southeast through northern and central California Friday and Saturday, onshore flow will continue to increase and peak Saturday afternoon at around 9mb with cooling temperatures each day. At the same time, cooling aloft will deepen the marine layer considerably. Latest forecast sounding across the LA Basin indicate the marine inversion depth rising to around 2000 feet Friday, then up to 4000 feet Saturday morning with a solid 5mb gradient. This combination of factors often, though not always, results in some drizzle across the coast and valleys. The one drawback in this case is the upper low is actually taking a more inside path through California with northwest flow aloft. Most of the models do favor a rapidly deepening marine layer but given the interior trajectory and winds aloft the best chances for any drizzle would likely be the San Gabriel Valley in eastern LA County. Further west it will be a battle between the northwest flow aloft and the marine layer expanding from the southeast. By Saturday temperatures will again be 5-15 degrees below normal. Gusty onshore winds will develop in the afternoon, especially across the Antelope Valley. With models now in agreement that the first trough will take a more inland track and the next upper low also moving farther inland through Utah, there is increasing confidence that a slow warming trend will begin Sunday with earlier clearing of the marine layer, especially inland. Model forecast gradients are in line with that as well indicating a 2-3mb offshore trend. .LONG TERM (MON-THU)...15/208 PM. Confidence remains high in much warmer temperatures next week, especially Tuesday and beyond as high pressure builds and onshore flow weakens. Highs in the 90s are expected in the valleys and possibly some isolated lower 100s across the western San Fernando Valley. Inland coastal areas will at least reach the mid 80s and possibly lower 90s in downtown LA. Warmest day are expected to be Tue-Thu, but well above normal temperatures will continue at least through next Friday. There still may be a shallow marine layer at the coast creating some areas of dense fog. && .AVIATION...15/2333Z. At 2253Z at KLAX, the marine inversion was around 900 feet deep. The top of the inversion was 2200 feet with a temperature of 18 degrees Celsius. High confidence in TAFs for KPRB, KPMD, and KWJF. Moderate confidence in remaining TAFs. Timing of cig/vsby restrictions may be off +/- 2 hours, with flight cats off by one. There is a 40% chance of VLIFR vsbys & LIFR cigs at KSMX/KSBP from 06Z to 16Z Fri. There is a 20% chance of LIFR conds at kvny from 09Z to 16Z Fri. KLAX...Moderate confidence in 00Z TAF. There is a 25% chance of IFR cigs 008-009 at some point between 06Z to 16Z Fri. No significant east wind component expected. KBUR...Moderate confidence in 00Z TAF. There is a 30-40% chance of IFR Conds and a 10% chance of LIFR cigs w/ vsbys <1SM from 06Z to 16Z Fri. && .MARINE...15/746 PM. For the Outer Waters, high confidence in a combination of Small Craft Advisory (SCA) level winds and seas (at times), will lull in winds possible in the morning hours through the weekend. There is a 40% chance of GALE force NW wind gusts for northern portions of PZZ670 late Fri afternoon into the evening hours. Better chances for GALES for the waters around Point Conception, Northern Channel Islands, and down to San Nicolas Saturday evening through late Sunday. Seas will peak around 13 feet towards the end of the weekend. There is potential for SCA winds and seas to persist through next week. For the Inner Waters north of Point Sal, there is a 80% chance of SCA level NW winds during the afternoon/eve hours on Fri - with a 30% chance of GALE force wind gusts across the waters > 5 NM offshore San Simeon. For the remainder of the weekend, high confidence in combination of SCA level winds and seas with a 30-50% chance of GALE force winds during the late afternoon/eve hours on Saturday and Sunday. Seas will build to around 12 feet during this time. Seas may fall below SCA levels sometime late Mon into Mid-week, while there is a moderate chance for SCA level winds during the afternoon/eve hours each day. For the Inner Waters south of Point Conception, there is a 60% chance of SCA level W winds across western portions of the Santa Barbara Channel Fri afternoon/eve. For the remainder of the weekend, high confidence in SCA level winds. There is also a 40-50% chance of GALE force winds across the western half of the SBA channel during the late afternoon/eve hours on Saturday and Sunday. Steep and choppy seas around 8 feet are expected during this timeframe. Other than low chances across western SBA channel, winds and seas will likely remain below SCA criteria through mid- week. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect until 9 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Friday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Saturday for zones 670-673-676. (See LAXMWWLOX). && $$ PUBLIC...MW AVIATION...Black MARINE...Black SYNOPSIS...MW/Smith weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox ####018007513#### FXUS61 KCTP 160324 AFDCTP Area Forecast Discussion National Weather Service State College PA 1120 PM EDT Thu May 15 2025 .SYNOPSIS... * Daily chances for thunderstorms continue through Saturday with potential for damaging winds and localized flooding. * Temperatures trend warmer Friday and Saturday with a notable uptick in humid/sticky weather. * A cold front will bring much cooler temperatures and less rainy/more sunny weather Sunday and early next week with breezy conditions. && .NEAR TERM /THROUGH TONIGHT/... With the last of the showers in the northern mountains fizzling out around 930 PM, we are now in a lull in terms of precip with generally clear skies overhead. Valley fog has formed across much of the area where it rained earlier today from Bradford to St. Marys to the forests of Clinton and northern Centre Counties. Fog will also expand over east central PA as the night progresses, first into portions of Schuylkill County and then expanding into the Susq Valley. The next issue of note is later tonight as forcing associated with the left-exit region of a jet max over the OH valley approaches. A complex of storms moving through Michigan and northern Illinois as of 11 PM Thu is progged to drop into OH/wrn PA toward morning. SPC still has the wrn 2/3rds of the CWA in a MRGL risk for SVR (primarily a marginal wind threat - limited by a lack of SBCAPE and DCAPE). The main uncertainty is just how far south the heavy shower/storm activity will reach, given the strongest forcing just clipping our northwestern zones, but a fair number of hires CAM guidance still show convection expanding far south enough to impact even Somerset and Bedford Counties. A flood watch has been issued for Somerset and Bedford Counties where it's been very wet and stream flows are running high. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Latest guidance indicates a lull in the precipitation during the late morning and afternoon on Friday following the passage of the warm front. Southwest flow will continue to funnel moisture up into the northeast US as dewpoints reach their highest values so far this year (in the mid to upper 60s). It will feel noticeably humid as well. Highs in the 80s across the area appear likely. Isolated to scattered thunderstorms are possible Friday afternoon as the warm and humid conditions across south central PA provide 1500 to 2000 J/kg of MLCAPE. The missing piece for a more widespread afternoon convective outbreak is a lack of upper level forcing for ascent through the dry midlevels. However, any isolated/scattered cells that do pop up in the afteroon have the potential to become briefly severe, especially if precip cores are lofted up above 3-4 km AGL, yielding more of a downburst potential. Another nocturnal MCS appears possible Friday night into Saturday morning as it moves across Pennsylvania from the Midwest. Severe weather appears a bit more likely with this round as up to 1500 J/kg of MLCAPE lingers into the overnight especially across the Laurels and Alleghenies. By Saturday, a cold front will approach the Commonwealth with a convective outflow boundary likely surging out ahead of it from the previous night's convection. The outflow boundary will encounter a warm and moist airmass that could lead to development of additional strong thunderstorms on Saturday afternoon. Still some uncertainty with how quickly a line of thunderstorms will congeal Saturday afternoon, but southeast PA would be favored for a primarily damaging wind threat, as outlined by SPC's Slight Risk (level 2 out of 5) that covers York and Lancaster County. With all 3 rounds of storms, progressive storm motions should limit the risk of significant flooding, but cannot rule out some isolated issues for locations who's soil moistures/creeks are already running high. Even outside of thunderstorms, wind gusts in excess of 30 mph are possible Saturday as westerly winds pick up behind the cold front. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... Dry conditions continue into the beginning of the long-term period as an upper-level ridge supplies fair conditions through Tuesday afternoon. Increasing moisture on Tuesday leads to a notable uptick in cloud cover for the second half of the day for most, especially across the Laurel Highlands as the next system pulls closer to the region. Temperatures for Monday and Tuesday are expected to trend slightly below seasonal averages, especially during the daytime hours. Model guidance promotes two different solutions for the area of low pressure approaching central Pennsylvania in the late Tuesday/early Wednesday timeframe. ECMWF/GDPS guidance tend to keep the approaching area of low-pressure west of the area for quite longer and does keep highest chances for precipitation until Wednesday afternoon/evening. Recent GFS/UKMET guidance outline a solution where the surface low-pressure dive further south and station over MD by Wednesday morning, allowing for precipitation chances to increase Tuesday night into Wednesday morning across the area. Given some model differences, have stuck close to NBM guidance while also trimming back timing on precipitation slightly due to some low-level drier air in place. After precipitation onset, generally expect showers to continue through the end of the long-term period given favorable moisture and lift associated with the area of low- pressure. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... All TAF sites are VFR at 00z Fri with scattered convection over the northwest mountains weakening and moving away from BFD. Expect several hours of continued VFR conditions tonight before some fog and low stratus begin to move in from the east, potentially impacting MDT and LNS (50% chance) as well as IPT, UNV, and AOO (40% chc). There is around a 30% chance of LIFR ceilings/vsby developing at MDT and LNS. Valley fog has also been observed at BFD, where the ground is still wet from rain earlier in the evening. The main concern for later tonight will be a line of thunderstorms that will track through the region in the 09-14Z timeframe. PROB30 groups have been added to all sites except MDT and LNS to highlight the most likely timeframe for impacts. These thunderstorms will likely be weakening as they move in from the west and encounter a more stable environment, but we can't rule out a few strong wind gusts, especially at western airfields. Conditions gradually improve during the late morning behind the line of storms, but additional thunderstorms will likely develop Friday afternoon/evening. Outlook... Sat...Showers/storms especially in the afternoon. West winds gusting 30-35 kts. Sun...Some improvement, as a series of cold fronts move southeast of the area. Mon...Mainly dry with VFR conditions. Tue...VFR with scattered showers across the west late. && .CTP WATCHES/WARNINGS/ADVISORIES... A flood watch is in effect form late tonight through Friday morning for Somerset and Bedford counties. && $$ SYNOPSIS...Jurewicz/Banghoff NEAR TERM...Colbert SHORT TERM...Colbert LONG TERM...Beaty AVIATION...Bauco