Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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257 FXUS66 KLOX 202110 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 210 PM PDT Fri Sep 20 2024 .SYNOPSIS...20/127 PM. Shower and thunderstorm chances have shifted to LA County and eastern Ventura County today into this evening as a cold upper continues to move through the area. Some showers or thunderstorms could have heavy downpours, and gusty winds. High pressure will build in over the weekend and bring a warming and drying trend to the region over the weekend into early next week. && .SHORT TERM (TDY-MON)...20/149 PM. An active upper low continues to generate showers and thunderstorms across southern California, though the dry/wet axis continues to shift towards the east following the low into Arizona. But at least until around 6pm the eastern portion of LA County will be susceptible to periods of heavy rain and thunderstorms. At this time all the activity is in San Bernardino and Riverside counties but there`s still just enough of a westerly trajectory that could bring those storms into LA County. Of particular concern is the area around the Bridge fire, which has the added factor of the mountain terrain to enhance updrafts. No flood watch is in effect at this time but chances aren`t zero that very heavy rain could still develop there and across other areas of eastern LA County. Based on the lack of cumulus clouds west of there it`s unlikely, but not impossible, that an isolated shower could drift off the Tehachapi mountains and move into northwest LA or northeast Ventura County this afternoon. After this evening the weather calms down considerably, returning to typical night and morning low clouds and fog and warming temperatures. However, models have definitely trended not as warm early next week as a weak upper low is now favored to develop just west of the Bay Area Sunday and drift slowly south Monday. Still expecting a warming trend but perhaps 2-4 degrees cooler than earlier forecasts. .LONG TERM (TUE-FRI)...20/209 PM. Very low impact weather next week with highs mostly within a few degrees of normal. A little cooling Tue-Thu with that upper low still lingering and onshore flow increasing. Likely a steady does of night and morning low clouds and fog at least for coastal areas. While the deterministic model solutions show significant differences for the latter part of next week and beyond and at least one solution showing a deep trough along the West Coast late next weekend, the ensemble means favor very little change or slight warming and overall very low impact weather conditions. && .AVIATION...20/1835Z. At around 17Z at KLAX, there was a deep moist layer up to roughly 4500 feet. The top of the weak inversion was at 6000 feet with a temp of 12 C. Moderate confidence in TAFs for KPMD and KWJF. There is a 20-30% chc of TSTMs thru 06Z. Low confidence in LA county TAFs. There is a 10-20% chance of TSTMS for KBUR AND KVNY thru 00Z. At KLAX, KSMO, and KLGB, there is a <10% chance of TSTMs this afternoon thru 00Z and a 10-20% chance of -DZ. Low confidence in remaining TAFs due to the uncertainty of cigs arrival time and height. There is a 20% chance KPRB remains VFR thru the period. There is a chance for VLIFR conds at KSMX (40%) and KSBP (30%) between 03Z and 16Z. For all coastal and valley sites, arrival of cigs may be off by +/- 5 hours from current forecast. The flight cat may be off by at least one cat during any point once cigs arrive. Any thunderstorms that form may produce brief +RA and gusty, erratic winds. KLAX...Low confidence in TAF. There is a <10% chance of TSTMs this afternoon thru 00Z and a 10-20% chance of -DZ. There is a 30% chance BKN010-020 may arrive as early as 02Z. There is a 10% chance for cigs BKN008-010 between 02Z-15Z, or once cigs arrive. There is a 30% chance for VFR conds by 18Z-20Z Sat. No significant east wind component expected. KBUR...Low confidence in TAF. There is a 10-20% chance of TSTMs thru 00Z. Low confidence in hgt and timing of CIGs, which might be off +/- 3 hours from current forceast and be between BKN008-015. && .MARINE...20/1251 PM. Isolated thunderstorms will be possible across the eastern portion of the Santa Barbara Channel through the southern inner waters and out to Santa Cruz Island into this evening. Any thunderstorm that forms has the potential for frequent cloud to surface lightning, gusty and erratic winds with rough seas, and small hail. For the Outer Waters (Central coast south to San Nicolas Islands), moderate to high confidence in the forecast. High confidence in winds and seas remaining below Small Craft Advisory (SCA) level thru early next week in the northern zone (off the Central Coast). For the southern zones (Pt Sal to San Nicolas Island), there is a 60-70% chance of SCA level winds continuing through late tonight across the waters from Point Conception to San Nicolas Island. From Saturday thru Wednesday, high confidence in winds and seas remaining below SCA level, and then there is a 20-30% chance of winds picking up Wednesday night. For the inner waters along the Central coast, high confidence in conds remaining below advisory levels through Wednesday. For the Santa Barbara Channel, moderate confidence in the forecast. SCA level winds expected in the western portion of the zone thru late tonight. Then, moderate to high confidence in conditions remaining below SCA levels through Wednesday. For the inner waters off the coast of LA and Orange Counties, moderate to high confidence in conditions remaining below advisory levels through Wednesday. However, there is a 20-30% chance of SCA level wind gusts thru the San Pedro Channel Sun afternoon. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect until 3 AM PDT Saturday for zones 650-673-676. (See LAXMWWLOX). && $$ PUBLIC...MW AVIATION...Lewis MARINE...Lewis SYNOPSIS...MW weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox