Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/03/21

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
802 PM PST Thu Dec 2 2021 .SYNOPSIS...02/146 PM. Temperatures will vary from below normal near the coast, near normal for the valleys, and above normal for the interior. Then warming most areas Sunday into Monday to above normal as high pressure develops along with locally gusty northerly winds. Then cooler Tuesday through the rest of the week with a deepening marine layer. && .SHORT TERM (THU-SUN)...02/759 PM. ***UPDATE*** Latest satellite and surface observations indicate widespread stratus/fog across the coastal plain with clear skies elsewhere. Current AMDAR soundings indicates marine inversion around 1400 feet deep. No significant winds are currently observed. For the immediate short term, main focus will continue to be on the marine layer stratus/fog. With weak onshore gradients (and moderate 24 hour onshore trends), the inversion has deepened. So, currently no dense fog is observed across the area. Later tonight, as the stratus/fog pushes into the lower coastal valleys, there could be some dense fog, but not likely widespread enough to warrant any advisories. However, the situation will need to be monitored closely overnight. Otherwise, the weather situation should remain very benign with light winds and mostly clear skies away from the marine layer. Overall, current forecast has good handle on the immediate short term. So, no significant updates are expected at this time. ***From Previous Discussion*** Solid marine layer stratus covers the central and southern California coastline with many beaches staying overcast all day. This combined with 3-4mb onshore trends has brought significant cooling to the coastal valleys and Central Coast as most areas are 15-20 degrees cooler than yesterday. However, above about 1500` elevation there has been little change in temperatures so places like the Santa Clarita Valley, the higher portions of the Santa Monicas, and the rest of the mountains and Antelope Valley are very similar to yesterday. AMDAR soundings indicate some deepening of the marine layer today which should help mitigate dense fog near the coast but this means likely dense fog issues farther inland into the coastal valleys. So dense fog advisories may again be needed tonight into Friday morning. Temperatures have likely bottomed out today for most coastal valley and Central Coast locations but expect at least some cooling to push into the interior sections Friday. Not much change overall on Saturday as a weak upper low passes to the south. Following that northerly gradients are expected to increase as ridging nudges in from the north. Light north to northeast winds could develop as early as Saturday afternoon across the interior then increase Saturday night into Sunday morning. ECMWF ensembles have really scaled back on the wind strength and the gradient forecast has dropped to only -2mb. The NAM is a little stronger and high res models still are showing some gusts as high as 40 mph. Those would likely be very isolated and at this point expecting most areas to be under wind advisory thresholds. One possible exception could be southern Santa Barbara County Saturday evening as the SBA-BFL gradient increases to -5.5mb. Most areas should warm up at least a few degrees Sunday as the ridge axis is overhead and heights rise to around 584 dam. A somewhat tricky temperature forecast though as there is potential for more warming if the northeast gradient increases and we get more downsloping. .LONG TERM (MON-THU)...02/210 PM. A complicated weather pattern follows for the rest of next week leading to a few possible scenarios. Models seems to agree on some form of an inside slider coming through early Tuesday, though big differences in strength. The vast majority of the ensembles favor a mostly routine north to northeast wind event, maybe low end advisory strength at best, though a handful are quite a bit stronger and similar to the GFS deterministic. This particular solution also spins up a strong eddy early Tuesday with the possibility of some drizzle or light rain in LA County before the northerly winds kick in. Wed/Thu weather mostly benign with lighter winds and near to slightly above normal temperatures. Beyond that there continues to be indications in the models for increasing chances of rain later next week into the weekend. However, it`s certainly not a slam dunk. The GEFS and Canadian ensembles are more in favor than the ECMWF ensembles where not even half of the solutions show any rain for southern California. The 12z deterministic GFS is interesting showing a 528mb low right over LAX next Friday afternoon. However, looking at the individual GFS ensemble members this is by far an outlier with most of the solutions in the 550-560mb range. Still quite a bit lower than the EC ensemble mean which is near 568mb. && .AVIATION...02/2359Z. At 2320Z at KLAX, the marine layer depth was 1300 feet. The top of the inversion was around 2600 feet at a temperature of 19 C. High confidence in desert 00Z TAFs. Low to moderate confidence in the remainder of TAFs. Timing of cat changes could be off by +/-2 hours. There is a 20 percent chance of marine clouds reaching KPRB. There is a 20% chance of KSBA, KOXR, and KCMA only going as low as IFR conditions. There is a 20% chance of KSMO, KLAX, and KLGB developing LIFR conditions. KLAX...Low to moderate confidence in the 00Z TAF. There is a 20% chance in bkn002-004 with 1/2-1 SM from 04-16Z. High confidence in no significant east wind component. KBUR...Low to moderate confidence in the 18Z TAF. There is a 30 percent chance of marine clouds reaching the airfield as early as 07-08z. && .MARINE...02/715 PM. High confidence that winds and seas will remain below SCA level through Friday. High confidence in widespread SCA level NW winds from the Central Coast to San Nicolas Island Saturday afternoon through at least Monday. There is a 10% chance of Gale Force gusts Sunday afternoon into Sunday night for the outer waters Southwest of Point Conception to Northwest of San Nicolas Island. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement in effect from 4 AM PST Friday through Sunday morning for zones 34-35-40-41. (See LAXCFWLOX). PZ...NONE. && .HAZARD POTENTIAL OUTLOOK (SUN-THU). Large high tides may result in minor coastal flooding each morning through Monday. Gusty north to northeast winds will result in elevated fire weather conditions Sunday and Monday. && $$ PUBLIC...MW/Thompson AVIATION...Lund MARINE...Lund SYNOPSIS...MW
Area Forecast Discussion
National Weather Service Phoenix AZ
502 PM MST Thu Dec 2 2021 .UPDATE...Updated Aviation Discussion. && .SYNOPSIS... Unseasonably warm temperatures and dry conditions with light winds will be common across the region through at least the weekend. Afternoon temperatures are likely to be within a few degrees of daily records through the period. A more active weather pattern will take hold by early next week, with a series of weather systems affecting the Southwest Tuesday and Wednesday, and again during next weekend. Rainfall amounts are expected to be limited, but temperatures will trend downward closer to seasonal normals by late next week. && .DISCUSSION... Satellite imagery this afternoon shows scattered clouds near 10 thousand feet across south-central Arizona, especially anchored near and downwind from mountain peaks. ACARS soundings reflect a modest moist layer at this level transported generally northwestward amidst a broader cyclonic circulation surrounding a series of weak upper lows extending from northern Mexico into the eastern Pacific. Broader scale ridging is more dominant across the west, and is shunting a belt of strong westerlies into the Pacific Northwest and Northern Rockies. The warm temperatures across the region reflect the anomalous heights in place, with daytime readings continuing to remain around 10 degrees above normal for the date. Into this weekend, temperatures will trend downward slightly as one of the aforementioned weak upper lows moves into Arizona and the upper ridge begins to lose its stranglehold over the western US. Other than occasional cloudiness, moisture will continue to remain meager and not bring any precipitation chances to the region through at least Monday. Another slightly stronger closed low will advance eastward early next week as the northern stream becomes more amplified and the primary jet dives southward across the Great Basin and southern Rockies. Individual model members are becoming more consistent showing a pronounced shortwave trough moving through Tuesday, with an increasing number breaking out some precipitation across south-central Arizona. NBM QPF guidance remains fairly lackluster on Tuesday with the 50th percentile values at 0.00" for nearly the entire CWA, but the 90th percentile depicts close to 0.25" of rain possible. The orientation and antecedent atmospheric conditions will not favor a widespread soaking rain regardless, but if trends continue to support a strong and dynamic trough moving through, rain potential will likely increase for southwest and south- central Arizona. Later in the week, uncertainty increases considerably due to the large pattern shift underway with potential solutions ranging from a strong bowling ball type low moving through the Southwest, to a pattern featuring a series of open shortwave troughs. WPC cluster analysis highlights strong negative mid-level height anomalies over the northern Rockies for nearly every solution, but the details of where and how the northern stream jet and associated amplification magnitude evolve vary considerably. NBM guidance is slightly more bullish than earlier in the week for precipitation in the Friday through Saturday period, so a somewhat pronounced signal is already evident in ensemble guidance. Temperatures may also finally return closer to seasonal normals during this period, with highs in the 60s possible. && .AVIATION...Updated at 0000Z South-Central Arizona including KPHX, KIWA, KSDL, KDVT: Winds will continue to be light, mainly favoring normal diurnal trends through the period. Speeds are also favored AOB 6 kt. Skies remain clear to mostly clear with the occasional FEW mid- high clouds near 11 and 25 kft. Southwest Arizona and Southeast California including KIPL and KBLH: No aviation impacts are expected through the TAF period. Winds will remain light and variable AOB 6 kts although with some NW winds at KBLH tonight. Skies to remain clear to mostly clear with FEW high clouds. There is a small (10%) chance of some fog developing in the Imperial Valley Friday morning though the chances were too low to include in the TAFs. && .FIRE WEATHER... Saturday through Wednesday: Dry conditions and occasional high clouds will be common through the period. Temperatures will remain well above normal through at least Monday before a mostly dry weather system moving through on Tuesday brings temperatures closer to normal. Winds through the period are expected to remain light with only occasional daytime breezes. Min RH values are likely to fall between 15-25% for most locations each day. Max RH values will be 35-55% each day. Moisture levels rise slightly by the middle of next week. && .CLIMATE... Record high temperatures: Date Phoenix Yuma El Centro ---- ------- ---- --------- Dec 2 84 in 2017 85 in 1959 85 in 1949 Dec 3 81 in 1940 86 in 1958 90 in 1958 Dec 4 83 in 1979 83 in 1958 84 in 1940 Dec 5 82 in 2012 84 in 1958 85 in 1938 Dec 6 83 in 1939 83 in 1966 87 in 1938 && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Rogers AVIATION...Sawtelle FIRE WEATHER...Kuhlman CLIMATE...18/Kuhlman