Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/28/17


Please see the 00Z aviation forecast discussion below.

AVIATION... Light to moderate rain continues over a good portion of south central Texas this evening, with the most persistent activity from SAT/SSF west toward DRT. We will continue to mention light to occasional moderate rain in the forecast for the evening and overnight hours. Otherwise, look for a gradual lowering of ceilings overnight with MVFR expected at AUS and upper end IFR for our remaining TAF sites. Gradual improvement is expected tomorrow afternoon. PREV DISCUSSION... /ISSUED 248 PM CDT Wed Sep 27 2017/ SHORT TERM (Tonight through Thursday Night)... A complex rainfall situation is setting up across the western half of the CWA this afternoon and evening. A combination of continued rich low level moisture advection, an approaching frontal boundary, and a mesoscale convective vortex will all come into play to continue the flash flood threat through tomorrow. Through the rest of the afternoon, while the majority of the heavy rainfall continues to develop well west of the I-35 corridor. Increased instability and another surge of low level moisture is pushing north from South Texas and resulting in isolated thunderstorm development. While this activity is mostly isolated in nature, CG lightning observed in the updrafts and significantly colder cloud tops indicate the possibility for intense downpours with the added low to mid level CAPE available. While these should weaken as they approach and are currently moving north rather quickly, they will still have the capability of dropping up to 2 inches of rain in an hour or two, which could exceed the very low flash flood guidance in Atascosa County, and to a lesser extent Bexar County. With this short term concern for localized flash flooding, it was decided to expand the flash flood watch to include both Atascosa and Bexar counties. After midnight, the MCV is progged to continue to shift northwestward, as evidenced in both hi-resolution guidance and in the GFS/ECMWF. This should focus the heavier rainfall potential overnight to Del Rio and Val Verde County. Thus, QPF was increased in these regions along the Rio Grande and for Val Verde. PoPs will begin to decrease overnight for the eastern areas as the aforementioned isolated activity wanes due to a lack of diurnal heating. Through Thursday, models continue to generate moderate to heavy rainfall over the extreme western areas of the CWA, with lighter rates from Uvalde and east. While there may be a drop off in precip coverage tomorrow over the eastern half of the flash flood watch, it may be worth maintaining through Thursday evening as currently issued due to rainfall amounts unofficially exceeding 20 inches in some spots in Zavala and Dimmit counties. LONG TERM (Friday through Wednesday)... Precip chances begin to decline beginning overnight Thursday and through Friday. Over the weekend, the parent low over the four corners currently will lift northward and take the upper level support with it, dramatically decreasing our chances for rain. A more typical late September, early October pattern will then take its place by early next week. By mid week, an elongated ridge axis will broaden over the state according to the ECMWF resulting in slight chances for rain, mainly over the southern and southeastern areas where better moisture resides. However, no hazards are expected. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 71 84 69 82 65 / 40 50 50 30 20 Austin Bergstrom Intl Airport 71 84 69 82 64 / 40 50 50 30 20 New Braunfels Muni Airport 71 84 69 84 65 / 40 50 50 30 20 Burnet Muni Airport 67 80 65 77 61 / 50 60 60 40 20 Del Rio Intl Airport 68 77 69 80 66 / 70 70 60 60 20 Georgetown Muni Airport 69 83 66 80 62 / 50 50 50 30 10 Hondo Muni Airport 69 85 70 86 65 / 60 50 50 40 20 San Marcos Muni Airport 70 84 69 83 64 / 40 50 50 30 20 La Grange - Fayette Regional 72 87 70 85 66 / 20 40 50 30 10 San Antonio Intl Airport 70 84 70 84 66 / 40 50 50 30 20 Stinson Muni Airport 71 84 71 84 67 / 40 50 50 30 20 && .EWX WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Thursday evening for the following counties: Atascosa...Bandera...Bexar...Dimmit...Edwards...Frio... Kerr...Kinney...Maverick...Medina...Real...Uvalde...Val Verde... Zavala. && $$ Mesoscale/Aviation...24 Synoptic/Grids...LH Public Service/Data Collection...YB
Area Forecast Discussion
National Weather Service Honolulu HI
318 PM HST Wed Sep 27 2017 .SYNOPSIS... Moderate trade winds will briefly increase to locally breezy levels on Thursday then ease on Friday. A stable rainfall pattern will focus clouds and showers over windward slopes. Winds will weaken and shift out of the southeast on Saturday then out of the south over most of the island chain on Sunday as a front approaches. A humid land and sea breeze pattern will develop over most areas, with clouds and showers favoring interior portions of the islands during the afternoon hours, and volcanic haze will likely spread over all islands. && .DISCUSSION... A stable, moderate trade wind flow has been carrying an area of slightly enhanced low-level moisture across the island chain today. A 1021 mb surface high far northeast of the state and an associated surface ridge extending to about 350 miles north of Kauai are driving the trade winds. A mid- to upper-level ridge overhead is producing stable conditions, with an inversion running between 6,000 and 8,000 ft according to afternoon soundings and aircraft data. An area of low-level moisture has provided a boost in trade wind showers today, mainly for windward slopes. Rainfall has been modest, roughly one quarter of an inch or less. Expect this area of moisture to clear the islands by midnight. A short-lived increase in the trades is due for Thursday. A front currently passing 375 miles north of the state will dissipate, and the surface ridge currently 350 miles north of Kauai will lift northward and strengthen. As a result, trade winds will temporarily build into the locally breezy range. A gradual decrease in winds is expected on Friday as another approaching front forces the ridge to retreat southward again. Conditions will remain stable with pockets of moisture producing modest rainfall over windward slopes. Humid and hazy conditions are expected to develop during the weekend. The advancing front will cause the local background winds to veer out of the southeast on Saturday, then out of the south across most islands by Sunday. Expect a land and sea breeze pattern to dominate, causing clouds and showers to favor interior area during the afternoon hours. By Saturday night, developing southerly flow will likely draw volcanic haze over the much of the state along with a humid tropical airmass with dew point temps in the lower 70s. Heading into Monday and Tuesday, uncertainty remains rather high. Both the GFS and ECMWF are cutting off an area of low pressure northwest of the state, but they differ greatly on how this feature effects the front. The models are also inconsistent from run to run as to whether or not the front will reach the western end of the island chain before retreating westward by midweek. We continue to paint a broad southeasterly flow over the islands during this time, but confidence is low. && .AVIATION... VFR conditions are expected to prevail, however increasing trade winds will focus clouds and showers over windward and mountain areas. Some brief MVFR conditions are possible in these areas. Leeward areas that clouded up today are expected to clear overnight. No AIRMETs are in effect at this time, however as the trades build tonight and tomorrow, and AIRMET for mechanical turbulence may be needed. && .MARINE... The trailing end of a front northwest of the area weakened the subtropical ridge and has kept the trade winds moderate to locally fresh. The ridge is forecast to strengthen tonight with winds reaching Small Craft Advisory speeds tomorrow and tomorrow night. Winds will weaken again starting Friday and will shift out of the southeast over the weekend as a new front approaches from the northwest. Surf will be below average along all shores through early next week. There will be a small north northwest swell tomorrow and Friday. A moderate northwest swell is expected to arrive Sunday night and peak Monday well below the advisory threshold. Surf may rise along the south and east facing shores by the middle of next week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory from 6 AM Thursday to 6 AM HST Friday for Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ Public...Wroe Aviation...M Ballard Marine...Donaldson
AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
821 PM PDT Wed Sep 27 2017 .SYNOPSIS... An onshore flow will bring coastal cooling and a overnight marine layer into the weekend. A high along with offshore flow should keep inland temperatures above normal into Friday. A low may approach on Saturday and combine with onshore flow into next week. This combination will increase the coastal marine layer and start a cooling trend. && .SHORT TERM...(TONIGHT-SAT) Weak low level offshore flow brought another very warm day across inland areas today, with many valley areas climbing well into the 90s. However, slight onshore trends and some patchy fog this morning led to some cooling for coastal areas today. Satellite imagery showing an area of low clouds and fog across the inner coastal waters, locally spreading into the LA County coast. There have already been a couple reports of low visibilities in the 1/4 to 1/2 mile range with this fog. Do expect low clouds and fog to expand some overnight into Thursday morning across the LA/Ventura County coastal areas. ACARS data continues to shallow and strong marine inversion, with marine layer depth currently around 800 feet. This in combination with weak flow near the surface (LAX- Daggett currently at -0.1 mb) will bring a strong potential for patchy dense fog through Thursday morning, and may sufficiently expand to warrant a dense fog advisory for LA/Ventura county coastal areas. Similar temperature contrast expected for tomorrow, with cooler conditions near the coast due to onshore marine influence, and much warmer temperatures inland due to persistent weak offshore flow (with LAX-Daggett gradient expected to be around -2 mb on Thursday morning). *** From previous discussion *** Aside from the low cloud uncertainty the conditions the next couple days aren`t expected to change much. Light offshore flow in the morning and weak onshore in the afternoon will continue and daytime highs should be more or less what we had today, possibly slightly cooler for the coast with a very minor onshore trend. Perhaps some increasing Sundowner winds in the SB area Thu/Fri evenings but mostly below advisory levels. On Saturday gradients trend noticeably onshore as another trough moves into the Pac NW and there should be a 4-8 degree drop in daytime highs on average as well as better marine layer coverage. .LONG TERM...(SUN-WED) Very minimal changes in the weather conditions Sun/Mon, then another downward trend in temperatures as models show a deeper trough developing along the west coast. Still some significant differences between the medium range models regarding how deep this trough will get, with the ECMWF continuing to develop more of a closed circulation and much cooler air while the GFS shows more of an open trough and not nearly as cold aloft. Since both solutions would result in additional cooling across the area and both have been pretty consistent with it confidence is pretty high that highs will drop below normal by the middle of next week with a deeper marine layer. How much below normal and how deep the marine layer gets is still in question, and there is the possibility of some morning drizzle with this pattern as well. && .AVIATION...27/2330Z. At 23Z, the marine layer depth was around 600 feet deep at KLAX. The top of the inversion was around 1900 feet with a temperature near 27 degrees Celsius. Satellite imagery showing an areas of low clouds/fog over the coastal waters advancing quickly towards the LA/Ventura county coastal areas. As a result, increasing confidence of LIFR/IFR cigs for KLAX, KSMO, KLGB, KOXR, and KCMA this evening, potentially lowering to LIFR/VLIFR conditions at each coastal site overnight into early Thursday morning. There is a 20 percent chance of LIFR cigs at KSBA and KSMX tonight. KLAX...VFR conditions are expected through at least 03Z. With low clouds advancing quickly across the coastal waters this afternoon, increasing confidence of LIFR cigs at KLAX this evening, potentially lowering to VLIFR conditions overnight into early Thursday morning. VFR conditions should redevelop between 16Z and 18Z. KBUR...VFR conditions are expected throughout the period. && .MARINE...27/800 PM. Moderate-to-high confidence in the current forecast. For the Outer Waters, winds and seas will remain below Small Craft Advisory levels through Thursday. There is a 50 percent chance of Small Craft Advisory level winds developing for Thursday night, then increasing to 80 percent Friday through Sunday. There is a 40 percent chance of gale force gusts on Saturday. For the waters north of Point Sal, winds and seas will remain below Small Craft Advisory levels through Thursday. There is a 70 percent chance of Small Craft Advisory each afternoon and evening between Friday and Sunday. For the waters south of Point Conception, winds and seas will generally remain below Small Craft Advisory levels through Sunday. There is a 40 percent chance of Small Craft Advisory level winds across the Santa Barbara Channel Saturday afternoon and evening. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && .HAZARD POTENTIAL OUTLOOK...(SAT-WED) No significant hazards expected. && $$ PUBLIC...Gomberg/MW AVIATION...Gomberg MARINE...Hall/Sirard SYNOPSIS...STu weather.gov/losangeles