Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/08/16


Area Forecast Discussion
National Weather Service Houston/Galveston TX
855 PM CST Wed Dec 7 2016 .DISCUSSION... Cold front to our north is still on schedule to move across Southeast Texas overnight. Some southwest to northeast moving showers and rain have developed across parts of the area this evening, and expect this to continue as the front moves into the area. Activity should gradually decrease in coverage behind the front, and look for cooling temperatures and strengthening north winds during the day tomorrow. Our counties that will be under wind advisories along with our coastal waters that will be under small craft advisories and gale warnings all look good for tomorrow. Everything looks good in the forecast, and only minor tweaks to the grids have been made this evening. 42 && .PREV DISCUSSION... /ISSUED 610 PM CST Wed Dec 7 2016/ AVIATION... Local aircraft soundings depicting a couple of lower level inversions that support recent obs of primarily MVFR ceilings...with periods of IFR anticipated. MVFR/IFR conditions will be the overnight theme as the region falls downstream of a cold frontal boundary that is now passing south of the Red River Valley. This cold front will be traveling through the area from around midnight (CLL) through sunrise (GLS)...strong northerly winds following in its wake. Drizzle...or light rain...may occur mainly across the metro and southern terminals ahead of this front ..quickly clearing out with the front`s passage. Moisture trapped under the low level post-frontal inversion will be slow to lift through the afternoon. Daytime MVFR decks with late afternoon into early evening clearing to VFR and a slight weakening of that once stout...brisk north wind. 31 PREV DISCUSSION... /ISSUED 349 PM CST Wed Dec 7 2016/ DISCUSSION... Surface analysis at 21Z shows the much discussed cold front slicing through Oklahoma and Texas Panhandle. A dissipating cold front was off the coast and responsible for trapping moisture in a frontal inversions over much of SE Texas. This has allowed for low clouds and patchy fog to continue through the afternoon. Patchy fog and low clouds will likely continue tonight as warm advection increases over the frontal surface. Latest NAM/GFS show subtle isentropic lift at 295K which will contribute to light showers/drizzle through the overnight. Rainfall amounts are not expected to be much but could get up to a tenth of an inch in a few locations. The cold front should push off the coast around 10-12Z Thursday which should slowly allow for rain chances to end through the morning. Cold front will bring a much colder Canadian airmass into SE Texas. Winds will be quite strong especially along the coast and offshore. Wind advisory will be needed for the coast and Gale warnings for the marine areas. Temperatures will fall at first into the 40s/50s but remain fairly steady during the afternoon. Temperatures should continue to drop into the 30s and 20s Thursday night. Winds will slowly decrease overnight and cloud cover may linger through Friday morning. Low temperatures Friday morning should reach sub freezing mainly north of Houston. The main problem may be lingering cloud cover which could hold temperatures a couple of degrees warmer. Cold advection will be strong so there is enough confidence that a freeze warning may need to be issued for Friday morning for areas basically from Columbus to Katy to Cleveland. Northern Harris County could see temperatures right at freezing but will be close. Temperatures should be in the mid/upper 30s south of that line. The other issue to be aware of is that winds will still be breezy at times overnight which means minimum wind chill values will be in the 20s for much of the area. In the extended forecast, look for a broad trough to persist across much of the central U.S. and Canada. Moisture will begin to return to the area from the Gulf late Saturday into Sunday allowing for another warm advection/isentropic lift rain event. Rain chances have increased slightly for Sunday as short wave trough moves across the Plains. GFS is faster than the ECMWF with this feature and as such slightly faster with another frontal passage. Front should push through Sunday night into Monday morning as high pressure builds into the Plains. The ECMWF holds onto the trough more than the GFS with McFarland like pattern next Tuesday and Wednesday. This allows for another 1040mb high to push into the Plains by Wednesday morning with another strong cold front pushing through the area. GFS has no such front or high pressure at this time. Forecast leans a bit more on the ECMWF given the upper level pattern evolution. This could allow for more chilly temperatures for the end of next week. Overpeck MARINE... As per coordination with surrounding offices, have upgraded the Gale Watch to a Warning for all of Thurs with this package. A strong cold front will be moving off the coast late tonight/early Thurs morning, with very strong N/NE developing in its wake. Sustained winds in the wake of the front will increases to 25-35 kts with higher gusts. SCA conditions will prevail over the bays Thurs/Thurs Night. There might be some impact on Thurs for the more north-to-south ship channels as water is pushed out of the bays. The N/NE wind direction is currently in the forecast...and not expecting any low water advisories at this time. The strong offshore flow will be decreasing and shifting to the east Friday as the surface high moves off to the east. A moderate onshore flow is forecast for Saturday...but winds will be increasing back to near SCEC/SCA criteria for Sat night/Sun as the gradient tightens in response to the next storm system moving across the Southern Plains. The winds will diminish on Sunday night ahead of another front early Monday. 41 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 42 44 30 47 35 / 40 20 10 0 10 Houston (IAH) 50 52 33 49 35 / 60 20 10 0 0 Galveston (GLS) 54 56 41 51 47 / 50 40 10 0 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Wind Advisory from 6 AM to 6 PM CST Thursday for the following zones: Brazoria...Chambers...Galveston...Harris...Jackson... Matagorda. GM...Small Craft Advisory from 6 AM Thursday to midnight CST Thursday night for the following zones: Galveston Bay...Matagorda Bay. Gale Warning from 6 AM Thursday to midnight CST Thursday night for the following zones: Coastal waters from Freeport to the Matagorda Ship Channel out 20 NM...Coastal waters from High Island to Freeport out 20 NM...Waters from Freeport to the Matagorda Ship Channel from 20 to 60 NM...Waters from High Island to Freeport from 20 to 60 NM. && $$ Discussion...42 Aviation/Marine...31