Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
Issued by NWS Austin/San Antonio, TX
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999 FXUS64 KEWX 171846 AFDEWX Area Forecast Discussion National Weather Service Austin/San Antonio TX 146 PM CDT Mon Jun 17 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (Tonight through Tuesday night) Issued at 145 PM CDT Mon Jun 17 2024 Moisture is on the increase across South-Central Texas with some showers noted across areas east of the I35 corridor. Expect this to continue through the afternoon with activity dwindling around sunset with the loss of day time heating. Temperatures are currently in the lower 90s for most locations and highs later today will be in lower 90s to 103 degrees out west. Most of the area will remain dry overnight, but can`t rule out some streamer showers once again across the eastern two-thirds of the area by daybreak. Will show some 20 PoPs to cover that. Otherwise, lows tonight will be in the middle to upper 70s with a return of nocturnal low-level stratus. Rain chances tomorrow will mainly be back to areas east of I35 where the best moisture will remain for one more day. Will show PoPs generally in the 20-40 percent range. Highs will be in the lower 90s to near 100 degrees out west. Moisture will begin to increase and move west by late Tuesday night as moisture associated with a tropical disturbance in the western Gulf of Mexico nears the area. PoPs Tuesday night will be in the 20-50 percent range. The bigger impacts will be in the long-term portion of the forecast below. && .LONG TERM... (Wednesday through Monday) Issued at 145 PM CDT Mon Jun 17 2024 To say the long term period looks active would be a bit of an understatement at this point. The latest info from the National Hurricane center gives the disturbance associated with the Central America Gyre over the southwestern Gulf of Mexico a 70% chance of becoming a tropical depression/storm over the next 48 hours. Within the 7 day window, the disturbance (91L) also has a 70% chance of development. Ultimately, whether or not 91L develops is not particularly important, as the bulk of the impacts from the system will be heavy rain/flooding impacts. With regard to the overall setup, the Subtropical High is situated over North Carolina and will strengthen and expand in size over the Ohio Valley by midweek. This will act to block 91L from moving into the central Gulf, and allowing it to move into northern Mexico or south Texas under southeasterly flow aloft. It looks as if PWATs will be near or close to top 10 all time values within the climatology based off of Corpus Christi`s sounding history. The max is 3.00" from July 2010, and based off of the ensembles from the GFS and ECM, that value could be challenged Tuesday evening through Thursday morning, with values in the 2.7-3.0" range, some 3-4 sigma above the mean. Those are some remarkable values given the climatology, so we are working with a DEEP tropical airmass moving into South Central Texas midweek. Showers and storms that develop within this airmass will be incredibly efficient rain makers, with rates likely approaching several inches per hour. The latest 12Z guidance from the GFS still indicates that the northern portion of the disturbance will send a bit slug of moisture inland as early as Tuesday night, with this area of showers and storms spreading inland over the Austin/San Antonio CWA from east to west on Wednesday afternoon. The primary window for heavy rainfall looks to be Wednesday morning through Thursday morning. WPC paints most of the Coastal Plains and portions of the I-35 corridor south of Austin through Bexar County in a Moderate Risk (level 3 of 4) for excessive rainfall Wednesday morning through Thursday morning. Flooding and flash flooding are looking increasingly likely, so flood watches may need to be issued overnight as we get closer to the event. Continued shower and storm chances are expected beyond Thursday as tropical moisture remains in place and the upper level pattern remains conducive to an active stretch. Temperatures will moderate, getting back into the 90s by the weekend. && .AVIATION... (18Z TAFS) Issued at 1223 PM CDT Mon Jun 17 2024 VFR conditions are prevailing across most locations at the present time and should remain so through the remainder of the afternoon and evening. There are some showers primarily east of the I35 corridor and will not mention anything in the TAFs for now. Another round of MVFR ceilings is expected overnight tonight into tomorrow morning. Winds will remain out of the south/southeast with speeds up to 15-20 knots at times. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 77 92 75 80 / 20 20 20 60 Austin Bergstrom Intl Airport 76 91 74 80 / 20 20 20 70 New Braunfels Muni Airport 76 93 75 80 / 20 20 20 70 Burnet Muni Airport 76 90 73 78 / 10 10 10 50 Del Rio Intl Airport 81 101 78 92 / 0 0 0 40 Georgetown Muni Airport 76 90 73 78 / 0 20 20 60 Hondo Muni Airport 76 95 76 81 / 10 10 10 60 San Marcos Muni Airport 75 91 74 80 / 20 20 20 70 La Grange - Fayette Regional 76 89 76 80 / 10 30 30 70 San Antonio Intl Airport 78 93 76 80 / 20 20 20 70 Stinson Muni Airport 78 95 77 81 / 20 20 20 70 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term...29 Long-Term...MMM Aviation...29