629 FXUS64 KBRO 130530 AAA AFDBRO Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 1230 AM CDT Mon Sep 13 2021 .DISCUSSION...Updated for latest aviation discussion below. && .AVIATION...Less-than-ideal aviation conditions are expected through the remainder of the overnight hours and into Monday as organizing Tropical Storm Nicholas moves along the Lower Texas Coast. Improved conditions will occur beginning around sunset on Monday as Nicholas moves farther north and away from the region. && .PREV DISCUSSION... /issued 640 PM CDT Sun Sep 12 2021/ DISCUSSION...Updated for latest aviation discussion below. AVIATION...After scattered to numerous showers blanketed deep south Texas this afternoon, KBRO radar shows convection activity has decreased, yielding generally VFR conditions as of 2330Z. Latest hi-res forecast models show shower activity will ramp back up around midnight and continue through the day on Monday. These showers will be capable of producing very heavy rainfall, gusty winds to 30-35 knots, and reducing visibilities and/or ceilings to IFR/LIFR levels. As Tropical Storm Nicholas continues to track towards deep south Texas, winds will gradually increase and turn out of the north or northwest by midday Monday. Gusts may approach 30-35 knots, depending on the exact track and location. There is also a slight chance of LLWS, specifically over the BRO aerodrome during the afternoon as Nicholas parallels the lower Texas coast. Due to low confidence, did not include in the 00z TAF. The overall forecast confidence is low, but confidence is high that each TAF site will be impacted by rain, reduced visibilities and reduced ceilings over the next 24 hours. PREV DISCUSSION... /issued 434 PM CDT Sun Sep 12 2021/ SHORT TERM (Tonight through Monday Night):The main concern for the short term will be impacts from Tropical Storm Nicholas that formed earlier today in the Bay of Campeche. Nicholas is currently positioned 240 miles SSE of the mouth of the Rio Grande and continues to move NNW at 14 MPH. Tropical Storm Warnings are in effect for coastal Kenedy, Willacy and Cameron counties. Currently the forecast track keeps Nicholas just offshore and passing through the coastal waters tomorrow morning into tomorrow afternoon. It is possible that this track and timing may shift slightly, so stay tuned for future updates. The main impact across the CWA with Tropical Storm Nicholas will be heavy rain. Current radar shows rain and storms, primarily over the Gulf waters, with this activity expected to continue to increase and move into Deep South Texas through the forecast period. The heaviest rainfall will likely be confined to coastal counties where 2 to 4 inches of rainfall is expected through early Tuesday morning. A Flash Flood Watch has been issued for Cameron, Willacy and Kenedy counties in Deep South Texas starting at 7 PM tonight until 7 AM Tuesday. The increased cloud cover and rain chances will keep temperatures near to below normal for the period. Tropical Storm Nicholas will also produce tidal runup with minor coastal flooding. Increase wave heights from swell are expected to build generally between 10 and 12 feet over the Gulf waters. This will also result in dangerous conditions at area beaches with a high risk of rip currents. A Storm Surge Watch is in effect for the lower Texas coast. Finally, winds are expected increase this evening, mainly along the coast as Tropical Storm Nicholas nears Deep South Texas. Winds will continue to increase overnight across the CWA through midday Monday as Nicholas moves through the lower Texas coastal waters. LONG TERM (Tuesday through Sunday): There is still a bit of uncertainty with the long term forecast due to the official track and strength of Tropical Storm Nicholas. At this time Nicholas is expected to be north of the CWA by Tuesday morning. With this said, rainfall will continue to be the main story through the long term period with plenty of deep tropical moisture in place. The heaviest rainfall will continue into early Tuesday though periods of rain and storms will continue through the remainder of the forecast. Temperatures will continue to remain near to below normal due to rainfall and excessive cloud cover across the CWA through Sunday. Coastal impacts will continue to cause concern through Tuesday. High astronomical tides along with swell from Tropical Storm Nicholas could continue to cause wave run up with minor coastal flooding along area beaches as well as enhanced rip current risks. MARINE (Now through Monday Night): Tropical Storm Nicholas formed earlier today in the Bay of Campeche and will continue to move NNW through the period. A Tropical Storm Warning is now in effect for all of the waters off the lower Texas coast. Winds will begin to increase and seas will begin to rise tonight across the Gulf waters. Nicholas is expected to pass through the near and offshore waters Monday morning into Monday afternoon. Expect tropical storm force winds and seas of 10 to 15 feet beginning early Monday morning into Monday evening. Tuesday through Saturday: The most uncertain time of this portion of the forecast will be on Tuesday, with any lingering hazards from Tropical Storm Nicholas. However, Small Craft Advisories for the Gulf of Mexico waters will be possible after Tropical Storm Nicholas passes due to lingering elevated seas. By Wednesday, more favorable marine conditions will develop for remainder of the period as a weak surface pressure gradient prevails over the western Gulf of Mexico. Showers and thunderstorms will continue through Saturday that could lead to brief periods of increased winds and elevated seas. && .PRELIMINARY POINT TEMPS/POPS... BAYVIEW/PORT ISABEL 76 89 78 90 / 40 30 20 30 BROWNSVILLE 77 91 78 92 / 40 30 20 30 HARLINGEN 75 91 76 92 / 40 30 20 30 MCALLEN 76 92 78 94 / 30 20 10 20 RIO GRANDE CITY 75 94 76 98 / 20 20 10 20 SOUTH PADRE ISLAND 80 85 82 86 / 50 40 30 30 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...Tropical Storm Warning for TXZ256-257-351. High Rip Current Risk through Tuesday morning for TXZ256-257-351. Storm Surge Watch for TXZ256-257-351. Flash Flood Watch through Tuesday morning for TXZ251-254>257-351. High Surf Advisory until 7 AM CDT Tuesday for TXZ256-257-351. GM...Tropical Storm Warning for GMZ130-132-135-150-155-170-175. && $$ This product is also available on the web at: https://weather.gov/rgv