320 FXUS64 KBRO 271203 AFDBRO Area Forecast Discussion National Weather Service Brownsville TX 603 AM CST Mon Jan 27 2020 .DISCUSSION...Updated for latest aviation discussion below. && .AVIATION...Areas of fog have developed across Deep South Texas early this morning, dropping the visibilities at all 3 Rio Grande Valley airports. The fog and low ceilings are expected to lift to VFR conditions by 15z or 16z this morning. As high pressure moves to the east, light to moderate southeast winds along with VFR conditions will be expected to prevail through the majority of the remaining TAF period. However, patchy fog may be possible early Tuesday morning. && .PREV DISCUSSION... /issued 340 AM CST Mon Jan 27 2020/ SHORT TERM (Now through Tuesday): The short term begins with weak ridging aloft and at the surface across Deep South Texas. Light winds and high humidity values along with mostly clear skies will support fog development especially across the eastern portion of our CWA. Dense fog has already developed across most of the eastern areas and is expected to last through the early morning hours. Cloud cover is expected to decrease throughout the day with temperatures reaching the lower to mid 80s this afternoon, which is about 10 degrees warmer than normal for this time of year. With the southeast flow continuing through the night, Monday night will be slightly warmer than last night, with temperatures cooling into the lower 60s. Some patchy fog will be possible early Tuesday morning with relatively high surface moisture, but winds look slightly too strong to support fog development at this time. As a shortwave trough along with an associated surface low pressure system form just east of the Rockies and move eastward into North Texas on Tuesday morning, a cold front is expected to approach our CWA later that morning. There should be enough moisture ahead of this front to spark some showers along and ahead of the front as is passes through. The greatest chances will be east of the I-69C corridor and offshore over the coastal waters. The timing of the front along with the rain chances will allow Tuesday's highs to be slightly cooler than today's, but still above normal. Behind the front, high pressure and drier air will begin to settle into the area. The majority of the cold air advection associated with this frontal passage will be felt at the beginning of the long term period. LONG TERM (Tuesday night through Sunday): A cold front will push offshore Tuesday night with the associated mid level trough axis swinging overhead. High pressure will build over the area Tuesday night and Wednesday with moderate northwest winds and much drier air moving into the area. Could see a bit more erratic fire behavior or slightly enhanced wildfire growth and spread potential on Wednesday, but the ingredients or values for fire weather products will fall a bit short of criteria. Relative humidity values across the interior will dip into the 20s, with only light to moderate 20 foot winds. Ridging will build over the area on Wednesday, resulting in seasonal weather. This trend will persist into Thursday. A shortwave trough will dig south over the Four Corners Wednesday to Thursday, shifting flow aloft to southwest and bringing upper moisture and instability over the region. As the trough lifts across the state Thursday night, a surface front will push through, bringing cloudy skies and cooler weather, with temperatures just slightly below average. Best chance of rain will be Thursday evening and night, but accumulations are not forecast to be above about a quarter of an inch. A few showers may linger into Friday until the upper trough moves through and conditions stabilize. Dry air and ridging will build in Friday night into the weekend. MARINE: Now through Tuesday: Buoy 42020 reported seas of 3 feet with light east winds as of 2:40 this morning. Favorable marine conditions are expected to continue through this evening with high pressure overhead before winds pick up slightly overnight with the increasing pressure gradient and small craft may need to exercise caution on the offshore Gulf waters. A cold front is expected to approach the area late Tuesday morning, bringing increasing rain chances and a slight chance for some embedded thunderstorms. The northwesterly winds are expected to be light to moderate, with little impact on the seas, but visibility may be briefly reduced with any rain activity. Tuesday night through Friday night...Strong northwest to north winds and building seas will be ongoing Tuesday night in the wake of a cold frontal passage. Small craft advisory conditions will be in effect for at least the open Gulf, with small craft should exercise caution conditions in effect elsewhere and otherwise. Conditions will improve on Wednesday, though exercise caution to borderline small craft advisory conditions will linger. Light to moderate winds and low to moderate seas will prevail Wednesday night through Thursday evening, before a cold front moves through Thursday night. Moderate to strong north to northeast winds will develop in the wake of the front, with building seas. Small craft advisory conditions will be possible initially due to winds, with advisory conditions due to seas potentially persisting on the Gulf Friday into Friday night. && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ This product is also available on the web at: HTTP://WEATHER.GOV/RGV Aviation Update...69