Area Forecast Discussion
Issued by NWS Brownsville, TX
Issued by NWS Brownsville, TX
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804 FXUS64 KBRO 281930 AFDBRO Area Forecast Discussion National Weather Service Brownsville TX 230 PM CDT Sun Apr 28 2024 ...New SHORT TERM, LONG TERM, MARINE... .SHORT TERM... (Tonight through Monday night) Issued at 225 PM CDT Sun Apr 28 2024 Key Messages: * Stagnant, tropical environment remains in place through the short-term period (warm to very warm, humid, and hazy) * Day-to-day chances, albeit low/ of an isolated shower or thunderstorm through Monday night Latest MSAS surface analysis and satellite imagery reveals a weak surface low/shortwave trough over the forecast area under a scattered to broken deck of strato-cumulus clouds this afternoon. Just to the west, is a weakening cold front that`s expected to wash out and transition to a dryline later this afternoon/evening. Steep mid-level lapse rates on the order of 7-8 C/km, surface- based and most unstable CAPE (SBCAPE/MUCAPEs) in excess of 2,000 J/kg, showalter values indicating a very unstable environment with values between -3 to -7 coupled with this weak meso-scale feature in place over the area would suggest the potential for showers and thunderstorms to develop this afternoon. However, per the 12z KBRO sounding from this morning, the atmosphere is strongly capped with a strong surface inversion in place at about 900 mb. Given the unfavorable jet structure overhead and weak winds aloft on top of the lack of a lifting mechanism at the surface suggests that shower and thunder activity will be severely inhibited over the area through the day today. That said, have maintained low grade (20%) PoPs over the northern half of the area or across the Northern Ranchlands this afternoon into tonight to account for the low but non-zero probability/risk of there being an isolated/rogue shower or thunderstorm developing. The Storm Prediction Center (SPC) in Norman, Oklahoma in it`s SWODY1 has maintained the northern half of our CWA under a General Outlook for thunderstorms through today. For tonight, continued onshore flow will allow for marine layer influences to increase. This will result in an increase in low clouds tonight. With clouds preventing any long wave outgoing radiation to take place, tonight will be another warm and muggy one with overnight lows projected to hold in the low to mid/upper 70s with similar dewpoint values. Southeast winds should be elevated enough to prevent the development of widespread fog. However, there could be patches of mist around tonight especially in areas where the winds are not strong enough. Though winds are not expected to be as strong, Monday will serve as a rinse and repeat from today with warm to very warm, humid, and at times hazy conditions continuing under partly cloudy to mostly cloudy skies in a likely capped environment. Despite the lack of a lifting mechanism and unfavorable winds/jet dynamics aloft, instability parameters will be in place to support maybe an isolated/rogue shower or thunderstorm on Monday, especially during the afternoon hours with max differential surface heating. Similar to today, have low grade (20-30%) PoPs in the grids to reflect this low, but non-zero probability/risk. The Storm Prediction Center`s (SPC`s) SWODY2 has the entire CWA or all of Deep South Texas under a General Outlook for thunderstorms on Monday and a Marginal (Level 1 out of 5) Risk for severe thunderstorms over our extreme northwestern sections (i.e. northern Zapata, northern Jim Hogg, and northwest Brooks Counties) for Monday. High temperatures are progged to be in the upper 80s to low/mid 90s on Monday. Monday night will feature another warm and muggy night with overnight low temperatures in the lower to mid/upper 70s (similar to tonight) with similar dewpoint values. && .LONG TERM... (Tuesday through next Sunday) Issued at 225 PM CDT Sun Apr 28 2024 Key messages will remain muted for the long term. Mid-level flow will remain unamplified for the most part. No deep troughs to the west. Nonetheless, minor disturbances may move over the Sierra Madres and across South Texas from time to time. This will show up in the forecast as regular (daily) mention of isolated to scattered convection out west. A punch of slightly higher ops farther east will occur Friday into Friday night with a weak surface cold front not too far away to the north. The dryline will hang out over West Texas. Did I mention a cold front? Moving south late in the week will be a weak cold front, driven by a Plains storm system, stalling out just to the north of the County Warning Area Friday into Saturday, then moving slowly back north. Slightly stronger southeast winds Wednesday and Thursday ahead of the front may agitate Gulf wave heights and push rip current risk into the high category Wednesday night through Friday. Seasonably above average temperatures will prevail with the region just north of a semi-permanent subtropical summer ridge. Lows will trend several degrees above average with highs a few degrees warmer than typical. Partly to mostly cloudy skies will dominate the local skies. && .AVIATION... (18Z TAFS) Issued at 1233 PM CDT Sun Apr 28 2024 Through 18z Monday.... Key Messages: * VFR-MVFR ceilings expected to continue through today. * MVFR-IFR ceilings are expected to develop tonight. * Ceilings expected to improve to at least MVFR levels on Monday. * Southeast winds, gusty at times, are expected to weaken this afternoon into this evening. As of this update, VFR to MVFR conditions were taking place at the terminals under a SCT-OVC deck of strato-cumulus clouds as indicated on the latest GOES-16 Visible Channel with ceilings ranging between 2,500-4,000 feet AGL. Latest surface analysis reveals a weak low pressure area over the area this afternoon. However, the latest forecast model and satellite trends indicate some clearing off to the west thanks to the strong April sun angle and rather weak upper level divergence taking place. This should allow for some improving sky coverage into the middle parts of this afternoon. That said, flying conditions due to ceilings could waffle back and forth between VFR to MVFR today. As we shift towards tonight, forecast models are suggesting marine influences to increase with increasing low level clouds (low stratus) from the Gulf. With plenty of low level moisture in place, MVFR to IFR conditions are expected to develop and take over the TAF sites tonight. As we shift into Monday, any MVFR to IFR ceilings/clouds are expected to improve to at least MVFR conditions. Moderate to at times gusty winds out of the southeast 10-15 kts this afternoon are expected to weaken as the day progresses as the surface pressure gradient continues to weaken. Tonight into Monday, southeast winds are expected to be at around 10 kts. && .MARINE... Issued at 225 PM CDT Sun Apr 28 2024 Tonight through Monday Night....Adverse to hazardous marine conditons will continue particularly for the Gulf Waters till Monday as seas/wave heights will range between 6-9 feet. Hence, a Small Craft Advisory remains in effect till 7 AM CDT Monday for the Gulf Waters (0-60 nautical miles out). A High Risk for Rip Currents will remain in effect to 7 PM CDT Monday evening. During the day on Monday and through Monday evening, Small Craft Exercise Caution (SCEC) conditions will remain in place over the Gulf Waters with seas/wave heights between 4-6 feet. Tuesday through Friday night...Moderate to fresh southeast breezes will prevail through the long term. With those winds will come moderate to occasionally elevated wave heights. Thus, expect here and there small craft should exercise caution to low end small craft advisory conditions. Synoptically, high pressure over the North Gulf will interact with lower pressure upstream to maintain a gradient supportive of moderate to fresh winds. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 77 89 77 90 / 10 10 20 20 HARLINGEN 74 90 75 93 / 10 20 20 20 MCALLEN 77 92 77 94 / 10 20 20 20 RIO GRANDE CITY 74 92 75 93 / 10 30 10 20 SOUTH PADRE ISLAND 76 80 77 81 / 10 10 20 20 BAYVIEW/PORT ISABEL 75 85 75 88 / 10 10 20 20 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk through Monday evening for TXZ451-454-455. GM...Small Craft Advisory until 5 PM CDT this afternoon for GMZ130- 132-135. Small Craft Advisory until 7 AM CDT Monday for GMZ150-155-170- 175. && $$ SHORT TERM...23-Evbuoma LONG TERM....54-BHM AVIATION...23-Evbuoma