FXUS64 KHGX 290949 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 349 AM CST Sun Jan 29 2023 ...New SHORT TERM, LONG TERM, MARINE... .SHORT TERM... (Today through Monday Night) Issued at 333 AM CST Sun Jan 29 2023 Another nocturnal 30-45kt LLJ draped from South Texas to the Mississippi River Valley is providing enough isentropic forcing and vertical wind shear for elevated showers and thunderstorms early this morning above the stubborn 700mb cap. The strongest portions of this LLJ will continue to push NE throughout the morning, but a remaining segment of a 30kt LLJ will remain along the coast and south of I-10 throughout the afternoon. Hi-res models are honing in on a window for severe weather later this afternoon if almost everything aligns correctly. As a shallow cold front approaches from the north early this afternoon, it'll slowly stall north of I-10. Meanwhile, southwesterly steering flow south of the front and aloft will provide diffluence aloft and plenty of low level wind shear (0- 1km and 0-3km SRH 200+ m2/s2) for our environment. Around 8-11am this morning, right as the sfc inversion and the 700mb cap start to erode and before the bulk majority of the LLJ departs to the NE, elevated storms could become rooted to the surface and tap into these favorable ingredients for severe weather. Therefore, SPC has placed our CWA in a Marginal Risk for severe weather with all hazard types possible, but especially hail and a few isolated tornadoes. Given how saturated the low levels are in forecast soundings, not anticipating widespread damaging winds, but a few of the strongest storms could produce strong to severe winds as well. All of this is highly conditional and depends on whether the CIN erodes as SRH is at its peak. Towards lunchtime and onwards, as SBCAPE climbs to 1500 J/kg, convection along and south of the front will increase in strength, prolonging the hail and wind threat through sunset tonight until the front starts to dissolve with the loss of daytime heating and starts to push towards the coast. Regarding rainfall, not only will this slow frontal boundary provide an area for heavy rainfall, but discrete cells south of the front will continue to train from the SW to the NE, providing an additional area for heavy rainfall. Given the lack of recovery time from last Tuesday's storms on top of expected rainfall rates of 2+ inches/hr, this has prompted the issuance of a Flood Watch for Liberty and Chambers county, where the highest rainfall amounts are expected to occur (2-3+ inches and isolated higher amounts possible). In addition, WPC has placed portions south of Walker County and east of Wharton County in a Slight Risk for excessive rainfall. As the front dissolves and pushes towards the coast late this evening and eventually offshore during the overnight hours, rain chances will drop off precipitously north of I-10, but lingering showers are possible along the coast. This front will become stationary just off the coast on Monday and generate a weak coastal trough that will meander offshore. This combined with continuous SW flow aloft from the sub-tropical jet sending little shortwave trough impulses, we can expect 30-50% PoPs to continue through Southeast Texas on Monday and through the evening, especially across our northern counties where there will be better upper level forcing. Walts && .LONG TERM... (Tuesday through Saturday) Issued at 333 AM CST Sun Jan 29 2023 The frontal boundary that will move through the region today (Sunday) will stall just offshore or inland during the next few days. This stationary boundary, along with different disturbances aloft and at the sfc will be the main focus for unsettled weather through the end of the week. By Tuesday, an inverted surface trough will develop over the region, that combined with subtle shortwaves embedded in the SW flow aloft, rain chances will be possible. Forecast soundings show decent instability in the vicinity of the stalled front over the waters/coastal zones. Further inland, models show elevated instability; therefore, have also included a chance for thunderstorms during the day. Forecast profiles remain saturated, at least below 700mb layer with above normal PWAT values remaining through Thursday. PWs in the 1.2 - 1.6 inch range are possible on Wed. To get an idea, the average for this time of year is 0.71 inches, thus it is more than the 90 percent moving average for January standards. The combination of abundant low to mid-level moisture and the passage of weak shortwaves aloft will again keep rain/storm chances for Wednesday. The best chance for precipitation will be Wednesday night into Thursday as a deepening upper low over the Southwest CONUS makes its way across TX. Widespread showers and thunderstorms can be expected during this time frame as forcing and instability increase ahead of the upper low. Precipitation should gradually taper off from west to east by Thursday night; however, breezy to windy conditions will remain through Friday. Behind this system, a dry and cooler airmass will filter in Friday into the weekend as an upper ridge builds over the Plains. Temperature forecast will be a challenge this week as it will depend on the location of the quasi-stationary sfc front. In addition, flow aloft will remain from the south-southwest, keeping temperatures on the warm side at the sfc, especially over the coastal counties. With that being said, a sharp gradient in temperatures can be expected through the week with the coolest values (below average) for our northern counties and warmest values (slightly above average) across the coastal counties. As of now, Wednesday looks to be the warmest day of the workweek as 850mb temperatures climb into the 11-13 degC, suggesting highs in the upper 60s to near 70 at the sfc. Overall, highs will range from the upper 40s and 50s roughly north of a line from Columbus to Conroe to Livingston and into the upper and 60s south of this line. JM && .AVIATION... (06Z TAF Issuance) Issued at 1110 PM CST Sat Jan 28 2023 No significant changes to the previous forecast. A mix of VFR-IFR cigs currently across SE Texas sites and will continue to lower to IFR-LIFR overnight into Sunday morning. Areas of patchy fog can occur tonight into Sunday across portions of SE Texas where winds reduce to around 6 KTS or less and is expected to reduce vis. The development of sea fog along the bays and nearshore Gulf waters may keep lower vis at LBX/GLS for much of the TAF period. S winds tonight at around 6-10 KTS. Areas of showers from the Gulf waters will begin to move into areas S of IAH late tonight early Sunday morning and develop N-NE of IAH a little before sunrise. As the morning progresses and a cold front approaches the region, scattered to widespread SH/TS is expected for much of SE Texas. Periods of mod-hvy RA is possible late morning to afternoon, in particular for locations S of I-10 and E of I-45. S winds at 5-12 KTS expected for much of the day, turning N in the wake of the front late afternoon to evening. Stronger gusty VRB winds, lower vis, and frequent lightning may occur in and around TSRA/+TSRA. Also, an 850 jet of 25-35 KTS will remain over the area through Sun evening and may result in LLWS on occasion. 24 && .MARINE... Issued at 333 AM CST Sun Jan 29 2023 Patchy fog, some locally dense, will continue to develop in the bays and nearshore waters through early this morning as wind diminishes. Moderate to strong south winds and seas around 7-9 ft are still expected well offshore (20-60 nm waters) through mid- morning. A Small Craft Advisory remains in effect. Scattered showers with isolated thunderstorms will continue to develop today with the best chances early this morning, and then again later tonight with the passage of a cold front. This front will slowly reach the coastal waters early Monday morning and then will stall over the waters or along the coast for the next few days. This will bring the potential for sea fog in the vicinity of the front. Light to occasionally moderate winds are expected this week, with increasing winds and seas towards the end of the week as a stronger cold front moves through. JM && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 65 41 41 36 / 80 30 40 60 Houston (IAH) 71 52 53 46 / 90 70 30 50 Galveston (GLS) 68 59 60 52 / 90 50 30 30 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Flood Watch from 9 AM CST this morning through this afternoon for TXZ200-214-300. GM...Small Craft Should Exercise Caution until 10 AM CST this morning for GMZ350-355. Small Craft Advisory until 10 AM CST this morning for GMZ370-375. && $$ SHORT TERM...Walts LONG TERM....JM AVIATION...24 MARINE...JM