482 FXUS64 KFWD 161029 AFDFWD Area Forecast Discussion National Weather Service Fort Worth TX 529 AM CDT Thu May 16 2024 ...New Aviation, Short Term... .SHORT TERM... /NEW/ Update: As previously discussed, the arrival of rich low-level theta-e air across the Big Country and western North Texas is leading to the development of widespread convection just northwest of the forecast area as of 530 AM. This trend will continue over the next few hours while convective clusters grow upscale and accelerate southeastward through North and Central Texas. Hazards for large hail, damaging winds, and flash flooding are likely through much of the daytime as this convection primarily impacts roughly the southwestern 2/3rds of the CWA. No significant adjustments were made with this morning's update other than to refine near-term trends. Isolated rainfall totals near 5" in Central Texas still look plausible for reasonable high-end amounts based on overnight high-res guidance. -Stalley Previous Discussion: /Through Friday/ With this update, the Flood Watch has been expanded northwestward to include the DFW area and additional locations to the south and west. While the heaviest rainfall is still expected in Central Texas with today's event, isolated totals in the 3-4" range will be possible near or even just north of the I-20 corridor, too. This flooding risk will unfold within an episode of strong to severe convection, with the greatest severe risk also across Central Texas. Modest ascent acting upon steep lapse rates has allowed fairly widespread high-based shower and thunderstorm activity to develop from Wichita Falls to Houston as of 1 AM, and this sub-severe activity is likely to continue through the morning while eventually moving off to the northeast. Outside of some small hail and brief heavy rainfall, this activity will be rather inconsequential compared to convection later this morning. The primary round of convection will get underway around or just after daybreak and will initially occur north and west of the CWA along a slow-moving frontal zone associated with a deepening surface low situated near El Paso. As intense poleward moisture flux occurs within a strengthening low-level jet, quick destabilization will occur as low-level moisture advection beneath steep lapse rates results in MUCAPE values of 2000-4000 J/kg. PWAT values will increase from 0.75-1" to 1.5-2" in the next several hours, and as this moisture arrives, rapid development of convection will ensue between 7 and 10 AM as it collides with multiple sources of lift. A steady ESE progression, likely to be accelerated by cold pooling, will send one or more convective clusters and/or line segments through North and Central Texas by late morning and early afternoon. This activity will be capable of very heavy rainfall with rates perhaps near 2" per hour, as well as large hail and damaging wind threats, the primary of which will be dependent on eventual convective mode. The heaviest rainfall totals and greatest flood threat are still expected in Central Texas where isolated amounts near 5" are possible. The aforementioned slow-moving frontal boundary (or effective frontal boundary modified by convective outflow) will also sag south of I-20 towards midday. Depending on the extent of convective activity during this time window, there could be a threat for new redevelopment along this feature which would likely be supercellular in nature. Backed easterly winds in the vicinity of this surface boundary and attendant increased helicity could result in an increased tornado threat across the southern fringes of our forecast area along a corridor from Lampasas to Temple/Killeen to Hearne. However, this will be very much mesoscale driven, and a scenario involving faster-than-expected upscale growth would act to minimize this threat in short order. Eventual upscale growth into a large convective complex is expected by late afternoon, with this main round of thunderstorm activity shifting southeast out of the forecast area this evening. However, lingering shower and isolated thunderstorm activity is possible back to the north and west as additional ascent continues to act upon steep lapse rates in areas that may not have been entirely worked over by convection earlier in the day. A relative lull in convective activity is expected overnight, although we cannot rule out additional light rainfall, while widespread low stratus engulfs most of the forecast area heading into Friday morning. Since the upper trough axis will still be upstream tomorrow, additional isolated showers and thunderstorms could redevelop during the daylight hours as the trough passes overhead, but this convection is unlikely to be strong, and rain rates should be unable to cause any further flooding issues even after widespread rainfall today. -Stalley && .LONG TERM... /Issued 330 AM CDT Thu May 16 2024/ /This Weekend Through Next Week/ Rain chances will come to an end across East Texas early Saturday morning as our storm system finally pushes off to the east. Ridging aloft will take its place, with positive mid-level height anomalies prevailing into the upcoming workweek assuring above normal temperatures. A shortwave will transit the Plains late in the weekend, dampening the flow, but it will neither reintroduce rain chances nor inhibit the warming trend. By Monday, nearly every location will see afternoon highs in the 90s. The subsequent (more potent) disturbance will take a more southerly track, which may guide a late-season cold front and associated rain chances into our area. While this could shave a few degrees off daytime temperatures, the current forecast will maintain above normal highs regionwide for day 7 (Wednesday, May 22). 25 && .AVIATION... /NEW/ /12z TAFs/ Scattered high-based convection rooted near 10 kft continues to drift across southern and eastern portions of D10 early this morning, although lightning activity has waned with these cells over the past couple of hours. Much more widespread and stronger convection is beginning to develop upstream across western North Texas, and will arrive at the TAF sites around 15-16z. A few hours of convective impacts are likely through mid afternoon before storms eventually shift southeastward. Following the departure of convection, MVFR/IFR cigs are expected to fill in within northeasterly surface flow, although the timing of these cigs and when category degradations will occur remains very uncertain. It's possible that a window of VFR time could exist through the late evening hours before these cigs develop early tomorrow morning. Additional isolated shower and thunderstorm activity is possible overnight into Friday, although the potential is currently too low to advertise in the TAFs. -Stalley && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 77 65 80 67 91 / 90 60 20 10 5 Waco 74 65 81 65 88 / 100 70 20 10 5 Paris 80 64 79 63 87 / 50 60 50 20 5 Denton 76 62 78 63 89 / 90 60 30 10 0 McKinney 78 63 79 64 88 / 70 60 30 10 5 Dallas 79 66 81 67 91 / 80 60 20 10 5 Terrell 77 64 80 65 87 / 80 60 20 10 5 Corsicana 78 67 82 67 89 / 100 60 20 10 5 Temple 75 65 81 65 89 / 100 60 10 10 5 Mineral Wells 74 62 79 63 91 / 100 70 20 10 0 && .FWD WATCHES/WARNINGS/ADVISORIES... Flood Watch through Friday morning for TXZ101>104-116>122- 130>135-141>148-156>162-174-175. && $$