665 FXUS64 KFWD 020504 AFDFWD Area Forecast Discussion National Weather Service Fort Worth TX 1204 AM CDT Thu May 2 2019 .AVIATION... /06Z TAFs/ Challenges: Tracking line of TS with +SHRA currently across DFW Metro airports southward through 12z Thursday. Cigs...chaotic with the linear line of TS with patchy MVFR/IFR cigs possible, especially the Waco Regional Airport area. We continue to track a line of TS with +SHRA along and just south of I-20. Latest CAMs are currently struggling with propagation and cold pools, so new TAFs will be challenging to say the least. For now, will time current convective activity out of the DFW airports in the 07z-08z time frame with lingering showers and N-NE flow 09-12 knots afterward. Flow will gradually back around to the east or southeast AOB 10 knots as back outflow occurs. At Waco, will time in VCTS/CB wording in the 07z-08z time frame, as outflow driven, mainly elevated TS arrives into the area with occasionally +SHRA. Will have this activity moving out, or dissipating across Waco airport by 11z-12z Thursday. Some off/on MVFR cigs may rear their heads throughout the day on Thursday, with redevelopment of TSRA/VCTS at Waco late afternoon and evening, with just a VCSH wording at DFW airports. All airports should see E-SE winds around 10 knots at that time. It must be stated this is a fairly low confidence forecast beyond 12z Thursday, as daytime heating and uncertainties exist regarding subtle old outflow boundaries and the next approaching shortwave late Thursday will dictate convective development and timing. 05/ && .UPDATE... /Issued 1048 PM CDT Wed May 1 2019/ Line of strong storms with heavy rainfall continues to slowly cold pool it's way southward into the I-20 corridor. As such, counties north of the main line of storms in Severe Tstorm Watch 118 are no longer in a threat for severe storms and have been canceled. That said, localized flooding or flash flooding remains in play so these areas should not let their guard down. Updates to the watch and zone forecasts have been issued. 05/ && .UPDATE... /Issued 954 PM CDT Wed May 1 2019/ Though an isolated severe risk for hail may remain across Severe Tstorm Watch 117, it appears it's evolving more into a linear, training, heavy rain situation as the nocturnal low level jet feeds into this line of storms across the watch area. As such, we'll be allowing Severe Tstorm Watch 117 for our NW counties to expire at 10 pm CDT. That said, the flash flood risk may actually increase through/past midnight parts of the watch area. 05/ && .SHORT TERM... /Issued 313 PM CDT Wed May 1 2019/ /Tonight/ Thunderstorms have erupted across Northwest Texas and Southern Oklahoma in the vicinity of a weak front and a remnant outflow boundary. These storms quickly became severe, which is not surprising given how unstable the atmosphere is this afternoon. Our 18Z sounding is good evidence of this instability with MUCAPE coming in at 4855 J/KG, and it is doubtful that the special 21Z sounding we have scheduled will be any different. Anyway, these storms are just now beginning to enter the northwest counties of the CWA, and this should be the primary area of convection to keep and eye on as it gradually organizes into a quasi-linear mcs this evening while progressing southeast across the forecast area. That said, isolated thunderstorms will still be possible farther southeast east late afternoon and early this evening along the I-35 Corridor from Temple to Waco to the DFW Metroplex. Though isolated in nature, this convection may remain more discrete and would be capable of both large hail and damaging downburst wind gusts. Looking back to the northwest, storms are currently equally capable of large hail and damaging winds. As time progresses, this activity should evolve into mainly a damaging wind threat as it sags deeper into the forecast area this evening and overnight. Recent convection allowing model guidance has trended slower with the overall southward progression of this evening's thunderstorms. This reinforces the idea that training thunderstorms with heavy rain will keep the potential for localized flash flooding going, initially from between the Red River and I-20 now through midnight, then south of I-20 and east of I-35 during the overnight into Thursday morning hours. The Flash Flood Watch will remain in effect for roughly the northeastern half of the forecast area where the more saturated soils exist. Adjustments to the watch area could be made in later forecasts depending on where the heaviest rains occur tonight. Otherwise, low temperatures will range from the lower 60s along the Red River to the lower 70s across the southern-most counties. 30 && .LONG TERM... /Issued 313 PM CDT Wed May 1 2019/ /Thursday through Wednesday/ In the wake of the expected overnight convective complex, odds are that the atmosphere will be fairly worked over as a cold front moves into the region from the northwest. However if the complex of storms does not materialize as expected, or instead of moving southward into southeast Texas - it heads more east and return flow can organize quickly by sunrise, then it's more likely that a line of showers and storms will develop along the front. Again, at this time the odds are that the front should be mostly devoid of deep convection in the morning hours due to tonight's activity, but it's still possible so PoPs will be set at 40% over the area in the morning. This frontal boundary should slow down and stall across the heart of the area by the afternoon hours. As we head farther out in time, the CAM solutions continue to diverge, with some showing vigorous convection along the front in the afternoon and some guidance keeping things fairly tame through sunset. While a moist, unstable, and uncapped airmass will be in place, the response to the waves of upper level forcing rippling through in southwesterly flow aloft will dictate the extent of convective activity. The global models (GFS/ECMWF/Canadian) are in good agreement that a shortwave trough will be moving through the region in the morning hours, leaving much of the region in subsidence during the afternoon hours. Despite the subsidence, the mid and low level flow will weaken and therefore we'll see convective initiation following a more summer-time mode where localized forcing and high buoyancy will lead to isolated to scattered storm activity. By the late afternoon and especially the evening hours, another strong shortwave will move toward the CWA from the west and southwest and organized forcing for ascent will spread across the region. It's likely that this shortwave will result in convective activity to our west and southwest that will move into the region after sunset. The best instability will be south of the front, and therefore the greatest severe threat will be generally south of I-20. The main threat will be damaging winds and large hail with the tornado threat being very low due to considerably weaker low level flow. This evening convection may evolve into a larger complex of storms which could bring the area another round of widespread rainfall into Friday. This rain would be heavy in spots, and could lead to flash flooding and river flooding. The flash flood watch will remain as is for now, but may be expanded southward for this round Thursday night and Friday at a later time. The significant convective overturning should produce a large cold pool and push the effective front farther south into South Central and Southeast Texas Friday. Total additional average rainfall Thursday and Friday should average 1-3 inches. While a lot of the guidance is still wet for Saturday, the general thinking is that the front will be farther south than the models forecast and it's possible we'll salvage the day for outdoor activities. Will undercut the guidance PoPs on Saturday and show high temperatures a little below normal and in the upper 70s with some sunshine and north winds. By Saturday evening westerly to northwesterly flow aloft will be in place over the region. We'll have to keep an eye on convective potential in the Panhandle as it could form into a complex and make a run at the CWA by early Sunday morning. The airmass over North Texas will be more stable, so this activity should weaken, but will keep some slight chance PoPs in the forecast to the west early Sunday. Otherwise Sunday should be a nice day for most with highs in the lower 80s. Lows Saturday night and Sunday night should drop into the mid 50s and lower 60s. The southwesterly flow aloft will return by Monday and Tuesday and as such the moisture/instability will increase. Subtle disturbances will likely ripple through early next week so some chance PoPs will return to the forecast. Otherwise the guidance is indicating a stronger trough by midweek that will probably bring a more organized threat of heavy rain and severe weather. Temperatures will remain warm and muggy Wednesday of next week with lows near 70 and highs in the mid 80s. TR.92 && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 64 81 64 75 62 / 100 40 60 70 40 Waco 70 83 64 76 62 / 60 40 60 70 50 Paris 61 77 63 73 60 / 100 40 70 70 50 Denton 63 79 63 75 60 / 100 40 70 70 40 McKinney 63 78 62 74 61 / 100 40 70 70 40 Dallas 66 82 66 75 62 / 100 40 60 70 40 Terrell 64 82 66 76 61 / 100 40 60 70 50 Corsicana 69 82 66 75 61 / 60 50 60 60 60 Temple 71 83 65 77 62 / 60 40 50 70 50 Mineral Wells 61 80 62 75 58 / 100 50 70 60 30 && .FWD WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Thursday evening for TXZ091>095- 101>107-116>123-133>135-146. && $$ 05