590 FXUS64 KFWD 262345 AFDFWD Area Forecast Discussion National Weather Service Fort Worth TX 645 PM CDT Fri Apr 26 2019 .AVIATION... /00Z TAFS/ VFR will prevail through the period with southerly flow increasing to around 20 kt during the morning hours on Saturday. There will be some forcing during the early morning hours on Saturday which could result in some scattered high based showers and perhaps a thunderstorm mainly northwest of the Metroplex airports. At this time, the coverage appears too low to mention in the TAF, but if any showers do develop, they could lead to a focused area of turbulence off to the northwest. Otherwise, a cold front will slide south toward the Red River late Saturday afternoon and will likely be the focus for at least scattered showers and thunderstorms by 00Z as weak upper forcing spreads through the region. We'll have a few hours of VCTS in at DFW through the late evening hours, although thunderstorms may be in the diminishing stages by this time. Outside of convective areas, VFR will prevail with winds becoming a little more southeasterly through the late evening. Dunn && .SHORT TERM... /Issued 350 PM CDT Fri Apr 26 2019/ /Tonight through Saturday Morning/ East/northeast low level flow will continue to become more southerly through the overnight period as surface high pressure slides eastward into the Ozarks. Flow aloft will remain northwesterly and this will allow for a perturbation or two to ripple through the swift flow aloft. This will also mean low rain and perhaps a thunderstorm chance through the overnight period. An ill-defined Mesoscale Convective Vortex or MCV across the Big Country will continue to slide eastward along the I-20 corridor this afternoon. With low level moisture being largely absent, it should pass through the area without much fanfare with only a slight uptick in mid-level clouds possible. Lee-side cyclogenesis is in full swing across the Big Country and Panhandle at this hour and it's probable that return flow will establish itself through the overnight hours. The southerly breezes should help keep conditions a bit milder tonight with most locales only slipping into the upper 50s to low 60s for overnight lows. Winds at 925mb will be stronger across the Big Country during the overnight hours (speeds near 50 knots per RAP guidance) and thus it's likely that some limited nocturnal mixing keeps these areas slightly warmer. During the pre-dawn hours on Saturday, short term model guidance indicates very robust isentropic ascent along the 300-310K theta surfaces near and northwest of a Gainesville to Decatur to Eastland line. These theta surfaces would support mainly mid- level ascent and forecast soundings do hint at some meager moistening in this layer. Low level moisture will be quite low thanks to the recent intrusion of drier air into the Gulf of Mexico and so the potential for widespread measurable rainfall looks low at this time. That being said, steep mid-level lapse rates (around 8 C/km) in the presence of ascent is a good recipe for high-based elevated convection. Given that model guidance tends to struggle with these situations and I'll advertise a 15 to 20 PoP mainly northwest of an Eastland to Decatur to Gainesville line. I'll mention showers and a few sprinkles, but a rumble of thunder or two isn't out of the realm of possibility. Some updates to the forecast to explicitly mention thunder may be needed if evening model guidance becomes more aggressive. Bain && .LONG TERM... /Issued 350 PM CDT Fri Apr 26 2019/ /Tomorrow into Next Week/ Main focus of the extended remains the notable increase in rain and thunderstorm chances during the upcoming week. Concurrently, severe-weather and flood potential will increase as well, primarily on Tuesday and Wednesday. Before then, low-level moisture will commence its northward return across our area tomorrow, in association with the eastward shift of a surface ridge towards the Southeast US. Most of the atmospheric column should remain too dry for any precipitation during the morning hours, especially given that any stronger large-scale ascent should stay north of the Red River. Still, higher-res guidance also indicates that a weak MCV or two (generated by southern High Plains convection this evening/tonight) may reach our northwest counties during the morning hours. This is not dissimilar from what is currently spinning near Breckenridge as of 20Z. Guidance indicates enough mid-level saturation could occur for a few showers from Graham to Sherman; therefore, included slight-chance PoPs in the morning. Would not be surprised to even see isolated lightning, owing to steep 700-500mb lapse rates. This possibility appears too low for inclusion in the grids, though. Thereafter, a front will slowly sag south across Oklahoma during the day, approaching the Red River during the evening and overnight. Although zonal flow will yield weak large-scale ascent, surface convergence along the front and near a weak triple point over northwest Texas is expected to foster isolated thunderstorms by mid/late evening. Only modest return moisture should keep the strongest storms dispersed, but 1000+ J/kg of MLCAPE and sufficient effective shear could yield isolated large hail and damaging gusts, primarily north of a Breckenridge-to-Paris line. Increasing inhibition and weak ascent will bring convection to an end across our area overnight Saturday. Deepening southerly flow will further transport moisture northward on Sunday, but rising/neutral height tendencies and persistent dry air aloft should keep conditions dry across our area. There is a very low potential for an isolated storm across our far northwest (with a conditional strong-storm threat), but this appears too low for any explicit mention in the forecast. A mid-level ridge axis builds from the Bay of Campeche to the Florida Panhandle on Monday, and our synoptic-scale flow turns southwesterly in response. With a maintenance of at least modestly steep mid-level lapse rates atop richening boundary-layer moisture during the early week, any small disturbances in this flow regime will have the potential to initiate severe convection. On Monday, the lower troposphere should remain capped, with only a plume of low clouds spreading across our area. However, a surface front will be driving south across the Texas Panhandle and parts of Oklahoma. By Monday night/early Tuesday, an initial impulse should promote a blossoming of convection near/north of this front. At present, it appears like initial severe/flood potential will likely be confined to points just to our northwest. However, the influence of a more robust shortwave trough over the Desert Southwest will likely enhance a low-level jet over parts of central/eastern Texas during the second half of the day Tuesday. Weakening inhibition and slowly deepening cells in the open warm sector could pose a threat for all severe hazards by late in the day. Meanwhile, the effective front (perhaps somewhere along/north of I-20) will also be a focus for strong/severe convection and perhaps a greater flood potential. This evolution may be in the form of an MCS that develops across northwest Texas and then moves east/southeast (given southwesterly mid-level flow as the advection component and robust southerly low-level flow as the propagation component). The movement of this effective front will be highly sensitive to diabatic influences from heavy precipitation, and thus the most likely areas of any severe/flood potential become even more uncertain on Wednesday. With that said, this front will likely be draped somewhere near North/Central Texas, while southwesterly flow aloft should favor at least one more round of renewed isentropic ascent and convergence on Wednesday. Our greatest concern may have shifted towards the flood potential by this point, but we may have to contend with at least some severe hazards as well. The bottom line is that all of North and Central Texas should be prepared for periods of heavy rainfall, associated flooding, and severe weather Tuesday into Wednesday. The second half of the week may still feature periods of showers and thunderstorms, but mid-level flow could turn more westerly, while the effective front possibly sinks even farther south. Therefore, any severe/flood potential appears lower/more uncertain during the second half of the week. Picca && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 60 84 63 83 65 / 5 10 20 5 0 Waco 58 81 62 82 64 / 0 0 5 0 0 Paris 55 79 60 78 61 / 5 10 30 10 0 Denton 58 84 62 83 64 / 5 10 30 5 0 McKinney 57 82 61 80 64 / 5 10 30 5 0 Dallas 61 84 63 83 65 / 0 10 20 5 0 Terrell 58 80 62 82 62 / 0 10 20 5 0 Corsicana 58 81 61 80 62 / 0 0 10 0 0 Temple 58 82 62 83 64 / 0 0 5 0 0 Mineral Wells 55 86 60 83 61 / 10 10 20 0 5 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 91