DFW FORECAST DISCUSSION
000 FXUS64 KFWD 270020 AAA AFDFWD Area Forecast Discussion...UPDATED National Weather Service Fort Worth TX 720 PM CDT Thu Apr 26 2018 .AVIATION... /00Z TAFs/ North flow. VFR but with some elevated showers/virga tonight. The tail end of a skinny upper trough will swing through North Texas tonight. The radar echoes along the Red River Valley suggest rain showers are ongoing within it, but with a deep layer of dry air beneath these convective elements, this has so far been mostly virga. The 00Z RAOB from KFWD found very dry air remained beneath the 18kft cloud bases; the relative humidity values around 700mb were still in the single digits. This virga will attempt to moisten the layer, but a few sprinkles would be the extent of any precipitation at the surface. However, some sub-cloud turbulence will accompany the evaporation process. A small cluster of thunderstorms has developed along the associated surface front in western Oklahoma. As the front approaches overnight, this complex will find inadequate moisture downstream, and only elevated showers are expected near the Metroplex TAF sites. The passage of the front will organize the timid northerly winds already in place, but postfrontal wind speeds at our TAF sites will be well below the windy conditions currently across the Texas Panhandle and West Texas. As the upper trough axis transits the area, skies will clear and will remain clear through the remainder of the valid periods of the TAFs. 25 && .SHORT TERM... /Issued 244 PM CDT Thu Apr 26 2018/ /Tonight/ Our cold front parade will continue tonight (although this one will bring almost imperceptible changes to the temperature and dewpoint fields). This front will be encouraged southward by a fairly potent upper-level disturbance which is presently tracking into Kansas, and this feature will zip overhead tonight and into Friday morning. While moisture has been effectively scoured out by Wednesday`s stronger cold front, 500 mb temperatures will cool into the -18 to -21 C range as the core of this feature approaches, resulting in steepening mid-level lapse rates. This will help carve out a small area of instability (less than 250 J/kg)--rooted above 850 mb or so. This will probably be good enough to support some bubbly elevated convective plumes embedded within an expanding mid-level cloud deck tonight. We`ve expanded the 20% PoP mention for rain showers across much of the forecast area late this evening and into the early-morning hours and will leave out an isolated thunder wording given the paucity of anticipated instability. Lingering dry air in the lowest 3-4 kft may help to evaporate a good deal of any precipitation, hence the lower PoP values. Otherwise, low temperatures tonight will be in the upper 40s and mid 50s with skies quickly clearing from northwest to southeast Friday morning. Carlaw && .LONG TERM... /Issued 244 PM CDT Thu Apr 26 2018/ /Friday through Thursday/ The weather over the next few days will be dominated by a high- amplitude, upper-level ridge that is in place from Baja California across the American West and into British Columbia. At the surface, a 1029 mb high is centered near Yellowstone National Park, with a cold front on the leading edge of it presently across the Central Plains. By Friday morning, this front should be south of our forecast area, with high pressure building in behind. This high should weaken, and slide off to the east quickly, so we likely will not have much in the way of sensible weather impacts by Friday afternoon. By Saturday, winds should return from the south, allowing for a steady warming trend to commence. Saturday should be a very lovely day with light southerly winds, temperatures in the upper 70s to near 80 (i.e. near seasonal normals), dewpoints in the upper 40s, and ample sunshine. Sunday will be slightly warmer and more humid as southerly flow continues. Overall, North and Central Texas are in for quite a lovely weekend, so make sure to get outside. Heading into next week, a potent upper-level trough will begin to dig in across the Rocky Mountains. Resultant lee cyclogenesis will act to enhance warm air advection across the Great Plains, with the axis of a low-level jet progged to move over our forecast area by late Monday. The GFS and ECMWF both advertise some light QPF in our southwestern counties near this low-level jet axis, and it is not entirely implausible. Despite a strong cap in place (as evidenced with forecast CINH values in excess of 100 J/kg) and a lack of upper-level support, strong moisture return and warm air advection may permit a few showers to develop. The chances for thunder should be low to nil however. At the very least, we are likely to see a marked increase in cloud cover by Monday afternoon. Will mention light, isolated showers in the forecast products for Monday afternoon. The middle of next week is when the forecast starts to get a little more complicated. Model guidance is in good agreement that a dryline should begin to sharpen over West Texas on Tuesday, with that dryline approaching a Vernon to Midland line by late afternoon. Forecast soundings suggest that capping may be weak enough to allow for some thunderstorm develop along the dryline. While most of the convection should stay west of our area, storm motions could bring some thunderstorms into our northwestern counties, thus carried slightly higher PoPs as well as mentioned thunder across our northwestern counties Tuesday late afternoon and evening. Coverage appears it may be higher on Wednesday given the approach of an upper-level trough, and thus more noteworthy height falls. We would likely see another round of thunderstorms develop along the dryline (which like Tuesday, will likely be situated across the Rolling Plains of West Texas by late afternoon). As is typically the case this time of the year, any thunderstorm threat in North and Central Texas brings with it the chance for severe weather. While it is too early to know the precise details and location of where the greatest severe weather threat will be, there will be a possibility of severe weather somewhere in the Southern Plains towards the middle of next week. Godwin && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 54 77 52 81 57 / 20 0 0 0 0 Waco 52 78 50 81 55 / 20 0 0 0 0 Paris 51 73 47 77 52 / 20 0 0 0 0 Denton 50 75 48 81 54 / 20 0 0 0 0 McKinney 50 75 48 79 54 / 20 0 0 0 0 Dallas 54 78 52 81 58 / 20 0 0 0 0 Terrell 52 77 47 80 53 / 20 0 0 0 0 Corsicana 53 75 49 79 54 / 20 0 0 0 0 Temple 52 79 51 81 55 / 20 0 0 0 0 Mineral Wells 50 76 47 82 53 / 20 0 0 0 0 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 25/30