494 FXUS64 KFWD 171207 AFDFWD Area Forecast Discussion National Weather Service Fort Worth TX 607 AM CST Thu Jan 17 2019 .AVIATION... /12Z TAFs/ A cold front is currently on the doorstep of the Metroplex, having just moved into the KLUD area and should enter the DFW area in an hour or so. The front will be accompanied by northwest winds and another stratus deck. Bases may initially be below FL010 but should fairly quickly rise into the FL010-015 range, so the forecasts will simply indicate MVFR conditions coinciding with FROPA. The front should reach KACT a few hours later, and will similarly be accompanied by the MVFR cloud deck. Cigs will erode this afternoon as dry air mixes in from the northwest, with VFR conditions expected this afternoon and evening. The front will stall and eventually return north overnight. There is a slim possibility that patchy fog may result from the clear skies and light return flow, but will hold off including any visibility reductions unless future guidance suggests otherwise. A few showers will be possible Friday, but mainly after the 18Z hour. 30 && .SHORT TERM... /Issued 355 AM CST Thu Jan 17 2019/ /Today and Tonight/ Low clouds lingering along and east of the Interstate 35 corridor are gradually shifting east as low level winds veer ahead of a cold front. The front is currently encroaching on the northwest corner of the CWA, and should barrel across the I-20 corridor between sunrise and 8 AM before clearing the southeastern zones by late morning. The boundary is accompanied by a second batch of stratus, so where skies are currently clear, another round of overcast conditions can be expected this morning as the front pushes through. Clouds will scatter, giving way to mostly sunny conditions at all locations this afternoon as dry air mixes within the boundary layer. Cool air advection behind the front will keep high temperatures in the upper 50s along the Red River with mainly 60s elsewhere. The front will stall just southeast of the area before lifting quickly back to the north overnight as the next shortwave crosses the Rockies and a lee cyclone intensifies. Winds will become light and variable this evening, with light southeast winds developing after midnight. Mostly clear skies and weak return flow sets the stage for patchy fog development, and have added this to the grids for the overnight hours. Otherwise, temperatures should remain above normal with lows ranging from the low 40s along the Red River to the low 50s across the far south. 30 && .LONG TERM... /Issued 355 AM CST Thu Jan 17 2019/ /Friday Through Wednesday/ Low level warm advection will be ongoing Friday morning with breezy south winds expected by 18z Friday. A lead shortwave will be lifting east across the Central and Southern High Plains and deepen the Eastern Colorado lee-side surface low. Model soundings continue to show a warm elevated mixed layer(or capping inversion) maintaining at least through the early afternoon hours. This should mainly result in scattered sprinkles or a few rogue showers underneath the slow-lifting cap aloft early on in the day. This lead mid-level shortwave will quickly shunt to the northeast of North and Central Texas through mid-afternoon. Meanwhile, the main mid-level energy will be moving readily through the Southern Rockies and moving east over the Texas/Oklahoma Panhandles after midday. Better large-scale ascent, pressure advection, and 30-40 knot southwesterly upglide on the 290-305K theta surfaces increase quickly late Friday afternoon/evening. There are some uncertainties to exactly where the pre-frontal trough sets up across the area by 00z Saturday. It appears the main mid-level ascent and left-exit region of a 160 knot+ upper jet max will coincide somewhere near or just west of I-35 late Friday per the GFS/SREF. However, the NAM12 looks to be 3-6 hours faster with surface features which could play a big role on where better moisture and resultant instability set up before the aforementioned upper jet max arrives. With the NAM12 being the outlier, I have opted to lean toward the slower WRF/SREF/GFS solutions on surface features. Regardless, I feel the cap will hold relatively strong within the southwest flow aloft until at least 21z or slightly later, before moistening and lifting of the cap occur quickly early Friday evening. I have adjusted highest convective chances across the northeast counties early in the evening, before better scattered storms zipper down the surface trough and southward down across our eastern counties. The arctic cold front should start overtaking the surface trough from northwest to southeast quickly by late evening and after. As in the previous few nights, I feel the current Marginal Risk from SPC looks overall reasonable with any brief 3-6 hour window late Friday across areas along/east of I-35/35W. Deep layer westerly shear, SBCAPE near a 1000 J/KG across Central Texas, and steepening lapse rates to near 7 deg/C certainly validate this concern. Main concern is large hail, though where richer surface dew point temperatures in the low-mid 60s surge into Central Texas, a localized damaging wind threat is certainly possible. Low level 0-1km shear is strong as well, but relatively veered and combined with marginal LCL levels Friday evening, the tornado threat will be very low, though not zero across our southeast counties. Lastly, it appears the heaviest rainfall in excess of an inch should be confined across the far eastern counties, where some run off and minor flooding is certainly possible Friday night. We are not expected widespread flash flooding, however, some minor rises on parts of the Sabine and maybe the Trinity River Basins are likely. Any convective strong-severe threat will come to abrupt end across our far eastern and Central Texas counties after midnight, as the upper disturbance passes across and drives an arctic front quickly through our region before daybreak Saturday morning. High temperatures will likely occur at this time, followed by slow- falling or at best, steady temperatures in the upper 30s and 40s on Saturday. In addition, a very strong pressure gradient will combine with strong low level cold advection to drive north- northwest winds 20-30 mph with gusts at times to between 35-40 mph. By Saturday afternoon, wind chill values in the 20s north and 30s south will become common. Now for what everyone is wanting to know regarding chances for wintry weather north of I-20 on Saturday. Some wrap around moisture is expected in wake of our departing mid-level disturbance and arctic front on Saturday. Sans the European model, all other models draw in top-drying into the region quickly with 40-50 knot downglide. As such, I will keep only slight chances for a brief bout very light snow or snow flurries north of I-20. We do not expect snow to be widespread enough to result in any accumulations along the immediate Red River Valley due to the aforementioned strong downglide and dry air advection by Saturday afternoon. Brisk north winds and clearing skies will occur Saturday evening with wind speeds settling down Sunday morning. The dry and dense arctic air will likely result in most areas falling well into the 20s. As such, wind chill values don't appear as brutal as previously thought, but values in teens and lower 20s by sunrise Sunday will still make for a frigid morning. I did remain on the cold side of guidance Sunday, despite the return of light south winds 10 mph or less across the western half of the area by afternoon. Despite the plentiful sunshine expected, I have highs only creeping into the 40s, which is still not as cold as previously thought yesterday. You just really never know how quickly shallow arctic airmasses modify. Sunday night will be brisk and still chilly, as south winds increase to between 10-15 mph with lows in the 30s. Breezy and warmer conditions return for the early work week with highs Monday warming well back into the mid 50s to lower 60s, before another cold front arrives Tuesday with support from yet another strong, but progressive mid-level shortwave. Highs will fall back into the upper 40s to 50s across Central Texas. Plenty of uncertainty regarding moisture in advance of this front and timing of the mid level system, so have stayed very conservative with low PoP across mainly our far eastern counties and Central Texas next week. 05/ && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 61 46 69 38 41 / 0 0 20 50 10 Waco 65 48 70 40 45 / 0 0 20 40 0 Paris 60 42 63 38 39 / 10 0 40 70 20 Denton 60 44 69 36 40 / 0 0 20 40 10 McKinney 60 44 67 36 39 / 0 0 30 50 10 Dallas 62 46 68 39 41 / 0 0 20 50 10 Terrell 63 45 68 38 41 / 5 0 30 60 10 Corsicana 64 47 67 39 43 / 5 0 30 60 5 Temple 68 50 70 41 46 / 5 0 20 40 0 Mineral Wells 61 45 71 35 42 / 0 0 30 30 10 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 30/05