115 FXUS64 KFWD 280843 AFDFWD Area Forecast Discussion National Weather Service Fort Worth TX 343 AM CDT Mon Oct 28 2019 .SHORT TERM... /Today and Tonight/ The challenge over the next 24 hours will be the position of the cold front and thus temperature and PoP forecasts. Confidence is high that the best rain chances will be late tonight into early Tuesday. While PoPs are in the 40 to 50 percent range, rain amounts are expected to be less than 1/2 inch. Early morning surface analysis revealed that the slow moving front was draped near a Hamilton to D/FW to Sherman/Denison line. Upstream pressure rises are quite meager and without a strong surge of colder air southward, it's likely that the front will only slowly progress to the east and southeast. GOES 10.3-3.9 micron difference channel indicates low level moisture---manifest in low stratus and fog---was slowly beginning to slosh back towards the west. VWP data from Metroplex radars sampled about 15 to 20 knot flow out of the south and southwest. These speeds should come down thanks to the looser pressure/height gradient associated with the front. At this time, observations are generally in the 1-3 mile range across East Texas and given the likely shallow nature of the moisture, I expect that any dense fog will be brief in nature and mix out quickly after sunrise. With these factors in mind, I will forgo any dense fog headlines for now. If visibilities rapidly deteriorate over the next 1-2 hours, it is conceivable that one may be needed. Through the day, the frontal boundary will likely meander somewhere near a Lampasas to Dallas to Bonham line. While there will be modest ascent atop this boundary, it appears unlikely that enough moisture exists in the lower troposphere for widespread measurable rain through the afternoon. Cloud cover will steadily expand in area as moisture advection continues. With regard to the temperatures, I've sided closely with the latest RAP guidance which seems to have a decent handle on the current and expected position of the front. In the warm sector, temperatures are forecast to climb into the 70s...with a few areas across Central Texas climbing to or just above 80 degrees. Behind the front, temperatures will be below normal with readings in the 50s and 60s. If cloud cover thins some, it's possible that current forecast temperatures in the post frontal airmass are too cool. 850-700mb WAA will increase some this afternoon as jet entrance forcing from a 80-90kt speed max sets up across Oklahoma and southern Kansas. Model guidance initially outputs a large area of measurable rainfall this afternoon, but closer look at forecast soundings from Stephenville...D/FW and Gainesville indicate that the moist layer just above the surface will be quite shallow. I've undercut some of the higher PoP forecast advertised by models and focused the highest rain chances (only about 20-30 percent) north of I-20, closer to the proximity of the synoptic scale ascent within the RRQ of the aformentioned upper jet. I've also inserted a mention of patchy drizzle into the forecast for this afternoon for areas along and north of I-20 as well given the shallow moist layer aloft. The magnitude of WAA increase further tonight and into the pre-dawn hours on Tuesday and the cold front should start to make a run at Central Texas and the Brazos Valley. I've made noticeable changes to the forecast and increased PoPs up to near 50% for a good portion of the area. Instability looks very low and with the steeper lapse rates focused below 0 C...thunder does not appear probable (though non-zero). As noted above, the QPF is very light with totals generally less than 1/2 inch. Colder air will slowly spill southward, with most locations in the 40s and 50s for overnight lows on Tuesday morning. The exception will be down across the Brazos Valley, where overnight lows may remain near 60 degrees. Bain && .LONG TERM... /Tuesday through the Weekend/ A digging low over the Great Basin and subsequent pressure falls in the lee of the Rockies will cause a cold front to stall over east/Southeast Texas during the day Tuesday. Strengthening upglide above the frontal layer will occur as the upper low progresses east into Colorado, creating an uptick in precipitation as we get into Tuesday afternoon. Scattered showers should become numerous Tuesday afternoon and be accompanied by isolated embedded thunderstorms as we enter the evening hours. Recent guidance continues to advertise that the front will be positioned near or immediately south and east of our forecast area. This location becomes somewhat important not only for the temperatures forecast, but will determine where any surface-based convection may occur. If so, convective parameters indicate that a few storms may be capable of gusty winds, with this potential likely confined to south of I-20 and east of I-35. For most of the region, however, convection will remain elevated, with threats from stronger cells being limited to hail and locally heavy rain. Wet weather will continue Tuesday night and persist for much of the day Wednesday. Wednesday high temperatures will range from the mid and upper 60s across the southeast in the vicinity of the front to the 40s across the northwest zones. Periods of light to moderate rain should produce another round of widespread 48 to 72 hour rainfall totals in the 1 to 2 inch range, though slightly lower amounts are forecast as you go west of Highway 281. Localized totals of 3+ inches are not out of the question based on the arrival of 1.5" PWATs, especially if cells containing heavier rain happen to train over one location. This may result in isolated instances of flooding, but at this time widespread or major flooding/flash flooding is not expected. A second and much stronger push of cold air will arrive on Wednesday as the upper low enters the Plains, which will push the front well south and into the Gulf Wednesday night. Precipitation will end from west to east during the late evening and overnight hours as cold, dry air moves in from the north and subsidence spreads in from the west. POPs should come to an end at all locations Thursday morning. Locations along and west of Highway 281 will be affected by the coldest air and will drop to or slightly below freezing by daybreak Thursday. Any precipitation will have ended well before freezing temps are attained. Morning lows in the mid and upper 30s can be expected elsewhere. Skies will eventually clear during the day Thursday, but strong cold air advection will work hard to offset insolation, and highs will struggle to reach 50. Halloween evening/night is looking like a cold one as the post-frontal surface ridge axis moves in and winds go light and variable. Clear skies, light winds and dry air will allow overnight low temps to bottom out in the 28 to 32 degree range in the west, with lower and middle 30s expected elsewhere. The record low at DFW for November 1 is 31 degrees set back in 1906, so it will be interesting to see just how low we go. For this forecast, I am banking on the urban heat island affect to win out, and have an official forecast low at DFW of 34. Even so, outlying areas will likely drop to or possibly a few degrees below freezing by sunrise Friday. As the upper level low pressure system exits to the northeast, we will switch over to a dry pattern with several days of northwest flow aloft and a gradual warm-up through the weekend. 30 && .AVIATION... /Issued 1135 PM CDT Sun Oct 27 2019/ /06z TAFs/ No major changes from the previous TAF issuance, with flying conditions expected to deteriorate throughout the period. A cold front has stalled northwest of the DFW Metroplex, and winds are light and variable in its vicinity. Ahead of the front, low-level moisture is surging into the area, which is leading to an expansion of low stratus into East Texas. These low cigs along with areas of fog will continue spreading westward towards the frontal zone by morning, and a window of IFR/LIFR cigs are possible roughly along and east of I-35 around daybreak. Have maintained Tempo groups to account for this potential at eastern Metroplex airports, as well as Waco. Am expecting the greater fog potential to remain east of the TAF sites, although this will be monitored over the next several hours. Conditions should improve later in the morning, albeit temporarily, with VFR cigs prevailing during the day Monday. The stalled front will receive a secondary push southeastward Monday afternoon and evening, resulting in a gradual wind shift to west and northwest over the course of several hours. Post-frontal MVFR stratus should also overspread the TAF sites beginning Monday evening. As ascent increases above the frontal inversion, light rain and drizzle should be able to develop, leading to a reduction in visibility. Cigs will continue lowering through the evening and overnight hours with widespread MVFR/IFR conditions likely at all airports. Have not introduced IFR conditions with this TAF package, although they could exist as early as midnight, and they'll undoubtedly be needed in subsequent TAFs. -Stalley && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 67 47 57 50 57 / 10 50 60 80 80 Waco 76 54 64 55 62 / 10 50 60 70 90 Paris 68 49 62 54 62 / 10 50 50 80 90 Denton 65 43 52 48 54 / 10 40 60 80 80 McKinney 69 46 56 50 57 / 10 50 60 80 80 Dallas 69 48 57 52 58 / 10 50 60 80 80 Terrell 72 51 63 55 62 / 10 50 50 80 90 Corsicana 72 56 65 56 62 / 5 30 60 70 90 Temple 80 57 64 57 61 / 10 30 60 70 90 Mineral Wells 62 42 50 44 50 / 10 50 50 80 70 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 24/30