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Displaying AFOS PIL: AFDFWD Received: 2018-04-20 02:36 UTC
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720 FXUS64 KFWD 200236 AFDFWD Area Forecast Discussion National Weather Service Fort Worth TX 936 PM CDT Thu Apr 19 2018 .UPDATE... Made a few cosmetic changes to sky grids and thus overnight low temperatures north of I-20. Otherwise, the remainder of the short term forecast is in fantastic shape. High level clouds associated with a compact upper trough will continue to lift northward, though it looks like it'll be at a slightly slower rate than previously thought. As a result, have delayed the onset of clouds for areas near/north of I-20. With the dry air, diminishing wind speeds and clear skies, decent radiational cooling along the Red River appears probable and I've nudged overnight low temperatures down by a few degrees here. Elsewhere skies will be partly to even mostly cloudy at times. Otherwise, the rest of the forecast looks to be on track and no other changes were needed. 24 && .AVIATION... /Issued 719 PM CDT Thu Apr 19 2018/ 00 UTC TAF Cycle Concerns---None major. VFR will prevail with chances for virga on Friday morning. VFR will prevail through the TAF cycle with northeast to east winds. Wind speeds should subside after sunset this evening and will fall below 10 knots, likely around 0300 UTC. A weak impulse is forecast to lift out of the Rio Grande River Valley and could fling some mid/upper level moisture northward. Some high based showers may develop as lapse rates steepen, but the low levels should remain too parched for rain at the surface. There could be some turbulence at or below FL100 associated with virga, however, especially at the Waco TAF site. East winds will increase through the day on Friday with speeds near 10 to 15 knots. 24 && .SHORT TERM... /Issued 250 PM CDT Thu Apr 19 2018/ /Tonight and Friday/ Temperatures this afternoon are running about 10 degrees below where they were 24 hours ago as cold advection continues behind yesterday's front. Passing high cloud cover will occasionally result in partly sunny conditions, but skies should (temporarily) clear out across all of the area early this evening. A weak/subtle mid-level impulse will emerge out of Coahuila late tonight and into Friday morning and proceed to rapidly track into the Hill Country and Central Texas. Mid-level lapse rates will steepen (slightly) and the 700-400 mb layer will moisten ahead of this feature. This combination may just eke out a sliver of elevated instability Friday morning and into the early afternoon from I-35 and west. This might be just sufficient to result in some convective elements within the blossoming mid-level cloud deck, similar to what has been showing up in recent runs of the 3 km NAM's reflectivity output. That said, forecast soundings reveal a surfeit of dry air in the lowest 10,000 feet or so. In addition, isentropic charts show the more robust upglide/ascent relegated just to the west of our CWA in association with strong warm advection ahead of the primary upper-low ejecting into the Great Plains. As a result, think the signal tomorrow is more for virga or sprinkles roughly near and west of the I-35 corridor through midday. By late-afternoon and into the early-evening, better upglide will begin to leak into our northwestern zones where we've inserted low chances for showers or an isolated thunderstorm. Severe weather is not anticipated. With the forecast of thicker cloud cover (at least into the early-afternoon), sided slightly on the cooler side of guidance for high temperatures. Winds will gradually return to favor a southeasterly direction into the afternoon-hours, with some occasional wind gusts to 20 mph. Carlaw && .LONG TERM... /Issued 250 PM CDT Thu Apr 19 2018/ /Friday Night through Thursday/ A potent closed upper level low will charge eastward across the Southern Plains during the day Saturday. While these types of systems in mid to late April would normally bring us a significant threat of severe weather (as this mid and upper level pattern matches a severe weather high risk day in 2007), the low level airmass is both too dry and cool for such a threat this time around. Still there will be a small window for severe storms south of I-20 and west of I-45 in the late afternoon hours along an advancing front/dryline and ahead of a well organized surface low. Because the initial low level airmass is so cool, as the warm conveyor belt ahead of the upper low begins to translate into the area, it will invoke strong isentropic lift and widespread showers and a few storms. This activity will begin a few hours before dawn across the western and northwestern zones, and spread eastward during the morning hours. Rainfall coverage and amounts will be highest generally north of I-20 where isentropic lift will be enhanced along and to the north of an intensifying baroclinic zone (or organizing cold front). On average rain totals will be around 1 inch in this area, but isolated higher totals of 2 or 3 inches could result in minor flooding issues. Since dewpoint depressions will be high when the rain starts, evaporative cooling will force temperatures to fall or remain in the lower 50s in rainy areas. This cold pool enhancement will help the cold front slide southward during the day with the remaining warm sector getting progressively squeezed and cornered to the southwestern zones and far southern zones. Prefer the NAM/WRF suite of guidance which has a slightly faster cold front progression. The SW zones are the area of the CWA with the best potential for a few severe storms to develop in the mid to late afternoon hours, but the limited flow in the low levels and forecast CAPE values only between 500 and 1500 J/kg suggest just a marginal threat of severe hail and wind reports. A few of these storms could head northeast and cross the frontal boundary and pose an elevated hail threat farther northeast which is why the severe risk area is advertised as the greater region south of I-20 and west of I-45. Obviously if morning rain is limited across the southwestern zones and afternoon sunshine can occur, instability would be higher for more robust storms, so this is something we will be monitoring. For now will forecast highs only in the low to mid 70s in the SW zones ranging down to the mid 50s along the Red River. Rainfall will end from west to east late Saturday afternoon and evening as the trough axis clears the region and dry/cold advection kicks into high gear in the wake of the now accelerating cold front. Sunday will see gradually clearing clouds, occasionally breezy northwest winds, and seasonably cool temperatures. Highs will range from the mid 60s to lower 70s. Lows Sunday night should fall into the 40s area wide. Upper level ridging will prevail across the High Plains and southern Rockies for the early to mid part of next week which will place our region in northwesterly flow aloft. This will mean pleasant and tranquil weather for Monday and Tuesday, but as an upper wave drops through the Midwest on Wednesday it will push another cold front through the area. Model guidance is not in good agreement with the speed and position of the upper wave, so while there is reasonable confidence on the timing of the front early Wednesday, the rain forecast is very uncertain which also impacts the high temperatures. For now will stay conservative on rain chances and keep them at 20 percent and stick with the median of the model suite for the temperatures. Late in the week model guidance continues to show a lot of uncertainty. Some guidance breaks the ridge down and brings another closed upper low toward the region, while others are much slower with this system. It is just too early to pick a solution and thus the official day 7 forecast is also the median from the model guidance which shows temperatures near normal and slight chances of rain. TR.92 && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 49 69 54 61 50 / 0 10 20 90 40 Waco 48 70 52 67 51 / 5 10 20 70 50 Paris 43 65 51 62 51 / 0 5 10 90 60 Denton 46 67 53 60 48 / 0 10 30 90 40 McKinney 45 66 51 60 49 / 0 5 20 90 50 Dallas 49 69 54 62 51 / 0 10 20 90 50 Terrell 45 68 51 64 51 / 0 5 10 90 60 Corsicana 47 68 51 65 52 / 0 10 10 80 60 Temple 49 70 54 70 51 / 10 10 20 70 40 Mineral Wells 47 69 53 61 47 / 10 20 50 80 30 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 24/79