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Displaying AFOS PIL: AFDFWD Received: 2019-09-22 09:25 UTC
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907 FXUS64 KFWD 220925 AFDFWD Area Forecast Discussion National Weather Service Fort Worth TX 425 AM CDT Sun Sep 22 2019 .SHORT TERM... /Today and Monday/ The main concern in the short term forecast period will be the risk for showers and thunderstorms across parts of the area. Widespread severe weather is not expected, but heavy rain may result in some flood issues near and north of US HWY 380 over the next 24 to 36 hours. A conveyor of rich moisture associated with T.S. Lorena continues to stream northward ahead of a trough now positioned across the Four Corners region. This moisture plume has resulted in multiple waves of showers/storms across West Texas---some of which may skim portions of our Big Country and western Texoma counties this morning. Associated with the Four Corners trough is a cold front that is steadily oozing southward into the Central and Southern Plains. These three weather features will result in rain/storm chances for North Texas and parts of the Big Country. Current indications are that the cold front will progress southward through the day today with occasional quicker surges southward as portions of the boundary are reinforced by convective cold pools. The aformentioned trough has been progged by the general model consensus over the last several days to translate eastward across the Panhandles. As this front slows near the Red River, forcing from the ageostrophic response beneath the entrance region of a 90 knot upper level jet streak around the base of the trough, in tandem with low level moisture convergence along the front, should result in an eruption of convection across southwestern Oklahoma and adjacent portions of North Texas. Most HREF members agree that convective initiation is probable by 2100 UTC today. The coverage, unfortunately, is a little uncertain, but given the aformentioned synoptic background, it appears that scattered to numerous showers and storms are a good possibility across the region this afternoon/evening. I've nudged PoPs upward into the likely category for this timeframe across areas west and north of the D/FW Metroplex given the decent agreement among many HREF members. PoPs generally taper downward toward 20 percent closer to I-20. Rain/storm chances across the Brazos Valley and Central Texas today are associated with streamer showers penetrating the underbelly of the mid-level ridge this morning, then afternoon convection associated with the reinforced sea-breeze front expected to drift northward. The potential for severe weather will be limited across North Texas as deep layer shear is expected to remain paltry further away from the core of the stronger mid/upper level flow. Deep layer shear vectors are largely parallel to the slow moving cold front, and with PWAT values forecast to be 175% of normal, there will be a heavy rain and subsequent flood risk. The moist regime may also promote some precipitation loading and a gusty downburst risk in the afternoon hours, but the flood threat appears more appreciable. 48 hour MRMS rainfall data appear to line up well with automated gauges and indicate that some areas along the Red River received between 2 and 4 inches of rain on Friday. With the potential for training convective cells over some of these areas, there will be a heightened risk for flooding. Confidence in the exact placement of the heaviest rain this afternoon/evening precludes the issuance of a Flood Watch for any of our counties at this time. Moreover, I expect that most of the flood issues can be handled with advisories. Otherwise, temperatures today will climb into the upper 80s (across the Red River) to mid 90s (across Central Texas). Extended reaches of hi-res guidance hint at another potential for showers and storms on Monday. Initially, convection may fire near/ west of US HWY 281 where modest flow atop the stalled frontal boundary/residual outflow may be sufficient to lift parcels upward to their LFC. Confidence in exactly where the boundary stalls is a little on the low side, but the scenario advertised by model guidance seems reasonable. For now, I'll paint a large area of 30-40 PoPs with the greatest rain/storm chances across the Big Country. Cooler conditions are forecast on Monday given the potential for rain/clouds. Unfortunately, a good portion of the area will remain in the 90s...except along the Red River and across parts of the Big Country where highs may remain in the 80s. Bain && .LONG TERM... /Tuesday Through Next Weekend/ A full-latitude trough will make landfall on the West Coast today. Despite spending a considerable amount of time over the relative data void of the North Pacific, guidance has been in lockstep with its evolution over the western U.S. early this week. It will become a closed low near Las Vegas on Monday, digging even more equatorward on Tuesday. It is at that point that an upstream jet streak emerging from the Pacific will pinch off the low, which will spend the middle of the week stranded in the Desert Southwest. Despite the calendar's transition to astronomical autumn, subtropical ridging will attempt to maintain power. But the proximity of the cut-off low upstream will keep a mid-level weakness in place, beneath which an onshore fetch will sustain a supply of unseasonably rich tropical moisture. Although the ridge's position will limit the extent of convection (while pushing afternoon temperatures into the 90s each day), the weather will remain a bit unsettled. The bulk of the convective activity Tuesday through Thursday will be within the more vigorous westerly flow through the Panhandles and Oklahoma, but some of this activity may be inclined to slip south of the Red River. This would apply to both nocturnal convection into the daylight portion of the mornings and the peak heating of the afternoons. More scattered (primarily diurnally driven) showers/storms will be possible elsewhere. Forecasters often bemoan the unpredictability of cut-off lows, but this particular version is remarkably well behaved with no more model spread than any other feature would have at day 5. Latest runs continue to project a northeastward ejection through the Texas Panhandle with the time more narrowly focused on Friday. Far removed from the forcing, North and Central Texas may miss out on the associated precipitation entirely. Ridging will attempt to retrograde back into Texas next weekend, but the tropical conveyor on its western periphery may keep the unsettled weather in place. 25 && .AVIATION... /Issued 1122 PM CDT Sat Sep 21 2019/ /06z TAFs/ While VFR conditions currently prevail at the TAF sites, another round of MVFR stratus is expected overnight. The onset of low cigs should occur around 09-10z at Waco and closer to 11-12z across the DFW area. Stratus is likely to be less widespread than the previous couple of nights, although at least some intermittent cigs will be possible through mid to late morning at any of the TAF sites. Cig heights will predominantly be at or above 2 kft, although some may briefly fall into the 1-2 kft range. Conditions should improve to VFR at all airports by late Sunday morning. Scattered afternoon convection is expected across parts of North Texas and southern Oklahoma, but at this time, am expecting all activity to remain north and west of the TAF sites. Will maintain rain-free TAFs for the time being, but northern arrivals/departures may be affected. South winds are expected to prevail, although outflow boundaries from any convection could result in temporary wind shifts late Sunday afternoon or evening. -Stalley && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 95 75 92 75 92 / 10 40 30 20 30 Waco 94 73 95 73 94 / 10 10 10 10 20 Paris 89 72 86 72 86 / 10 30 60 40 50 Denton 92 74 88 74 91 / 10 60 40 30 40 McKinney 93 74 89 74 91 / 10 40 40 30 40 Dallas 95 76 92 76 93 / 10 40 30 20 30 Terrell 93 74 94 74 93 / 10 20 30 20 30 Corsicana 95 72 93 72 91 / 10 10 20 10 20 Temple 94 72 94 72 91 / 10 10 10 10 20 Mineral Wells 92 71 89 72 91 / 20 50 40 20 30 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 25/24