DFW FORECAST DISCUSSION
000 FXUS64 KFWD 152118 AFDFWD Area Forecast Discussion National Weather Service Fort Worth TX 318 PM CST Fri Feb 15 2019 .SHORT TERM... /Through Tonight/ Big temperature changes coming to North and Central Texas tonight. 1800Z surface analysis revealed a 1004 mb surface low over Dallas. A cold front runs through this surface low out into West Texas, and to the east into southern Arkansas. This cold front demarcates the boundary between continental arctic (cA) air to the north and maritime tropical (mT) air to the southeast of the surface low. The air mass over East Texas is characterized by temperatures in the 70s and dewpoints in the 50s, while the air mass to the north of the cold front over the Sooner State is characterized by temperatures in the 30s and dewpoints in the 20s. The cold front has been shy about moving south through the day with little in the way of upper-level support to encourage it to continue southward. The southward push should begin forthwith however as an upper-level shortwave trough along the lee of the Colorado and New Mexico Rockies ejects into the Great Plains. The cold front should clear Dallas/Fort Worth in the next few hours, and reach the Killeen/Temple/Waco area a little after sundown. Cold air advection behind the front will result in rapidly falling temperatures, with lows tonight expected to drop into the 30s for the northern two-thirds of our forecast area, and into the 40s in our two southeasternmost tiers of counties. A light freeze is expected in rural areas north of Interstate 20 (the urban heat island effect should keep overnight lows in the Dallas/Fort Worth Metropolitan Area just above the freezing mark). While winds will not be particularly strong overnight, northerly winds at around 10 MPH will result in wind chills in the 20s for most areas north of Interstate 20 (including in Dallas and Tarrant Counties). In terms of precipitation potential, the 1200Z RAOB from Fort Worth showed very dry air immediately above the boundary layer ahead of the cold front, with both mid-level and low-level mean relative humidity values below 35%. This lack of moisture should keep precipitation chances near zero through the overnight period. Godwin && .LONG TERM... /Saturday through Next Week/ Main focus of the long-term forecast is the return to a southwesterly mid/upper flow regime through most, if not all, of next week, and a resultant increase in precipitation chances (primarily on Tuesday). Right now, we are not anticipating any significant winter-weather impacts across our area, but surface temperatures will be close to freezing across western North Texas so this area will likely be the largest focus going forward. More info below. In the meantime, Saturday presents another tricky temperature forecast, with a large gradient possible across North and Central Texas. Low clouds, in association with the frontal surface aloft, are forecast across much of the region during the morning hours. Through the day, though, strengthening west/southwesterly flow aloft and increased low-level mixing will advance east across the region. Cloud cover is expected to gradually diminish from west to east through the day, but broken/overcast skies will likely hold steady east of I-35 and north of I-20 into the afternoon/evening. Therefore, forecasting a tight gradient in high temps (mid 70s southwest, near 50 northeast) and these cooler conditions may not be cold enough. Later updates may have to tweak highs downward for locales in the direction of Sherman/Bonham/Paris/Sulphur Springs. Additionally, some patchy drizzle will be possible across East Texas during the day, under the influence of poleward 925mb theta-e advection. A passing front brings a low chance for light showers across East Texas Saturday night. Then temperatures cool on a broader scale Sunday and especially Monday, as high pressure builds over the central/southern Plains in response to building heights aloft behind a Missouri Valley system. Conditions should be relatively dry, although strengthening southwesterly mid/upper flow will likely yield a solid plume of upper-level cloud cover across Texas into early next week. Meanwhile, in the western-US pattern that can`t stop (won`t stop), another strong jet streak will drop south along the Pacific Coast Monday, amplifying an already well- established trough over the Inter-Mountain West. Ahead of this trough, isentropic ascent atop a shallow, cold air mass will stream low-level clouds northward Monday night. Precipitation chances will increase accordingly and should be light initially. Towards Breckenridge/Graham/Bowie, surface temperatures may be close to freezing initially, although guidance continues to suggest any potential for more significant issues will be just northwest of our area. Still, given the proximity of sub-freezing temps and also potential for wet-bulb cooling, have advertised a slight chance of freezing rain across the far west/northwest Tuesday morning. With only marginal surface temperatures, though, believe the potential for significant impacts is low at this time. Expect a cold rain everywhere else on Tuesday, as temperatures range from the mid 30s to upper 40s. The amount of precipitation over Central and North Texas will likely be a function of the amplification of an ejecting mid/upper system over the Plains (related to the jet streak discussed above), given its impact on low/mid- level thermal advection and frontogenetic ascent. The 15/12Z ECMWF cycle suggests a more amplified solution, but this potential remains uncertain. Regardless, a developing cyclone ejects northeast across the lower Mississippi Valley Tuesday night, which should bring drying mid levels and an end to any deeper precipitation processes. There could be a quick mix of light rain/snow (once again across far northwestern areas) before precipitation ends Tuesday night, in tandem with a cooling column behind the aforementioned departing low. Still, not anticipating any notable impacts at this time due to precipitation ceasing before surface temperatures cool dramatically. The region remains under the influence of southwesterly flow aloft and a switch to low-level return flow by late week. Temperatures are expected to modify slowly, but precipitation timing/distribution remains of low predictability, due to the subtle nature of shortwave troughs within the broader synoptic regime. In turn, only show slight rain chances by Friday. Picca && .AVIATION... /Issued 1216 PM CST Fri Feb 15 2019/ /18z TAF Cycle/ The main concern continues to be the wind shift expected in the next couple of hours, as the ongoing stationary front slowly moves south and out of our area. North winds 10-12 knots will prevail, but there will be a brief window late afternoon into the evening where winds could gust up to 17-20 knots. So far, the low clouds have remained north and east of the DFW Metroplex and Waco area this morning. Overall, VFR conditions will continue, but some of the guidances are moving some of the low level clouds near the DFW Metroplex tomorrow afternoon. Confidence is low at this time to introduce MVFR cigs, but trends will be monitored this evening and will make the necessary adjustment to the forecast. Sanchez && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 34 57 41 60 34 / 0 0 5 0 5 Waco 39 65 45 61 39 / 0 0 5 0 10 Paris 35 50 41 58 33 / 0 0 10 0 5 Denton 31 55 38 57 31 / 0 0 5 0 5 McKinney 33 51 40 58 33 / 0 0 5 0 5 Dallas 36 58 44 60 35 / 0 0 5 0 5 Terrell 37 57 45 60 36 / 0 0 10 0 10 Corsicana 40 61 48 62 39 / 0 0 10 0 10 Temple 42 68 48 64 41 / 0 0 5 0 10 Mineral Wells 32 61 39 60 31 / 0 0 5 0 5 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 11/37