####018007292#### FXUS64 KFWD 181840 AFDFWD Area Forecast Discussion National Weather Service Fort Worth TX 140 PM CDT Thu Apr 18 2024 ...New Short Term, Aviation... .SHORT TERM... /NEW/ /Through Friday Night/ An active afternoon is in store for some of us across North and Central Texas as a fairly decent cold front continues its way across the region. As of 1 pm, surface analysis shows the front entering the northwestern zones from Montague to Stephens counties. Isolated to scattered showers and storms are still expected to develop this afternoon and evening as the front moves through. While the overall timing of the storms hasn't changed much from previous forecasts, some of the latest high-res models are pushing storm initialization closer to 5-6 pm and perhaps just east of the I-35 corridor. Based on the latest ACARs soundings, it looks like the environment is still capped, but surface heating through the afternoon should help with buoyancy. There is a potential that storms won't develop or remain very isolated until the the front moves east of I-35 into East Texas. Not everyone will see showers/storms as the front moves through their location. With very high instability in place, IF storms are able to develop, they will be capable of becoming severe with large hail as the main threat. Very large hail (up to 2.5 inches in diameter) can't be ruled out with some of the more intense supercells. The threat for damaging winds will be there as well, especially with some of the storm clusters. The tornado threat is low, but we can't completely discard a brief spin-up with any bowing segment. The good news is that the threat for storms and severe weather for any location is brief as the front steadily pushes eastward through this evening. Most of the activity should be east of us after midnight, but breezy northerly winds will continue through tomorrow morning. Dry and cooler conditions are expected on Friday with high temperatures staying in the 60s and 70s under mostly cloudy skies. Sanchez && .LONG TERM... /Issued 248 AM CDT Thu Apr 18 2024/ Update: /Friday night through Wednesday/ The long term portion of the forecast has not changed much over the past few days and the detailed discussion below covers the specifics very well. We still anticipate an extended period of rain and storms this weekend with the highest rain chances on Saturday. Locally heavy rainfall will still be the primary hazard. The rain will come to an end Sunday but will return to the forecast around the middle of next week. 79 Previous Discussion: /Friday Through Mid Next Week/ By daybreak Friday, the aforementioned cold front is expected to be slowly drifting or stalled near or just north of the Hill Country as it becomes oriented parallel to the upper-level flow. Moisture advection overtop of the shallow frontal surface should quickly yield widespread dense cloud cover early Friday. By the afternoon, an approaching weak shortwave trough embedded within the zonal flow aloft...in combination with the established isentropic ascent regime...will lead to isolated to scattered showers and thunderstorms developing in the vicinity of the 850mb front, which is expected to still be draped across North Texas (near the Red River). Rain/thunderstorm chances will increase Friday night in response to increasing large scale lift associated with another weak shortwave shifting across Central/South Texas. While buoyancy will be somewhat limited, there should be sufficient elevated instability for convective elements/embedded thunderstorms capable of producing small hail late Friday into early Saturday. With PWAT values near or exceeding the 90th percentile of the daily climatological mean, locally heavy rainfall may lead to flooding impacts on Saturday, especially wherever higher convective rain rates materialize. The prevailing drought and drier antecedent conditions in the southwest portions of our forecast area will likely limit most flood concerns in this area. However, ponding or minor nuisance flooding cannot be completely ruled out. Conversely, given the degree of soil saturation in areas east of the I-35 corridor and current reservoir conditions, rapid surface runoff and minor river flooding issues are likely to emerge this weekend. In general, 1.5 to 2.5 inches of rainfall is expected with isolated higher totals possible. There is a 30-40% chance that total accumulated rainfall exceeds 3 inches in a few different areas across North and Central Texas. Increasing subsidence in the wake of the departing shortwave should bring an end to rain chances by Sunday afternoon with drier conditions prevailing through early next week. In contrast to the unseasonably hot temperatures in the short term period, temperatures will fall from near/slightly below normal to as much as 15-20 degrees cooler than 1991-2020 averages by Sunday. This is due to weak cold air advection behind the cold front in combination with rain chances and extensive cloud cover. The surface high will shift east over the Lower Mississippi Valley Monday, allowing for onshore flow to return. The return of southerly winds and ample sunshine early next week will lead to a quick warm up with highs back into the 70s and lower 80s by Tuesday. 12 && .AVIATION... /NEW/ /18Z TAFs/ Concerns...Thunderstorms chances this afternoon. Breezy conditions through Friday morning. VFR cigs have returned to most sites as a cold front approaches the DFW Metroplex. Showers and storms are still expected to develop along the front during the afternoon and evening hours. Based on the most recent high-res guidance, a few storms may develop near the DFW sites between 21-23Z, and 01-03Z at KACT. To account for this potential, we introduced a TEMPO TSRA for all the sites. This activity should be east of the sites in the evening as the front continues to move east/southeast. Gusty northerly winds are also expected behind the front, staying breezy through early Friday morning. Another round of low cigs is forecast to arrive early Friday morning with MVFR ceilings prevailing through much of the day. Otherwise, surface winds will remain from the northeast around 10-15kt. Sanchez && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 56 70 59 65 50 / 20 5 80 90 90 Waco 59 73 62 70 51 / 30 5 50 80 100 Paris 54 67 54 59 48 / 40 10 80 90 80 Denton 52 68 55 62 47 / 10 5 80 90 90 McKinney 54 68 56 63 48 / 20 5 80 90 90 Dallas 57 71 59 64 51 / 20 5 80 90 90 Terrell 56 70 57 65 49 / 40 5 70 90 100 Corsicana 59 72 61 70 51 / 30 5 50 80 100 Temple 60 74 63 73 51 / 40 5 40 80 100 Mineral Wells 53 68 56 64 47 / 10 5 80 90 90 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ ####018006362#### FXUS63 KIND 181840 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 240 PM EDT Thu Apr 18 2024 .KEY MESSAGES... - Severe storms and locally heavy rain are possible this evening into tonight. - Colder but dry Friday through Monday. Some frost potential mainly north Sunday morning. && .SHORT TERM (Today and tonight)... Issued at 258 AM EDT Thu Apr 18 2024 Latest surface observations show surface high pressure building into the region. Winds have decreased dramatically from earlier this evening, and are now becoming light and variable. Skies have cleared and temperatures are falling quickly. Ideal radiational cooling potential will persist through sunrise and a couple more degrees of cooling are likely. A few locations may see lows in the upper 40s by dawn. After sunrise, winds gradually take on a southeasterly component as surface low pressure develops to our west. Yesterday's cold front did not make much progress southward, and rich moisture will advect back north through the day as the low strengthens. Convergence along the system's cold front combined with favorable dynamics aloft will set the stage for showers and thunderstorms by evening. Some of these storms may becomes severe, especially from IND southwestward. More details below. Regarding severe weather potential, we'll start with the bigger picture. Much of the driving energy for today's system lies in the mid-levels...namely, a potent mid-level vort max and associated speed max. Closer to the surface, a modest low-level jet will help instability and moisture advect back into the region. The primary axis of instability looks to be quite narrow, given the short amount of time taken to bring it back north. Still, enough instability is present to support convective potential into the overnight hours. Effective shear over 30kt could lead to some convective organization and thus severe weather. As for hazards, CAMs are in relatively good agreement on showing convection organizing into a line/broken line. Given the primary forcing mechanism being the surface cold front, this makes sense. The line may race ahead of the front during the course of the evening and lead to primarily a damaging wind threat. Model soundings show steep lapse rates (6.5-7.5 C/km) but relatively skinny CAPE...still, an isolated instance of large hail is possible especially earlier in the day when storms are still discrete. The hail threat may be more into Illinois before becoming mainly a wind threat into Indiana. This depends on how fast the transition to linear mode occurs. The tornado threat appears to be minimal and far to the southwest where better low-level instability and shear exists. As such near our southwestern border the line of storms will need to be watched mainly for QLCS spin ups...even though the treat is low. To summarize, the primary convective hazard is strong wind gusts with lower threats of hail and embedded tornadoes. Best timing places storms arriving at the Illinois/Indiana state line after about 6-8pm. Showers, storms, and the cold front should be mostly through the CWA by 12z Friday. Strong northwesterly winds are likely behind this boundary with gusts between 30-35kt at times. Winds diminish quickly during the day on Friday as the system departs rapidly to the east. We'll be left with a much cooler and dry day along with high cirrus clouds passing through at times. && .LONG TERM (Friday through Wednesday)... Issued at 258 AM EDT Thu Apr 18 2024 Friday through Monday... Central Indiana will remain on the southern side of a large upper trough through much of the period. This will keep most moisture confined to south of the area. A few smaller troughs will rotate through the large one. At the surface, high pressure will remain in control for much of the period. The surface high plus lack of significant moisture will lead to dry conditions. Colder air will remain in place cold advection continues at times. Highs will be in the 50s to lower 60s, with lows in the 40s Saturday morning and in the mid to upper 30s Sunday and Monday mornings. The coldest temperatures are expected Sunday morning and winds will be light. However, clouds may linger, potentially inhibiting frost formation. Will have to keep an eye on it. Tuesday and beyond... A stronger upper wave will move in around Tuesday, and this one looks to have more moisture with it. There remains some timing uncertainties with the system though. Will go no higher than chance category PoPs due to the uncertainty. For now, Wednesday looks dry, but that could change if timing of the aforementioned system changes. Temperatures will be closer to, but still below, normal. && .AVIATION (18Z TAF Issuance)... Issued at 240 PM EDT Thu Apr 18 2024 Impacts: - Thunderstorms moving in 01-02Z and lasting through 06-09Z - MVFR ceilings to move in after 03z and IFR possible from 05-10Z, visibilities may drop within storms - Winds sustained at 10 kts or higher from 00z and on with gusts up to 25 kts possible at times with storms Discussion: VFR conditions expected through early evening. Light and variable winds will start off the TAF period but are expected to increase this evening with the approach of a low pressure system. Winds will be southerly to southwesterly ahead of the system but will shift northwesterly during the late overnight hours and through tomorrow. High-level clouds will continue to increase through the day as the front approaches. By about 01-02z, showers and thunderstorms will begin working their way in from the west. Expect MVFR conditions from around 03 to 13Z with several hours of IFR ceilings possible with the passage of the storms and cold front. Visibilities may drop as well with the storms. The front should be through Indiana by 10z at the latest, and conditions will improve to VFR by the morning. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Eckhoff LONG TERM...50 AVIATION...KF ####018006215#### FXUS64 KMRX 181842 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 242 PM EDT Thu Apr 18 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (This evening through Friday) Issued at 237 PM EDT Thu Apr 18 2024 Key Messages: 1. Showers and thunderstorms expected overnight, stronger storm potential is quite low, and exists west of Knoxville. 2. A second chance for scattered strong thunderstorms exists Friday afternoon across the Tennessee valley. Gusty winds and large hail possible with the afternoon thunderstorms. Discussion: Cold front begins the period across Missouri and will march eastwards with time until making it to Tennessee by the end of the short term Friday evening. A couple rounds of showers and thunderstorms will exist in the warm sector ahead of the front. First round of showers and thunderstorms is expected overnight tonight. This means that the remainder of the evening today is expected to remain dry, so that's good news. Guidance indicates showers and storms tonight will generally ride the midlevel heights axis as the ridge continues to move off to our east by Friday morning. Given the time of the day being the most unfavorable for thunderstorm intensity and the ability of storms to mix winds down to the surface, not feeling aggressive with the idea of strong storms overnight. Additionally, the more recent CAM runs have backed off on storm cell intensity and organization for overnight. HRRR has trended towards an even more scattered, unorganized, depiction for overnight into morning storms. Still, a few rumbles of thunder are possible given elevated CAPE as the remnants of the convection from Western Kentucky and Middle Tennessee move into East Tennessee. Convection should exit or dissipate by mid-morning, yielding a few hour pause until the second round during the afternoon. An approaching 500 mb speed max moves from west to east across Tennessee heading into peak daytime heating, increasing flow aloft from 30 knots to 50 knots. Some of the guidance (notably the HRRR and high res NAM) depict a quick and robust recovery into Friday afternoon, along with a favorable convective initiation in the Tennessee valley to take advantage of their modeled environments. Hodograph shapes are fairly linear, and given the increasing flow providing plenty of effective shear, a risk for damaging winds and severe hail is possible. One big uncertainty is cloud cover is expected to be present in the morning through the afternoon storms, so not certain how that hinders the convective environment. Still, the environment will need to be watched for strong thunderstorms. && .LONG TERM... (Friday night through next Thursday) Issued at 237 PM EDT Thu Apr 18 2024 Key Messages: 1. Outside of rain chances on Sunday, drier and cooler conditions are expected into early next week, especially on Monday. 2. Rain chances and more seasonal temperatures will return by Wednesday and Thursday. Friday Night through Monday At the start of the period, subtle troughing will be in place across the eastern U.S. with a strong upper jet to our north. A cold front will be moving through the area ahead of high pressure expanding from the northwest. During this time, lingering showers and storms from the short term period will be exiting the area west to east with a shift to northwesterly flow. This will advect cooler and drier conditions into the area heading into the day on Saturday. Subsidence and efficient mixing will certainly allow for a drop in RH's into the 30s, but luckily low-level winds will be fairly light, not to mention the return of vegetation in most places. Heading towards Sunday morning, focus will turn towards a developing Gulf low, following the recent CAA. During the daytime, a shortwave will approach from the west with increasing upper divergence as the jet becomes centered over the northeast. The result will be increasing PoPs, especially further south where better moisture exists. By Monday morning, high pressure will be expanding from the west again, which will produce additional subsidence. Depending on how much cloud cover and MSLP gradient-induced winds linger, patchy frost will be at least possible in the morning hours. Notable height falls and recent CAA will keep temperatures fairly cool. Tuesday through Thursday High pressure will keep the area dry and mild on Tuesday. Heading towards Wednesday, another shortwave will pass to the north with a surface front also drifting southeastward from the central Plains. This will lead to an increase in rain chances Wednesday and Thursday. The overall pattern currently indicates a setup supportive of showers with only limited thunder coverage due to fairly cool low- levels. Moisture will also be fairly limited for the time of year, given PWATs of only around 1 inch. && .AVIATION... (18Z TAFS) Issued at 136 PM EDT Thu Apr 18 2024 CHA skies are imminent to clear out, otherwise VFR conditions will prevail until 12z in the morning. Overnight convection with TSRA possible at CHA, rain at TYS, and rain at TRI by the morning. Then all showers will end around or just after 14z, with afternoon convection beginning to develop by the end of the period. A MVFR cloud deck is likely to maintain after 12z for much of the region through the end of the TAF period. Winds are expected to be light, though gusty winds in any TS is possible. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 65 80 57 73 / 80 40 10 20 Knoxville McGhee Tyson Airport, TN 63 75 54 68 / 80 80 20 10 Oak Ridge, TN 62 77 53 69 / 80 80 10 10 Tri Cities Airport, TN 57 73 51 66 / 50 80 20 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...Wellington LONG TERM....BW AVIATION...Wellington