643 FXUS64 KSHV 091804 AFDSHV Area Forecast Discussion National Weather Service Shreveport LA 104 PM CDT Tue Oct 9 2018 .AVIATION... A line of convection slowly breaking up as it moves closer into area from the west. Prevailing tstm conditions may hold at ktyr and possibly kggg and ktxk by 09/20-22z. Elsewhere, Isold showers developing with increased scattered tstm potential by 09/20z. Some storms may contain wind gusts over 40 kts. A line of convection assoc with cdfnt slowly movg east across area after 10/03 at ktyr and movg east of kmlu after 10/12z. South winds around 10 kts this aftn becmg lgt later tonight with patchy fog and low clouds possible outside of rain and storms overnight. Fropa bringing nw winds 5 to 10 kts and cigs becmg high mvfr to low vfr to possible scattered before the 10/18z fcst cycle./07/. && .PREV DISCUSSION... /issued 1118 AM CDT Tue Oct 9 2018/ UPDATE... Line of weakening convection approaching western portions of area late this morning. These storm have a history of stg winds and heavy rain so wil make mention of that this aftn across western zones but not expecting flooding or svr this aftn. Have lowered rain chances slightly this aftn further east with daytime heating triggering scattered convection by early to mid aftn. Daytime highs will reach the upper 80s to possible near 90 where thinning of clouds over Northcentral La/Southcentral AR, with more limited heating further west with highs in upper 70s to lower 80s expected./07/. PREV DISCUSSION... /issued 402 AM CDT Tue Oct 9 2018/ SHORT TERM.../Today through Wednesday/ Vigorous synoptic pattern across the Lower 48 this morning defined by a well established ridge of high pressure aloft across the Eastern Seaboard, a well defined longwave trough axis across the Great Basin into the Intermountain West and Hurricane Michael taking up residence across the Southeast Gulf of Mexico. While Michael should not be a player for our region through the short term, what will be a significant player in our weather will be the trough to our west. Strong southerly flow through all levels of the atmosphere across the Southern Plains and Lower Miss Valley will continue to pump moisture into our region as we await the effects of the trough to our west late this afternoon through the evening and overnight hours for the possibility of strong to severe thunderstorms across our northwest third. Convection coverage should really ramp up this afternoon across most of our region but the more significant convection should be coming together near and just to the west of the I-35 Corridor of Central and North Tx into Central Ok by Noon today with this activity expected to make quick progress eastward, nearing the Middle Red River Valley of Northeast Texas, Southeast Oklahoma and extreme Southwest Arkansas near or just before 00z this evening. Unidirectional shear values throughout a deep portion of the atmosphere suggests a broken squall line nearing the I-30 Corridor late this afternoon/this evening with damaging thunderstorm wind gusts the most likely severe weather threat with any bowing segments that emanate from the line. SPC has our extreme northwest zones outlooked for a Slight Chance of severe weather late this afternoon through the evening hours and this looks plausible given the above mentioned parameters. As the line moves further east overnight into more of Southwest Arkansas, Northwest Louisiana and Northeast Texas, we lose more of the upper level support with the longwave trough lagging behind the eastward moving convection. Still could see some strong storms further east of the Slight Risk area but given the fact that as the storms move further east overnight, they will be encountering a more stable boundary layer which suggests storm intensity should fall off even through storm coverage will remain very high. A strong cold front will swing in behind the convection late tonight and should be east of the I-30 Corridor by 12z Wed, and through all but our extreme southeast parishes in Northeast Louisiana by 18z Wed. Much cooler temperatures will be felt in the wake of this boundary for Wed and continued through the remainder of the work week which will be detailed in the extended forecast package discussion. 13 LONG TERM.../Wednesday Night through Monday Night/ An upper trough axis extending from a deep low in Minnesota should be moving east of the forecast area by late Wednesday. Farther to the east, Hurricane Michael should be moving northeast into Georgia. Any precip should be east of the area by Wednesday evening. The flow aloft will remain southwesterly behind the departing upper trough. However, northerly surface winds will advect some cooler and drier air into the region. Combined with mostly clear skies, overnight low temperatures Wednesday night/Thursday morning should fall into the low 50s to low 60s. Thursday night/Friday morning should be even cooler as light winds and more dry air advection will keep most locations in the 50s. Portions of Southeast Oklahoma may fall into the upper 40s. During the weekend, the remnants of Hurricane Sergio from the Eastern Pacific will move east-northeast and into the Southern Plains while merging with another broad upper trough. Rain chances will begin to gradually increase from northwest to southeast beginning during the day Saturday. Increasing southeasterly surface winds should also bring additional low-level moisture into the region from the Gulf of Mexico. The large upper trough will also help to push a cold front towards to the area, which should provide an additional focus for convective development Saturday night and into Sunday. Medium range guidance shows considerable disagreement with this setup. The latest GFS has most of the rain occurring with the remnants of Sergio and quickly moves the precip out of the area by Monday morning. The ECMWF is much slower and has considerably more precip with the cold front. It is worth noting that the GFS shows better agreement with the ECMWF in regards to the speed of the main upper trough axis. Therefore, I favored the slower ECMWF and kept at least slight chance PoPs in the forecast through Monday afternoon. Besides the rain, the big story will be the cold air behind this front. Daytime highs next Monday and Tuesday may stay below 70 degrees F across most of the forecast area, and overnight lows Monday night/Tuesday morning should fall into the mid 40s to near 50 degrees F. CN && .PRELIMINARY POINT TEMPS/POPS... SHV 83 73 84 58 / 50 90 30 0 MLU 90 74 84 60 / 40 70 60 10 DEQ 78 68 79 53 / 60 100 30 0 TXK 81 69 79 54 / 50 100 30 0 ELD 89 72 80 57 / 40 100 50 0 TYR 79 66 78 56 / 60 90 20 0 GGG 81 68 82 57 / 60 90 20 0 LFK 83 71 84 60 / 50 70 30 0 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...None. OK...None. TX...None. && $$