Scientific Forecaster Discussion
000 FXUS64 KLCH 201755 AFDLCH Area Forecast Discussion National Weather Service Lake Charles LA 1155 AM CST Mon Feb 20 2017 .DISCUSSION... 20/18Z TAF Issuance. && .AVIATION... A mix of MVFR/VFR cigs acrs the area this morning with an area of rain spreading east into SE TX. The leading band of convection is now approaching BPT where prevailing SHRA and isltd TS expected through early evening. The area of rain will spread slowly east today reaching LCH by 21Z, AEX by 22Z and further east toward LFT/ARA by 00Z. Through the aftn, isltd TS will be possible with the lead band as it moves east, with TS potential diminishing this evening with decreasing instability/loss of heating. Prevailing cigs will lower to MVFR as the rain shield moves east with periodically lower cigs/vsbys in heavier SHRA. SEly winds around 10 kt will weaken and become VRB this evening through Tuesday morning. SHRA will decrease from west to east late this evening through Tuesday morning, with IFR conditions in low cigs/fog lingering in its wake. 24 && .PREV DISCUSSION... /issued 1045 AM CST Mon Feb 20 2017/ DISCUSSION... Regional 88Ds show the expected rainfall event playing out as expected with a large area of precipitation beginning to make its way into our far wrn zones. Convection had been on the wane the previous couple of hours but is showing signs of recovery last half-hour or so with multiple cells popping up along the leading edge of the band. Previous forecast was in good shape with just minor tweaks to POPs. Although rain looks to be heavy at times, still not expecting flooding issues so not planning any flood watch issuances at this time. Elsewhere, inherited grids/zones look good as is based on latest obs/trends. 25 PREV DISCUSSION... /issued 524 AM CST Mon Feb 20 2017/ DISCUSSION... 12z taf issuance. AVIATION... MVFR to IFR ceilings this morning ahead of the area of TSRA over SE TX. This area of TSRA will slowly spread/develop eastward over SE TX later this morning, and into LA this afternoon and evening, showing this progression in the terminals. SHRA/TSRA expected to end from west to east between 06-12z TUE. DML PREV DISCUSSION... /issued 434 AM CST Mon Feb 20 2017/ DISCUSSION...Low level jet at 850 mb of 30-40 kts has now overspread the area ahead of a vigorous and sharp mid/upper level trof advancing east across west Texas. Feature will be the focus of a very unsettled weather pattern over the next 24 hours. Aforementioned jet among other things acting to mitigate any inland fog development this morning. Have seen a continuation of sea fog over the near shore waters and have a dense fog advisory out until 9 AM. Rains will eventually end this issue as the day progresses. Regional radar depicting a couple of lines of active convection at this time over east Texas. More eastern line appears focused along axis of strong warm advection in conjunction with low level jet maxima. Line further to the west more in line with surface trof and associated low level convergence. East Texas rains will be spreading west to east across the forecast area through today and tonight. Deep moisture on a strong southerly flow through the column will be transported over the region with precipitable water values maxing out near record levels aided by the unusual mid-February warmth. Expecting much of the area to see 1.5-2.5 inches. Have maintained locally heavy rainfall possible wording in forecast. Weather prediction center has the forecast area within a marginal risk of flooding rains. Rain chances then diminish Tuesday as the mid/upper low advances across south Louisiana then dips southeast into the north- central gulf. A dry weather pattern then is ahead through the remainder of the week. A dry frontal passage is on tap for late Friday into early Saturday bringing somewhat cooler temperatures for the weekend. MARINE...Dense fog will remain into this morning as a long fetch of relative warm and moist southeasterlies advance over the cooler shelf waters of the northwest gulf. widespread shower and thunderstorm activity is expected today, lessening Tuesday as low pressure advances east through Texas and into the gulf waters. a brief northerly flow will develop in the wake of the low for Tuesday, returning to onshore Wednesday and holding until our next frontal passage expected late Friday into early Saturday. 23 && .PRELIMINARY POINT TEMPS/POPS... AEX 76 59 72 56 / 60 80 40 10 LCH 75 60 73 58 / 80 80 40 10 LFT 76 62 73 58 / 50 80 50 20 BPT 73 60 74 58 / 90 80 30 10 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...None. TX...None.