Scientific Forecaster Discussion
000 FXUS64 KLCH 290232 AFDLCH Area Forecast Discussion National Weather Service Lake Charles LA 932 PM CDT Fri Apr 28 2017 .UPDATE...Isolated showers have developed over the region through the past few hours. These showers are rapidly moving north and are generally producing light amounts of rainfall. The only update this evening was to start precip a bit earlier to match with the current trends, otherwise the forecast remains on target. && .PREV DISCUSSION... /issued 629 PM CDT Fri Apr 28 2017/ DISCUSSION... For the 29/00Z TAF Issuance. AVIATION... Gradient between high pressure over Southeast US and developing storm system east of the Rockies, will allow for windy conditions during the period with south winds between 15 and 20 knots, with gusts near 30 knots during the day on Saturday. The south winds will continue to bring in Gulf moisture with overcast ceilings mainly at MVFR levels around 1500 feet, although some periods of ceilings at IFR levels will be possible during the late overnight and early morning period. Most of the shower activity is expected to hold off until Saturday afternoon, with more widespread activity beyond the TAF period. Rua PREV DISCUSSION... /issued 507 PM CDT Fri Apr 28 2017/ DISCUSSION... Brisk and gusty south winds are expected to subside this evening, though will remain elevated along the coast, but are expected to begin intensifying again after midnight as a 40-50kt LLJ at H925 develops over the region downstream of an upper trof digging into the Four Corners and its associated SFC low over the Southern Plains. Have issued a wind advisory for coastal SE TX/SW LA beginning later tonight, with the advisory expanding east and then north on Saturday in tandem with the expected strong and gusty winds. Speeds of 20 to 30 mph with gusts to near 40 mph are expected. Winds will subside a bit over inland areas Saturday evening, but are expected to remain above advisory criteria along and south of I-10 into Sunday, ending from west to east with the passage of a cold front. This persistent and strong southerly fetch will result in above normal tides (around 1.5 to 2 feet above the astronomical tides), resulting in minor coastal flooding at the time of high tide SAT morning. From a convective standpoint, potential for isolated to scattered convection Saturday afternoon and evening continues as it appears one or more subtle impulses will translate through the SW flow aloft downstream of the main upper trof. Both shear and thermodynamic profiles will tend to become increasingly favorable for a severe risk through the day, so any late day activity will have some potential. Bulk of convection still appears like it will be tied more closely with the front itself, with this activity posing an attendant severe and locally heavy rainfall risk. There is generally good consensus on the timing of the front, with activity entering E TX after midnight SAT and exiting east of the Atchafalaya by early/mid afternoon SUN. Looks like an average of 1 to 2 inches of rain is expected areawide, with locally higher amounts possible. Progged PWATs suggest efficient rain producing convection, with most of this rain likely falling within a relatively short period of time. This could pose a risk of rate- driven low lying/urban type flooding, so will maintain the locally heavy rainfall wording. Drier and cooler air to push in behind the front SUN through MON, with temperatures starting to recover MON night as south winds return. Rain chances return TUE night and continue through THU as another upper trof impacts the region. 13 MARINE... Strong and gusty southerly winds will increase further tonight into SAT as a CDFNT approaches the area. Seas of 10-12 FT are expected over the outer coastal waters with 7-9 FT over the nearshore waters. Winds of 20 to 30 knots with gusts in excess of gale force are expected. In addition to the strong winds and rough seas, numerous showers and thunderstorms will move through the coastal waters late SAT night into SUN afternoon. as the front pushes through the area. Behind the front, winds will turn offshore and subside. 13 && .PRELIMINARY POINT TEMPS/POPS... AEX 75 86 70 74 / 20 40 90 90 LCH 78 84 68 75 / 20 40 90 90 LFT 78 87 75 81 / 10 30 40 100 BPT 78 85 66 78 / 20 30 90 60 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...Coastal Flood Warning from 5 AM to noon CDT Saturday for LAZ073- 074. Wind Advisory from 1 AM Saturday to 7 AM CDT Sunday for LAZ073- 074. Wind Advisory from 9 AM to 9 PM CDT Saturday for LAZ027>033- 043>045. Wind Advisory from 7 AM Saturday to 7 AM CDT Sunday for LAZ041- 042. Coastal Flood Advisory from 5 AM to noon CDT Saturday for LAZ041- 052. Wind Advisory from 7 AM Saturday to 11 AM CDT Sunday for LAZ052>055. TX...Wind Advisory from 1 AM Saturday to 7 AM CDT Sunday for TXZ215. Wind Advisory from 7 AM Saturday to 7 AM CDT Sunday for TXZ216. Coastal Flood Advisory from 5 AM to noon CDT Saturday for TXZ215. GM...Small Craft Advisory until 7 AM CDT Sunday for GMZ450-452-455- 470-472-475. Small Craft Advisory from 1 AM Saturday to 7 AM CDT Sunday for GMZ430-432-435. Small Craft Exercise Caution until 1 AM CDT Saturday for GMZ430- 432-435.