104
FXUS64 KLCH 171759
AFDLCH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
1259 PM CDT TUE SEP 17 2019
DISCUSSION
18Z TAFS
AVIATION
TROPICAL BANDING ASSOCIATED WITH NEWLY DEVELOPED TROPICAL STORM
IMELDA WILL CONTINUE TO PUSH INLAND ACROSS SOUTHEAST TEXAS
THROUGH THE TAF PERIOD. BPT WILL SEE THE MOST SIGNIFICANT IMPACTS
WITH GUSTY WINDS AND PERIODS OF VISIBILITY REDUCING HEAVY
RAINFALL. LOUISIANA TERMINALS WILL SEE MORE SCATTERED RAINFALL.
CEILINGS WILL FLUCTUATE BETWEEN VFR AND IFR DEPENDING ON THE
PROXIMITY OF BANDING.
JONES
PREV DISCUSSION
/ISSUED 913 AM CDT TUE SEP 17 2019/
UPDATE...AN AREA OF LOW PRESSURE WILL CONTINUE TO MOVE INLAND TO
THE CENTRAL TEXAS COAST THROUGH THE NEXT 24 HOURS. THIS WILL KEEP
POPS ELEVATED WHILE KEEPING TEMPERATURES LOWER. THE PREVIOUS
FORECAST REMAINS ON TRACK AND NO CHANGES ARE NEEDED AT THE CURRENT
TIME.
PREV DISCUSSION... /ISSUED 632 AM CDT TUE SEP 17 2019/
DISCUSSION...
FOR THE 17/12Z TAF ISSUANCE.
AVIATION...
RAIN BANDS ROTATING AROUND A TROPICAL DISTURBANCE OFF THE MIDDLE
TEXAS COAST WILL IMPACT THE AVIATION TERMINALS DURING THE PERIOD.
THIS MORNING KBPT WILL HAVE THE MAIN IMPACTS WITH PREVAILING LIGHT
SHOWERS THAT WILL BE OCCASIONALLY STRONG. MVFR TO IFR
CEILINGS/VISIBILITIES WITH THE ACTIVITY AND SOME WIND GUSTS TO 25
KNOTS CAN BE EXPECTED. THE ACTIVITY WILL GRADUALLY PUSH INLAND
DURING THE AFTERNOON HOURS WITH IMPACTS AT KLCH/KLFT/KARA, WITH
THE POSSIBILITY OF SOME MORE SCATTERED ACTIVITY REACHING KAEX BY
LATE AFTERNOON. DURING THE EVENING HOURS, ACTIVITY INLAND WILL
DISSIPATE WITH MAINLY VFR EXPECTED AT KAEX/KLCH/KLFT/KARA THROUGH
THE OVERNIGHT. KBPT HOWEVER, AFTER A BREAK IN THE EVENING, WILL
SEE A REDEVELOPMENT OF SHOWER ACTIVITY DURING THE OVERNIGHT.
RUA
PREV DISCUSSION... /ISSUED 415 AM CDT TUE SEP 17 2019/
DISCUSSION...
SHORT TERM [TODAY THROUGH THURSDAY]
WATER VAPOR GOES-16 IMAGERY THIS MORNING INDICATES AN UPPER LEVEL
LOW REMAINS LOCATED ABOVE A SURFACE TROUGH EXTENDING ALONG THE
NORTHWESTERN GULF OF MEXICO. THE UPPER LEVEL LOW IS EXPECTED TO
SUPPORT THE SURFACE TROUGH BECOMING MORE ORGANIZED AS IT GRADUALLY
MOVES INLAND OVER THE NEXT 48 HOURS. THE 2 AM TROPICAL WEATHER
OUTLOOK NOTED THAT WHILE SURFACE PRESSURE IS ALREADY FALLING
ACROSS THIS PORTION OF THE GULF, NO EVIDENCE OF A SURFACE
CIRCULATION CURRENTLY EXISTS. HOWEVER, GIVEN THE POTENTIAL FOR THE
SYSTEM TO BECOME MORE VERTICALLY STACKED BASED ON THE COLLOCATION
OF THE UPPER LEVEL AND SURFACE FEATURES, NHC IS INDICATING AT
LEAST A LOW (30% CHANCE) THAT A WEAK SURFACE LOW COULD DEVELOP
OVER THE NEXT 48 HOURS.
REGARDLESS OF THE DEVELOPMENT OF ANY SURFACE SYSTEM, THERE WILL BE
THE POTENTIAL FOR HEAVY RAINFALL AND FLASH FLOODING ALONG THE
TEXAS COAST THROUGH THURSDAY. SATELLITE DERIVED SOUNDINGS INDICATE
PWAT VALUES OF 2"-2.5" ARE ASSOCIATED WITH THIS SYSTEM AND WILL BE
BROUGHT INLAND AS IT MOVES NORTHWARD. MEANWHILE, FAIRLY
UNIDIRECTIONAL FLOW IN THE LOW- TO MID- LEVELS OF THE ATMOSPHERE
WILL SUPPORT THE POTENTIAL FOR BANDS OF CONVECTION TO TRAIN OVER
THE SAME AREA. THESE TRAINING BANDS MOVING THROUGH AN ENVIRONMENT
THAT IS SUPPORTIVE OF EFFICIENT PRECIPITATION WILL SUPPORT THE
THREAT OF VERY HEAVY RAINFALL AMOUNTS AND FLASH FLOODING. MUCH OF
THE CAM GUIDANCE SUPPORTS THE POTENTIAL FOR LOCALIZED AMOUNTS OF
6-9"+ OF RAINFALL SOMEWHERE ALONG THE TEXAS COAST. CURRENTLY, THE
GREATEST POTENTIAL FOR THESE HEAVIER RAINFALLS LOOKS TO BE AROUND
THE HOUSTON AREA. HOWEVER, THESE HEAVIER RAINFALL TOTALS CANNOT BE
RULED OUT FOR PORTIONS OF SOUTHEAST TEXAS AND ADJACENT WESTERN
LOUISIANA AS THE EXACT PLACEMENT OF BANDS WILL BE DEPENDENT ON
WHERE A MORE ORGANIZED SURFACE CIRCULATION IS ABLE TO DEVELOP.
IN COORDINATION WITH WPC AND NEIGHBORING OFFICES, THE FORECAST
TODAY INCLUDES A MARGINAL RISK (5%-10%) OF FLASH FLOODING FOR THE
ALL OF SOUTHERN LOUISIANA AND A SLIGHT RISK (10%-20%) OF FLASH
FLOODING ACROSS SOUTHEAST TEXAS. ONE HOUR AND SIX HOUR FLASH
FLOOD GUIDANCE ACROSS PORTIONS OF SOUTHEAST TEXAS RANGES FROM 3.5"
TO OVER 6" RESPECTIVELY. MEANWHILE THE BEST FORCING FOR
PRECIPITATION IS EXPECTED TO BE CONFINED TO THE SOUTH-CENTRAL
TEXAS COAST TODAY. THEREFORE, ELECTED NOT TO ISSUE A FLASH FLOOD
WATCH FOR SOUTHEAST TEXAS AT THIS TIME.
THE GREATER POTENTIAL FOR FLASH FLOODING WILL COME ON WEDNESDAY
AND THURSDAY AS THE SYSTEM LIFTS NORTHWARD INTO EASTERN TEXAS.
THIS WILL ADVECT RICHER PWATS INTO THE REGION AND ALSO PROVIDE
GREATER SUPPORT FOR CONVECTIVE BANDS TO DEVELOP ACROSS SOUTHEAST
TEXAS AND WESTERN LOUISIANA. AS A RESULT, WPC EXPANDED THE SLIGHT
RISK OF FLASH FLOODING EASTWARD INTO WESTERN LOUISIANA AND A
MODERATE RISK (20%-50%) OF FLASH FLOODING CLIPS THE WESTERN EDGE
OF THE CWA. THESE AREAS COULD SHIFT FURTHER EAST OR WEST DEPENDING
ON THE EVENTUAL DEVELOPMENT AND TRACK OF ANY ORGANIZED SURFACE
LOW. SHOULD CONFIDENCE INCREASE, A FLASH FLOOD WATCH WILL BE
ISSUED FOR SOUTHEAST TEXAS AND POSSIBLY AREAS FURTHER EAST.
REGARDLESS OF ANY WATCHES BEING ISSUED, THOSE IN SOUTHEAST TEXAS
AND WESTERN LOUISIANA SHOULD CONTINUE TO BE PREPARED FOR THE
POTENTIAL OF FLASH FLOODING ON WEDNESDAY AND THURSDAY.
LONG TERM [FRIDAY THROUGH MONDAY]
THE LONG TERM PERIOD WILL FEATURE A RETURN TO A MORE TYPICAL
SEPTEMBER WEATHER PATTERN AS THE UPPER LEVEL AND SURFACE LOW LIFT
NORTH OF THE GULF COAST. THIS WILL ALLOW FOR WEAK RIDGING TO BUILD
INTO THE AREA. AS A RESULT, PWATS ARE FORECAST TO RETURN TO
AROUND 1.7"-2" BY THE LATER HALF OF THE WEEKEND. THIS WILL SUPPORT
THE TYPICAL 20%-30% CHANCE OF AFTERNOON SHOWERS AND THUNDERSTORMS
EACH DAY WITH HIGHS IN THE LOW TO MID 90S.
MARINE...
AN UPPER LEVEL LOW OVER THE WESTERN GULF OF MEXICO WILL MOVE
INLAND ACROSS EAST TEXAS OVER THE NEXT FEW DAYS. THIS WILL RESULT
IN ELEVATED PRECIPITATION CHANCES OVER THE COASTAL WATERS THROUGH
THURSDAY. THE SURFACE PRESSURE GRADIENT ASSOCIATED WITH THIS
SYSTEM WILL ALLOW FOR ELEVATED SOUTHEAST WINDS WILL CONTINUE TODAY
AND WEDNESDAY, PARTICULARLY OVER THE COASTAL WATERS WEST OF
CAMERON WHERE WINDS WILL RANGE FROM 15 TO 20 KNOTS. THEREFORE,
SMALL CRAFT EXERCISE CAUTION HEADLINES REMAIN IN THE FORECAST.
WINDS AND SEAS WILL BEGIN TO DECREASE ON FRIDAY AS THE UPPER LEVEL
AND SURFACE LOWS LIFT NORTH OF THE REGION. THIS WILL ALSO RESULT
IN WINDS BECOMING MORE SOUTHERLY BY EARLY NEXT WEEK.
PRELIMINARY POINT TEMPS/POPS
AEX 71 91 70 90 / 0 50 20 40
LCH 76 85 76 87 / 70 80 50 60
LFT 75 88 74 90 / 20 60 20 30
BPT 76 83 76 82 / 80 90 70 70
LCH WATCHES/WARNINGS/ADVISORIES
LA...COASTAL FLOOD ADVISORY UNTIL 1 PM CDT WEDNESDAY FOR LAZ052>054-
073-074.
TX...COASTAL FLOOD ADVISORY UNTIL 1 PM CDT WEDNESDAY FOR TXZ215-216.
GM...SMALL CRAFT EXERCISE CAUTION UNTIL 7 PM CDT THIS EVENING FOR
GMZ450-470.
AVIATION...04
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