549
FXUS64 KSHV 210356
AFDSHV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SHREVEPORT LA
1056 PM CDT SUN SEP 20 2020
UPDATE
FOR THIS UPDATE, DECIDED TO ADJUST POPS DOWN TO 20 PERCENT FOR
AREAS SOUTH OF INTERSTATE 20 DURING THE REMAINDER OF THE EVENING
HOURS. ALSO, DECIDED TO TREND POPS DOWN A TAD DURING THE
OVERNIGHT HOURS AS SHORT-TERM MODELS HOLD OFF PRECIP UNTIL AFTER
3 AM. OTHERWISE, THE REMAINDER OF THE FORECAST REMAINS ON TRACK.
PREV DISCUSSION
/ISSUED 842 PM CDT SUN SEP 20 2020/
AVIATION...
FOR THE 21/00Z TAF PERIOD, VFR CONDITIONS WILL CONTINUE FOR THE
FIRST HALF OF THE TAF PERIOD. HOWEVER, THE EFFECTS FROM TROPICAL
STORM BETA WILL BEGIN TO BE FELT ACROSS THE REGION AS LOW CLOUDS
BEGIN TO MOVE INLAND AND RESULT IN MVFR/IFR CIGS SPREADING NORTH
THROUGH THE OVERNIGHT AND EARLY MORNING HOURS. SHOWERS AND SOME
ISOLATED THUNDERSTORMS WILL ALSO GRADUALLY SPREAD NORTH THROUGH
THE LATTER HALF OF THE PERIOD AS OUTER BANDS FROM BETA ADVANCE
INTO OUR REGION. EXPECT CONVECTION TO INCREASE THROUGHOUT MONDAY
WITH CIGS DROPPING EVEN FURTHER THROUGH THE END OF THE PERIOD.
WINDS WILL ALSO BE INCREASING FROM THE E/NE BETWEEN 10-15 KTS
ALONG WITH SOME HIGHER GUSTS NEAR 20 KTS POSSIBLE, ESPECIALLY
DURING THE DAYTIME HOURS.
PREV DISCUSSION... /ISSUED 341 PM CDT SUN SEP 20 2020/
SHORT TERM.../TONIGHT THROUGH MONDAY NIGHT/
WE HAVE MANAGED TO MAINTAIN DRY CONDITIONS OVER THE VAST MAJORITY
OF THE REGION TODAY WITH ONLY A FEW VERY LIGHT SHOWERS ASSOCIATED
WITH TROPICAL STORM BETA GRAZING OUR EXTREME SOUTHERN ZONES THIS
AFTERNOON. MOISTURE HAS HAD A DIFFICULT TIME OVERCOMING THE VERY
DRY AIR MASS IN PLACE, BUT EXPECT INCREASING MOISTURE ADVECTION
OVERNIGHT WITH SHOWERS GRADUALLY INCREASING AND EXPANDING FROM
SOUTH TO NORTH. HOWEVER, IT STILL APPEARS THAT COVERAGE MAY NOT BE
ALL THAT IMPRESSIVE BASED ON THE LATEST HI-RES GUIDANCE BECAUSE OF
THE DEPTH OF THIS DRY AIR IN PLACE. HOWEVER, HAVE GONE AS HIGH AS
LIKELY POPS ACROSS OUR SOUTHERNMOST ZONES AND TAPERED THEM BACK AS
YOU GO FARTHER NORTH. THE GENERAL THINKING IS MOST OF THE SHOWERS
THAT DO DEVELOP SHOULD REMAIN ALONG AND SOUTH OF I-20 THROUGH THE
OVERNIGHT HOURS AND GRADUALLY EXPAND FARTHER NORTH ACROSS THE REST
OF THE REGION THROUGH THE DAY ON MONDAY. TEMPERATURES WILL BE HELD
WELL BELOW NORMAL DUE TO THE EXTENT OF CLOUD COVER AND INCREASING
CONVECTION WITH AFTERNOON HIGHS ONLY MANAGING THE LOWER TO MID 70S
ON MONDAY.
CONVECTION WILL REMAIN ONGOING INTO MONDAY NIGHT AS TROPICAL STORM
BETA NEARS LANDFALL ALONG THE MIDDLE TEXAS COAST. THERE MAY SOME
OCCASIONAL PERIODS OF HEAVY RAINFALL, BUT OVERALL DON'T ANTICIPATE
A SIGNIFICANT FLOODING THREAT AT THIS TIME GIVEN THE EXTENDED DRY
PERIOD WE HAVE EXPERIENCED THROUGH THE MIDDLE THIRD OF THIS MONTH.
THEREFORE, NO FLOOD HEADLINES ARE PLANNED FOR THE SHORT TERM BUT
THAT COULD CHANGE AS WE MOVE LATER IN THE WEEK DURING THE LONGER
TERM PART OF THE FORECAST.
LONG TERM.../TUESDAY THROUGH SATURDAY NIGHT/
A PROLONGED PERIOD OF INCLEMENT WEATHER IS STILL ANTICIPATED ACROSS
THE ENTIRE FOUR STATE REGION TUESDAY AND WEDNESDAY AS THE REMNANTS
OF TROPICAL STORM BETA AND A STRENGTHENING UPPER LEVEL TROUGH TO OUR
WEST FOCUS LIFT, MOISTURE ADVECTION, AND MARGINAL INSTABILITY OVER
THE AREA. SOME GRADUAL DECREASE IN RAIN COVER FROM WEST TO EAST IS
EXPECTED THURSDAY AND FRIDAY, ALTHOUGH A GENERALLY UNSETTLED PATTERN
SHOULD REMAIN IN OUR REGION THROUGH THE WEEKEND AND THIS WILL
CONTINUE 20 TO 40 PERCENT RAIN CHANCES.
DETAILS IN THE TIMING AND FOCUS OF HEAVY RAINFALL POTENTIAL TUESDAY
AND WEDNESDAY ARE STILL VERY UNCERTAIN GIVEN MANY DIFFERENT MODEL
IDEAS OF HOW THE REMNANTS OF BETA WILL REACT WITH THE AFOREMENTIONED
UPPER LEVEL TROUGH. THE MOST RECENT RAINFALL GUIDANCE FROM THE
WEATHER PREDICTION CENTER HAS REACTED TO THE UNCERTAINTY (AND
POTENTIAL FOR HEAVIER CONVECTION TO GET ANCHORED NEAR THE COAST) BY
LOWERING EXPECTED PEAK TOTALS IN OUR REGION A GREAT DEAL THROUGH
FRIDAY. OF COURSE THIS IS GOOD NEWS, AS IT REPRESENTS LESS POTENTIAL
FOR EVENTUAL FLOODING IMPACTS (ESPECIALLY IN LA SOUTH OF I-20). OUR
LATEST GRAPHICS REPRESENT A STRONG TREND TOWARD THIS ADJUSTMENT.
HOWEVER, IT IS WORTH POINTING OUT THAT THERE IS STILL CONSIDERABLE
UNCERTAINTY WITH HOW THE INLAND RAINFALL WILL PAN OUT IN OUR
VICINITY AND WE CANNOT YET COMPLETELY LET OUR GUARD DOWN FOR THE
THREAT OF FLOODING.
OTHERWISE, EXPECT LOW TEMPERATURES TO BE NEAR NORMAL THROUGH THE
PERIOD WITH HIGH TEMPERATURES AT LEAST SLIGHTLY BELOW NORMAL MOST
DAYS THANKS TO AN ABUNDANCE OF CLOUDS AND PRECIPITATION BEING
AROUND. HUMIDITY WILL DEFINITELY BE HIGHER THAN HAS BEEN THE CASE
THE LAST FEW DAYS. DECENT MODEL CONSENSUS ON A POSSIBLY BIG COLD
FRONT COMING DOWN VERY EARLY NEXT WEEK, BUT THIS IS PAST THE
OFFICIAL LONG TERM PERIOD. /50/
PRELIMINARY POINT TEMPS/POPS
SHV 64 73 64 74 / 40 80 80 70
MLU 65 75 64 74 / 30 60 60 70
DEQ 63 76 62 70 / 10 50 70 70
TXK 63 72 63 68 / 20 60 80 80
ELD 62 74 61 70 / 20 50 70 70
TYR 64 70 64 74 / 40 80 80 70
GGG 64 72 64 76 / 40 80 80 70
LFK 65 76 67 79 / 60 80 80 70
SHV WATCHES/WARNINGS/ADVISORIES
AR...NONE.
LA...NONE.
OK...NONE.
TX...NONE.
20
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