000
FXUS64 KLIX 240927
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
427 AM CDT Thu Aug 24 2017

.SHORT TERM...
Tropical Storm Harvey re-developed last night over the southern
Gulf of Mexico. This storm will not only impact the Texas coast
this week into this weekend...it could also have an impact across
much of the southern United States. More on Harvey later, but
today we can expect showers and storms to develop this afternoon.
There has been some nocturnal development over Lake Pontchartrain
and along the coast. Some that has already weakened but thinking
that convection could develop early over the southeastern portions
of the forecast area. Overnight 6z sounding showed PW value of
2.33 inches and a convective temperature of 88 degrees...I am
thinking that once the sun comes up and we get a little heating
showers and storms will start developing. With that type of PW,
showers and storms will be efficient rain producers and locally
heavy rainfall or some minor flooding is possible today as we
still have a frontal boundary stalled over the forecast area. This
will serve as a focus for development as well. Have kept POPs the
same with a solid 60 percent over portions of the forecast
area...and have expedited the upward trend in POPs this morning. 
Temperatures should reach near 90 today before convection starts. 
By tomorrow, some weak subsidence on the outer periphery of a 
Tropical Storm Harvey and an northward push of the low level 
boundary back toward central Mississippi and north Louisiana 
should result in lower POP values for much of the forecast area. 

.LONG TERM...
Going into the weekend the big story will be Tropical Storm
Harvey. Latest advisory from the National Hurricane Center has
Harvey becoming a hurricane before landfall. Harvey then stalls
across southeast Texas for the majority of the weekend. All
guidance still suggest this solution and even has it slow to move
east into our forecast area. We may not see the heaviest solid
area of rainfall until Tuesday or Wednesday across our forecast 
area. This is because Harvey gets caught between two ridges 
stalling it over Texas for a few days...and it has to wait for a 
trough to dig in over the eastern United States to pull it out 
across the country. Have maintained the forecast for the most 
part. Have adjusted temperatures in the long range and adjusted 
POPs in the long range to show the trends in guidance. Just a note
here...just because we possibly won't see the heaviest rain from 
this complicated pattern until early next week does not mean that 
heavy rainfall is not possible this weekend with any shower or 
storm. There will be plenty of moisture around the area with a 
stalled boundary in place over the area. Do not let your guard 
down. Locally heavy rainfall will be possible each and every day 
starting Saturday and possibly lasting through Wednesday. There is
a large degree of uncertainty in the forecast for next week, so 
the forecast could change dramatically over the next few days

&&

.AVIATION...
Better chance at areal convective coverage to include TEMPO groups 
for mainly afternoon convection this afternoon and evening. Will 
have to closely monitor banding behavior on outer bands of Harvey, 
which may move into KHUM and possibly into the New Orleans metro 
area overnight into Friday morning. Otherwise, VFR conditions 
expected outside convection. Gust potential appears low, 
generally 10-15 kts from weak outflow gusts features. 24/RR

&&

.MARINE...
Gradual increase in seas with swell generation from Harvey through 
the weekend. Periods should attain 8-10 seconds Friday then slowly 
erode into 6 seconds for the weekend. This will support a SW ground 
swell that will be intersecting a SE to E wind wave for steep sea 
state for much of the weekend into early next week. 24/RR

&&

.SOUNDING DISCUSSION...
06Z special release sounding in support of Tropical Storm Harvey 
modeling went off without a hitch. Very light winds throughout kept 
much of the flight within 2 miles of the station but managed to 
terminate over Lake Pontchartrain about 4 miles SE of the mouth of 
the Tchefuncte River, about 18 miles downrange at an altitude of 
18.9 miles at the 11.3 mb level. Very soggy air mass with a 
precipitable water now up to 2.33 inches, which can see efficient 
rain rates today, particularly with slow-moving nature of any storms 
that do form. Showalter is an unstable -3 in the middle of the night 
with a lifted index of -7. CHAP shows a 50% PoP with rain potential 
in the 5.72-7.09 inch range. Average winds throughout the column was 
7 knots. 24/RR

&&

.DECISION SUPPORT...
DSS Code...Blue.
Deployed...None.
Activation...Special Upper air releases at 06Z/18Z. 
Activities...Monitoring Tropical Storm Harvey..  

DECISION SUPPORT SERVICES (DSS) CODE LEGEND
GREEN  = NO WEATHER IMPACTS THAT REQUIRE ACTION
BLUE   = LONG FUSED WATCH/WARNING/ADVISORY IN EFFECT OR HIGH       
         VISIBILITY EVENT
YELLOW = HEIGHTENED IMPACTS WITH SHORT FUSED
         WATCH/WARNING/ADVISORY ISSUANCES; RADAR SUPPORT
ORANGE = HIGH IMPACTS - SLIGHT TO MODERATE RISK SEVERE; NEARBY
         TROPICAL EVENTS; HAZMAT OR OTHER LARGE EPISODES
RED    = FULL ENGAGEMENT FOR MODERATE TONIGHT RISK SVR
         AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL 
         SIGNIFICANCE

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  89  71  87  73 /  60  60  30  30 
BTR  89  74  87  75 /  60  60  30  40 
ASD  90  76  90  77 /  50  50  30  30 
MSY  90  79  89  79 /  50  50  30  30 
GPT  90  77  89  78 /  50  50  30  30 
PQL  91  76  91  77 /  50  50  20  30 

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&

$$

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  National Oceanic and Atmospheric Administration
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