Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
FXUS64 KLIX 281351
Area Forecast Discussion
National Weather Service New Orleans LA
851 AM CDT SUN AUG 28 2016
Moisture is down a bit in the sounding this morning with PW at 1.8
inches. There is still plenty of instability though with mixed
layer CAPE at 2500 J/KG despite a weak inversion near 800 mb.
Winds are southeast to 500 mb and bringing in a wave of moisture
across southeast LA. Scattered showers and storms will be mainly
from the I 10/12 corridor and south during the daytime hours.
Storm motion in this pattern the past couple days has been about
20 kts but localized flooding from heavy rain rates is still a
.PREV DISCUSSION... /issued 454 AM CDT SUN AUG 28 2016/
No significant changes in the forecast in the short term although
some tweaking of the precipitation chances and the temperatures
were made. Our slow moving upper level feature over the Gulf of
Mexico will continue to bring increased rain chances to the area
as a series of disturbances move across the area. Several rounds
of shower and thunderstorm development will be possible today and
tomorrow keeping daytime highs slightly cooler than normal.
Overall, the majority of the rainfall should fall over the Gulf
but there is a chance that some rainfall amounts of 1-2 inches
(with some higher amounts) over the two day period could spread
into the coastal areas south of Interstate 10. Otherwise, rainfall
amounts generally on the order of one inch can be expected.
Welcome to another edition of as 99L turns.
Once again, the most likely outcome at this point remains as it
was at this time yesterday for our area. High pressure will build
in across the region and remain in place for most of the rest of
the work week. This will lower precipitation chances to 20 percent
or less across the area beginning on Wednesday and in turn cause
temperatures to rise into the mid 90s in most places. With the
increase in temperatures and the lack of convection in the area,
heat advisories may be needed later in the week. I did opt to
back off a touch on the high temperatures and up a touch with
precipitation chances with the uncertainly about 99L but
temperatures are still forecast to be in the mid 90s.
The National Hurricane Center has increased the chances of
development on 99L to 40 percent over the next 48 hours and 60
percent over the next five days. The system is still looking
ragged (and that is being kind) and suffering the effects of
unfavorable upper level winds as well as interaction with Cuba.
That said, the system should be entering a somewhat more favorable
area for some development as it moves through the Florida Straits
today and into the eastern Gulf of Mexico. The biggest development
tonight is probably in that there is once again model support for
99L to develop into a tropical cyclone and possibly impact some
portion of the Gulf Coast. The GFS, ECMWF, NAM and Canadian models
all develop 99L at this point but send it east of the area as a
trough dives down along the east coast and allows for a weakness
in the Atlantic ridge. Should this scenario play out, there would
be some uneasy moments waiting for the system to turn to the north
and east as it could get rather close for comfort. At this time
though, that is simply one of many possibilities.
As has been the case from the beginning of this, it is late August
and the tropics should be being watched closely for any
development. However, and most importantly; everyone should be
working on their normal yearly preparedness plan in the event
that something warrants action...whether that be sooner or later.
VFR conditions are forecast to generally prevail at most terminals
through the TAF forecast period outside of convection areas. The
convection will be most prevalent during the late morning and
afternoon hours and more likely to affect the more coastal TAF
sites. Therefore, KHUM, KMSY and KNEW are the terminals most likely
to be impacted by showers and thunderstorms today. The convection
will begin to wane somewhat after sunset, especially across the more
Moderate easterly flow will continue through mid week across the
coastal waters with seas generally running in the 2 to 4 feet
range. The persistent easterly winds will result in tides running
5 to 1 feet above normal, or perhaps just slightly higher. There
remains much uncertainty with respect to the tropical wave that
should enter the Gulf through the Florida Straits by Monday. If
this system develops and strengthens and moves into the central
Gulf, then conditions could be far different than what is in the
forecast for Wednesday and the end of the week.
DSS code: Blue
Activities: Flood recovery support
Decision Support Services (DSS) Code Legend
Green = No weather impacts that require action.
Blue = Long-fused watch, warning, or advisory in effect or
high visibility event.
Yellow = Heightened impacts with short-fused watch, warning
or 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 risk of severe and/or
direct tropical threats; Events of National Significance.
.PRELIMINARY POINT TEMPS/POPS...
MCB 89 74 91 74 / 40 30 40 20
BTR 89 73 90 73 / 60 30 40 20
ASD 89 76 89 77 / 60 40 40 20
MSY 88 78 88 79 / 60 40 40 20
GPT 88 77 89 78 / 60 40 40 20
PQL 88 76 90 77 / 60 40 30 20