Gale Warning 7, NWS New Orleans, LA

Area Forecast Discussion
National Weather Service New Orleans LA
335 PM CST Tue Dec 10 2019

.SHORT TERM...Strong cold air advection across the tidal lakes and
sounds tonight will allow for boundary layer winds of 20 to 30 mph
with higher gusts to translate down to the surface tonight. The
strongest winds are expected along the immediate coast in
Mississippi and coastal Louisiana and across metro New Orleans to
the south of Lake Pontchartrain. A wind advisory will be issued
for these areas as wind gusts of 35 to 40 mph could occur tonight.
The main concern in wind advisory will be high profile vehicles
encountering difficult driving conditions in open areas like
bridges.

Outside of the wind threat, isentropically induced cloud cover
and showers will continue to develop across the forecast area this
evening and tonight. A gradual shifting of the main rain band
from around Baton Rouge toward the coastal counties and parishes
is expected through the night. By tomorrow morning, most of the
rain should be offshore with only scattered showers expected along
the immediate Louisiana coast. Increased dry air advection and
some weak subsidence aloft will bring mostly clear skies and dry
weather to the remainder of the forecast area during the day
tomorrow. Strong cold air advection will continue, and expect to
see temperatures well below normal in the middle to upper 50s
tomorrow.

The brief interlude from cloudy and rainy conditions will come to
an end on Thursday as a low pressure system develops in the Gulf
of Mexico. As the low forms, warm-frontal processes will become
dominant. Another isentropically forced cloud cover and rainfall
event is expected to take hold Thursday morning and persist into
Friday morning as the low tracks just offshore. The coastal waters
should be in the warm-sector to the south of the cold front, and
some thunderstorm activity will be possible offshore. Temperatures
will remain below normal on Thursday with highs only warming into
the upper 50s and lower 60s. As the low departs on Friday and
drier air begins to move in from the west, gradually clearing
skies and decreasing rain chances can be expected. Some moderation
in temperatures is also expected as a more Pacific based airmass
advects in. Highs should warm into the middle to upper 60s.

.LONG TERM...A zonal flow pattern will dominate the Gulf South in
the mid and upper levels of the atmosphere over the weekend. At
the surface, high pressure will be in control and expect to see
partly cloudy skies and dry weather through Sunday night.
Temperatures will continue to slowly modify with highs in the
upper 60s and lower forecast each day. The drier airmass should
allow for a greater diurnal range, and expect to see lows in the
40s over inland areas and the low 50s along the coast both Friday
and Saturday nights. Increased onshore flow and moisture advection
into the area Sunday night should keep temperatures warmer in the
lower to middle 50s.

Model guidance is in good agreement that another positively tilted
upper level trough axis will begin to move toward the area on
Monday and Tuesday. A deepening low over the Midwest will drive
another cold front through the region Monday into Monday night.
Conditions look somewhat favorable for a few thunderstorms to
develop in advance of the front, but the severe risk looks
limited as the strongest dynamics remain well north of the region.
Temperatures will remain warmer than average on Monday with highs
lower to middle 70s. In the wake of the front on Tuesday, colder
air moving in will push highs back below average in the upper 50s
and lower 60s.

&&

.AVIATION...MVFR to occasionally IFR conditions, mainly due to low CIGS and
occasional lower visibility in SHRA/RA are expected to continue
through the afternoon with mainly MVFR expected tonight before
improvement to VFR expected mid to late morning on Wednesday.
Northerly winds are expected to remain gusty at most airports in the
wake of the cold frontal passage through the afternoon and most
airports near the coast and tidal lakes through tonight and
Wednesday morning. 22/TD

&&

.MARINE...Strong cold air advection across the coastal waters will
easily transport down boundary layer flow of 20 to 30 knots with
higher gusts to the surface through tomorrow. A developing low
pressure system in the central Gulf will also keep winds elevated
into Thursday. This low pressure system is expected to pass
through the eastern waters Thursday night and early Friday. As a
result, small craft advisories are in effect due to rough boating
conditions through Thursday evening. The pressure gradient will
begin to relax on Friday as the low departs and high pressure
begins to build in from the west. Winds and seas should decrease
to between 10 and 15 knots as the high settles in. Seas should
also respond to these lighter winds and fall to between 2 and 4
feet.

&&

.DECISION SUPPORT...

DSS code: Green.
Deployed: None.
Activation: None.
Activities: Forecast Support for the City of New Orleans.

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; Marginal risk severe or excessive rain.
Yellow = Heightened impacts with short-fused watch, warning or
         advisory issuances; radar support for slight risk severe
         or excessive rain.
Orange = High Impacts; Enhanced risk severe; nearby tropical events;
         HazMat or other large episodes.
Red =    Full engagement for Moderate to high risk of severe and/or
         excessive rainfall, or direct tropical threats; Events of
         National Significance.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  39  56  39  59 / 100  10  10  30
BTR  41  58  39  59 / 100  10  10  30
ASD  40  58  39  61 / 100  10  10  40
MSY  46  56  47  61 / 100  10  10  40
GPT  42  56  43  60 / 100  10  10  50
PQL  42  57  41  62 /  90  10  10  50

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Wind Advisory until 9 AM CST Wednesday for LAZ040-058-060>064-
     066>070.

GM...Small Craft Advisory until 6 AM CST Thursday for GMZ530-532-534-
     550-552-570-572.

     Small Craft Advisory until 9 PM CST Thursday for GMZ536-538-555-
     557.

     Small Craft Advisory from 9 PM this evening to 9 PM CST Thursday
     for GMZ575-577.

MS...Wind Advisory until 9 AM CST Wednesday for MSZ080>082.

GM...Small Craft Advisory until 6 AM CST Thursday for GMZ532-534-550-
     552-570-572.

     Small Craft Advisory until 9 PM CST Thursday for GMZ538-555-557.

     Small Craft Advisory from 9 PM this evening to 9 PM CST Thursday
     for GMZ577.

&&

PG

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