Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA

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961
FXUS64 KLIX 210931
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
331 AM CST Mon Jan 21 2019

.SHORT TERM...Another day of below average temperatures and clear
skies is expected today as a thermal trough and surface high
continue to influence the region. In the upper levels, the
northwest flow pattern will turn more zonal through the day.
Temperatures should be around 5 degrees below normal today with
highs climbing into the middle to upper 50s. Skies will remain
clear and humidity values will remain low.

The low to mid-level ridge axis will continue to push to the east
tonight and tomorrow, and this will open the door for Gulf
moisture to surge back into the region. A fairly large region of
subsidence will remain in place in the upper levels tonight, and
have dry conditions persisting. However, an elevated inversion
should promote the development of a stratus deck tonight. The
surge in low level moisture and dewpoints will also push overnight
lows back to more normal readings in the 40s. Tomorrow will see
the flow aloft turn more southwesterly, and a gradual increase
positive vorticity advection through the day should promote the
development of a few showers by the afternoon hours. Temperatures
will also continue to warm on the back of this deep layer onshore
flow with highs climbing into the upper 60s and lower 70s.

A vigorous positively tilted shortwave trough will begin to take
on a neutral tilt as it moves through the forecast area Tuesday
night through Wednesday night. High omega values combined with
ample moisture will allow for a band of showers to form in advance
of a cold front and then sweep across the entire forecast area
during the day on Wednesday. At this time, it looks like
instability values over most of the area will remain on the weaker
side, and do not expect to see much in the way of thunderstorms
over land. In the offshore waters, there could be a few
thunderstorms that develop as some weak instability is expected
Wednesday afternoon. Have categorical POP of 80% or greater in the
forecast for Wednesday, and expect to see continued warm
temperatures in the upper 60s over the eastern two thirds of the
CWA in advance of the cold front. The western third of the CWA
should see the front move through earlier in the day, and highs
will be significantly cooler in the lower to middle 50s. Rain
chances should quickly come to an end from west to east Wednesday
night as the cold front and associated trough axis move into
Florida. Strong dry air and negative vorticity advection behind
this system will bring clearing skies, lower humidity values, and
cooler temperatures by late Wednesday night.

.LONG TERM...Deep layer northwest flow will take hold on Thursday
and remain in place on Friday.  A reinforcing front should push
through the area Thursday night into early Friday, but this front
will be moisture starved as it moves through. At most, a few
passing clouds are expected as the boundary pushes across the
forecast area. Cold air advection will keep temperatures well
below normal with highs in the lower to middle 50s both Thursday
and Friday. Lows will cool into the 30s for most locations both
Wednesday and Thursday nights. In the wake of the reinforcing
front on Friday, temperatures should plunge into the middle to
upper 20s for most areas Friday night. Only areas south of Lake
Pontchartrain should remain at or slightly above freezing with
lows in the lower to middle 30s.

Both the GFS and the ECMWF indicate that another vorticity max
will slide down from the northern Plains and pass through the Gulf
south over the coming weekend. Both model solutions indicate the
potential of a Gulf low forming off the Louisiana coast and then
pushing eastward toward the Florida Panhandle Saturday into
Sunday. The region will remain on the northern and colder side of
the system through the weekend, and currently think temperatures
will remain just warm enough to keep any precipitation in all
liquid form. Have put a high end chance of rain in the forecast
beginning Saturday afternoon and ending by Sunday morning.
Saturday night has the highest rain chances, and temperatures
should cool into the upper 30s and lower 40s during this period.
Daytime highs should be well above freezing in the lower to middle
50s both Saturday and Sunday. At this time, it does not appear
that wintry precipitation will affect the area, but this is highly
dependent on how much cold air advection accompanies the system.
By Sunday afternoon and night, strong negative vorticity advection
and subsidence in the wake of the departing low will produce
rapidly clearing skies and cooler temperatures in the lower to
middle 30s.

&&

.AVIATION...VFR through the early evening hours. Ceilings will begin to develop
after sunset and should move from SCT020 to BKN025. Decks become
well established by Tuesday morning at OVC035. Some TEMPO decks at
BKN015 may develop Tuesday morning as well.

&&

.MARINE...A very progressive pattern is setting up for the next several days.
The next front will begin to bring return flow back to the area
today. This front may move through the northern gulf during the day
Wednesday with strong northerly winds around 25kt with gusts
possibly into the lower 30s. Wind speeds will only back off a little
before the northerly winds are reinforced by another cold front
moving through Friday. Southerly winds will be back by late Saturday
ahead of the next front moving through Saturday night into Sunday of
next weekend with another set of strong winds.

&&

.DECISION SUPPORT...

DSS code: Green
Deployed: None
Activation: None
Activities: None
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 rain; direct tropical threats; Events of National
         Significance.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  55  42  66  50 /   0   0  20  50
BTR  56  47  70  49 /   0   0  30  50
ASD  55  42  69  57 /   0   0  10  50
MSY  56  50  71  58 /   0   0  10  40
GPT  53  44  66  58 /   0   0  20  70
PQL  55  40  67  58 /   0   0  20  70

&&

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

$$

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