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

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105
FXUS64 KLIX 212128
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
328 PM CST Tue Jan 21 2020

.SHORT TERM...Little change from the previous forecast through
Thursday night. A very progressive pattern will be in place across
the nation. Initially, a shortwave ridge axis will be over the
area tonight into tomorrow morning. A strong surface high will
also remain in place in the low levels through tomorrow morning.
Light northeasterly flow will continue to advect in a colder and
drier airmass through tomorrow morning, and this will allow for
another night of freezing and near freezing temperatures. This
weak cold air advection should linger into tomorrow afternoon
before finally abating as the 925mb thermal trough axis pulls
further to the east by the evening hours. Another factor limiting
temperatures tomorrow will be an increase in high level cloud
cover through the day. Lower solar insolation values are
anticipated due to this thick cirrus deck, and temperatures
should be a good 5 to 10 degrees below normal tomorrow afternoon.
The cirrus deck itself will form as the shortwave ridge axis pulls
east tomorrow afternoon, and a shortwave trough moves into Texas
and the Southern Plains. Strongly difluent flow will develop
across the Gulf South by tomorrow afternoon and evening, and the
increase in upper level lift combined with a feed of Pacific based
moisture will support the development of the cirrus deck through
the day.

The trough axis will pass across the forecast area tomorrow night
through Thursday night. Rainfall should initially begin as light
showers over the far western zones tomorrow evening, and then
spread eastward through the night. The intensity of the rain
should increase across the western zones by Thursday morning with
some moderate rain showers expected. These moderate rain showers
should then spread east and be over the Mississippi coastal
counties by Thursday evening. The increase in rainfall intensity
on Thursday will be driven by a nose of higher theta e values
pushing into the area as southerly winds increase in advance of a
developing low pressure over eastern Texas. Even though the
surface low is expected to pass directly over the area Thursday
into Thursday night, the risk of severe weather and even
thunderstorms is nearly non-existent across much of the area. This
is largely due to moist adiabatic and weak mid-level lapse rates
limiting the amount of instability in the area. At most, the
coastal waters may see a few thunderstorms develop in advance of
weak dryline feature that forms to the south of the low Thursday
evening. Even there, the thunderstorms should remain on the weaker
side. Temperatures will be closer to average with lows in the 40s
Wednesday night and highs in the lower 60s on Thursday. By late
Thursday night, the parent trough axis should be east of the area,
and an increasing subsidence and dry air advection will take hold.
Rain chances should come to an end over the western zones by late
Thursday evening and be completely clear of the area by early
Friday morning. The airmass will be largely Pacific based, so
littler in the way of the cold air advection is expected. Lows
should be near average in the 40s and lower 50s.

.LONG TERM...A strong surface high and a zonal flow pattern will
be the rule through Saturday. Mostly clear skies and dry weather
can be expected. Temperatures will be near average both Friday and
Saturday. However, this progressive pattern we are in will push
another shortwave feature into the area by Sunday. Cloud cover
should be on the increase Saturday night, and expect to see light
rain showers develop across the Louisiana coast and the coastal
waters for Sunday and Sunday night. Fortunately, the main thrust
of this next system will be largely over the Gulf of Mexico, and
this will keep most areas along and north of the I-10 corridor on
the drier side of the system. At most, a few light sprinkles and
mostly cloudy skies can be expected on Sunday over the northern
half of the CWA. Temperatures will remain near average Sunday into
Sunday night.

A deep layer ridge axis will dominate the region Monday into
Monday night. As a result, clear and dry conditions can be
expected. Temperatures will remain close to seasonal averages for
late January with highs in the 60s and lows in the 40s. This ridge
axis should shift to the east of the area by Tuesday as another
fast moving shortwave feature approaches from the west. Increasing
cloud cover is expected on Tuesday, and rain showers may
overspread the forecast area by Tuesday night.

&&

.AVIATION...VFR conditions are expected at all of the terminals
through tomorrow afternoon. Some mid and high level cloud cover is
expected to develop tomorrow, but no impacts to aviation will
occur from this cloud cover. Some MVFR conditions may develop at
KMSY tomorrow evening as ceilings fall to around 2000 feet and
light rain showers begin to form.

&&

.MARINE...Gusty northerly winds will persist through the rest of tonight and
into the day tomorrow. Stronger winds - at or slightly above Small
Craft Advisory Criteria will likely continue for the outer Gulf
marine zones GMZ 555,575 and 577 through late evening/early tonight -
and have extended advisory highlights in these areas through 03Z.
Elsewhere, exercise caution headlines will be in place for all
marine areas except for the tidal lakes/MS sound regions where
latest observations indicate a steady lowering in wind speeds. Winds
will diminish and shift more from the east tomorrow, out ahead of
the next storm system expected through the region on Thursday. At
this time, main hazards associated with this system will be periodic
heavy rain showers and a few thunderstorms which may likely cause
gusty, erratic wind gusts and locally higher waves/swells. This
system quickly departs on Friday leaving behind drier conditions
through the upcoming weekend.

&&

.DECISION SUPPORT...

DSS code: Blue.
Deployed: None.
Activation: None.
Activities: Forecast support for Stennis.
            Small craft advisory.
            River flood warnings.

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  30  51  42  59 /   0   0  70  90
BTR  33  53  46  63 /   0   0  80  90
ASD  30  53  45  63 /   0   0  60  90
MSY  39  55  50  64 /   0   0  60  80
GPT  33  52  45  60 /   0   0  50  80
PQL  28  52  42  62 /   0   0  40  80

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory until 9 PM CST this evening for GMZ555-575-
     577.

MS...None.
GM...Small Craft Advisory until 9 PM CST this evening for GMZ575-577.

&&

$$



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