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

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FXUS64 KLIX 200947
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
447 AM CDT Fri Apr 20 2018

.SHORT TERM...

Temperatures are on the cool side for late April early this
morning with readings ranging from the upper 40s in many northern
locations to mostly 50s south, except for some lower 60s on the
immediate southeast Louisiana coast. A large dome of surface high
pressure associated with a Continental Polar airmass was centered
over the Mississippi valley and eastern Plains region. This has
brought yet another round of unseasonably cold temperatures to
many northern and central states. In the mid to upper levels, a
closed low over the southwest U.S. will move east into the
southern Rockies late today and tonight while an Atlantic coast
trough also moves east into the western Atlantic. This will push a
mid/upper level ridge axis across the Mississippi Valley late
today and tonight. Even with this warming pattern aloft, the cool
and dry airmass will continue to be felt across the forecast area
today and tonight as the surface high pressure dome slides slowly
east.

The upper low and strong shortwave trough will push east into the
southern Plains Saturday and early Saturday night with a weak
surface low pressure area expected to develop from central Texas
into the Ark-La-Tex region. A warm frontal boundary will push
north and should cross the western to central Gulf coast region by
late Saturday. Moisture return and warm air advection could cause
a few showers to develop Saturday afternoon, however higher rain
chances are expected to spread from northwest to southeast late
Saturday night into Sunday as the upper low, shortwave trough and
surface low all move across the lower Mississippi valley. There
will be a combination of ample dynamics/lift, instability and
shear to bring a chance of thunderstorms across the region,
however the threat of severe thunderstorms looks to be marginal at
best at this point. This is reflected in the Day 3/Sunday
Convective Outlook from SPC. Rainfall amounts are not expected to
be that high with this system across the forecast area with the
heavier amounts expected to remain to the north of the area.
Expect average amounts ranging from around one inch near the
Mississippi/Louisiana border to 1/3 to 1/2 inch on the southeast
Louisiana coast. The cold front is expected to move through the
forecast area Sunday afternoon and evening, so rain chances should
diminish as the front moves through with only a few lingering
showers expected (mainly in northern and eastern areas) Sunday
evening. Lingering cyclonic flow and cold air advection will
likely lead to at least partly cloudy skies on Monday, however am
expecting any lingering showers to remain isolated over mainly far
northern and eastern locations.

.LONG TERM...

As the weekend storm system moves across the east coast early next
week, a reinforcing series of shortwave troughs in the larger
longwave trough over the eastern U.S. are expected to move
southeast from the northern Plains and upper Mississippi valley
across the mid to lower Mississippi valley and southeast states
Wednesday through Thursday. This should maintain generally dry
conditions with temperatures averaging slightly below the
seasonal averages, however the ECMWF produces some light
precipitation amounts on Thursday, so have carried a slight chance
of showers over much of the forecast area. The end of next week
and start of the weekend look to dry at this point with near
normal temperatures. 22/TD

&&

.AVIATION...

VFR conditions will prevail at all of the terminals through the
entire forecast period.  Gusty north winds of 15 to 20 knots should
persist through mid-morning before dissipating at KNEW. 32

&&

.MARINE...

A decreasing pressure gradient across the coastal waters will result
in winds falling below advisory levels early this morning.  The wind
field should turn more easterly tonight at around 10 to 15 knots as
high pressure settles into the Southeastern states.  This brief
respite in stronger winds will come to an end by tomorrow as a low
pressure system strengthens over the Southern Plains.  Increased
gradient flow from the southeast and south will result in a return
to exercise caution and possibly advisory level conditions over much
of the open Gulf waters and sounds.  These conditions should persist
through Sunday morning.  The low pressure system and a cold front
will sweep through Sunday afternoon, and winds are expected to shift
to the northwest for Sunday evening and night.  Weak cold and dry
air advection behind the front should keep winds elevated at 15 to
20 knots through at least Tuesday morning.  A slight decrease in the
pressure gradient and wind field by Wednesday should allow winds to
fall to 10 to 15 knots and seas to drop below 4 feet.  However, a
reinforcing front moving through Wednesday night should result in
higher winds of 15 to 20 knots and more exercise caution headlines.
32

&&

.DECISION SUPPORT...
DSS code: Blue.
Deployed: None.
Activation: None.
Activities: Assessing thunderstorm risk for Sunday
            Sandhill Crane NWR Outreach Support
            New Orleans Navy Week 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; 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
         direct tropical threats; Events of National Significance.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  70  50  74  62 /   0   0  20  60
BTR  71  52  76  64 /   0   0  20  70
ASD  71  52  75  64 /   0   0  20  40
MSY  70  58  76  66 /   0   0  20  40
GPT  70  56  74  66 /   0   0  10  40
PQL  71  52  75  63 /   0   0  10  40

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory until 6 AM CDT early this morning for
     GMZ530-532-534-536-538-550-552-555-557-570-572-575-577.

MS...None.
GM...Small Craft Advisory until 6 AM CDT early this morning for
     GMZ532-534-536-538-550-552-555-557-570-572-575-577.

&&

$$


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