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

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FXUS64 KLIX 250902
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
402 AM CDT Mon Sep 25 2017

.SYNOPSIS...

At the surface, high pressure over the St. Lawrence River Valley
extends southwest into east Texas. Aloft, a weak low is centered
near Gulfport. Some convection moving westward over the Gulf of
Mexico with a few showers over land just south of New Orleans.
Most of the local area not seeing much in the way of clouds at 3
am. Temperatures away from direct marine influences are mainly in
the upper 60s and lower 70s. The 06z special sounding for NHC
showed little change in moisture with precipitable water values
around 1.6 inches.

&&

.SHORT TERM...

The weak upper low near Gulfport will gradually sink southward
into the northern Gulf of Mexico as it weakens. This will bring
one more day of rain chances a little higher than climatology with
most areas in the 40-50 percent range, before falling to 30-40
percent tomorrow as mid level ridging starts to build back in.
This will lead to a dry forecast on Wednesday. Little difference
in temperature guidance and will go with a consensus. 35

&&

.LONG TERM...

Mid level ridging continues building into the area Thursday before
a strong northern stream shortwave pushes a moisture-starved cold
front through the area Friday and Friday night. Expect little, if
any, precipitation with this front. What the front will do is
bring drier and cooler air into the area for the weekend.

Medium range models starting to struggle with timing/location of
shortwaves beyond Sunday. Moisture return begins as high pressure
along the Atlantic coast turns winds onshore. This will return
small chances for precipitation to the forecast beginning Monday.
ECMWF solution begins looking like an outlier solution at it gets
out to Tuesday and Tuesday night and beyond.

Regarding temperatures, guidance pretty consistent for Thursday
and Friday. Have trended low temperature forecast somewhat toward
the ECMWF cooler overnight readings for the weekend. 35

&&

.AVIATION...

VFR conditions are expected to prevail through the early morning
hours as most TAF airports had relative humidity still down in 88 to
93% range which is not very favorable for fog formation. Isolated
showers will continue to develop and move near coastal areas and
south of Lake Pontchartrain during the early morning hours, and
these should have only brief impacts if at all in the vicinity of
terminals like KGPT, KNEW, KMSY and KHUM. Greater coverage of
isolated to scattered SHRA and some TSRA are expected near the
coastal airports by late morning and the more inland airports during
the afternoon, but will likely just carry VCSH in the TAFS. There
will be a chance of MVFR to brief IFR conditions at a few airports
due to patchy fog late tonight/early Tuesday morning. 22/TD

&&

.MARINE...

Combination of a large surface high pressure ridge covering most of
the eastern U.S. and an weak inverted trough of low pressure over
the north central Gulf of Mexico continued to sustain a moderate
pressure gradient and easterly winds of 10 to 15 knots over the
coastal waters and sounds. The winds should slowly subside later
today as the surface pressures lower on the southern periphery of
the high, however winds across the coastal waters east of Southwest
Pass to Pascagoula will likely remain elevated in part due to bands
of showers and thunderstorms producing some gusts up to 20 to 30
knots.

A weaker pressure gradient with weak high pressure over the central
Gulf coast region should keep wind down in 5 to 10 knots range
tonight through Thursday with seas generally 1 to 2 feet offshore. A
cold front is then expected to push through the region Thursday
night into Friday which will bring rising northerly winds and higher
seas offshore late Thursday night and moreso Friday night as cooler
and drier air moves into the region. 22/TD

&&

.DECISION SUPPORT...

DSS code: Green.
Deployed: None.
Activation: None.
Activities: Special 06z/18z upper air soundings for NHC UFN.

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  88  68  90  70 /  40  20  30  10
BTR  88  70  90  71 /  40  20  30  10
ASD  87  69  88  71 /  50  30  30  10
MSY  86  74  88  75 /  50  30  40  20
GPT  85  71  88  73 /  50  30  30  10
PQL  86  68  89  70 /  50  30  30  10

&&

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

$$



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