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

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000
FXUS64 KLIX 241311
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
711 AM CST Fri Feb 24 2017

.UPDATE...
Patchy radiation fog became a bit more expansive over the last
few hours as temperatures dropped as much as 6 degrees in two
hours at a few locations. Most of the dense fog remained confined
to the Dense Fog Advisory area of the southeast/coastal
Mississippi counties, so an expansion in area of the advisory is
not anticipated. Fog is mostly shallow and should burn off fairly
quickly between 7:30 and 9:00 am. 22/TD

&&

.AVIATION...
Updated TAFS since 1130z to account for greater fog development
and LIFR conditions than earlier anticipated. Otherwise, expect
improvement back to VFR around 15z or shortly thereafter.

&&

.DECISION SUPPORT...
DSS code: Blue.
Deployed: None.
Activation: None.
Activities: DSS Support for City of New Orleans.
            Dense Fog Advisory MS Coast until 9 am today.

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.


&&

.PREV DISCUSSION (issued at 449 am)
SHORT TERM (Today through Sunday night)...

A broad mid/upper level trough over about the western half of the
continental U.S. will have a series of shortwave troughs moving
east and northeast across the plains and upper Mississippi valley
today. An associated, rather strong surface low over the mid to
upper Mississippi Valley is expected to continue moving northeast
into the western Great Lakes region today. This low will drag a
cold front southeast into the Ark-La-Tex region this morning, and
the central Gulf coast region tonight. Today will be a rather warm
and more humid with highs around 80 in most areas except for mid
to upper 70s near the coast and offshore. There will not be much
moisture for this front to work with (precipitable water 1.0 to
1.2 inches), but there should be isolated showers along the front
starting in southwest Mississippi and east central/south central
Louisiana this evening, and areas near Lake Pontchartrain and the
coast after midnight.

Drier and cooler air will precede the cold front Saturday into
Saturday night as surface high pressure builds over the forecast
area. High temperatures will only be cooling back to the seasonal
normals in the upper 60s. Low temperatures Saturday night will be
quite a bit cooler and below normal ranging from mid to upper 30s
north to the 40s south. This dry and cooler airmass will remain
over the region into Sunday even as the surface high center moves
east of the forecast area, but southerly winds Sunday night will
keep the lows not nearly as cool as Saturday night.

LONG TERM (Monday through Thursday night)...

A broad mid/upper level trough will once again set up over the
western states Tuesday (Mardi Gras) as a series of shortwaves
move through the fast flow in both the northern and southern
streams during the early to middle of the week. The 00z GFS/ECMWF
operational runs today indicate a fast moving shortwave trough a
will move east-northeast across the southern plains and lower to
mid Mississippi valley Sunday night into Monday morning while
dampening out. Southern stream energy/forcing and possibly a weak
surface boundary (more a trough, not a front) will likely interact
with sufficient moisture and instability to produce scattered
showers and thunderstorms across the forecast area Monday (Lundi
Gras), with some isolated showers north and west starting Sunday
night. Isolated showers and storms could linger Monday night into
Mardi Gras Tuesday and Tuesday night, but the latest model runs
have trended to shift the focus for showers to the north as the
next cold front approaches and moves into the region on Wednesday.
Have maintained rain chances in the 30 to 50 percent range on
Wednesday. Regarding temperatures, it is expected to be rather
warm early in the week, with Mardi Gras Tuesday likely the warmest
with upper 70s to lower 80s for highs with Wednesday only slightly
cooler in advance of the cold front. 22/TD

&&

AVIATION...

Low stratus has begun to spread over most of the area the last
couple of hours.  Ceilings are generally ranging from 500 to 1000
feet resulting in prevailing IFR conditions.  Some fog is developing
as the stratus builds down, but visibilities are not expected to
fall any further than one mile at times.  The low ceilings should
persist through around 16z before gradually lifting to broken deck
between 3000 and 4000 feet by 20z.  The brief window of VFR
conditions will quickly revert back to MVFR and then IFR conditions
as a frontal system sweeps through after 06z tomorrow and produces
another round of low ceilings between 500 and 1000 feet. 32

&&

MARINE...

Southerly flow of 10 to 15 knots will continue through this evening.
Later tonight, a strong frontal boundary will quickly sweep through
the coastal waters resulting in a period of strong northwest and
then north winds of 20 to 25 knots through Saturday morning.  Seas
should also ramp up quickly due to these winds with seas of up to 6
feet possible over the offshore waters by tomorrow morning.  As high
pressure settles over the Tennessee Valley, winds will relax
slightly into exercise caution range of 15 to 20 knots by Saturday
afternoon. A decent pressure gradient will persist over the Gulf,
and expect to see winds remain in the 15 to 20 knot range through
early next week even as high pressure shifts to the east and winds
turn back to the south by Sunday night.  A fast moving low pressure
system will race from the Southern Plains into the Midwest Monday
keeping a tighter pressure gradient and persistent onshore flow of
15 to 20 knots in place.  Seas will remain rather choppy at 3 to 5
feet through this period.  The wind field may relax a bit by
Wednesday as the pressure differential over the Gulf weakens, but
still expect an onshore wind of 10 to 15 knots to be the rule.
Another cold front is then expected to bring stronger offshore winds
to the coastal waters for the latter part of next week. 32

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  81  48  63  35 /   0  20   0   0
BTR  81  50  67  37 /   0  20   0   0
ASD  80  54  69  36 /   0  20  10   0
MSY  79  54  68  47 /   0  20   0   0
GPT  75  54  68  39 /   0  20  10   0
PQL  78  56  70  36 /   0  20  10   0

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...Dense Fog Advisory until 9 AM CST this morning for MSZ077-
     080>082.

GM...None.
&&

$$



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