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

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873
FXUS64 KLIX 251047
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
447 AM CST Sat Feb 25 2017

.SHORT TERM (Today through Monday night)...

Shortwave trough is moving east across the Mississippi Valley
early this morning, and will continue to move east of the forecast
area by mid to late morning. The associated cold front, located
over the coastal areas and near-shore coastal waters, will push
southeast of the outer coastal waters by late morning. Drier and
cooler air has already caused quick drops in temperature in
northern areas the last couple hours, and this trend will continue
through about 7 am before full sunshine starts the typical diurnal
warming. Cold air advection will not be strong enough to keep
temperatures from reaching near the seasonal averages for highs
today, but it will be a bit breezy, particularly this morning.
Low temperatures tonight will be quite a bit cooler and below
normal ranging from mid to upper 30s north to the 40s south. The
below normal temperatures will come to an end by Sunday afternoon
as southerly winds return as high pressure moves east. Highs on
Sunday are expected to reach the upper 60s and lower 70s, and much
warmer lows are expected Sunday night.

.LONG TERM (Mardi Gras Tuesday through Friday night)...

Much warmer weather will return for the beginning of the work
week with a warm front pushing north across the area on Monday.
Impulses in the fast west southwest flow aloft out ahead of a
broad western conus upper trough will act on increasing and
deepening moisture over the area to yield scattered to numerous
showers and thunderstorms on Monday, with the best chances across
the northern half of the forecast area. There will be ample shear
early in the day and moderate instability by afternoon that would
support a few strong storms and even a severe thunderstorm or
two, but the threat was not quite at the level of confidence to
support a marginal risk in the SPC Convective Outlook. Will
continue to evaluate this risk through the weekend.

Lower rain chances will be in the offing for Mardi Gras day with
the best chances remaining to the north of the forecast area.
However, as an upper trough traverses the central U.S. by mid
week another cold front will be pushed across the forecast area
Wednesday resulting in another round of convection Wednesday into
Wednesday evening. Drier and cooler weather is then expected for
the end of next week. 22/TD

&&

.AVIATION...

Cold front progressing quickly eastward, and should be east of all
terminals prior to 12z TAF package issuance. About a 50 mile wide
band of stratocumulus clouds, with most based FL025-035 should also
be east of all terminals prior to 12z. Do not anticipate any ceiling
or visibility restrictions beyond this morning. Main forecast issue
will be winds downwind of Lake Pontchartrain. This will allow winds
to gust to 25 knots or so at KMSY and KNEW this morning. By
afternoon, any gusts above 20 knots should be limited to KNEW. 35

&&

.MARINE...

Will continue headlines as earlier issued during the evening shift.
While Small Craft Advisory conditions will abate this morning,
guidance indicates that Exercise Caution headlines may be necessary
for a prolonged period, into Monday for much of the open waters, as
well as Breton and Chandeleur Sounds. Cold air only remains around
for about 24 hours or so, with onshore flow returning during the day
on Sunday, along with significant warming. Quick moving upper system
may bring thunderstorms back to the coastal waters on Monday. Next
front will move through Wednesday night, with rather strong wind
fields associated for Thursday. Small Craft Advisories look to be
necessary at that point. 35

.FIRE WEATHER...

Surge of dry air behind cold front, that caused dewpoints at KMCB
and KHDC to plummet in the 4 to 6 am time frame, is a concern for
lower RH carrying forward through the day. This may be especially
true during the afternoon hours when GFSBufr soundings indicate
there may be lower dewpoints of several degrees below the MOS
guidance. Because of this, have lowered the forecast dewpoints and
RH from the previous forecast. The combination of forecast RH
below 25% and north winds in the 10 to 15 mph range with some
higher gusts means conditions will be approaching red flag warning
criteria over portions of the Mississippi Gulf coast and a few
locations south of Lake Pontchartrain.

&&

.DECISION SUPPORT...

DSS code: Blue.
Deployed: None.
Activation: None.
Activities: Support for City of New Orleans through Tuesday.

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  62  36  70  55 /   0   0   0  40
BTR  65  39  71  59 /   0   0   0  50
ASD  68  38  70  57 /   0   0   0  20
MSY  67  48  70  62 /   0   0   0  30
GPT  69  40  66  57 /  10   0   0  10
PQL  71  37  68  54 /  10   0   0  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory until noon CST today for GMZ530-532-534-536-
     538-550-552-555-557-570-572-575-577.

MS...None.
GM...Small Craft Advisory until noon CST today for GMZ532-534-536-538-
     550-552-555-557-570-572-575-577.

&&

$$



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