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

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FXUS64 KLIX 171733

Area Forecast Discussion
National Weather Service New Orleans LA
1233 PM CDT Sat Mar 17 2018

Pretty chaotic sky situation with variable cloud decks ranging
from IFR levels where residual moisture and cool river water
affects may be maintaining lower than normal ceilings in a few
drainage prone locations. Other locations are VFR but lowering at
times to MVFR with convective bases under developing SHRA/TSRA
between KLFT and KHDC. Light winds and boundary layer decoupling
will lead to widespread IFR and LIFR conditions developing
overnight in fog and low marine layer cloud deck. Slow
improvements expected towards 15Z then destabilizing due to large
scale lift over the region in advance of approaching frontal
boundary heading into Sunday afternoon. 24/RR


Pretty unstable sounding with a most unstable lifted index of -6
destabilizing to -8 with daytime heating. CHAP output does show a
14% chance of severe thunderstorm potential with gusts 45 kt the
main threat likely in downbursts as sounding shows a large dry
mid-layer then saturated above, which is optimal for wet-
microburst production. Precipitable water 1.31". Wind profile is
essentially unidirectional SW 10-20kt to 6500 ft, then W-WNW 15-94
kt above. Winds in the dry layer 35-50 kt which is in line with
CHAP guidance and basis for HWO expectations today. 24/RR


.PREV DISCUSSION... /issued 355 AM CDT Sat Mar 17 2018/

Elevated rain chances will continue today. A weak upper level ridge
will be passing across the area as it follows the trough that
brought rain to the region yesterday. Southeast flow wrapping around
a surface ridge centered near the Bahamas will keep dewpoints well
into the mid 60s. Temperatures will moderate to near 80 as heights
increase from the upper ridge aloft. The combo of warming temps and
ample moisture in place will allow for scattered to numerous showers
and a few thunderstorms to develop. Maintained similar POPS as
previous forecast.

Meanwhile, an upper level trough is moving into and across the
Pacific northwest. This feature will progress east across the lower
Rockies on Sunday. Thunderstorm coverage will increase throughout
the CWA as surface pressures begin dropping and lift along a pre-
frontal trough swings through. Increasing wind shear and instability
will provide the potential for low end severe storms...mainly in
northern portions of the forecast area near southwest Mississippi.
Lingering showers will probably persist into Monday morning as the
trough tracks across the lower Mississippi Valley.

The actual cold front associated with this early week system will
not get here until Tuesday morning as a secondary nose of the trough
digs south across the central Gulf Coast. Broad troughing will then
persist across the CWA through much of the rest of next week. This
will keep temps at to below normal during that time frame and a dry
forecast with no rain till possibly the following weekend.


Variable conditions were being observed at the terminals late
this evening...ranging from VFR to IFR. In general, MVFR to IFR
conditions will develop and prevail overnight and into early
Saturday as a result of ceilings and/or restricted vsbys due to
patchy fog. Isolated LIFR category conditions are also possible at
times. Conditions will mostly improve to IFR to MVFR by Saturday
afternoon outside areas of convection. /11/

Light to moderate onshore flow will continue through Sunday
before moderate to possibly strong onshore flow develops Monday as
a strong sfc low gets going over the Mid and Lower MS Valley.
This will drive a cold front through the coastal waters overnight
Monday with strong offshore winds in its wake. SCY conditions will
develop and continue through Tuesday night before winds finally
begin to relax Wednesday with high pressure building in. /CAB/


DSS code: Blue.
Deployed: None.
Activation: None.
Activities: Monitoring river flooding

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; Enhanced 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.


MCB  79  64  78  65 /  50  20  60  40
BTR  79  65  80  65 /  70  20  60  30
ASD  77  64  78  66 /  60  20  40  30
MSY  77  65  79  66 /  60  20  40  40
GPT  74  64  75  68 /  60  20  40  40
PQL  75  64  77  66 /  50  20  40  40



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