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

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FXUS64 KLIX 280443
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
1143 PM CDT Tue Jun 27 2017

.AVIATION...
Convection is expected to develop and expand in coverage mainly
after 17Z at nearly all terminals. Otherwise, VFR conditions are
expected outside convection where IFR to MVFR conditions are
likely. Downburst wind potential around 35 knots Wednesday. 24/RR

&&

.PREV DISCUSSION... /issued 309 PM CDT Tue Jun 27 2017/

SHORT TERM...

A stationary front lingering just off the Louisiana coast will
slowly push inland tonight and tomorrow morning in response to an
approaching upper level vorticity max slowly ejecting out of Texas
and the western Gulf. A weak mid-level reflection of this upper
level feature will also assist in pushing the stalled boundary
inland over the 24 hours. Forcing along this boundary combined
with favorable jet dynamics and lift aloft will allow for
increased rain chances beginning late tonight for areas south of
I-10 and then expanding across the entire forecast area by
tomorrow afternoon. POP should remain fairly low tonight, but is
expected to rise into the 50 to 70 percent range by tomorrow
afternoon. Highest POP will be nearest the boundary south of the
I-10 corridor tomorrow afternoon. With extensive cloud cover and
convective activity around, afternoon highs will remain held in
check with readings only expected in the middle 80s.

A slight decrease in convective activity should occur tomorrow
night as temperatures cool back into the middle 70s, but decent
mid and upper level omega values will support continued convective
activity near the low level boundary through the night. Have high
end chance POP around 50 percent areas along and south of the I-10
corridor to reflect this continued convective risk. Thursday
should be the most active day in terms of overall convective
coverage as the low level boundary will draped along the I-10
corridor and the upper level trough axis will be directly over the
region. Ample forcing and instability will be in place as
temperatures rise back into the middle 80s. Have likely POP of
around 70 percent in the forecast for the entire region. Severe
weather threat should be fairly limited, but above average
precipitable water values and mixing ratios support some locally
heavy downpours and possible street flooding issues on Thursday.

The upper level trough will begin to shear out and weaken Thursday
night and Friday and the weak low level boundary will continue to
shift further inland over this period. As a result, overall rain
potential will begin to decrease on Friday. Expect to see slight
chance and low end chance POP Thursday night as temperatures cool
off and overall instability decreases, and then a return to more
scattered to numerous showers and thunderstorms by Friday
afternoon as lingering moisture and ample instability combines
with the weaker omega aloft to produce a POP of 40 to 60 percent.

LONG TERM...

A more normal Summer weather pattern will become established by
Saturday and then remain in place through early next week. A broad
ridge will extend westward across the eastern and central Gulf
from the western Atlantic through the period placing the area on
the western side of this ridge. Deep layer southerly flow in the
low levels will take hold of the area resulting in warm and muggy
conditions each day. However, the influence of the ridge in the
upper levels will introduce some subsidence and drier air in the
mid and upper levels. This will produce a weak mid-level cap which
will inhibit most convective activity. However, localized forcing
mechanisms associated with the seabreeze cycle should allow for a
general 20 to 30 percent POP and isolated to scattered convection
each afternoon as temperatures climb into the lower 90s. The
convection should dissipate fairly quickly in the evening as
temperatures cool into the 80s and then middle to upper 70s
resulting in mainly dry conditions each night.

AVIATION...

TAFs will continue to show mostly quiet conditions with
a great deal of mid and high clouds over the area but can`t
completely rule out low cigs that may lead to MVFR for a very short
time. this afternoon. Very light showers are mainly located south of
the coast but a stray shower or two could impact HUM. Other than
that look for VFR conditions to remain. /CAB/

MARINE...

No change in the thinking as winds should begin to
slowly veer around tonight with onshore flow returning by tomorrow.
Onshore flow will be in place through the remainder of the forecast
maybe picking up to 10 to 15 knots at times but overall the onshore
should remain weak for most of the forecast. Other concern will be
convection that should impact at least the near shore waters each
day. /CAB/

DECISION SUPPORT...

DSS code: Blue.
Deployed: None.
Activation: None.
Activities: Monitoring Hydro

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  68  86  70  83 /  10  50  30  70
BTR  70  86  71  85 /  10  60  40  70
ASD  72  85  73  82 /  10  60  50  70
MSY  74  83  74  84 /  20  70  60  70
GPT  74  84  74  82 /  10  50  50  70
PQL  73  84  73  82 /  10  50  50  70

&&

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

$$



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