282
FXUS64 KLIX 171926
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
226 PM CDT Fri May 17 2024

...New UPDATE, SHORT TERM, LONG TERM, AVIATION, MARINE...

.UPDATE...
Issued at 200 PM CDT Fri May 17 2024

Updated forecast through Saturday with a focus on timing of severe
wx and heavy rainfall threat for the next event.

Convection has struggled to develop so far today (and we aren`t
complaining). A special 18Z RAOB sounding from KLIX shows a
subsidence inversion near 850 mb in wake of last night`s MCS that
has helped to cap convection thus far. We are closely monitoring for
convection to initiate along the quasi-stationary frontal boundary
that is located just south of a line from Lafayette to Baton Rouge
to Hattiesburg. This boundary has become increasingly better-defined
as differential heating has magnified the temperature gradient
(upper 60s/lower 70s on the cool side of the boundary and mid 80s in
the warm sector). Low-level convergence has also strengthened near
the front and this will provide a source of lift, but appears to be
too shallow for convective updrafts to reach the LFC. Recent
satellite trends show the CU field is building just south of the
warm front along the Southshore, Coastal MS, and parts of coastal
southeastern LA. This is the area where storms are most likely to
initiate through mid afternoon. Expect coverage of storms to be
widely scaterred given the absence of deeper forcing. However, any
storms that to break the cap has the potential to quickly become
severe with an EML overhead and strong instability rooted in the
boundary layer. These storms will be capable of producing locally
damaging winds (favorable wet microburst environment with high
instability and mid-level dry air) and large hail (steep mid-level
lapse rates).

&&


.SHORT TERM...
(Today through Saturday)
Issued at 235 AM CDT Fri May 17 2024

Although there are a few storms remaining early this morning, any
severe threat likely limited to borderline hail as main portion of
shortwave is east of the area. Quite a bit of uncertainty
regarding severe threat and heavy rain threat over the next 24
hours. Deepest moisture remains just offshore where dew points are
in the mid and upper 70s, but drier air is over the northern
portion of the area, where dew points are in the lower 60s. Next
shortwave actually won`t approach the area until the overnight
period tonight into Saturday morning when precipitable water
values will again approach 2 inches, as southerly surface winds
pull moisture back into the area. Quite a bit of mid level dry air
for much of the area until perhaps 06z Saturday, and would
anticipate that instantaneous areal coverage during the day today
should remain on the scattered side, with a significant increase
in areal coverage during the mid to late evening hours. Drier air
returns during the day Saturday.

Will keep the Flood Watch in place, as there was a fairly sizeable
area of 1.5 to 3 inch rainfalls, and another inch or two on top of
that overnight tonight could cause runoff issues.

Will not move off the NBM temperature forecast at this time, but
the main question for high temperatures today will be cloud cover.

&&

.LONG TERM...
(Saturday night through Thursday)
Issued at 235 AM CDT Fri May 17 2024

Upper ridging builds from Mexico into the Lower Mississippi River
Valley beginning Saturday evening through much or all of the
workweek. At present, it appears that any significant chance of
precipitation beyond tomorrow morning is likely to wait until
beyond the end of the forecast package, with at least some
potential to remain dry through next weekend. Temperatures are
expected to remain above normal through the forecast period.

&&

.AVIATION...
(18Z TAFS)
Issued at 108 PM CDT Fri May 17 2024

A stationary boundary was drapped across the region this
afternoon. Low clouds and fog has been socked in north of the
boundary at KBTR and KMCB. Expected IFR conditions to continue
through most of the afternoon although eventual improvement to
MVFR should occur late in the day (between 21Z and 00Z). South of
the boundary, CIGs are higher but a CU field has developed and
kept the other TAF sites in MVFR CIGs. Expect bases to gradually
increase through the rest of the afternoon and eventually VFR CIGs
will become increasingly common south of the front. Coverage of
showers and storms will be too isolated to mention in 18Z TAFs
before about 02Z this evening. Showers and storms will become
better organized late this evening and especially overnight as a
disturbance approaches. This activity will be focused along the
front which will progress slowly southward through the area.
Confidence in heavy rain and an extended period of IFR/LIFR
conditions increases farther south. This is reflected in the 18Z
TAFs with the greatest restrictions and longest period of TSRA
mentioned for HUM, MSY, NEW, and GPT.

&&

.MARINE...
Issued at 108 PM CDT Fri May 17 2024

The strongest winds thus far today has been present across the far
southeastern coastal waters, but even here observations marginally
support a SCA with occasional gusts to 20 kt. Winds have actually
become light over the lakes where the pressure gradient is light
near a stationary boundary.

Isolated thunderstorms are expected to develop near the coast late
this afternoon and early evening. Although coverage will be
limited, any of these storms have the potential to produce
locally strong winds in excess of 34 kt, large hail, heavy
downpours, lightning, and higher seas. The risk of hazardous
conditions on the waters will increase overnight and continue
through Saturday morning as storms organize along the front and
move southward. Some of our model guidance is showing the
potential for intense convective wind gusts in excess of 50 kt,
perhaps locally to hurricane strength.


&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  66  84  65  88 /  60  30   0  10
BTR  70  87  70  93 /  60  30   0   0
ASD  69  84  69  92 /  70  70   0  10
MSY  71  84  73  90 /  80  70   0  10
GPT  69  81  69  89 /  80  80  10  10
PQL  69  82  67  91 /  70  80  10  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Small Craft Advisory until noon CDT Saturday for LAZ068.

     Flood Watch through Saturday morning for LAZ034>037-039-046>048-
     057-058-060-064-071-076>087-089.

GM...Small Craft Advisory until noon CDT Saturday for GMZ530-532-534-
     536-538-550-552-555-557-570-572-575-577.

MS...Flood Watch through Saturday morning for MSZ068>071-077-083>088.

GM...Small Craft Advisory until noon CDT Saturday for GMZ532-534-536-
     538-550-552-555-557-570-572-575-577.

&&

$$

UPDATE...JK
SHORT TERM...JK
LONG TERM....RW
AVIATION...JK
MARINE...JK