245
FXUS64 KLIX 162343 AAA
AFDLIX

Area Forecast Discussion...UPDATED
National Weather Service New Orleans LA
643 PM CDT Sun Jun 16 2024

...NEW AVIATION...

.SHORT TERM...
(This evening through Monday night)
Issued at 245 PM CDT Sun Jun 16 2024

Scattered showers and thunderstorms in association with a weak
inverted surface trough continue to move inland over southeast LA
this afternoon. Primary impacts are heavy downpours, lightning,
and gusty winds in excess of 30-40 mph. This activity will
gradually wane into the evening hours as daytime heating
dissipates and weak subsidence from high pressure on the back side
of the trough moves in. This will create a lull in rainfall
tonight through early Monday morning.

Monday we`ll see PWATs surge in excess of 2" (near daily record
maximums) and more widespread convective coverage develop over the
coastal waters and spread inland through the morning hours. Locally
heavy downpours (rain rates as high as 2"/hour possible),
frequent lightning, and gusty winds in excess of 35-40 mph will be
the primary impacts, similar to today. With coverage being more
widespread, however, this does increase the potential for
localized flash flooding especially in urban and poor drainage
areas. Be extra careful on your morning commute and give yourself
extra time to arrive to work. Timing appears to focus heaviest
rainfall through the first half of Monday with lesser coverage and
concerns as we progress into the late afternoon and evening hours.

Gradual deepening of a broad low over the Bay of Campeche up
against a strengthening high pressure system over the southeast
CONUS will generate a strong pressure gradient over the northern
Gulf Coast. As such, surface winds will increase on Monday and
continue to intensify through Tuesday. Immediate coastal areas
where friction is weaker coming off the water will see sustained
winds of 20-25 mph with gusts as high as 35 mph. This is right at
the cusp of wind advisory criteria, but will hold off on this
forecast package. If confidence increases in more frequent gusts
exceeding 30 mph this would probably prompt issuance of one. While
breezy, areas further inland will see reduced winds by comparison
due to frictional forces as these stronger winds push inland.

&&

.LONG TERM...
(Tuesday through Saturday night)
Issued at 245 PM CDT Sun Jun 16 2024

The plume of deep tropical moisture associated with the broad
area of low pressure in the southwestern Gulf will continue to
push westward in conjunction with the low moving toward the
western Gulf coast. Based on the trends associated with the track
of this low, the axis of heaviest storm total rainfall has
shifted further southwest. Highest totals are still focused along
coastal Southeast LA of 2 to 4" and lower amounts further inland
and northeast. Tuesday should still see a fair amount of coverage
of showers and storms with similar timing and impacts to Monday.
Additional concern at this stage would just be the antecedent
conditions present from any heavy rainfall that occurred on
Monday.

Rain chances will be tempered slightly Wednesday into the latter
part of the week as drier continental air on the western flank of
the surface high pressure is able to infiltrate from the northeast
and decrease PWATs. This will put us back into a more typical
summer convective regime with morning marine convection and
afternoon thunderstorms. Slightly more ridging is able to nose
into the latter part of the week which will help dry things up and
help us see more sunshine (and heat things up slightly).
Uncertainty is much higher Friday into the weekend as we monitor
the progress of an inverted surface trough currently situated over
the southwestern Atlantic. Some of the deterministic guidance has
indicated the potential that this weak surface trough rounds the
southern flank of the high pressure of the eastern CONUS and
arrives into the area around this timeframe, but the exact track
and strength of this feature varies greatly in the ensemble
guidance. Just something to watch for now.

&&

.AVIATION...
(00Z TAFS)
Issued at 637 PM CDT Sun Jun 16 2024

Most of the convection has moved out of the region this evening.
Think this will be a brief break in the rain/storm chances so
carried only VCs overnight for showers. That said mostly VFR
anticipated overnight.MCB may drop into IFR ranges with CIGs
overnight with also a reduced VIS. Otherwise, convection will
again develop Monday morning and continue to stream south to
north. A bit higher confidence in convection on Monday vs today as
well as timing. Continued VCTS as exact timing of embedded
thunder is currently tough to pin down. Otherwise, southeasterly
winds will begin to increase across the region with many sites
gusting over 20kts by mid to late morning through the end of the
cycle. (Frye)


&&

.MARINE...
Issued at 245 PM CDT Sun Jun 16 2024

Have been dealing with clusters of storms producing gusty
conditions across the waters, but should see a lull in activity
overnight with weak surface high pressure nosing in. This also
will briefly weaken the pressure gradient and result in winds
relaxing, but this will be very short-lived.

Conditions will gradually worsen Monday morning over the open
Gulf waters as the pressure gradient between a high to the
northeast and a low to the southwest strengthens. By tomorrow
morning, small craft advisory conditions are expected to be in
place as easterly winds ramp up to 20 to 25 knots. These easterly
winds will remain in place through the end of the week and could
further strengthen to near gale levels on Tuesday and Wednesday as
the low to the southwest continues to deepen. Given the long
fetch of these 20 to 30 knot winds from the southeast Gulf into
the coastal waters a swell train of 3 to 4 feet is expected on top
of the wind waves of 5 to 8 feet, and this will push seas to
between 8 and 12 feet over the open Gulf waters on Tuesday and
Wednesday.

Additionally, water will continue to pile up on east
and south facing shores over this period, and minor coastal
flooding of 1 to 2 feet above ground level is expected from
Tuesday through Thursday. A coastal flood warning may be necessary
for areas around Lake Borgne and Bay St. Louis on Wednesday if
confidence increases for inundation closer to 2.5 feet or so. Will
monitor levels within Lake Pontchartrain as this fetch gradually
funnels into the lake Thursday into Friday.

The low in the southwest Gulf should move into Mexico on Thursday
and Friday and the pressure gradient will begin to ease as the
low weakens. Winds will slowly ease from 20 to 25 knots on
Thursday to 15 to 20 knots by Friday. Given the extended duration
of small craft conditions, a small craft advisory is in effect for
the open Gulf waters and the Chandeleur and Breton Sounds from
Monday morning to Thursday morning. There is the potential that
winds could further increase into gale conditions, and a gale
watch may be issued closer to the event on Tuesday and Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  72  85  71  83 /  30  90  20  50
BTR  76  87  76  86 /  40  90  30  70
ASD  76  88  76  87 /  50  80  50  70
MSY  79  87  79  86 /  60  90  60  90
GPT  77  87  76  86 /  60  80  50  60
PQL  75  90  75  91 /  60  80  40  50

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Small Craft Advisory from 7 AM Monday to 7 AM CDT Thursday for
     LAZ068.

     Coastal Flood Advisory from 1 AM Tuesday to 4 PM CDT Wednesday
     for LAZ066>070-076-078.

GM...Small Craft Advisory from 7 AM Monday to 7 AM CDT Thursday for
     GMZ536-538-550-552-555-557-570-572-575-577.

MS...Coastal Flood Advisory from 1 AM Tuesday to 4 PM CDT Wednesday
     for MSZ086>088.

GM...Small Craft Advisory from 7 AM Monday to 7 AM CDT Thursday for
     GMZ538-550-552-555-557-570-572-575-577.

&&

$$

SHORT TERM...TJS
LONG TERM....TJS
AVIATION...RDF
MARINE...TJS