LIX issues Area Forecast Discussion (AFD) at Mar 8, 11:47 AM CST ...New AVIATION...717
FXUS64 KLIX 081747
AFDLIX
Area Forecast Discussion
National Weather Service New Orleans LA
1147 AM CST Sat Mar 8 2025
...New AVIATION...
.UPDATE...
Issued at 1027 AM CST Sat Mar 8 2025
Performed a gridded forecast update this morning to match up with
obs and short-term models/trends. Ongoing this morning, showers
and a few thunderstorms have developed generally south of I-10/12,
north of a stationary/warm front settled across coastal SE LA.
Quick glace at the low-levels illustrates adequate low- level
isentropic ascent ongoing within an increasing warm air advection
regime. This first impulse of showers storms appears to be focused
within the leading edge of a 35kt low-level jet over the NW Gulf,
maximizing isentropic upglide within an elevated regime north of
the warm front. Recent HRRR runs struggle with what's ongoing now
progressing through the afternoon, likely due to the lead LLJ
impulse weakening with time and drifting north, reducing low-level
lift as we get into the afternoon. Approached PoPs by increasing
coverage ongoing now, keeping this activity drifting northeast,
but weakening with time likely reaching a brief period of a lull
in activity this afternoon.
Still looking like the bulk of the activity will come with the
actual surface warm front drifting north later today, fueled by
diurnal destabilization and more ample frontogenetic isentropic
ascent to produce showers and storms, generally over the same
areas drifting north. Here, localized low- level shear provided by
the frontal boundary may lead to a few cells needing to be
monitored for an isolated tornado potential, albeit overall a low
risk. Looking at the 12Z RAOB combined with recent RAP soundings
illustrate it is chilly aloft, with H5 temperatures in the -12 to
-14C range and a well-defined mixed layer between H7 and H5 owing
in good lapse rates supporting mid-level instability (hail growth
CAPE in the 350-450j/KG range, lifting from a MU parcel level).
Given all of this, still looking like the primary risk today will
be hail, potentially large up to 1" (or greater) in diameter.
Beyond going into tonight, the actual front associated with a
developing weak surface low across the area will swing through.
CAMs are not picking up on much activity associated with the low
and front itself, which is a bit hard to believe given the surface
low position and convergence under a moist low-level profile, and
should atleast squeeze out one last round of showers/few storms
overnight before swinging through early daybreak. Approached PoPs
here slightly by increasing some, but will take a closer look
later this afternoon at the full forecast package to see if any
additional adjustments are needed.
Otherwise, will also monitor for if we could see another round of
patchy (potentially dense) fog again ahead of this front
overnight, as NBM probabilistic guidance is coming in mainly for
areas south of I-10/12 and east of I-55 focused along coastal
areas. We typically see these "surprises" ahead of fronts, so will
dive deeper into the forecast analysis later this afternoon. KLG
&&
.SHORT TERM...
(Today through Sunday)
Issued at 357 AM CST Sat Mar 8 2025
Upper ridging over the Gulf early this morning with a closed low
over New Mexico. At the surface, high pressure extended from near
Bermuda to the Florida Straits, with a second high over Nebraska.
Low pressure over Kentucky had a frontal boundary extending
southwest toward Memphis and Texarkana, then westward into New
Mexico. Moisture returning northward from the Gulf had produced
isolated showers near and south of Interstate 10, and over the
coastal waters.
Temperatures were generally in the 60s at 3 AM CST, but were as
cool as 57 at New Roads. With 70+ dew points just offshore flowing
over much cooler waters in the tidal lakes and over the
Mississippi and Atchafalaya Rivers, dense fog has developed.
Originally had planned to only cover with a Special Weather
Statement, but traffic cameras over the last 15-30 minutes have
shown conditions deteriorating enough to justify a Dense Fog
Advisory.
The closed low aloft and surface low pressure over New Mexico will
move eastward today and tonight, probably not getting much further
north than Interstate 10, if that far north. Forecast soundings
currently make it questionable whether we can develop truly
surface based convection, even over lower portions of the
Louisiana coastal parishes. Mid level lapse rates in excess of
7C/KM and wet bulb zero levels below 10K feet would at least leave
marginally severe hail on the table, but it will take surface
based convection for damaging winds/tornado threats to increase
threat levels. Best timing continues to be afternoon into the
overnight hours.
As cooler and drier air arrives on Sunday, it might be able to
squeeze out a few showers Sunday morning, but sunshine is likely
to be a sparse commodity on Sunday. Temperature recovery during
the day Sunday is likely to be rather limited, perhaps no more
than 5-10 degrees, unless we get some sun.
&&
.LONG TERM...
(Sunday night through Friday)
Issued at 330 AM CST Sat Mar 8 2025
As cooler air plugs in Sunday night, overnight lows will fall back
into the 40s across much of the area, which actually isn't very
far below normal for mid-March. Similar lows are expected Monday
night before warmer weather returns. Another southern stream
shortwave moves across the Gulf Coast States Wednesday night or
Thursday, with the 00z operational GFS solution quicker than the
ECMWF operational. Deep moisture return appears to be somewhat
limited, especially with the GFS solution. Would note, however,
that the 00z ECMWF operational PoPs are pretty much the wettest
member of their ensemble envelope, so the drier solution may be
the way to go. Another strong system moves through the Plains
States Friday and Saturday, with current solutions keeping the
more significant impacts to the north of our area.
Monday high temperatures will struggle to get much above 70, which
is right around normal. Tuesday through the end of the week will
bring warmer than normal temperatures, perhaps reaching 80 in some
spots the second half of the week.
&&
.AVIATION...
(18Z TAFS)
Issued at 1141 AM CST Sat Mar 8 2025
Main impacts in the short-range this afternoon will be ongoing
SHRA and embedded TSRA across area terminals, generally along the
I-10/12 corridor. This activity is expected to steadily diminish
with time, however isolated -SHRA could progress periodically.
Another round of more widespread scattered TSRA/SHRA is expected
later this afternoon/evening, following by a FROPA across all
terminals going into daybreak Sunday. Could see some areas of fog
causing periodic lower VIS/CIGS before this front overnight into
early Sunday, reducing flight categories accordingly but is
expected to dissipate around sunrise following the FROPA. Beyond
this period into early Sunday, could likely see low CIGs
progressing with low clouds at times across all area terminal
continuing through the day. KLG
&&
.MARINE...
Issued at 330 AM CST Sat Mar 8 2025
As noted in the short term portion of the discussion, where moist
air with 70 degree dew points are moving over much colder water
temperatures, areas of fog have developed. Will carry a Marine
Dense Fog Advisory until 16z for now, for the tidal lakes, Breton
Sound and inner coastal waters bordering outlets for the
Mississippi and Atchafalaya Rivers. May need to be extended, but
will wait for visible satellite pictures to redefine trouble
areas.
Probably won't need much in the way of wind related hazard
headlines until late in the day Sunday into Monday as cooler and
drier air reaches the waters. Small Craft Advisories will likely
be necessary at that time. Conditions should improve Monday night
into midweek. A more significant wind producer looks to be in the
cards for next weekend.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 76 55 65 42 / 60 80 20 10
BTR 77 59 67 44 / 60 70 20 0
ASD 78 62 73 47 / 50 70 30 10
MSY 75 63 71 49 / 70 50 30 0
GPT 77 61 72 48 / 40 80 40 10
PQL 78 61 74 48 / 50 80 40 20
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&
$$
UPDATE...KLG
SHORT TERM...RW
LONG TERM....RW
AVIATION...KLG
MARINE...RW
Source:
LIX issues Area Forecast Discussion (AFD) at Mar 8, 11:47 AM CST ...New AVIATION...---------------
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