Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/24/22
Area Forecast Discussion
National Weather Service New Orleans LA
724 PM CDT Sat Apr 23 2022
.AVIATION...
00Z TAFs - Mainly VFR this evening and a scattered leftover CU
field early with bases 2.5-4 ft. There is also mid-level clouds
from some earlier convection that will stream northward across our
western-most terminals but have little impact to flight operations
with CIGs 8-10 kft. The pressure gradient on the western periphery
of high pressure off the eastern seaboard looks strong enough to
prevent winds in the boundary layer from decoupling in most spots
tonight. The setup is not particularly favorable for fog as a
result. Stratus is more likely, especially toward dawn and across
inland zones. NBM/HREF CIG probabilities favor bases in the 1-2
kft range for places like BTR, ASD, and MCB. There was enough
support from the ensemble guidance to include a tempo IFR group
for MCB toward daybreak.
SE winds increase and CU field with bases between 2.5-3.5 kft AGL
should develop after a few hours of daytime mixing Sunday
morning. This could result in a brief MVFR restrictions between
about 15-18Z. Additionally, the flow is expected to veer slightly,
becoming S-SE and strengthening to 9-14 kt with gusts to 20 kt.
Widely scattered showers and isolated t-storms are expected to
develop during peak heating in the late morning and afternoon,
especially north and west of the NOLA terminals. -JRK
&&
.PREV DISCUSSION... /issued 533 PM CDT Sat Apr 23 2022/
LATE AFTERNOON UPDATE...
Just sent a forecast update with minor tweaks to the PoPs and
Weather grids through 9 PM. Kept in a small area of isolated
showers north and west of Lake Maurepas and along the Atchafalaya
basin through sunset. Removed mention of thunder. Despite SPC
mesoanalysis showing SBCAPE over 1000 J/KG, HRRR model soundings
and recent ACARS soundings near MSY indicate a thermal cap around
700 mb for mixed-layer parcels. This has led to an unfavorable
environment to sustain deep convective updrafts needed for
lightning development. -JRK
PREV DISCUSSION... /issued 328 PM CDT Sat Apr 23 2022/
SYNOPSIS...
High pressure off the New Jersey coast extended southward into the
Carolinas and then westward into our area. Aloft, upper ridging
was noted over the Appalachians with a deep upper low over the
Dakotas.
Locally, onshore flow continued with a rather extensive cumulus
field again this afternoon. The minor difference from yesterday
has been very isolated rain showers to the west of Interstate 55.
By very isolated...it`s likely that the showers are covering less
than one percent of any particular parish at one time.
Temperatures were generally in the lower and middle 80s at mid-
afternoon, with dew points in the mid and upper 60s, slightly
higher than yesterday at this time.
SHORT TERM (through Tuesday)...
Continuing Coastal Flood Advisory as configured through 7 PM
tomorrow, but that should be the last tide cycle of this event as
winds relax tomorrow evening and the astronomical tide ranges also
decrease.
Upper trough over the Dakotas will gradually lift northeast into
Ontario over the next 36 hours, suppressing the southeast US ridge
a bit. A subtle southern stream shortwave may provide enough
forcing to produce scattered showers and perhaps a thunderstorm or
two tomorrow afternoon as it crawls up the west side of the ridge.
Another strong shortwave dropping into the western side of the
trough to our north will give the cold front to our west a slow
shove into and through the area Monday night and Tuesday. As noted
above, scattered showers and perhaps a few thunderstorms will be
possible tomorrow afternoon, but a better opportunity tomorrow
night into Tuesday. Front should be exiting the area by sunset
Tuesday.
Little variance in guidance temperatures through Monday night.
Highs Tuesday will be dependent on timing of frontal passage, with
current numbers more supportive of the warmer ECMWF solution. 35
LONG TERM (Tuesday night and beyond)...
Ridging shifts eastward for the middle and end of the week. Drier
air will move in, with dew points falling into the 40s and 50s for
Wednesday through Friday. Probably won`t see any significant
return flow of moisture until about Friday or Saturday, so no
mention of precipitation will be noted in the forecast until
Saturday night or Sunday of next week, when the next frontal
passage will be expected. The ECMWF solution is a bit slower than
the GFS, and we`ll see how the timing shifts over the next several
days.
Regarding temperatures, with a drier airmass moving into the area,
there are trends to follow that have served well over the last few
months. Where differences in guidance have existed, trending
toward cooler low temp guidance and warmer high temp guidance has
generally been beneficial. Ranges between the 25th and 75th
percentiles of the NBM for the middle and end of next week are
around 4-6F, which isn`t bad for forecast confidence, with the
deterministic numbers are coming in similar to the trends noted
above. Would note that once we get beyond next Saturday, those
ranges open up considerably, indicating very limited confidence in
the forecast beyond that point. 35
AVIATION (valid through 00z Monday)...
Most terminals VFR this afternoon, but where the cumulus field is
a little more widespread, there are a couple terminals reporting
ceilings right around FL030. Introduced VCSH to KMCB and KBTR
based on radar, but that`s probably overkill to some extent. The
showers and most of the cumulus should dissipate as we approach
sunset today.
Winds aren`t expected to totally decouple tonight again tonight,
which should reduce the threat of fog being a significant impact.
More likely, there will be a few locations with low stratus around
sunrise, similar to this morning. Looking at the NBM guidance it
shows that the probability of visibilities <3 miles is in the
single digits at all terminals except KMCB (17%). Expect a brief
period of MVFR to IFR conditions at several terminals, with
improvement to general VFR conditions by 15z Sunday.
The threat of SHRA/TSRA increases during the afternoon hours on
Sunday, primarily at terminals west of Interstate 55. At this
point, vicinity mention probably more realistic than TEMPO or
prevailing mention. 35
MARINE...
Will extend Small Craft Exercise Caution headlines overnight
across all waters, with the expectation that they will need
continued on Sunday across most or all waters. May see some
relaxation in the winds/seas Sunday night into Tuesday evening,
until a cold front moves through the waters. Even Tuesday night
into Wednesday, it appears that conditions may not reach Advisory
criteria. 35
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 64 84 65 84 / 0 30 0 50
BTR 66 84 67 85 / 10 40 0 60
ASD 65 85 66 85 / 0 20 0 30
MSY 69 83 70 84 / 0 20 0 30
GPT 67 82 68 82 / 0 10 0 20
PQL 64 82 63 83 / 0 10 0 10
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Coastal Flood Advisory until 7 PM CDT Sunday for LAZ064-069-070-
076-078.
GM...None.
MS...Coastal Flood Advisory until 7 PM CDT Sunday for MSZ080>082.
GM...None.
&&
$$