269
FXUS64 KMEG 302018
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
318 PM CDT Sun Jun 30 2024

...New SYNOPSIS, DISCUSSION...

.SYNOPSIS...
Issued at 318 PM CDT Sun Jun 30 2024

Scattered thunderstorms will end this evening as slightly cooler
and drier air moves into the Mid-South. Monday will provide a
respite from the oppressive heat with high temperatures mainly in
the 80s. No rain is expected Monday or Tuesday, but the heat will
return Tuesday with humidity back in the picture by midweek. A
more unsettled weather pattern is expected late week through the
weekend.

&&

.DISCUSSION...
(This evening through next Saturday)
Issued at 318 PM CDT Sun Jun 30 2024

An anomalous 598 dam subtropical ridge continues to bring
significant heat and humidity to the Southern Plains and
Southeast. To put the strength of this ridge into perspective,
500 mb heights across the Mid-South are in the 99.5th percentile
with record values (based on 30-year CFSR climatology) to our
south and west. The good news is this ridge will abate over the
next 24 hours, concomitant with the passage of a surface cold
front. In the interim, we`re going to be dealing with dangerous
heat and humidity through this evening across much of the area.
Moisture pooling south of the cold front has kept dewpoints from
mixing with many areas with dewpoints along and south of I-40
(many of the AWOS dewpoints are exhibiting a high bias or simply
bad data). Farther north, north winds have kept temperatures
slightly cooler with dewpoints dropping into the mid 70s. Some
areas will gain some relief from the heat as scattered storms form
across the Mid-South. This activity will generally remain along
and south of a line from Forrest City, to Memphis, to Parsons,
quickly ending by sunset.

We`re in for a real treat on Monday with afternoon highs in the
80s across the majority of the CWA. Combined with dewpoints in
the upper 50s to lower 60s, heat indices look to be a good 20-25
degrees lower than today. No rain is anticipated in the wake of
the cold front under mostly sunny skies. If you have yard work
you`ve been putting off, tomorrow is the day to get it done!

The subtropical ridge is progged to expand across the Southeast
and into the Mid-Atlantic states on Tuesday as a trough digs
over the western CONUS. Temperatures will respond by returning to
the 90s and moisture return will commence as southerly flow
develops. Fortunately, heat indices generally look to remain below
105F in most areas for one more day. The ridge centered over the
Mid-South and modest dewpoints should preclude diurnal convection.

By midweek, we see a series of shortwave troughs move through the
longwave trough over the western/central CONUS. These systems will
act to damp the ridge`s amplitude and cause it to to spread
longitudinally. A subtle wave is forecast to move through the Mid-
MS Valley Wednesday and may provide enough forcing to aid in
convective development, though coverage may be limited. The
deterministic ECMWF tends to have more in the way of instability
than the GFS with the NBM favoring the deeper moisture of the
former solution. The deeper moisture will also come with heat
concerns as temperatures climb into the 90s. Heat Advisories may
be needed for portions of the area Wednesday and/or Thursday.
We`ll move into a more unsettled weather pattern late week through
the weekend as the influence of the ridge is shunted south and
east of the CWA and we pick up southwesterly flow aloft and
precipitable water climbs back into the 90th percentile vicinity.

The ensembles are in pretty good agreement through late week, but
uncertainty increases by the weekend regarding the amplitude of the
ridge off the West Coast and its evolution toward the end of the
forecast period. Most of the ensemble members keep this feature near
the CA coast, but around one-third of the Grand Ensemble members
(EPS, GEFS, and GEPS) develop this ridge farther east over the
Four Corners, enhancing the northwesterly flow aloft upstream of
the Mid-South. This could certainly have ramifications on rain
chances (or potential MCS activity) late in the period, but
confidence remains low.

MJ

&&

.AVIATION...
(18Z TAFS)
Issued at 1231 PM CDT Sun Jun 30 2024

SHRA/TSRA may affect all terminals except JBR this afternoon.
Have elected to keep VCTS for MKL and MEM, as confidence was not
high enough to include a tempo at this time. VFR conditions are
expected to prevail thereafter with the potential for winds to
remain elevated through the overnight period.

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Heat Advisory until 8 PM CDT this evening for ARZ027-028-035-036-
     048.

     Excessive Heat Warning until 8 PM CDT this evening for ARZ049-
     058.

MO...None.
MS...Heat Advisory until 8 PM CDT this evening for MSZ001>006-009-
     013>017-023-024.

     Excessive Heat Warning until 8 PM CDT this evening for MSZ007-
     008-010>012-020>022.

TN...Heat Advisory until 8 PM CDT this evening for TNZ048>053-088>092.

&&

$$

PUBLIC FORECAST...MJ
AVIATION...JPR