Forecast Discussion

FXUS64 KMEG 110439 AAA

Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
1139 PM CDT Fri Jul 10 2020

Updated for 06Z Aviation Forecast Discussion below.


.PREV DISCUSSION... /issued 900 PM CDT Fri Jul 10 2020/

DISCUSSION...00Z upper air analysis and evening GOES-16 Satellite
trends indicate an upper level ridge axis centered over the
Southwest United States with the Lower Mississippi Valley
remaining on the eastern periphery of this ridge axis. Rain free
conditions persist into this evening with temperatures as of 8 PM
CDT in the upper 70s to middle 80s.

Rain free weather is expected to persist into the remainder of the
night with the current forecast on track.


PREV DISCUSSION... /issued 353 PM CDT Fri Jul 10 2020/


A hot and dry afternoon across the Mid-South for the first time
in awhile. Latest GOES east visible imagery shows a mature MCS
near the ArkLaTex, with associated high cirrus spilling into the
Mid-South from the west. Temperatures range from the upper 80s
across the north to lower 90s further south. Heat index values
have remained at 100 or below for much of the day. Northwest
winds have advected in a slightly drier airmass across the north,
characterized by upper 60s dewpoints. This drier airmass will
allow areas across west Tennessee and northeast Mississippi to
fall into the mid to upper 60s overnight. Further west, including
the Memphis Metro, lows will likely stay in the lower 70s.

By late tonight, a MCS is forecast to develop over Missouri and
track SSE into the Lower Mississippi Valley by late tomorrow
morning. CAMs are still struggling with the exact location of this
system as it translates downstream in to our area. Nonetheless,
have latched onto the HRRR`s general location and timing of the
system for this package. It appears that an MCV or remnant outflow
will move into northeast Arkansas as early as 11AM tomorrow and
push through the area through the afternoon hours. The instability
mass field will vary greatly tomorrow afternoon, as drier air
will still reside over portions of west TN and NE MS. However,
along and west of the MS River, a hefty amount of CAPE will exist.
Values may exceed 3000 J/kg of SBCAPE. Storm mode will be outflow
dominant clusters, as only 20 kts of shear will be on hand. If an
organized cold pool can maintain, a more widespread risk of
damaging winds can be expected.

The Mid-South will remain in northwest flow again tomorrow night.
The 18Z HRRR depicts another MCS lining up behind the afternoon
convection tomorrow evening. This system will also have the
ability to produce instances of damaging winds, if it materializes
and pushes through our area. All models suggest this solution, but
timing will still need to be sorted out for this period.
Nonetheless, will add the mention of strong to severe
thunderstorms to the HWO for both Saturday and Sunday.

The forecast is still on track for a July heatwave next week. The
expansive ridge out west will begin to build into the region
early next week. Right now, Monday looks to remain the coolest day
with highs only in the lower 90s. However, the ridge axis will
become nearly centered over the Lower Mississippi Valley by
midweek. Preliminary blended guidance suggests highs in the upper
90s to possibly 100F Wednesday through Friday next week. The
combination of highs in the upper 90s and dewpoints in the low to
mid 70s, will yield heat index values in excess of 105F. Heat
advisories will likely be needed for several days. Guidance
trends will need to be watched for Excessive Heat.

Some weakening of the ridge is possible by next weekend, which
could break the streak of excessive heat. Stay tuned.



06Z TAFs

Few changes expected for the overnight periods, with light winds
scattered cirrus.

For the outer periods of the TAF, 00Z model consensus points
toward a later than currently forecast arrival of TSRA chances to
after 09Z Sunday at MEM. Timing of convective complexes embedded
in northwest flow is typically tricky, and will bear watching
through the day Saturday.