FXUS64 KMEG 210450

Area Forecast Discussion
National Weather Service Memphis TN
1150 PM CDT Mon May 20 2019


Updated to include 06Z aviation discussion below.


.PREV DISCUSSION... /issued 951 PM CDT Mon May 20 2019/

Midevening regional radar mosaic and GOES IR imagery showed
extensive thunderstorm coverage extending from west TX through
OK, into southwest MO. South and east of this area, coverage was
isolated, mainly over north central AR, where a lone thunderstorm
was lifting north.

Across the Midsouth, the lower atmosphere remained capped to deep
convection, under the northern periphery of a midlevel height
ridge centered over the northern gulf. AMDAR soundings from
Memphis showed a warm layer just above 700mb, indicative of
subsidence aloft.

Looking toward the overnight periods, 00Z NAM model does not paint
a particular favorable scenario upper level jet position with
respect to organized storm development. As the upper ridge axis
translates east overnight, the chances of shallow layer showers
will increase a bit north and northeast of Memphis, along and north
of a slowly lifting surface warm front. Current forecast has this
handled well. Only minor adjustments to hourly temps and dewpoints
needed at midevening.



.PREV DISCUSSION... /issued 343 PM CDT Mon May 20 2019/

A deep trough continues to spin over the Four Corners region this
afternoon with a ridge building over the Gulf of Mexico. A strong
jet max is rounding the base of the trough, helping support
today's anticipated severe weather outbreak across the Southern
Plains. Farther east, we'll be dry for the most part this evening,
but there is a potential for some weakening convection to move
out of the Ozarks and into the northwest portion of the CWA after
midnight as the Four Corners trough lifts northeast across the
Central Plains. Slight chance PoPs were included for areas north
of Memphis after 06z.

A few lingering showers will be possible along the KY/MO border
early Tuesday, but most of the area will be warm and dry
throughout the day. A secondary trough will move across the
Southern Plains tomorrow afternoon and evening and will force
ongoing convection to our west into a linear mode. This convection
is expected to approach the MS River around or after 00z. There is
a risk for severe weather, primarily across northeast AR and the
MO Bootheel, with the primary concern being damaging winds.
However, this line will be weakening as it moves into the Mid-
South and shouldn't pose a significant severe risk for most of
west TN and north MS.

An outflow boundary from this convection is expected to linger
across the CWA on Wednesday and may serve as a focus for
additional development of showers and thunderstorms. However, a
mid-level capping inversion will become an issue as the ridge
over the Gulf builds poleward. PoPs were generally capped at 40%
or so for Wednesday afternoon with precipitation diminishing by
sunset. Temperatures through Wednesday will range from the highs
in the mid/upper 80s to overnight lows in the mid 60s to lower

The subtropical ridge becomes the dominant factor in our weather
pattern for the remainder of the forecast, with 500mb heights
perhaps building as high as 595dam by the end of the week,
approximately 2 standard deviations above the norm. While an
isolated diurnal shower/thunderstorm will be possible during this
time frame, this ridge will generally suppress convective
development and will result in warming temperatures. Temperatures
will gradually climb into the lower 90s across much of the Mid-
South by late week with overnight lows creeping into the lower
70s. Heat indices will respond in the same manner, reaching into
the mid 90s in some areas Thursday-Sunday.

The global models differ on the timing of a potential pattern
change early next week. The GFS swings another strong trough
across the Plains on Monday, but the ECMWF/GEM maintain ridging
over the central CONUS for at least an additional 24 hours,
pushing any potential for precipitation into the midweek period.



06Z TAF Cycle

VFR conds expected through most of the period. Southerly winds
overnight will range between 5-10 kts. Strong and gusty south
winds will develop at all sites after 21/13Z as a low pressure
system approaches from the west. Gusts at JBR and MEM may approach
30 kts by early afternoon.

Showers and thunderstorms will develop along a front around
22/00Z...with best chances on site at JBR and MEM through the end
of the period.




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