Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 241736 AAA

Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
1236 PM CDT Sun Sep 24 2017

Updated for 18Z Aviation Forecast Discussion below.


.PREV DISCUSSION... /issued 604 AM CDT Sun Sep 24 2017/

DISCUSSION... /issued 320 AM CDT Sun Sep 24 2017/

The synoptic pattern has become rather amplified over the past
several days. A strong, quasi-stationary longwave trough continues
to dig over the western half of the CONUS with a blocking high
over low setup found to its east. The upper-level ridge we`ve been
talking about the past few days has finally shifted north and is
now centered over the southern Great Lakes and Mid-Atlantic
region. The broad cyclonic circulation to the south of this ridge
continues to drift to the west and will gradually impinge on the
Mid-South today and Monday.

Precipitable water is not progged to be appreciably higher with
this wave nor will associated lift be all that strong. We will,
however, see slightly cooler mid-level temps which should weaken
the cap and allow a bit more diurnal convection to develop this
afternoon. PoPs range from 20-30% across the area this afternoon,
suggesting isolated to scattered showers and thunderstorms.
Temperatures today may be a degree or two cooler than Saturday`s
highs, but I remain hesitant to cool the forecast too much based
on the cool bias we`ve seen in much of the NWP this past week.
Expect afternoon highs in the upper 80s and lower 90s. Any
convection that develops should dissipate around sunset with
generally dry weather overnight. Temperatures are forecast to fall
into the mid 60s to around 70 degrees.

While the closed upper-level low remains in the vicinity on
Monday, a slightly drier boundary layer coupled with the
enhancement of a subsidence inversion ~700mb will limit convective
development. Low PoPs were continued to the southwest of Memphis
where the influence of the ridge will be felt the least.
Otherwise, expect afternoon temperatures in the neighborhood of 90
degrees. Dry conditions are anticipated area wide on Tuesday and
Wednesday as the upper-level cyclone moves off to the southeast
and the ridge builds back over the Lower Mississippi Valley.
Temperatures may eventually need to be warmed slightly for Tuesday
and Wednesday but the current forecast maintains highs generally
in the upper 80s during this time.

A notable change in the synoptic pattern will occur during the
latter half of the week. A portion of the western CONUS trough
lifts northeast into the Great Lakes on Wednesday, followed by a
strong northern stream shortwave trough Thursday. This will break
down the upper-level ridge, opening the door for yet another
shortwave trough over the weekend. At this time, rain chances look
to remain low given the dearth of low-level moisture but
temperatures will take a hit. A cold front is forecast to move
south across the CWA sometime Wednesday, resulting in highs
around 80 degrees for Thursday. As cooler air filters into the
area over subsequent days, temperatures are expected to continue a
downward trend. In fact, highs are forecast to remain in the 70s
on both Friday and Saturday. Low temperatures will be in the 50s.



18Z TAFs

Similar conditions to the past several days, but with added
coverage of afternoon SHRA/TSRA, courtesy of an easterly wave
evident on GOES water vapor imagery. Pending radar trends through
20Z, may need to insert TSRA at MEM, where coverage seems most




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