Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 211139

Area Forecast Discussion
National Weather Service Memphis TN
639 AM CDT Sat Apr 21 2018


Updated for the 12Z Aviation Discussion


.PREV DISCUSSION... /issued 332 AM CDT Sat Apr 21 2018/

The strong trough over the Southern Rockies will continue to move
slowly eastward over the next several days, providing a good
chance for widespread rainfall this weekend. Shortwave ridging
aloft downstream of this trough will gradually shift east today.
Increasing southwest flow aloft will advect mid/upper-level
moisture into the area today and tonight, resulting in increasing
cloud cover in the short-term. Southeast surface winds will not be
optimal for low-level moisture advection, but dewpoints are
forecast to climb into the 50s across most of the area by sunrise
Sunday. Precipitable water across the Mid-South is currently less
than 1/2 inch but is progged to increase to 1.2 to 1.4 inches in
the next 24 hours. That`s a significant increase, but these peak
PWATs will still be at or below the 90th percentile of

Expect dry weather across the Mid-South today given the scant
moisture and capping inversion between 6-8 kft AGL. However, the
cap will weaken this evening as synoptic forcing for ascent
overspreads the region. Showers, and a few thunderstorms, will
increase from west to east this evening, becoming more widespread
late tonight and Sunday. The trough will become vertically
stacked as it approaches the Mid-South, indicating the transition
to the occluding stage. The attendant surface low will trek ENE
across AR but is expected to redevelop south of the CWA once the
occlusion begins. Thus, we`ll see more of a backdoor cold front as
winds back around the cyclone, eventually becoming northerly as
the surface low passes.

Instability will be limited with this system but there may be just
enough destabilization in the warm sector (far southern portion of
the CWA) to support a few strong storms on Sunday. Otherwise, we
anticipate primarily elevated thunderstorms with minimal severe
threat. Instability shifts east Sunday evening and light rain
showers will be possible on the backside of the very slowly
departing trough, potentially through early Tuesday. QPF for this
weekend into early next week remains 1-2 inches, with localized
higher amounts.

By midweek, we`ll enter a more progressive pattern with a compact
shortwave trough diving southeast across the Midwest. As this
wave approaches the Mid-South on Wednesday, a weak cold front will
move through the region. Moisture will remain limited, but strong
forcing may be sufficient to produce scattered showers. That
said, QPF is certainly not impressive. A brief quiet period is
expected Thursday as transient shortwave ridging affects the
region, but another fast- moving trough is progged to affect the
area on Friday. This will provide a chance for showers and
thunderstorms to end the work week. Temperatures will remain below
normal for most of next week. Expect highs primarily in the mid
60s to lower 70s with overnight lows in the 40s and 50s.



12Z TAF cycle

VFR conditions will continue into this evening. Low clouds and
rain showers wILL start to move into the region tonight and
continue to move during the overnight hours. Winds will be mainly
from the east at around 5 knots this morning and then shift to
the southeast and increase to 10 to 15 knots with higher gusts by
this afternoon.




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