Area Forecast Discussion
Issued by NWS Memphis, TN
FXUS64 KMEG 271745
Area Forecast Discussion
National Weather Service Memphis TN
1245 PM CDT Thu Apr 27 2017
Updated for the 18z Aviation Discussion.
.PREV DISCUSSION... /issued 455 AM CDT Thu Apr 27 2017/
DISCUSSION...Surface analysis places a cold front from Southern
Illinois back through West Tennessee near the Tennessee River and
Northeast Mississippi early this morning. Showers and thunderstorms
have moved well east of the Mid-South some post-frontal cloud
cover remaining across the area. As of 4 AM CDT, temperatures
across the Mid-South range from the lower 60s over Northeast
Mississippi and 50s across the remainder of the forecast area.
Severe thunderstorm and heavy rainfall potential Friday night into
the upcoming weekend remains the primary focus in this morning`s
Clearing skies are expected across the Mid-South today as high
pressure builds back in across the area. Temperatures will be
cooler with afternoon highs in the upper 60s to around 70 degrees
north and lower 70s south. Last night`s cold front will begin to
return back north as a warm front on Friday into Friday night. The
last few runs of the WRF have placed a warm front much further
north than the GFS/ECMWF consensus and have consequently leaned
forecast towards the latter solutions for the time being.
Increasing surface dewpoints into the upper 60s to lower 70s, the
development of an 850mb low level jet across the Lower
Mississippi, a very unstable airmass characterized by surface
based CAPE values between 1500-2000 J/kg, and favorable winds
aloft suggest a potential for severe thunderstorms along and north
of I-40 with large hail and damaging winds as the primary severe
threats. Sufficient shear may result in a tornadic risk along the
warm front if any thunderstorms become surface based.
In addition to the severe thunderstorm threat the potential will
exist for heavy rainfall Friday night across portions of
East/Northeast Arkansas, the Missouri Bootheel, and far Northwest
Tennessee in association with the warm front and the arrival of a
subsequent cold front Saturday night into Sunday morning. Models
indicate shower and thunderstorm chances will diminish on Saturday
as the warm front moves northwest of the forecast area but return
by Saturday night with the cold front. Model run rainfall
accumulations suggest the potential for 3-7 inches, with locally
higher amounts across the aforementioned area. After coordination
with surrounding offices to the north and west, a Flash Flood
Watch has been issued for these areas for Friday night through
Sunday. Saturated soils from last night`s rainfall and any
subsequent heavy rainfall may become conducive for flash flooding
and river flooding. Later shifts will continue to monitor trends
and adjust any subsequent threats as needed as this event evolves.
An additional risk for severe thunderstorms will be possible as
the cold front moves through the Lower Mississippi Valley later
Saturday night into Sunday. Large hail and damaging winds will be
the main threats for any thunderstorms that reach severe limits.
Long term models indicate rain chances will diminish into early
next week as high pressure builds back in across the region.
Additional rain chances may return by the the middle of next week.
MVFR cigs at KMKL and KTUP will continue to erode early in the
forecast period with VFR cigs developing later this afternoon.
Elsewhere VFR conditions will prevail through the first half of
the forecast period. West winds around 7 kts or less can be
expected this afternoon.
VFR cigs should continue through much of the night with mainly
just an increase in mid and high level clouds. Late tonight into
early Friday morning, an MVFR stratus deck should develop. This
should occur first near KTUP prior to sunrise, then overspreading
the remainder of the terminals after sunset as a warm front lifts
north towards the region.
The warm front should advance through the area by mid to late
morning with deeper mixing helping to lift the cloud deck. Winds
will also increase from the south and become gusty at times behind
the warm frontal passage. A few warm advection showers will be
possible but coverage remains too low to include in the latest TAF
AR...Flash Flood Watch from Friday evening through Sunday evening for
MO...Flash Flood Watch from Friday evening through Sunday evening for
TN...Flash Flood Watch from Friday evening through Sunday evening for