Forecast Discussion

FXUS64 KMEG 121719

Area Forecast Discussion
National Weather Service Memphis TN
1119 AM CST Wed Dec 12 2018

Updated for 18Z Aviation Discussion.


.PREV DISCUSSION... /issued 1010 AM CST Wed Dec 12 2018/

South to southwest winds have increased to 10-15 mph this morning
with temperatures generally in the mid 40s to near 50 degrees.
Low-level warm advection will be offset somewhat by mostly cloudy
skies, limiting the diurnal range. Clouds will continue to stream
across the Mid-South today with cloud bases gradually lowering
throughout the day. Dry weather is anticipated through sunset, but
light rain will be possible this evening, becoming more widespread
overnight. Only minor changes were made to the forecast, namely
increasing sky cover and tweaking hourly temperatures and



.PREV DISCUSSION... /issued 340 AM CST Wed Dec 12 2018/


Southerly winds have warmed temperatures to be nearly 20 degrees
warmer than this time yesterday. The latest surface analysis
shows a surface high centered roughly over the Gulf Coast,
resulting in the southerly flow for the local area. Meanwhile, H5
analysis depicts quasi zonal flow aloft over the region. An
amplifying trough currently present along the West Coast will
bring an extended period of rain and perhaps a few thunderstorms
to the region beginning tonight.

Temperatures will warm into the 50s this afternoon with clouds
covering the region. By early Thursday the aforementioned
amplifying trough digs into the Southern Plains as a sfc low
deepens across northern Texas. The flow aloft over the local
region becomes more southwesterly, the prelude to rain which will
stick around into the weekend. By late Thursday the rain will
have overspread the entire region in earnest as the sfc low treks
from northern Texas and into south central Arkansas. A few
thunderstorms could be possible throughout the day on Thursday and
even on Friday as the sfc low moves over the region, with modest
elevated instability present. Temperatures will remain in the 50s
on Thursday and Friday as the region remains in the warm sector of
the sfc cyclone.

By early Saturday the upper low meanders over the Mid-South,
becoming nearly vertically stacked with the sfc low, allowing
conditions to begin to dry out as the latter becomes less
organized. By the time the rain ends on Saturday 1.00" to 3.00"
of rain will have fallen over the region. Currently it appears the
wettest locales will be in the western counties closest to the
center of the sfc low on Friday when it becomes the most
organized, with lighter amounts nearer the Tennessee River.

By early Sunday the upper low moves to the east of the region.
Models diverge on the upper level pattern at this point, with the
GFS offering a cooler solution than the ECMWF, creating some
uncertainty with just how warm Sunday highs will be. Regardless, a
drier pattern sets up, with high pressure invading at the sfc and
a ridge of high pressure aloft by Tuesday, keeping temperatures a
couple of degrees above where they should be for mid December.



18Z TAFs

VFR to start this period but as system approaches and rainshowers
develop conditions will drop to MVFR and IFR tonight. JBR may
even fall to LIFR cigs after sunrise. Gusty south to southwest
winds will back southeasterly later in the period. Border-line
wind shear developing again at MEM and JBR late this evening.