Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion...updated 
National Weather Service Memphis Tennessee
1152 PM CST Sat Feb 13 2016

Update...
updated for 06z aviation discussion below.

&&

Previous discussion... /issued 952 PM CST Sat Feb 13 2016/

Update...

Uncertainty still remains with regard to the winter weather event
beginning late tonight/Sunday morning. Surface temperatures have
cooled as expected this evening with a strong shortwave diving
south from the northern plains. Precipitation will arrive slightly
earlier than expected most likely in the form of light snowfall at
the onset of the event. Strong warm air advection will ensue
within the 850-700 mb layer which should allow a warm nose aloft
to development quickly Sunday morning changing the precipitation to
sleet...then eventually freezing rain. The concern is that with
cloud cover/falling precipitation...surface temperatures may remain at or
below 32 degrees for longer than currently projected...and also a
few counties further south. The heaviest precipitation will likely fall
between 12 and 18z when temperatures are still below freezing. The
00z run of the nam12 strongly supports this scenario...therefore
near-term trends will need to be closely monitored through the
overnight.

It is important to remember that this forecast is dependent upon
temperature variances of 1-2 degrees and is therefore
exceptionally challenging. Folks across northeast Arkansas and
west Tennessee are advised to check the forecast early tomorrow
morning in case adjustments are needed to the current
forecast...especially for areas around Jackson Tennessee where the
greatest uncertainty exists. As of now...no changes to the
advisory have been made.

Tvt

Previous discussion... /issued 544 PM CST Sat Feb 13 2016/

Update...
update for 00z aviation discussion below.

Previous discussion... /issued 338 PM CST Sat Feb 13 2016/

Discussion...

Currently... at 3 PM around the midsouth winds are out of the
north with temperatures ranging from the upper 20s north to the
middle 40s south. 500 mb analysis places a potent upper low over the
northeast United States with resultant northwest flow aloft over
the midsouth. Latest surface analysis centers a 1039 mb Arctic
high over eastern Iowa with the influence of this feature felt
locally with mostly sunny skies present over much of the region
this afternoon.

The Arctic high to the north will gradually lose its influence on
the region tonight as it migrates to the east to eventually being
centered just east of the Great Lakes region by Sunday morning as
the potent upper low transits to the northeast. Subsequently flow
aloft will become more zonal. Warm air advection will enhance
between the 700 and 950 hpa levels overnight which will create a
warm nose aloft with surface winds becoming more southerly.
Meanwhile weak impulses embedded in nearly zonal flow aloft will
interact with a surface boundary that will wedge into the region
early Sunday morning with precipitation ensuing after 12z.
Precipitation between 12z and 18z will likely be light and
contained along and north of a line from Harrisburg Arkansas to
Parsons Tennessee. With the warm nose aloft and subfreezing
temperatures at the surface this precipitation will initiate as
sleet and quickly transition to freezing rain as warmer air
advects at and near the surface. Current temperature profiles are
only conducive for snow in the extreme northeastern portions of
the region as warm air advection is a bit slower to nose into
those regions.

The lower atmosphere will moderate nicely throughout the day
on Sunday as surface winds become more southerly which will cause
the region of frozen or freezing precipitation to shrink
throughout the day. Nonetheless...a Winter Weather Advisory will
be in effect from 14/12z through 15/00z as light but impactful ice
and sleet accumulations are possible in the top two tiers of
counties. Sunday highs will range from the middle 30s north to the
lower 50s south. All of the region will see rain on Sunday as the
surface boundary slowly migrates south...however only rain is
expected in most areas outside the advisory. The flow aloft will
amplify by early Monday as a low deepens along the surface boundary
and moves across north Mississippi. This will enhance rain on
Monday along and south of I-40 with 1 to 2 inches of rainfall
possible for these areas before the rain exits the region on
Monday night.

Temperatures will warm into the middle 50s to middle 60s on Tuesday with
models depicting an upper low and attendant surface low to move
in the vicinity of the midsouth by late Tuesday providing
additional probability of precipitation. Drier conditions return on Wednesday with high
pressure building under northwest flow aloft. A ridge aloft will
begin building into the region by Thursday which will set the
region on a warming trend with temperatures on Thursday and
Friday in the 60s and even near 70 in southern extents of the forecast area.
The next chance for precipitation could be late Friday and into
Saturday as models depict a trailing cold front attendant with a
low centered well to the north of the midsouth traverses the
region.

Zdm

&&

Aviation...
06z tafs

Complex scenario aviation weather scenario for jbr...with timing
of Arctic air retreat and onset of precipitation. 00z GFS appeared to
mix the Arctic north too quickly and have continued to base 06z
tafs heavily on the 00z NAM. NAM bufr soundings warm jbr
sufficiently near midday for changeover to -ra...before
transitioning back to -fzra as the boundary sags south. Cold
advection north of the boundary not particularly strong Sunday
evening...in advance of another upstream wave.

Mem appears will remain above freezing...at onset of precipitation just
prior to 00z...with transition to MVFR toward 00z.

Pwb

&&

Meg watches/warnings/advisories...
Arkansas...Winter Weather Advisory from 6 am to 6 PM CST Sunday for Clay-
Greene-Lawrence-Randolph.

MO...Winter Weather Advisory from 6 am to 6 PM CST Sunday for Dunklin-
Pemiscot.

MS...none.
Tennessee...Winter Weather Advisory from 6 am to 6 PM CST Sunday for Benton
TN-Carroll-Dyer-Gibson-Henry-Lake-Obion-Weakley.

&&

$$

National Weather Service Glossary of Abbreviations