Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Memphis Tennessee
430 am CST sun Feb 1 2015
An active weather pattern can be expected for the first week of
February across the midsouth. Early this morning...southeast winds
were pushing mild air into the region with temperatures in
some locations warmer than they were during the day yesterday. The
lower levels were very dry across much of the area with surface dew
points in the teens along the Tennessee River valley. A warm front was
pushing toward the midsouth from the southwest with widespread
showers...the rain was having a difficult time reaching the ground
in our forecast area with the dry low levels. Surface low pressure
was developing over the Central Plains with much colder air located
across the northern plains pushing southward behind the low.
Not much change from the earlier forecast. As a upper level trough
digs into the middle MS River Valley today...the surface low will
strengthen to near 1000 mb and be located over southern in by sunset.
A cold front trailing southwestward from the low will approach
eastern Arkansas by noon and move rapidly to near the Tennessee River and the MS /
Alabama border by sunset. Showers will quickly spread across the midsouth
this morning ahead of this system as upper lift increases
dramatically and the lower levels become saturated. Based on the
forecast elevated instability...isolated thunderstorms are
expected along and south of Interstate 40. Also...some surface based
instability may push into north MS during the day. The models
including the hrrr and rap are showing the rain beginning to push out
of portions of northeast Arkansas and portions of the MO bootheel by early
afternoon...so began to show the probability of precipitation decreasing from the west at
Rain is forecast to quickly end from the west early this evening.
Latest models are not showing much if any precipitation once temperatures
become cold enough for snow...but did continue to mention a slight
chance of flurries after midnight in association with a trailing
upper level trough. Otherwise...strong and gusty northwest winds
will push much colder air into the area with wind chill readings
dropping to between 10 and 20 degrees after midnight.
Monday will be a very cold day as modified Arctic air settles over
the midsouth. Highs will only be in the 30s with some locations
near the MO and Kentucky borders remaining a little below freezing. Clouds
are expected to begin clearing by afternoon. Monday night will
see low temperatures dip into the lower and middle 20s.
High pressure will move to along the Atlantic coast by late Tuesday
with winds turning to the south across the midsouth. This will
allow temperatures to warm to between the middle 40s and lower 50s
during the afternoon with abundant sunshine.
Attention turns to our the next weather system Wednesday...an
upper low over Texas in the southern stream. The upper low is
forecast to become an open trough as it moves into the western Gulf.
Surface low pressure will develop over the western Gulf Wednesday as
an Arctic front approaches the midsouth from the north late in the
day. Looks like the midsouth will be between these two systems
Wednesday with most rain being to our south along the northwest
The weather becomes interesting and complicated Wednesday night and
Thursday...although the GFS and European model (ecmwf) still are not in good
agreement. As the upper level trough and associated surface low to
our south move eastward with the upper trough weakening...it looks
like most of the rain with this system will stay to our south
possibly moving into portions of north MS. Meanwhile...models show
the Arctic front continuing to push southward through the midsouth.
The GFS is faster with the colder air than the European model (ecmwf). Some light rain
is indicated with this front Wednesday night...changing to light
snow from the north with some sleet or freezing possible in the
transition zone. For Thursday...the European model (ecmwf) shows the light wintry
precipitation moving further south as the Arctic front continues south...
but the European model (ecmwf) quickly moves the precipitation out of the area by
afternoon. On the other hand...the GFS shows a stronger upper level
trough from the northwest interacting with the cold air Thursday
which could lead to some light snow accumulations. For now...lots of
uncertainty during this time frame. Will have to see how the models
come together on this situation regarding precipitation if any and precipitation
06z taf cycle
Definitely not good conditions for flying over the next 24 hours.
Conditions are VFR currently at all sites...but deteriorating
conditions are expected tonight...with IFR conditions prevailing
tomorrow. Expect ceilings to lower to IFR by middle morning...01/14z-01/17z.
Light southeast winds will veer southerly overnight...increase and
become gusty Sunday morning. Sustained speeds should be 10-15kt
with gusts to 20kts. Further veering is expected tomorrow
afternoon when southwest winds are expected. Visible will be MVFR for
most of the day tomorrow due to rain. Although thunderstorms
cannot be ruled out...do not feel they will be numerous to include
in tafs at this time. Some improvement to ceilings is possible late
tomorrow...near and after 00z. However guidance typically clears
low clouds out too quickly so will hold onto low clouds through
the taf cycle. Rain should come to an end for jbr before
00z...around 00z at mem...and a couple of hours later at mkl.
Will keep prevailing rain at tup through 06z.