Scientific Forecaster Discussion
fxus64 kmeg 300425
Area forecast discussion
National Weather Service Memphis Tennessee
1125 PM CDT Sat Apr 29 2017
Previous discussion... /issued 944 PM CDT Sat Apr 29 2017/
Skies are cloudy over much of the forecast area this evening with
temperatures ranging from the mid 60s to around 80 degrees.
Showers and thunderstorms cover much of the western half of the
forecast area. Some of the thunderstorms have produced severe
wind gusts and some large hail. These thunderstorms should calm
down some before midnight with more rain expected overnight. Have
adjusted pops for the overnight hours.
Previous discussion... /issued 252 PM CDT Sat Apr 29 2017/
Currently feels like Summer outside with temperatures running in
the mid 80s for most and dewpoints near 70f. Gusty south winds
were adding some relief to heat indices near 90f.
For the next 36 hours...conventional and short term models
continue to struggle with the evolution of the current upper
level low in New Mexico and the convection out ahead in the
eastern plains and Ozarks. Leaning with the slower solutions
generated from the European model (ecmwf) and NAM keeping the low delayed tomorrow
as it moves into central Kansas. In addition the surface low in
Oklahoma will move only slightly into southwest Missouri before
occluding. Storms seen currently out in western Arkansas have
been able progress a bit farther east this afternoon as midday
lzk sounding now reflects a broken cap. The activity so far has
remained subsevere despite this and the stronger midlevel flow in
the region. With the cap stronger in our region believe the
eastern extent of this activity will remain west of the
Mississippi for the majority of the night...after 30/09z thinking.
Low level winds will remained backed as the line of convection
arrives lending to some low level rotation...however midlevel
winds will also be backed...allowing for slower moving and
training of cells. Due to storm coverage...have backed off the
Flash Flood Watch until 12z tomorrow morning. Models are also
hinting on a wake low situation developing behind the line as
gradient winds from the south will remain strong. So the highest
winds may occur outside of convection. A Wind Advisory may be
needed. Cape amounts today are running around 3500 to 4000
j/kg...but will easily be cut in half tomorrow as thicker cloud
cover keeps high temperatures in the 70s. All in all a slight risk
for severe weather and a moderate flooding risk for 3-5 inches of
rainfall seems reasonable. Tomorrow evening rain and clouds will
transition east as the storm lifts into the western Great Lakes.
Some clearing will allow for overnight lows to drop into the
50s...but a continuing breeze should damper any fog potential.
Monday and Tuesday...weak high pressure will build into the
midsouth with dry and cool conditions. Overall temperatures will
run just below seasonal normals with a mix of clouds and sun.
Wednesday through early next weekend...mid range models have
consistently shown a shortwave dropping south from the northern
plains this period...with the next cutoff 500mb low forming in the
Red River valley. Have sided with the European model (ecmwf) solution tracking the
low farther south across the Arlatex and into Mississippi. This
should keep clouds and a rain threat across the area each day with
temperatures remaining below normal. Cut-off lows are known for
remaining stationary well beyond model forecasts so confidence is
low for any big weather improvements through next Saturday.
Attempted to time the next round of thunderstorms based on hrrr
Model guidance tendency has been to slow down the onset of
showers/thunderstorms...will continue that trend. Brief IFR or
even lirf conditions due to heavy rain can be expected in
association with any thunderstorms. However prevailing conditions
should remain MVFR or better.
Backed off of the development of low clouds overnight....but any
that do develop should quickly dissipate after sunrise.
Winds will remain southerly through the taf period between 10 and
15kt overnight 15-20kt tomorrow. Higher gusts to around 35kt will
return tomorrow. Winds will remain strong through 31/06z.
Arkansas...Flash Flood Watch from 7 am CDT Sunday through Sunday afternoon
for Clay-Craighead-Crittenden-cross-Greene-Lawrence-Lee Arkansas-
MO...Flash Flood Watch from 7 am CDT Sunday through Sunday afternoon
MS...Flash Flood Watch from 7 am CDT Sunday through Sunday evening
Tennessee...Flash Flood Watch from 7 am CDT Sunday through Sunday evening