Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Memphis Tennessee
322 PM CDT Thursday Apr 17 2014
Discussion...20z surface analysis places a surface low over
Western Lake Superior with a cold front extending south across
Missouri...eastern Kansas...and back into Oklahoma and Texas.
Meanwhile...a shortwave trough is moving across portions of the
lower Mississippi Valley near the northern Gulf Coast this
afternoon. Across the middle south...sunny to mostly sunny skies have
prevailed with temperatures as of 3 PM CDT in the 60s at most
locations. Precipitation challenges tonight into Friday and again
for late this upcoming weekend into early next week are the
primary challenges in this forecast.
Short term...(tonight through saturday)...a longwave upper level
trough and associated weak cold front will move across the lower
Mississippi Valley later tonight into Friday. I think it will
take some time for the atmosphere to moisten up to produce some
rain showers across the middle south with a relatively dry airmass
already in place across the forecast area. Thus...have held off
low rain chances until the overnight hours...given current short
term trends. Short term models indicate this upper level trough
and associated cold front will move east of the area by Friday
night with mainly rain free conditions returning through the first
half of the weekend. Afternoon highs in the 70s are expected for
Friday and Saturday.
Long term...(sunday night through wednesday)...12z GFS/European model (ecmwf) long
term models remain in somewhat good agreement except for some
timing differences as another upper level trough and associated
cold front move through the lower Mississippi Valley between Sunday
night through Tuesday. Enough instability should be present to
support a mention of thunderstorms during this timeframe. Mainly
rainfree conditions will return by the end of the period.
18z taf cycle
VFR conditions to start off the period with some high clouds present.
Ceilings will be lowering into this evening as a weak cold front
and upper level disturbance approach the area. Winds will be from
the south southeast from 8 to 10 knots to begin the period but
will become lighter and more easterly later in the period. Have
included a vcsh for all sites during the morning hours as the
front moves through. Moisture will be limited...but I included a
tempo for MVFR conditions for kmem and kmkl between 11z and 15z as
ceilings and visibilities lower with the possibility for some moderate
precipitation. VFR conditions expected for all sites after
15z...although lower ceilings will stick around through the end
of the period.