Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Memphis Tennessee
839 PM CDT Thursday Jul 2 2015
At middle evening...scattered showers and storms were across the
northern third of the County Warning Area. While a severe storm cannot be ruled
out...the primary threats from these storms should be lightning and
heavy rain. Storms have been producing around 1 inch/hour
accumulation based on dual pol radar estimates. A shortwave
approaching from the northwest should assist in additional storm
development. Overnight...we will need to watch for training of
storms which would increase accumulation and flash flood potential.
Overall forecast appears in good shape. Will adjust the 00-06z quantitative precipitation forecast
to better fit current trends. Short-term guidance /hrrr and 18z NAM/
suggest area of showers/storms will sag south through the night as
currently depicted. Timing/location of areas of showers/storms on
Friday will largely depend on overnight evolution of current
Previous discussion... /issued 214 PM CDT Thursday Jul 2 2015/
Clouds beginning to erode...with atmosphere finally seeing a slow
destabilization. A few storms on radar have popped up across
northwest Tennessee...but have remained below severe limits. Storm
coverage has also remained steady. Current temperatures are
running in the low to middle 80s with breezy southwest winds. Highs
should climb to the middle and upper 80s with a mix of clouds and sun.
For tonight through Saturday...main focus for scattered showers
and storms will be just along and south of a weak cold front
running from northwest Arkansas to the Ohio River...while a
series of shortwaves drop southeast from the Central Plains. The
first wave will arrive late this evening which could provide for
more organized activity. Models however have been very bullish
with this scenario...leading to much higher quantitative precipitation forecast...but only
portions of northwest Tennessee has really seen this action.
So am a bit hesitant on keeping probability of precipitation higher than 60 percent
beyond the first 12 hours. There are just too many factors that
could muck up the area...cold pools...low level cloud cover...etc.
This in turn would lead to prolonged stability during the
day...generating only widely isolated activity late in the
afternoon and evening.
The severe weather threat will remain low through the
period...with areas along and north of Interstate forty seeing
the greatest amount of bulk shear...25 to 30 kts...with the
approaching wave. The worst threat the next 48 hours will continue
to be very localized flash flooding...such as was seen in Obion
County last night. Due to rain chances and significant cloud cover
high temperatures will remain below normal Friday and Saturday
with near normal lows.
Sunday through Thursday...a weaker northwest upper flow is
projected to slowly develop over the middle Mississippi Valley as
heights build in the Ohio Valley and Great Lakes. Temperatures
will slowly creep back up to the upper 80s and low 90s..or near
normal for early July. Convection will be more diurnally driven
with maximum heating and will likely become more isolated in coverage.
00z taf cycle
VFR conditions will continue for most of the forecast period.
Showers and thunderstorms will continue to move across northern
sections of the forecast area this evening with a better chance
for thunderstorms overnight across the entire area. Some of the
thunderstorms may produce MVFR ceilings and visibility at times
overnight. More thunderstorms will be possible during the day on
Friday. Winds will be mainly from the southwest at 10 to 15 knots
with some higher gusts possible at times.