Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Memphis Tennessee
1102 am CDT Thursday Oct 8 2015
As of 11am...temperatures are in the middle to upper 70s across the
region. Some clouds were noted on satellite...mainly over north
Mississippi where middle and high level cumulus are prevalent.
Short term model guidance is indicating anywhere from 600-1000
j/kg of SBCAPE over north Mississippi this afternoon. To account
for this and have went ahead and added wording for isolated
The rest of the forecast is on track and no further changes are
needed. Have updated zones to remove morning wording.
Previous discussion... /issued 337 am CDT Thursday Oct 8 2015/
One more day of well-above average temperatures is expected on
Thursday before a strong cold front pushes through the middle-south
bringing a chance for showers and thunderstorms Friday and Friday
The upper air pattern continues to be unusual for middle-October with
a cutoff low spinning over the Desert Southwest. Higher momentum
flow associated with the polar jet is relegated well to the
north. The middle-south was situated under low-amplitude ridging
aloft with a sprawling surface high pressure dominating much of
the central and eastern Continental U.S.. a strong shortwave and associated
surface low was moving southeast into the northern plains.
Temperatures were quite mild with readings either side of 60
across the region.
On Thursday...another very warm day is forecast with high
temperatures a solid 5-10 degrees above average. Guidance
continued its cool bias on Wednesday...underestimating
temperatures by 2-4 degrees. This is likely due to over-
forecasting middle-level cloud cover across the region. Atmospheric
conditions on Thursday are very similar to those of
Wednesday...and see no reason to follow guidance with respect to
forecast highs. Therefore...bumped up temperatures 3-4 degrees
given sufficient solar heating and slightly warmer temperatures
and 850 and 925 mb.
By Friday...the aforementioned shortwave is forecast to be
traversing the Great Lakes region with a trailing frontal boundary
racing southeast through the Ohio Valley. Moisture advection is
not overly strong but dewpoints ahead of the front should climb
into the low 60s by late Friday morning. Point forecast soundings
are actually slightly more unstable than they were from the 00z
model suite last night...with MUCAPE nearing 1000 j/kg. Given
strong frontal forcing...thunderstorms are likely to develop along
the boundary as it pushes southeast with the best chances across
west Tennessee during the early to middle-afternoon hours. The GFS
and European model (ecmwf) linger precipitation across the region through Saturday morning
but only isolated showers are expected after midnight...mainly
across northeast Mississippi.
Over the weekend...strong Canadian high pressure builds into the
middle-south with cooler temperatures returning. Lows in the 40s and
50s with highs in the 70s are expected both Saturday and Sunday
with Sunday night being the coolest of the two.
In the middle and long-term periods of the forecast...a strong warm
signal exists in model guidance as the polar jet stream retreats
well north into Canada allowing building heights across the
western and central Continental U.S.. this favors near to above average
temperatures with no precipitation in sight.
12z taf cycle
VFR ceilings will prevail through the period at all sites with middle and
high level clouds continuing to streak across the region. There
will be IFR reductions in visibilities at kmkl due to fog early this
morning. Later this afternoon...isolated showers and thunderstorms
should develop near ktup and have maintained thunderstorms in the vicinity. Winds should
remain light and variable.
Light winds and high clouds will continue tonight at all sites.
There will likely be some lowering of cloud decks at kjbr just
beyond this taf period.