Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Jackson Kentucky
1055 am EDT Tuesday Jul 29 2014
issued at 1055 am EDT Tuesday Jul 29 2014
14z surface analysis shows high pressure over the Midwest and Ohio
Valley. A nearby upper low is keeping strato-cumulus around and from
this...similar to yesterday afternoon...a few sprinkles will be
possible. Have added this to the forecast and also adjusted the sky
cover through the afternoon. Also...fine tuned the T and dew point grids
based on the latest observation...trends...and consshort guidance. These have
been sent to the ndfd and web sites along with a freshened set of
Update issued at 750 am EDT Tuesday Jul 29 2014
Freshened up the hourly temperatures...dew points...and sky cover to
match up better with the latest trend in observations.
Otherwise...the forecast remains on track.
Short term...(today through wednesday)
issued at 339 am EDT Tuesday Jul 29 2014
Broad cyclonic flow will remain entrenched across the Ohio and
Tennessee valleys through the short term...bringing unseasonably cool
temperatures to the region. Weak surface high pressure will become
more established across eastern Kentucky through the period...
keeping our weather mainly dry.
Highs today will reach into the low and middle 70s under partly cloudy
skies. Lows tonight will drop well into the 50s as skies become
mostly clear. Can not rule out a few upper 40s...which would most
likely eclipse record lows at some locations. Temperatures will
rebound on Wednesday as heights recover....ranging from the upper 70s
to around 80.
Long term...(wednesday night through monday)
issued at 339 am EDT Tuesday Jul 29 2014
Strong upper level troughing will be center stage through the
extended...being blocked between two strong ridges...one across the
southwest Continental U.S....and one off the Atlantic Seaboard. This trough
currently extends from an upper level low over the Hudson Bay and
pulls southward all the way to the Gulf Coast. So long as this
pattern is in place...we will experience well below normal
temperatures. Every day during the extended period is looking at
upper 70s and low 80s for highs...and upper 50s to low 60s for lows.
There will be no distinct shortwaves which will traverse the path of
the upper level trough...but the jet stream set up in this regime
will have a strong influence in the precipitation chances for the time
Given the unusually southward progression of this polar low...the
polar jet stream will also pull uncommonly far southward /especially
for this time of year/...rounding the trough along the Ohio River
and Tennessee Valley region. For Thursday...this jet will be west to
east oriented across the Ohio River valley...pulling in dry northwest flow.
Some low level moisture and surface upslope flow could produce a few
isolated showers and thunderstorms across the highest terrain in the
southeast...but otherwise predominately dry weather is expected. By Friday
however...the jet shifts slightly westward so that it becomes more
SW to NE oriented across eastern Kentucky. This will pull deep moisture in
the middle and upper levels across the appalachian and eastern Seaboard
region...and bring the chance for diurnally driven showers and
thunderstorms across eastern Kentucky and points south and east during the
afternoon hours. The jet will then remain in this position through
the end of the forecast period...with showers and thunderstorms
expected during the afternoon hours across eastern Kentucky each day.
Given the lack of shortwaves moving through the flow of the
trough...no widespread precipitation chances are expected across the
remainder of Kentucky during the extended forecast.
Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 750 am EDT Tuesday Jul 29 2014
Spotty MVFR/IFR stratus and fog will mix out across the area through
13z this morning. Expect scattered to broken stratocu in the 4-6k
feet above ground level range through the day before dissipating this evening. Winds
will remain out of the northwest to north-northwest in the 5 to 10 knots range through
early this evening...before diminishing.