Scientific Forecaster Discussion
fxus63 kjkl 201554
Area forecast discussion
National Weather Service Jackson Kentucky
1054 am EST Sat Jan 20 2018
issued at 1054 am EST Sat Jan 20 2018
Issued an update to input obs and trend them into the midday
hours. Cloud cover will slowly be on the increase. However, some
peaks of sunshine may occur in the far north. Thus have adjusted
cloud cover as well. Temps this hour seems a tad warmer so
expected warm air advection may lead to high temps today a degree warmer than
whats in the forecast so have updated this as well.
Update issued at 751 am EST Sat Jan 20 2018
Temperatures have warmed a little faster than was forecast early
this morning. Have rerun a temperature curve for the day, based on
the observed starting point. There is no overall change to the
Short term...(today through sunday)
issued at 429 am EST Sat Jan 20 2018
Flow around high pressure over the southeast Continental U.S. Will bring
warm air advection, along with an increase in low level moisture
today into Sunday. The moisture is already resulting in clouds,
but is very shallow and capped by a steep inversion. With time,
the inversion is expected to rise and the moist layer grow
deeper, but still be capped below 700 mb. Forecast soundings
suggest the possibility of a few showers late tonight into Sunday,
mainly over our northern counties.
Temperatures will continue to trend warmer. The question is how
much. Clouds will likely keep US from seeing our potential, but if
there are enough breaks, readings could shoot up either day,
especially with snow cover becoming more scant.
Long term...(sunday night through friday)
issued at 355 am EST Sat Jan 20 2018
The models are in reasonable agreement with the long wave pattern
for most of the extended period. The period will begin with
ridging ahead of a closed low across the Central Plains. This
upper level closed low will move into the Midwest by the Monday
into Monday evening. This upper low will track across the Great
Lakes Monday night into Tuesday and then the pattern almost
flattens briefly in the wake of the trough. Then another wave
dives into the area by Thursday before a ridge axis moves out of
the plains bringing height rises back into the area Friday.
Sensible weather wise, we will be watching an upper level low in
the plains that will move into the Midwest Monday. A deepening
area of low pressure will become vertically stacked with the upper
low and track in the same fashion. The attendant cold front will
move across the Tennessee and Ohio valleys. This will bring rain
showers across the region late Monday into Monday evening. The
models have been in some disagreement on the speed of this system,
but latest runs indicate better and better agreement on timing.
The blended guidance suggests between a quarter and half an inch
of total rainfall amounts and this looks reasonable. The other
story will be the gusty winds ahead and behind this system as the
pressure gradient increases along with a strengthening low level
jet. This lead to larger adjustments from the washed out blended
guidance. The front will exit east Monday night into Tuesday, but
the models disagree on the amount of moisture left in the wake.
Overall kept with blended guidance at this point. The forecast
soundings indicate this will probably fall as snow or rain/snow
mix on the backside of the boundary early Tuesday. Then we will be
met with drying conditions through the remainder of the period.
The temperatures will be near normal Tuesday through Wednesday
night and then with the previously mentioned height rises
temperatures will climb back above normal for this time of year
Thursday into Friday.
Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 752 am EST Sat Jan 20 2018
A cloud deck around 3k feet above ground level covers most of the area, and will
be rather persistent during the period. It will continue to bring
low end VFR and high end MVFR conditions. South to southwest
winds will pick up to around 10 kts in most places during the day.