Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jackson Kentucky
1236 PM EST sun Feb 7 2016
issued at 959 am EST sun Feb 7 2016
Updated to reduce sky cover early in the day and blend other
observed parameters into the forecast.
Update issued at 721 am EST sun Feb 7 2016
A few pockets of lower and middle clouds have developed across
portions of eastern Kentucky in the past hour or so. Have updated
the sky cover to include these clouds...although a mostly sunny
day will still be on tap overall...so additional updates are
not needed at this time.
Short term...(today through monday)
issued at 353 am EST sun Feb 7 2016
A surface high pressure ridge currently remains nosed in across
the Ohio and Tennessee valleys from the northwest Gulf
Coast...keeping tranquil conditions across eastern Kentucky.
Meanwhile...surface low pressure is moving in from southeast
Manitoba...with a cold front extending south across the plains.
Arctic air remains locked up for now across eastern Canada.
Aloft...amplifying flow is underway...with the main player of
interest a short wave trough swirling across the U.S./Canadian
border just west of the Great Lakes.
The models are in good agreement through the short term...with the
northern stream short wave diving south and establishing a cutoff
low across the Great Lakes...with deep troughing encompassing the
eastern Continental U.S. By late Monday. This will bring unsettled weather
and much colder air to the Ohio and Tennessee valleys.
A mostly sunny day will be on tap for eastern Kentucky today...with
highs rebounding to the low to middle 50s for most locations. Tried
to stay on the warmer side of guidance...given a slightly slower
trend to the thicker cloud cover and the mild response that occurred
from yesterday. The plains cold front will track towards the area
late tonight...with precipitation mainly breaking out across the
area from northwest to southeast between midnight and dawn.
Wetbulbing will battle southwest flow out ahead of the boundary.
For now...will continue to allow for a mix of rain and snow.
Another potential concern will be the eastern valleys likely
dropping quickly with sunset this evening. Some of the coop MOS
suggests upper 20s for lows...and this seems reasonable given the
dry low level air in place. Have allowed for a quick drop off
through around midnight and then brought temperatures back up to
around freezing or slightly above once the thicker clouds arrive.
The first initial shot of precipitation associated with the
passing cold front will move through Monday morning. A brief lull
in the activity may occur behind this...before additional
precipitation develops as the longwave trough quickly develops
across the eastern Continental U.S.. the mix of rain and snow will go over to
all snow everywhere by late Monday afternoon. Warm ground
temperatures will likely keep accumulations restricted to elevated
and grassy surfaces. The only exception will be the higher
elevations above 2500 feet...where mainly snow will fall through
the day...with 1 to 2 inches of accumulation by dusk Monday. This
storm system will continue to affect our area into middle-week with
additional light snow and colder air moving in. As such...will
highlight this with a Special Weather Statement.
Long term...(monday night through saturday)
issued at 438 am EST sun Feb 7 2016
In general models are in good agreement through the extended with
reasonably decent run to run continuity as well. As expected
solutions diverge a bit more with details during the latter
portions of the period. Main challenge will be timing individual
shortwave impulses moving through a broad mean trough in place
over the eastern Continental U.S. Through the first half of the period.
Thereafter both the operational European model (ecmwf) and GFS indicate a weak
disturbance passing just to our south late Friday night into
Saturday. At present it appears there could be a light snow or
snow/rain mix type event depending on the exact track of the very
weak surface wave across the Tennessee Valley. With overall similarities in
model solutions stayed close to our typical blend of solutions and
For sensible weather...confidence is high that we will experience
a prolonged period of light snow shower activity from Monday
night through Wednesday night...with snow showers tapering off to
just a few flurries by around dawn Thursday. The direction of
boundary layer winds are not ideal for significant upslope flow
type snowfall. In addition...quantitative precipitation forecast for the event as a whole is
fairly light. But column moisture is deep and snow ratios are
quite high as well. Therefore while overall snowfall totals will
gradually increase to some decent amounts with time over the two
to three day period...it should be more powdery in nature.
Considering this type of scenario...expectations are that this
will turn out to be more of an advisory type impact in general.
The late week disturbance does not look to be any type of major
storm system at this time...with only light snow accumulations possible.
Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 1236 PM EST sun Feb 7 2016
VFR will last well into the night. After about 06z...a rain/snow
mixture and MVFR conditions and will begin to move in from the
northwest...reaching the Virginia border by about 11z. Conditions will
likely fall to IFR for a time as the precipitation moves through.
A break in the precipitation is likely on Monday morning...but
rain and snow showers should redevelop from west to east during
the late morning and early afternoon. There could even be a few
lightning strikes with the second round of precipitation.