Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Jackson Kentucky
728 PM EST Friday Feb 27 2015

Update...
issued at 728 PM EST Friday Feb 27 2015

Updated to reflect more clear skies this evening with overcast
skies expected later on tonight. This will allow for a quick drop
in temperatures this evening before they hold steady or at least
slow down the fall for the second half of the night under the
cloud cover. Also based on the NAM bufr sounding out of
Lexington...opted for some flurries across the northern half of
the area late tonight into tomorrow morning. GFS bufr soundings
showed a bit more dry air...but still cloud heights low enough to
support some flurries.

&&

Short term...(this evening through Saturday night)
issued at 413 PM EST Friday Feb 27 2015

Middle and upper level pattern remains zonal through the short term
with little sensible weather to speak of other than the approach
of a storm system over the weekend. Main concern will be the cold
air in place across the area at the onset of any precipitation
late Saturday night...early Sunday morning.

NAM advertises a 40-50 knots h925-h850 low level jet developing late Saturday
night into Sunday morning...which brings in a warm nose of at least
+5c. Typically the NAM handles the warm nose better than the GFS so
expect any precipitation that may develop during that time frame to
melt aloft. The rest depends on boundary layer and surface temperatures. With a
decent snow pack still in place...only a brief few hours of temperatures
above freezing Saturday afternoon...and a 5-6 inch frost depth
expect much of the area would be at risk for a wintry mix at the
onset of precipitation.

Otherwise we are looking at another very cold night tonight as
temperatures drop into the single digits for a good portion of the
area...middle teens for the rest. Consequently...any melting of surface
snowfall and ice will refreeze overnight. Some area Road will likely
continue to see some isolated slick spots. Temperatures will make a
effort to rebound tomorrow but incoming cloud cover may dampen the
warm up considerably. For now went more optimistic and took
afternoon highs into the middle and upper 30s...near 40 for most
locations.

Long term...(sunday through friday)
issued at 413 PM EST Friday Feb 27 2015

Complex long term forecast with the primary concern remaining the
possibility for flooding. Anytime you see an upper low ejecting
out of The Four Corners region with deep southwest flow aimed
toward the Ohio and Tennessee valleys...you need to take notice.
This is a pattern that produces heavy precipitation amounts in an
axis somewhere underneath the right rear quadrant of the upper
level jet. Typically this seems to set up just to our west...
however 12z models continue to target central and eastern Kentucky
as having a shot at receiving 2 to 4 inches of rainfall next week.
With temperatures warming and snow pack melting in the headwaters
of the Cumberland...Kentucky and Big Sandy rivers...this potential
rainfall continues to be worrisome. There are no big changes in
the modeling from yesterday regarding this flood threat so will
continue to highlight and raise awareness of this potential threat.

As for the details...a slug of precipitation will spread across
the area on Sunday as a warm front gets drawn to the north into
our region. There may be some patchy freezing rain Sunday morning
with surface temperatures likely slow to warm above freezing while strong
warm nose punches in aloft. All rain is expected by the afternoon
into Sunday night...with a quarter to half inch of precipitation
expected. This warm front will get pushed back to our south on
Monday as the sponsoring trough aloft swings off to the northeast
and high pressure builds in at the surface. This will allow for a
break in the precipitation Monday afternoon into Monday night.

The focus then shifts to the developing southwest flow aloft...
which will send the warm front back through US and to our north.
Strong low level jet will send moisture surging northward with
precipitable waters prognosticated to exceed 1.25 inches by Tuesday night. As a
result...expect rain...locally heavy...to overspread the region
Tuesday and persist through the day on Wednesday. The upper level
trough then eventually shifts east...pushing the front to our
east and current indications are that the precipitation will end as a
period of snow Wednesday night into Thursday as colder air filters
into the region.

&&

Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 728 PM EST Friday Feb 27 2015

VFR conditions will continue through the taf forecast period.
Clear skies will give way to some middle level clouds later
tonight...but ceilings will remain above 6kft. Light winds are
expected through tomorrow.

&&

Jkl watches/warnings/advisories...
none.
&&

$$

Update...kas
short term...ray
long term...Abe
aviation...kas

National Weather Service Glossary of Abbreviations