Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jackson Kentucky
335 PM EST Friday Nov 28 2014
Short term...(this evening through Saturday night)
issued at 335 PM EST Friday Nov 28 2014
Current surface analysis as of 20z shows surface high pressure
draped along the appalachian chain. This has allowed for dry
conditions across eastern Kentucky with surface southerly winds
beginning to set up into the area this afternoon. Northwest flow
still continues in the upper levels as cloud cover ahead of a
developing warm front over the middle MS River Valley continues to
move into eastern Kentucky. This continued middle and upper level cloud
cover moving into mainly the northern part of the forecast area will
pose a difficult temperature forecast for tonight as some of the
deeper eastern valleys will drop off quick early into the night but
may become steady late. With the coupled insulation from cloud cover
and increased southwest flow bringing warmer air into the
area...thinking these Deep Valley lows will not realize their full
potential with min temperatures despite dew points in in the lower 20s. This
is also complicated by the developing low level jet ahead of the next
system and whether it will mix to the surface at times overnight.
This likely won't happen in the deeper valleys to the east but the
shallower valleys in the west will be problematic at best. At this
point will expect most locations in western portions of the forecast
area to reach their low before 06z and stay mixed nearly all night.
Locations in the east will reach their lows later in the night with
middle 20s for lows in the deeper valleys.
Headed into the day on Saturday with gradient on the increase...model
soundings show a 50 to 60 knot low level jet developing...some
locations could see some 30 knot gusts into Saturday afternoon...but
mainly those higher elevations as the inversion looks to hang around
a bit longer through the day keeping the stronger winds out of the
valley areas. Have put these values into the forecast as well.
Temperatures for Saturday afternoon will be a bit tricky with cloud
cover hanging around and warmer air being advected into the area. The
boundary layer will still be quite dry still heading into this event
as well with dew points still in the low 30s by Saturday afternoon.
Mentioning the dry air in place for Saturday night...this will be
present at the surface with quite a dry middle level in place to start
this event. With a shallow moist layer only up to 800mb and little
lift making it into eastern Kentucky...expecting only a slight to low
chance of measurable precipitation to make it into the Bluegrass counties.
In fact...even the NAM which is usually biased toward being wetter
shows the low levels struggling to moisten up. Went with low chance
probability of precipitation into Sunday morning and no quantitative precipitation forecast forecasted. Low temperatures for
Saturday night will be later in the night and those mainly in the
valleys as ridge temperatures will be near steady due to increased warm air
Long term...(sunday through friday)
issued at 335 PM EST Friday Nov 28 2014
Models have come into much better agreement through the majority of
the extended period...with the exception being the Thursday/Friday
At the beginning of the period...continued southerly ll flow helps
to increase ll moisture across the region. Forecast models continue
to show some light quantitative precipitation forecast over our west and northwest counties and
would expect cloudy skies with some patchy drizzle and light rain
Sunday mainly west and north of Jackson. Moisture deepens Sunday
night into the day on Monday as a cold front sags into the area and
rain chances increase. Precipitation associated with the front appears to
be rain during Monday afternoon/evening before possibly changing to
a wintry mix or light snow by Tuesday morning...though this depends
on how quickly the frontal precipitation drops to our south and the timing
of the cold air mass moving into the region. Fortunately it appears
that the bulk of the precipitation should be to our south by the time the
colder air makes it in.
Southerly flow returns Post-frontal helping to usher in warmer
temperatures...ll moisture... clouds...and some showers Tuesday night and
Wednesday. GFS appears to be the wetter of the solutions. However...
models really start to diverge in their solutions Wednesday so
forecast confidence is low for any sensible weather for days 6 and 7.
Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1255 PM EST Friday Nov 28 2014
Much of the area this afternoon and tonight will be under VFR
conditions with a mainly 7 kft ceiling or later streaming in from the
northwest. Though a few ceilings may dip to MVFR ceilings but this is
becoming more unlikely as the cloud layers lift and more middle level to
upper level cloud cover moves in from the northwest. These conditions
will likely continue into tonight and into tomorrow afternoon. The
only real concern will be gusty winds developing out of the southwest
tomorrow after 14z with some gusts reaching 25 knots.