Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Jackson Kentucky
225 am EDT Friday Mar 27 2015
issued at 225 am EDT Friday Mar 27 2015
Precipitation is winding down across the southeast and the
widespread activity will likely be ending in the next 1 to 2
hours. Freshened up the forecast to reflect the latest trends in
radar and observations. Temperatures have fallen off quickly for
the higher elevations...with the Dorton mesonet now down to 34
degrees. Can only assume that Black Mountain is at or below
freezing given the trends...so continued with the snow mention for
elevations above 2500 feet.
Update issued at 1029 PM EDT Thursday Mar 26 2015
Updated to reflect better hourly temperatures and probability of precipitation coverage.
Precipitation continues to spread across southeast Kentucky.
Temperature at Dorton mesonet site is down to 37...so some snow
may start mixing in across the high terrain in the next few hours.
Warm ground should keep any accumulations at Bay...but a quick
dusting will be possible. No other changes at this time.
Update issued at 648 PM EDT Thursday Mar 26 2015
Light rain with embedded pockets of moderate rain continue to
sweep east across the eastern half of Kentucky. Precipitation
still extends well back to our west and north. Have increased probability of precipitation
across the board through the rest of the evening and extended the
better probability of precipitation well into the night...especially in southeast Kentucky
where latest models support precipitation lingering through at
least 2 or 3 am. With this in mind...latest NAM and GFS both
support a changeover to all snow for the higher elevations near
the Virginia border. Will go ahead and introduce some snow on the
back edge of the precipitation. Snow shouldn't be a big issue
given the current temperature near 54 degrees on Black Mountain.
Precipitation should end by daybreak..with perhaps some clearing
trying to work into the area. Not convinced it will spread in as
quickly as models suggest given the northwest flow. Latest grid
updates have been saved and sent.
Short term...(this evening through Friday night)
issued at 321 PM EDT Thursday Mar 26 2015
A line of showers and isolated embedded thunderstorms is currently
moving across the far eastern portion of the state...about to exit
into Virginia and WV. This convection is riding along the cold
front...which will also be exiting to our east over the next 1 to 2
hours. Behind this front...there is a dry slot...encompassing much
of the County Warning Area west of convective line. However...stratiform precipitation is
still slowly making its way across western and central Kentucky...and
should be making it into our County Warning Area over the next few hours. The
biggest thing to note behind this front is the quick change in wind
direction from the SW to the northwest...and the sharp drop in temperatures
as a result. Some 20 degrees difference has been noted across our
western County Warning Area in less than one hour.
An upper level longwave trough is currently moving across the
Mississippi River valley and should spread across the Ohio River
valley overnight. As it does...a strong upper level jet streak will
develop across eastern Kentucky. This will likely intensify the light
stratiform rain across eastern Kentucky late this evening...before best
forcing shifts east of the region and the rain shield follows.
Models are in fairly good agreement that any lingering rain should
be out of the County Warning Area between 12 and 18z tomorrow. However...dry
conditions will be short lived...as energy along the trough axis
shifts directly over the region...and works with lingering low level
moisture to create the chance for more light quantitative precipitation forecast. Expect this to be
out of the region by around 12z Saturday.
As for precipitation types...temperatures will cool to around freezing in
many locations overnight. However...any lingering moisture will
likely be low and shallow and out of the dendritic growth zone. As
such...will keep with previous forecast thinking that ice growth
should be unlikely and rain will prevail. Temperatures will rise back above
freezing Saturday...though cold northwest flow and cloud cover will only
allow for temperatures to reach the middle 40s by the afternoon with a cold
rain potential. Moisture and clouds will begin tapering off and
moving out late Friday night...but not before some of the rain may
have a chance to mix with a few snowflakes. Very little impact /if
any/ is expected with this snow. If we are able to clear out late
Friday night...temperatures will likely plummet down into the low to
middle 20s. This will result in a hard freeze in most areas across the
County Warning Area...though after discussions with ag extension of UK...the impacts
from this event will likely not warrant any headlines at this
Long term...(saturday through thursday)
issued at 305 PM EDT Thursday Mar 26 2015
There is good model agreement on the overall evolution of the mean
pattern as we move from a highly amplified pattern with a deep
trough in the eastern United States at the beginning of the
forecast period to zonal flow next week. This will spell a
moderating trend after the weekend...but with fast zonal flow we
will see a series of weak frontal systems affect the area next
week...with each one bringing a chance for rain. In fact the
chance of rain will return Sunday night. Temperatures at the start
of next week will return to near normal readings and will then
trend to above normal readings during the second half of the week.
However...before the moderating trend of next week we will need to
endure unseasonably cold weather for the first part of the weekend.
Temperatures from Saturday into Sunday morning will average about 20
degrees below normal. Surface high pressure will settle into eastern
Kentucky Saturday night. Clearing skies and light winds will allow for
good radiational cooling...with lows dipping down into the lower to
middle 20s by Sunday morning. As high pressure shifts east on Sunday
and winds become southerly temperatures will rebound into the lower
to middle 50s Sunday afternoon.
Aviation...(for the 06z tafs through 06z Friday night)
issued at 225 am EDT Friday Mar 27 2015
IFR/MVFR ceilings will gradually break up from northwest to
southeast through dawn as precipitation winds down across the
area. VFR conditions will likely hang on through Friday despite
the approach on an upper level disturbance which will bring the
threat of a few more showers to the area for the afternoon and
early evening hours. Winds will remain at 5 to 10 kts through the
period...generally out of the north and northwest.