Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Jackson Kentucky
655 am EST Wednesday Jan 28 2015
issued at 655 am EST Wednesday Jan 28 2015
Still some low clouds over the far east along with a stray flurry
possible. Have slowed this clearing down and also fine tuned the
hourly temperatures and dewpoints for the next several hours based on the
latest observation and trends. These have been sent to the ndfd and web
Short term...(today through thursday)
issued at 350 am EST Wednesday Jan 28 2015
08z surface analysis shows high pressure moving through the Ohio Valley.
This high is providing a decent night of radiational cooling for the
vast majority of the area with the only exception found in far
eastern parts of the state where northeast low level flow is keeping
some stratus around. In fact...a few snow showers have been falling
out of these as seen in the kpbx observation and the radar images from rlx.
In the clear areas temperatures have been falling steadily with the
ridges and the valleys leading the pack...though as the night has
worn on the deeper valleys have dropped the furthest...while the more
open locations have been lagging...thus far. Readings at 3 am vary
from the middle teens on the ridges and those sheltered valleys while
lower 20s are found in more open places like sme and loz as well as
southern valleys of ekq and 1a6. Dewpoints...meanwhile...are
generally in the middle teens to near 10 above as winds remain light...
generally from the north to northeast.
The models are in pretty good agreement aloft for the short term
portion of the forecast as they all depict The Retreat of the deep
northeast trough and with it the energy stream that ran from north-northwest to
south-southeast over our eastern border. Brief ridging will follow into Thursday
morning for Kentucky though another developing trough will be
trailing quickly behind these higher heights. This trough slips into
the southern Ohio Valley by midday Thursday with a couple of batches
of trailing energy that will eventually form a deeper trough for the
northeast coast by week/S end. Given the model similarities in the
short term...have favored a blended solution with a lean toward the
nam12 for weather details on Thursday.
Sensible weather will feature a chilly start to the day with some
single digits possible at dawn. Plenty of sunshine will allow
readings to climb smartly into the middle 30s in the north and lower 40s
south even as high clouds start to arrive ahead of the next clipper
system. These high clouds...and winds starting to react to the surface
low...will likely not prevent a decent drop off in temperatures
following sunset for the bulk of the area tonight. Expect the
eastern valleys to fall off the furthest and be the last to engage
with the increasing southern surface flow...waiting until closer towards
dawn to break their temperature fall and start to rise. Meanwhile...
ridges and more open locations in the west will only slowly drop off
through the first part of the night. Expect the thickening clouds and
increasing southern winds to allow temperatures to climb in the hours before
dawn most places along with rising dewpoints. Precipitation chances should
arrive from northwest to southeast during Thursday morning with
places likely warming quick enough to prevent a mix at the onset.
This will still need to be watched but at this point is not enough
of a concern to highlight in the grids...zones...or severe weather potential statement. As the surface
low passes to the north later Thursday...its front will push through
a band of rain for most of the area that afternoon. Colder air does
follow on west to northwest winds for late in the afternoon and into
the evening Thursday. As a result...some snow may mix in with the
lingering rain by 00z Friday in the northwest parts of the area.
Have added a mix for this in the weather grids towards the end of the
short term period.
Again used the bcconsshort as a starting point for temperatures...
dewpoints...and winds through this evening and the superblend
thereafter. Did make some fairly substantive...terrain based...
adjustments to hourly and minimum temperatures...as well as winds...
tonight ahead of the inbound frontal system. As for probability of precipitation...ended up
close to a combination of the mav and met numbers through the day
Thursday...though with added timing details in the spatial coverage
of the pop/weather grids during the afternoon...in particular.
Long term...(thursday night through tuesday)
issued at 425 am EST Wednesday Jan 28 2015
Clipper system will be exiting to the east of the region as we move
into Thursday night. There will be a change over from rain to mix and
then to all snow. Given limited moisture with this system would think
accumulations would be quite light. Do keep the mention of slight
chances right along the ridges into early Friday given the northwest flow
that setup across the region through that period. This surface low
will restrengthen across New England states as surface high dives
across the Ohio Valley through the day Friday. Skies are expected to
clear out through the day as high pressure and drier air build across
eastern Kentucky. This front does bring colder airmass with temperatures dropping
into the teens Friday night.
Saturday high pressure will shift east and this will bring return
flow to the region. This will translate to reasonable rebound in temperatures
with highs reaching into the upper 30s to lower 40s across most
spots. Then all focus shifts to developing storm system across the
desert SW and plains Saturday. This developing low pressure system
combined with upper level trough that develops across the plains will
be the next big weather maker to affect eastern Kentucky this coming
weekend. That said the forecast uncertainty for this storm system has
been quite noticeable from run to run. Previous runs of the GFS in
regards to this system suggested more progressive low pressure
system...however latest 00z/28 is a bit more inline with the latest
00z/28 European model (ecmwf). It should also be noted that even the 00z/28 GFS
ensemble mean is more progressive than the operational solution and
looking at some of the perturbations the surface low locations vary
quite a bit. These differing solutions will have implications on
timing and amts of precipitation. This timing will also play a big roll in
timing of precipitation change over to snow Sunday night and how much
snow we actually see. Given uncertainty have tried to follow a model
blend approach at this point and also tried to stay in reasonable
collaboration with surrounding offices. Keep in mind right now much of
the quantitative precipitation forecast associated with this system still looks to fall in the form
of rain on Sunday where better moisture and lift will take place
during that period. Given all the uncertainty think there is still
potential for accumulating snow Sunday night into Monday and this
will have to be fine tuned in subsequent forecast updates.
Moving into Monday would expect temperatures to generally drop through the
day and the amount of drop will depend on timing and evolution of this
system. That said this system does look to usher in well below normal
temperatures Monday night with lows dropping into the teens and even
single digits in some spots. High pressure will move east through the
day Tuesday bringing some return flow and highs generally in the low
to middle 30s south and upper 20s to lower 30s north.
Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 630 am EST Wednesday Jan 28 2015
Aside from some low...MVFR...clouds over sjs...sky clear conditions will
prevail through the morning hours before some high clouds start to
push in from the west in the afternoon ahead of the next clipper.
Winds through the day will be generally light from the north to
northeast initially then switching around to the south by afternoon.
Winds will pick up in the evening from the south and continue through
the night with some gustiness possible towards dawn in the northwest
parts of the area as ceilings start to drop.