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Area forecast discussion 
National Weather Service Jackson Kentucky
411 PM EST sun Feb 1 2015

Short term...(this evening through Monday night)
issued at 335 PM EST sun Feb 1 2015

19z surface analysis shows a rather deep area of low pressure moving
across the Mississippi River into Illinois. A cold front from this is
stretched to the southwest down into Texas. As this low pushes
further into the Ohio Valley...the core of its precipitation shield is now
entering eastern Kentucky with light to moderate rains overspreading
the area. Under thick clouds and the arriving rains...temperatures
have peaked this afternoon with readings in the middle 40s to lower 50s
across the area. Dewpoints...meanwhile...are coming up with the
arriving rains and now vary from the low to middle 20s in the east and
the upper 30s to lower 40s to the west. Wind have also picked up with
the arrival of the rain with gusts to 20 to 25 kts from the south
over the Cumberland Valley and 15 to 20 kts elsewhere.

The models are in good agreement aloft through the short term
portion of the forecast as they whip a sharp trough through the
southern Appalachians by midday Monday. In the northwest flow that
follows...a trailing shortwave will pass through eastern Kentucky
into early Tuesday morning...seen as strongest in the European model (ecmwf) when
compared to the nam12 and GFS/Gem. Have mainly followed a model
blend through Monday night with an emphasis on the higher resolution
details from the nam12 before leaning more on the GFS and nam12 with
the trailing wave through Tuesday morning.

Sensible weather will feature a good soaking rain for east Kentucky
through the evening and into the overnight along with breezy
conditions as the wrapped up surface low moves through. The low passes to
the east by sunrise Monday with winds switching to the west and
increasing as the tight gradient on the low/S backside exits the
area. In addition to the breezy conditions in the wake of the
low...an Arctic boundary will bring in much colder air from west to
east across the County Warning Area between 08 and 13z resulting in a switch over for
any lingering precipitation to snow. The winds will become more upslope while
the surface low further deepens into Monday morning. This will add to the
snow fall for our far eastern counties with the winds blowing the
snow around keeping the visible low in any showers. Expect the snow to be
worst between 11 and 15z for most of the area with light
accumulations expected aside from the ridges and locations in the far
east. Along those places near the Virginia border some higher snow
totals will be possible with between 2 and 3 inches seen on the peaks
above 2500 feet and up to 2 inches on the lower ridges while valleys
generally pick up an inch or less. Finally...in addition to the snow
and winds...the cold air could move in quick enough...trailing the
rains and limited dry slotting to result in icy conditions on area
roads. For this reason...will have an Special Weather Statement or Winter Weather Advisory
out for the entire area...hitting the east progressively harder for
amounts and impacts. Our Virginia border counties will have an
advisory for snow going until 23z while to the west the advisory will
run through 19z with lesser totals. The snow tapers off from west to
east Monday afternoon with cold air advection sending temperatures down into the teens most
places by dawn Tuesday...though low clouds will likely keep readings
from completely bottoming out for eastern parts of the area.

Used the bcconsshort followed by the superblend as a starting point
for temperatures...dewpoints...and winds through Tuesday morning.
Made only minor adjustments to winds and temperatures to account for
the terrain effects of the cold air advection winds late tonight into Monday
morning. As for probability of precipitation...ended up on the high side of MOS guidance
through Monday afternoon owing to the tendency for the model/MOS
guidance to under do upslope snow situations.

Long term...(tuesday through sunday)
issued at 410 PM EST sun Feb 1 2015

Tuesday will start out with generally zonal flow aloft and surface
high pressure in place. Temperatures will warm from the previous day
with surface winds becoming more srly and skies clearing...though
still expected to be a few degrees below seasonable normals. A
shortwave will begin to traverse along a trough axis well north of
the region...reaching the upper Great Lakes by Wednesday evening and
strengthening as it shoots off to the southeast and across the eastern
portion of Kentucky. This course of action...including the amplitude and
timing...is very much a result of which model is correct. As of
now...there is still quite a bit of disagreement between the GFS and
European model (ecmwf)...which leads to low confidence on the resulting surface
features. The GFS continues to be the strongest with the
system...showing a 1009mb low pressure system moving across New
England Wednesday evening. The European model (ecmwf) is in a similar location for
the low...but is slightly weaker at 1013mb as of the 12z run. A cold
front will extend southwest of this low...and bring frontal
precipitation to much of the Ohio Valley Wednesday evening through
Thursday morning for the GFS...and somewhat later Wednesday night
through Thursday afternoon for the European model (ecmwf) and Gem.

Regardless...this will be a quick hitting system...with much of the
moisture falling along or just behind the frontal passage. If this
holds true...winds will make a quick shift to the north and begin
pulling in much colder air around the time the precipitation starts.
This will quickly drop temperatures below freezing...so expect any precipitation
that falls to be mainly in the form of snow...with maybe a small
amount of rain at the onset. Highs on Thursday are only expected to
reach the upper 20s to around 30. Dry air will then quickly work in
and cut off any remaining snow potential sometime Thursday
afternoon. Do note...given the discrepancies between the
models...the timing of onset and departure is likely to change. This
will then likely affect the snow totals. At this time...forecasting
generally a half inch or less across the County Warning Area...with the highest
amounts in the southeast where snow will linger the longest and some
upslope flow will take place.

After this system passes through the region...upper levels will
slowly transition back to zonal flow. Colder Canadian air flowing
into the region will eventually give way to more seasonable norms by
Saturday. High pressure will be in control through much of the
remainder of the extended. Our next threat for precipitation will occur
sometime Saturday night/Sunday on day 7 of the forecast as models
hint at another shortwave developing over the Central Plains.

&&

Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 115 PM EST sun Feb 1 2015

VFR conditions will persist through most of the afternoon. However...
the ceilings will begin to drop as moderate rainfall begins to move into
the area along with a lowering of the visibility. In general...IFR
and below conditions can be anticipated through the area after 00z
with the moderate rains moving through. The rain will then change to
snow as the colder air moves in with reduced visibility and lower
visible being the main AVN concern. Winds will be increasing through the
afternoon and evening from the south to southwest. These will start
shifting to the southwest and later tonight and then to the west
predawn. Gusty winds will blow as high as 25 kts through the night
and into the day Monday as the system moves on through. These
winds...combined with snowfall will keep the visible rather low through
middle morning in most places. Look for conditions to start improving
by midday from west to east.



&&

Jkl watches/warnings/advisories...
Winter Weather Advisory from 6 am to 6 PM EST Monday for kyz088-
118-120.

Winter Weather Advisory from 3 am to 2 PM EST Monday for kyz086-
087-104-106>117-119.

&&

$$

Short term...greif
long term...jmw
aviation...greif

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