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Area forecast discussion 
National Weather Service Jackson Kentucky
1022 PM EST Wednesday Jan 28 2015

Update...
issued at 1021 PM EST Wednesday Jan 28 2015

Only a few minor changes to the forecast were necessary this evening.
Had to remove some outdated wording from the first period of the zones
regarding tonights cloud cover. The transition from partly to mostly
cloudy skies has already begun and the zones were updated to reflect
that trend where necessary. Also tweaked the temperature range for
tonights low temperatures in a few counties...but nothing major
overall. The updated zones have already been sent out.

Update issued at 731 PM EST Wednesday Jan 28 2015

The forecast for the most part was on track this evening. One minor
change was made to the 9z weather grid for Thursday. For whatever
reason several pixels depicting a slight chance of precipitation were
showing up at 9z with no pop grid at 9z to support them.
Therefore...these apparently erroneous pixels were removed from the
9z weather grid. Aside from that...the forecast is good to go.

&&

Short term...(this evening through friday)
issued at 415 PM EST Wednesday Jan 28 2015

High pressure centered over the Ohio Valley will shift eastward
tonight as a clipper system takes shape to our west. Return southerly
flow will strengthen through the overnight under the influence of a
50-60kt low level jet that will develop across the region. This combined with
a rapid increase in cloud cover towards dawn will likely lead to an
early Thursday morning low for portions of our area with temperatures
rising back up again towards dawn. Locations most likely to fit this
description will be our western zones where the gradient flow should
become strong enough to mix out the nocturnal inversion. As is more
typical our eastern valleys will be much more difficult to scour
out...though it will not be out of the question.

Models have trended slightly slower with the onset of any
precipitation tomorrow morning. Have taken the forecast in the same
direction though surface temperatures may be cold enough that
precipitation could begin as a mix of some rain and light freezing
rain near dawn for our northwestern most Bluegrass counties. But
temperatures will be warming quickly through the early morning as the
southerly gradient winds increase...so thinking is that the threat is
minimal at this time. Just the same will pass on concerns to the following
shifts.

Rain showers will continue to develop through the day Thursday with
highest probability of precipitation focused closer to the main storm track just north of the
Ohio River. This systems cold frontal boundary will push through our
area...beginning sometime during the middle to late afternoon time frame
and push to the east of our forecast area by late Thursday evening.
There may be a short period of light drizzle due to a loss of ice
nuclei during the transition between rain and snow Thursday night.
Expecting any light rain...or drizzle to convert over to snow
showers by late Thursday night with the help of northwest upslope
flow. This will keep snow showers going through much of Friday
morning...especially in our higher terrain to the southeast. In
general any snow accumulations will be light and mainly confined to
the higher elevations along the Virginia...West Virginia state lines.
However...would not be surprised if Black Mountain picked up a couple
of inches of snow by middle day Friday.

Long term...(friday through wednesday)
issued at 415 PM EST Wednesday Jan 28 2015

Quite an active pattern in the extended period with quick moving
shortwave troughs over the eastern US. This period begins with yet
another coastal low moving up the New England coastline... with
quiet weather on the homefront. High pressure settles into the
region on Friday night into Saturday with return flow from the Gulf
ushering in additional moisture ahead of the next system.

The end of the weekend features a system that still has a lot of
uncertainty tied to it. The big question is how quickly the northern
and southern stream energy phases together...if at all... the 12z/28
GFS shows a more lackluster solution with a weaker trough whereas
the 00z/28 European model (ecmwf) shows the energy phasing in the Midwest and forming
a well-defined low pressure system lifting up along the New England
coast. Both solutions indicate a rain to snow changeover event for
eastern Kentucky Sunday night into Monday but the European model (ecmwf) solution has
quite a bit more organized quantitative precipitation forecast associated with it. As of right
now... the majority of the precipitation should fall as rain on Sunday when
there is better moisture and lift. Though... given all of the
uncertainty... still think there is potential for accumulating snow
early Monday morning so this will have to be monitored and fine
tuned in subsequent forecast updates.

Temperatures on Monday are expected to generally drop during the day
as cold air continues to push in behind the exiting system. How
quickly the system exits will determine how much and how quickly the
temperatures will drop. That being said... it does appear that well
below normal temperatures will settle into the region with lows Monday
night dipping into the middle and upper teens. High pressure and
southerly flow return Tuesday helping temperatures recover into
lower 30s. By Wednesday night another system looks to bring another
chance for a mixed precipitation event into the day on Thursday.

&&

Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 731 PM EST Wednesday Jan 28 2015

Mostly clear skies and fair weather will give way to deteriorating
conditions during the latter third of the forecast period. A clipper
system will sweep through the Ohio Valley during the day Thursday.
Rain showers will develop ahead of this system before changing over
to snow showers behind the front. It appears the surface cold frontal
boundary will move across our Bluegrass counties by about middle
afternoon and push across the rest of eastern Kentucky through the
remainder of the day on Thursday. Brought showers into the forecast
during the morning hours Thursday. Rain will change over to snow
Thursday evening/night and linger into Friday as upslope snow showers
gradually taper off. As is typical with clipper systems...surface winds
will increase considerably...to between 10 and 15 kts from the
southwest ahead of the front and from the west...northwest Post
frontal. Winds will be gusty as well. We can expect MVFR visibilities and
borderline MVFR ceilings once the precipitation becomes more widespread
on Thursday. Also added in some low level wind shear around 9 or 10z
tomorrow...as the latest forecast soundings were pretty favorable for
it...along with the latest model plan view data...which is still
supportive of a 50 to 60 knots low level jet moving across the Ohio and
Tennessee Valley regions between 9 and 12z Thursday.



&&

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

$$

Update...Arkansas
short term...ray
long term...jvm
aviation...Arkansas

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