Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 201959

National Weather Service Jackson KY
359 PM EDT Mon Mar 20 2017

.SHORT TERM...(This evening through Tuesday night)
Issued at 359 PM EDT MON MAR 20 2017

The latest surface map features broad low pressure sprawled from
the southern Plains into Ohio Valley, with high pressure having
retreated to the Gulf Coast. Aloft, fairly zonal flow exists
across the heart of the CONUS, with several embedded weaker short
wave troughs. A more vigorous short wave trough is rotating
through south central Canada.

Convection has been dominating the synoptics thus far over the
past 24 hours, with a decaying MCS exiting eastern Kentucky.
This left an impressive differential heating boundary across the
Commonwealth, with a nearly 40 degree gradient in place at one
point earlier this afternoon. Temperatures are now rebounding in
our area, as clouds have thinned, and better low level warm air
advection has engaged. Meanwhile, upstream convection is growing
across Indiana and into western Ohio, closer to the surface low
and surface boundary, along with a secondary line of activity
forming along a leftover outflow boundary.

There is general model agreement with modest short wave energy
helping to bring the surface front southeast into our area
overnight, with convection likely recycling or sustaining
itself. Have maintained categorical POPs to the northeast, and
chance POPs west of I-75. Lows tonight will be much milder
compared to previous nights, with readings generally ranging from
the upper 40s to lower 50s.

Convection will be exiting to our east Tuesday morning, before
refiring along the surface cold front during the afternoon and
early evening. Highs will range from around 60 north, to the upper
60s south. The models have trended further south with the
boundary position, and the best POPs for the afternoon will be
along the Cumberland Valley. Convection will gradually wind down
through Tuesday night, as high pressure builds in from the north.
Lows Tuesday night will range from the lower 30s north of I-64, to
the lower 40s bordering Tennessee and Virginia.

.LONG TERM...(Wednesday through Monday)
Issued at 330 PM EDT MON MAR 20 2017

Rain will push south of eastern Kentucky Wednesday morning as an
upper low across the Northwestern Passages and Hudson Bay dislodges
east, sending a trailing trough axis through the Great Lakes and
upper Ohio Valley. Surface ridging will follow a similar trajectory
along the southeastern Great Lakes, ushering a cooler airmass into
the Commonwealth in wake of a cold front. High temperatures look to
largely drop into the mid 40s to low 50s, prior to lows Wednesday
night dipping into the upper 20s to low 30s. Valley locales across
far eastern Kentucky may even drop into the mid 20s, promoting frost
formation by daybreak Thursday. Will have to monitor exactly how far
aforementioned surface ridging pushes south, as the possibility may
exist for a stray shower or two to develop into south central
Kentucky through Wednesday evening as energy moves through in a
northwest flow regime aloft. Not currently expecting anything
measurable out of this given overall subsidence in place, but
again will have to see if a clean frontal passage can occur
earlier in the day to completely scour out available moisture.

A warming trend will take place Thursday into the weekend as upper
ridging slides in aloft with winds veering southerly at the surface.
This will be in response to surface high pressure moving into the
Atlantic while lee cyclogenesis materializes in the southern to
central Great Plains downstream of a digging upper low east of the
Four Corners Region. Dry conditions look to remain in place through
the end of the week, as precipitation stays shunted off farther
north across the Ohio Valley and upper Midwest into the Great Lakes
nearer greater forcing from another Hudson Bay upper low. Greater
moisture will also reside at farther north latitudes along a cold
front extending south off of this feature, as well as along a warm
front passing north of eastern Kentucky Thursday into Friday.

Rain chances will increase into the weekend as the stacked low
pressure system plows east, bringing both an increase in forcing and
moisture out of the Gulf of Mexico. Thunderstorms will also be
possible by Saturday afternoon as temperatures warm to near 70
degrees. Will have to continue monitoring synoptic/mesoscale details
later in the week regarding strong to severe thunderstorm potential
for the weekend. A brief dry period looks to ensue by late weekend
into early next week, before cyclonic flow loads up once again off
to the southwest. This should preclude much in the way of any
significant cooldown in wake of the weekend system.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)

Generally VFR conditions will hang on through this evening, as a
weakening complex of showers and isolated thunderstorms exits off
to our east. Additional showers and a few thunderstorms will move
into the area this evening and into the overnight as a cold front
drop southeast across the area. Better coverage will generally
occur along a line from KSYM to KSJS, with more scattered activity
expected west of I-75. Ceilings will drop down to MVFR and
eventually IFR towards dawn, as south to southwest winds of 5 to
10 kts become northerly behind the cold front, and low level
stratus sets in across the area. Additionally, some marginal
wind shear will set up across LOZ and SME tonight, as a low level
jet ramps up across the Ohio Valley.




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