Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 190600 AAA

National Weather Service Jackson KY
100 AM EST Mon Feb 19 2018

Issued at 1245 AM EST MON FEB 19 2018

Did a quick update to adjust the near term PoPs as some bonus
showers have formed ahead of schedule over the western parts of
the area and are moving/developing deeper into the CWA. The
updated grids have been sent to the NDFD and web servers.

UPDATE Issued at 1114 PM EST SUN FEB 18 2018

Temperatures have reached their lows at most locations, as clouds
have thickened up, and even a few showers are starting to develop
across the southern portions of the area. Have fine-tuned the
temperatures and POPs through Monday morning, with chances
ramping up quite a bit over the next few hours, and cooler valley
locations gradually mixing out. Shower chances will then
gradually shift to the north through Monday morning as the warm
front exits north of the Ohio River. Updates will be out shortly.

UPDATE Issued at 707 PM EST SUN FEB 18 2018

Clouds are on the increase tonight out ahead of the approaching
warm front, with scattered light showers already moving across
southern Tennessee. It will take a little while to moisten up, so
will leave the POP timing as is, with the better increase
occurring after midnight. Eastern valleys are decoupling as
scheduled, and will only make a few adjustments to the hourly
temperatures and dew points over the next few hours to account for
the trends in observations.


.SHORT TERM...(This evening through Monday night)
Issued at 400 PM EST SUN FEB 18 2018

At mid and upper levels, a ridge was centered south and southeast
of Bermuda with a trough over much of the western to central
Conus. A series of shortwaves were moving from the Rockies into
the Plains while a closed low was moving through the Northwest
Conus. An area of low pressure was moving across the upper MS
Valley with a stronger sfc low over eastern CO/western KY.
Meanwhile over the east, high pressure was centered to the east
and northeast of the area while a warm front extended through the
Gulf Coast states and then west and northwest into the Plains.
Some mainly high clouds are working across the region with thicker
high clouds and some low and mid clouds over the MS Valley.

Surface high pressure will depart to the north and east with mid
level heights expected to rise along the eastern seaboard tonight
and into Monday. The initial surface low now over southwest MN
should track into WI and Lake Superior and then on into Ontario
and weaken while a surface low now over CO and KS tracks across
the Central Plains and into the MS Valley as a couple of
shortwaves move through the southwest flow between ridging off
the southeast coast and troughing over the west. A warm front
should develop over or move into the area tonight and lift north
of the area on Monday. Southerly flow should transport deeper
moisture into the region with isentropic lift. PW initially in
the quarter to one half of an inch range should reach in excess of
one inch by dawn. Behind the boundary on Monday, the region will
get into the warm sector with shower chances diminishing. Further
west, an upper low/shortwave should track south over the western
Conus tonight and then begin to move east across the Intermountain
west and into the Monday to Monday night period. The southwest to
south southwest flow aloft should keep the baroclinic zone well
to the west and northwest of the area through the end of the
period. Meanwhile, the mid and upper ridge should build back into
the southeast with rising heights and surface high pressure
increasing across the southeast.

As for temperatures, there should be a window of opportunity for
eastern valleys to decouple this evening and make a run at the
upper 30s, before clouds thicken and lower around or just after
midnight. Showers should also move into the area or develop
shortly after as moisture increases, especially aloft rather
dramatically and insentropic lift increases as southwest low level
jet increases. This should be a low qpf event with most locations
measuring. The increase in winds aloft may also lead to increased
winds above 2000 or 2500 feet with gusts on the order of 30 to 35
mph possible overnight into early on Monday.

Well above normal temperatures are expected on Monday and Monday
night. Record highs on Monday may be broken at JKL and LOZ as
temperatures should reach the lower to perhaps mid 70s in many
locations. A small ridge/valley split could occur on Monday night
if clouds were to thin for a while. However, lows will be very
mild for February likely not falling below 50 in all locations.

.LONG TERM...(Tuesday through Sunday)
Issued at 245 PM EST SUN FEB 18 2018

An anomalous ridge will remain anchored over the eastern US at
the start of the period. Downsloping southerly flow, combined with
3 to 4 standard deviations above normal height anomalies will
allow for a very warm day on Tuesday. Afternoon highs will be
nearly 30 degrees above normal with readings topping out around 80
degrees. This will clearly be good enough for daily records, and
will threaten our all time February high temperature records.

While we are enjoying the warmth on Tuesday, a baroclinic zone
will set up over the western Ohio river valley, focusing very
heavy rain across that region. This boundary will eventually be
pivoted eastward as a shortwave pushes northeast across the area
on Wednesday. Models continue to slow down the precipitation
chances, but still looks like a decent chance activity could reach
us by late Wednesday. If nothing else, a little weakness in the
heights could allow a few showers or storms to pop up on
Wednesday, especially in our western zones. For the first time in
quite a long time, LI`s are actually below zero Wednesday
afternoon, so a few storms certainly are possible if enough
instability can develop. The main axis of precipitation will shift
into our area Wednesday night with the highest rain chances
occurring at this time.

Uncertainty increases greatly as we go into Thursday and beyond as
it looks like we may have a few more rounds of rain targeting the
Ohio river valley late in the week into the following weekend. At
this point, looks like the best rain chances may come Friday and
Saturday. Models show the baroclinic zone finally exiting as a
cold front late next weekend allowing drier conditions to finally
return late in the weekend or early into the following week.

Given the tremendous uncertainty with rainfall amounts and
timing, opted to hold off on any ESF or mention in the HWO at this
time with regards to heavy rain. With 3 to 4 days of dry weather
expected going into the next chances of rain, that may be enough
time to allow rivers to recede and ground to dry out a tad.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)

An approaching warm front will bring a period of showers and MVFR
ceilings to most of the area into early Monday morning. Will
lower all ceilings by 09z, where they are not already starting off
as MVFR - along with the presence of passing rain showers - VCSH.
Ceilings will raise back up to VFR levels by mid to late Monday
morning, as the boundary lifts north of the area. An increasing
low level jet, associated with the developing warm front will
bring low level wind shear through at least the mid-morning hours
on Monday. At the surface, light and variable winds will veer to
the south at around 5 to 10 kts overnight, before increasing to
around 10 kts, with gusts of 15 to 20 kts by mid to late Monday
morning. Wind shear will also be a concern Monday night even as
cigs will hold in the VFR category.




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