Area Forecast Discussion

FXUS63 KJKL 201735
National Weather Service Jackson KY
Issued by National Weather Service WILMINGTON OH
135 PM EDT Tue Mar 20 2018
Issued at 825 AM EDT TUE MAR 20 2018
The mid-level short wave continues to cruise eastward, with
a quickly diminishing precipitation shield across southern Ohio. 
Meanwhile, some showers have developed along the remnant cold
front still aligned across far southeastern Kentucky. Have
adjusted the POPs through the day, which keep at least some
scattered activity along the boundary. Elsewhere, the lull looks
to be more pronounced through much of the day, as we will be in
short wave ridging, so kept lower in POPs a bit longer. Temperatures
have also cooled quite a bit in the northwest, with some mid 30s
noted. While a little recovery will take place today, adjusted 
some of the high temperatures down to account for this cooler 
trend. Updates have been sent. 
.SHORT TERM...(Today through Wednesday)
Issued at 359 AM EDT TUE MAR 20 2018
The latest surface map features broad surface low pressure
situated from eastern Kentucky down to South Carolina. Aloft, a
short wave trough is moving nearly along the Ohio River, with a
secondary trough moving across the Plains. Widespread showers 
have lifted north out of our area, with dry slotting working in 
from the southwest, keeping showers limited in areal coverage. 
Expect a general lull in the action through early this afternoon,
as the short wave trough continues to move off to our northeast
and east, leaving us in temporary short wave ridging. The next
wave will move in from the west. This wave will cutoff and help 
to deepen surface low pressure that will be developing just off to
our east and southeast. Wrap around moisture will fill in across 
the area late today and especially tonight into Wednesday. Winds 
will become northwesterly, with the column gradually cooling off 
enough to allow for snow. Will be leaving much unchanged from the 
previous forecast, although, given the generally lighter 
precipitation rates, have allowed for a bit more disparity 
between the valley accumulations and ridgetop amounts in some 
areas. Most of the valleys will range in the 1 to 2 inch range, 
while ridges will be in the 2 to 3 inch range. The exception to 
this will be our southeast terrain, with the higher elevations 
along the Pine and Black Mountain chains seeing 3 to 5 inches by 
Wednesday evening. 
Temperatures will be averaging well below normal through the short
term, and have favored the cooler NAM MOS numbers, especially for
tonight and Wednesday. Highs today will range from the lower 40s 
in the northwest to the mid 50s in the far southeast. Readings 
will drop down into the lower 30s tonight, with readings likely 
not moving much on Wednesday, given the ongoing precipitation and 
cold air advection. Highs will be in the upper 30s for most 
locations, some 20 degrees below the normal highs for the latter 
half of March. 
.LONG TERM...(Wednesday night through Monday)
Issued at 407 AM EDT TUE MAR 20 2018
The extended period begins with the remnants of a system moving to
the east. Lingering snow showers will be possible with the exiting
system early Thursday. The main feature of interest is forecast 
to occur this weekend, with another potential system to begin the 
next work week. 
Before the main system makes its way through Saturday afternoon, 
an upper level jet streak coming from the northwest will set up 
over the western part of the Commonwealth. The GFS shows a small 
band of precipitation Friday morning into the afternoon associated
with this source of lift. However, the ECMWF does not show as much
QPF. This could be because the lift is coming from an area of 
ridging to the northwest. Therefore, whether or not there will be 
sufficient moisture to go along with the lift generated from the 
jet streak before the main system moves in Saturday afternoon is 
still uncertain. To account for this, it looks like the Blend gave
slight PoPs in the south Friday morning into the afternoon.
The models are coming into better agreement in terms of timing with
the weekend system, but the GFS is still slightly quicker than 
the ECMWF. The GFS also shows higher QPF whereas the ECMWF shows 
the precipitation tracking a bit more to the north with lesser 
QPF. Most of the precipitation from this will be rain, but there 
are chances of a rain/snow mix in the mornings due to the lower 
morning temperatures. However, with temperatures gradually on the 
increase over the course of the extended period, the better 
chance for rain/snow is on Friday as opposed to Monday morning. 
Furthermore, where the ECMWF shows showers tapering off early 
Monday morning, the GFS shows lingering showers for Monday with a 
stout system moving in later Monday into Tuesday. With the model
uncertainty towards the end of the extended period, have opted to
go with the Blend at this time.
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Low pressure at the surface and aloft will adversely affect
aviation through the forecast period. Ceilings starting IFR and 
as low as LIFR will stay down in the nearly saturated circulation
surrounding the low. Precip redevelops later this afternoon and 
evening as the strengthening system moves overhead. Rain will 
change to snow tonight as colder air arrives around the low. The 
snow will reduce visibilities down to 2SM/IFR. Snow is then 
forecast to continue through the end of the TAF period in 
lingering moisture and forcing behind the departing system. North 
winds will become northwest to west as the low progresses across