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FXUS61 KILN 251820

Area Forecast Discussion
National Weather Service Wilmington OH
120 PM EST Sat Feb 25 2017

A much cooler airmass will continue to settle into the region 
today as a weak upper level disturbance brings a few rain and 
snow showers. High pressure will build into the Ohio Valley 
tonight into Sunday, leading to mainly clear skies. Seasonable 
temperatures will remain in place across the area for Sunday.


Shower activity will continue to move east this afternoon and
experience a slow but steady diminishing trend, ending by
evening. This is as the h5 trough is crossing the region and
downward motion with building surface high pressure in the lower
Midwest. Temperatures will slowly drop as the westerly winds
continue through the day.


The trough axis will push off to the east tonight with surface
high pressure building into the region later tonight. This will
lead to decreasing clouds southwest to northeast and overnight
lows in the low to mid 20s. Mostly sunny skies are expected on 
Sunday with highs in the low to mid 40s.


Sunday night surface high pressure will be centered near the 
coast of NC with southwest flow across the region. At the same 
time an upper level disturbance over AZ will eject east and push
towards the forecast area. Both the GFS and ECMWF have come 
into fairly good agreement here with this system ejecting east 
and spilling vorticity across the area Monday morning. As this 
happens high cloud bases will thicken and slowly lower with 
precipitation moving in from the west. Initially Monday morning 
a rain/snow mix will be supported with the entire sounding below
freezing except right at the surface. Behind the remnant 
shortwave Monday afternoon dry mid and upper level air will work
into the area helping to cut off the precip a bit. 

Monday night into Tuesday morning there will be a brief break as the 
next upper level disturbance over the Mountain West gets its act 
together. Later Tuesday morning into afternoon the upper level 
disturbance will push northeast into Minnesota pulling a warm front 
north across the area. Widespread overrunning will commence with 
PWATs approaching 0.85". Widespread weak lift will also accompany 
the WAA which is supported by GFS omega fields. Tuesday afternoon a 
surface low will track northeast towards WI allowing temperatures to 
rise into the 60s. Shear values Tuesday afternoon will also become 
impressive as ILN gets warm sectored with SFC- 3 KM shear 40 + kts 
at times. GFS soundings currently show a CAP across the area though 
which would limit convection across the region.

Tuesday night into Wednesday morning another upper level disturbance 
will swing around the base of the upper level trough axis centered 
over the Western United States and push towards the forecast area. 
As this happens another surface low will form in the plains and push 
northeast along a baroclinic zone. At the same the upper level jet 
will begin to strengthen and briefly place ILN in a RRQ. Also a weak 
split will occur in the jet. The GFS/ ECMWF/ and CMC all show this 
happening. The difference between the three is placement of the 
baroclinic zone (e.g., front), and track of eventual surface low as 
it heads northeast. The NAEFS shows PWAT anomalies of 2 SD. The GFS 
also has a PWAT of 1.35" just south of the region. As mentioned 
above though these small differences in track between models has a 
big difference on rainfall distribution. The ECMWF is furthest north 
with the second surface low and has heavier rainfall totals across 
our northwestern zones while the GFS is furthest south with the 
track and has the heaviest totals across central KY. The CMC is a 
compromise between the two and have trended the forecast this 
direction. Given the RRQ, splitting upper level jet, abundant 
moisture and lift have raised PoPs for Wednesday. 

Wednesday evening into Thursday morning a stronger upper level 
disturbance will push east over the area finally pushing the surface 
cold front through the area. Thursday afternoon into Friday another 
upper level disturbance will head southeast out of southwestern 
Canada and bring a chance of snow and rain to the area Friday 
morning. GFS soundings completely saturate Friday morning with almost 
the entire forecast sounding below freezing. As of now mostly snow 
Friday morning would be expected given the thermal profile of the 
GFS. Eventual track and strength of this disturbance remains in 
question though as the ECMWF is weaker with the disturbance so have 
kept PoPs at chance for now. Friday night into Saturday surface high 
pressure will dip south into the area from Canada and bring below 
normal temperatures to the area. Saturday afternoon the surface high 
pressure will already be east of the forecast area as the upper 
level trough axis heads east.


Significant cloud cover with mvfr cigs and passing snow showers
will lift later this afternoon and break up this evening, latest
in the eastern TAF sites of KCMH and KLCK. Winds will lose any 
gustiness by nightfall, and then skies will clear for the 
overnight period. 

A surface high will be south of the area at daybreak Sunday and
winds will switch to the south as it passes. High clouds will
stream in from the west later in the day.

OUTLOOK...MVFR ceilings and visibilities possible Monday, 
Tuesday night, and Wednesday.





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