Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 121738
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1238 PM CDT Thu Oct 12 2017

.UPDATE...
Issued at 1010 AM CDT Thu Oct 12 2017

Some trend adjustments made for late today into tonight across the
WFO PAH forecast area, along with subtle
temperature/dewpoint/relative humidity tweaks for today and
tonight.

The trends from the 13-14z runs of the 13km RAP guidance closely
mirror the concentration and lifting of boundary layer moisture
over the area. The RAP relative humidity/lapse rate/isentropic
lift profiles most closely ties in with the METAR (surface
weather observations) and PIREP (pilot reports) across the WFO PAH
forecast area, especially in the 0 to 1-1.5km layer. May be a
little optimistic with the percentage of opaque cloud cover later
this afternoon over parts of west Kentucky and southwest Illinois,
but clearing over western sections of southeast Missouri appears
on track. Slight adjustments were made to winds, temperatures and
dewpoints, but should hopefully remain within one to units of
actual values of these weather elements.

&&

.SHORT TERM...(Today through Saturday night)
Issued at 322 AM CDT Thu Oct 12 2017

The main story for today remains the low overcast conditions that
cover the entire forecast area as of 08Z. The 925mb RH from the
NAM and RAP have handled the low clouds very well to this point
and they were followed closely for cloud trends and temperatures
today. The clouds should erode from the west, resulting in plenty
of sunshine this afternoon over our western 4 to 6 counties in
southeast Missouri. However, the remainder of the area will not
see much clearing until late this afternoon or this evening. If
the NAM/RAP trends are right we may be clearing out the eastern
half of the region too quickly this evening.

To be consistent with the cloud forecast, the RAP temperatures
were used for trends through the day. Most locations east of the
MS River will not climb much above 60 degrees this afternoon, but
out in Ripley and Carter counties temperatures may climb well into
the 70s.

South southeast winds will develop throughout the region on
Friday, and with mostly sunny skies expected, temperatures will
climb well above normal, generally ranging from 75 east to 80
west. South winds will increase and may be stronger than forecast
on Saturday. As a result, temperatures will continue to trend
warmer with highs ranging from 84 east to 89 west. For reference,
normal highs are in the lower 70s over most of the region.

The 00Z GFS and ECMWF bring our next cold front into our northwest
border region by 12Z Sunday, while the 00Z NAM keeps it farther
northwest. We will have a sliver of a slight chance of showers and
thunderstorms along our northwest border after midnight Saturday
night. Otherwise it will be a very mild night with lows only in
the mid 60s, which is only around 5 degrees cooler than our
normal high temperatures.

.LONG TERM...(Sunday through Wednesday)
Issued at 322 AM CDT Thu Oct 12 2017

Models are in good agreement with the cold front extending northeast
to southwest across the PAH forecast area at 12z Sunday, then just
southeast of our region by 18z Sunday.  With the majority of the
precipitation post frontal, we have high chance to likely pops for
showers and some thunderstorms in our northern and western counties
to slight chances in our southeast counties Sunday morning, with
high chance to likely pops across the entire area Sunday afternoon.
Chances will decrease Sunday night from northwest to southeast, with
a few showers and maybe a couple of storms lingering only in west
Kentucky after midnight.

High pressure will build across the central U.S. Monday, and slowly
slide east through mid week.  Temperatures will be well above normal
Sunday, then by Monday we will be a few degrees below seasonal
normals.  Readings will moderate a couple of degrees by Tuesday,
then a return of southerly winds by Wednesday will provide seasonal
conditions.

&&

.AVIATION...
Issued at 1237 PM CDT Thu Oct 12 2017

The trend of MVFR ceilings is maintained through 00z Friday for
KCGI and KPAH and for the KEVV and KOWB TAF locations for the
entire forecast period (until 18z Friday). Although not explicitly
suggested in the model guidance, diurnal thermal stratification in
the boundary layer, in the absence of significant mixing, will
develop localized visibility restrictions in the 1-3 nm range for
the KCGI and KPAH TAF sites in the 06z-13z Friday time frame. The
RAP model guidance appears to have the most reasonable solution
for the evolution and departure of the low ceilings as compared to
METAR and PIREP observations.

The speed and intensity of warm air advection will determine the
overall impact and influence of the departing surface ridge axis
oriented northeast to southwest across the area. Should the
process accelerate more rapid clearing may take place at KCGI and
KPAH this evening.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&

$$

UPDATE...Smith
SHORT TERM...DRS
LONG TERM...CW
AVIATION...Smith



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