Area Forecast Discussion
Issued by NWS Paducah, KY

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440
FXUS63 KPAH 212031
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
231 PM CST Sat Jan 21 2017

.SHORT TERM...(Tonight through Monday night)
Issued at 231 PM CST Sat Jan 21 2017

As stated earlier today, the 12Z guidance has trended slower with
the arrival of convection associated with the storm system moving
through the southern Plains. It now appears that it will be late
this evening before it spreads into the far western portions of
southeast Missouri. A few showers may develop earlier near the
I-64 corridor, but that activity may end up just north of our
region.

The 12Z models still take the upper low eastward to our south
Sunday into Sunday evening, while the consensus surface low track
is from the Bootheel eastward along the KY/TN border. This will
keep us from getting much surface moisture return to the region
and keep temperatures in check.

Given that we will be north of both the upper and surface lows,
severe weather potential is quite limited. There will be some
fairly steep lapse rates, but the lack of stronger moisture return
will limit updraft strength. Wind fields will be a mess with the
upper low to our south, so a few stronger updrafts may produce
some small hail from late tonight into Sunday, but just cannot see
much chance of large/severe hail.

Precipitable water levels will be just over an inch which is close
to 2 standard deviations above the climatological mean for our
region, so some heavy rain will be possible. Storm total QPF is
3/4-1" over much of the region. With thunderstorms expected,
instantaneous rainfall rates may be high enough to tax some
drainage systems, but significant flooding issues are not expected.

The precipitation should push east of the area early Monday, and
then we will remain dry through Monday night. Behind the system,
strong northwest winds will overspread the area from late Sunday
through Sunday night. Some gusts up to 30 mph will be possible.
These strong winds will bring an end to the mild temperatures we
have had of late. We should be down near normal on Monday.


.LONG TERM...(Tuesday through Saturday)
Issued at 231 PM CST Sat Jan 21 2017

The medium range models were in reasonably good agreement as the
weather pattern becomes generally drier for us.

The extended period forecast will start out with ridging aloft
between low pressure systems. The next rather vigorous shortwave
aloft is progged to evolve out of a larger western CONUS trof, and
move rapidly across the Midwest by midweek. There were some model
differences in speed (as much as 12 hours) of the surface low which
will pass north of us, but model consensus suggests that warm fropa
will occur sometime Tue night, followed by cold fropa during the day
Wed. The large scale wind pattern suggests that deep Gulf moisture
will not be part of the equation for the PAH forecast area, so the
only PoP (of measurable rain) for the entire extended period will be
early Wed morning for the eastern half of southwestern IN, just
ahead of the cold front.

The breeziest conditions for us should be associated with the cold
front/pressure trof on Wed, as mid level trof energy lingers in the
wake of the closed low (which will be absorbed into existing trof
energy over eastern Canada), and contrasts with a southeastern CONUS
ridge at the surface and aloft.

Cloudiness and a persistent cool westerly surface wind should be our
main sensible elements Thu as a secondary lobe of mid level
shortwave energy rotates through the upper Midwest. Southwestern IN
should see the most, southeastern MO the least, cloudiness Fri/Fri
evening as the aforementioned trof axis passes by to the north.

Unseasonably warm temperatures will prevail Tue and Wed, followed by
near seasonable temperatures through the remainder of the extended
forecast period.

&&

.AVIATION...
Issued at 1154 AM CST Sat Jan 21 2017

A few southerly gusts into the teens will be possible mainly early
this afternoon at KEVV and KOWB, but the pressure gradient will be
weakening and winds will back to southeast by 00Z, as our next
storm system approaches. It appears that the surface low may track
near to the south of KPAH and KOWB, so kept winds east or
northeast through the morning.

As stated above, the trend is for a later start to the precipitation
and associated visibilities and ceilings. The guidance is still
quite pessimistic once the rain sets in. IFR or LIFR conditions
can be expected through the morning hours Sunday. Certainly cannot
rule out some TS, but probabilities at any point are not great
enough to mention at this time.


&&

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

$$

SHORT TERM...DRS
LONG TERM...DB
AVIATION...DRS



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