Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 191749
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1249 PM CDT Fri May 19 2017

.UPDATE...
Issued at 1249 PM CDT Fri May 19 2017

The cluster of showers/storms near KCGI is expected to dissipate
in the next hour or two as it heads northeast into southern
Illinois. With upper heights rising, all available 12Z and later
guidance is having a hard time developing convection in our area
this afternoon and for much of the evening. Tried to push the
PoP/Wx/QPF grids in that direction. Feel that most of the area
will be dry through 03Z. The lone exception may be the EVV Tri
State Area 20Z-01Z, but confidence in convection then and there
is still quite low.

The AVIATION section has been updated for the 18Z TAF issuance.

&&

.SHORT TERM...(Today through Sunday night)
Issued at 240 AM CDT Fri May 19 2017

Rather complicated pattern shaping up in the short term. Quasi
stationary sfc boundary located just north of the region should
play one role for focus of convection today into tonight. Another
focus could lie with the line of strong/severe storms/outflow
boundary currently moving east through central MO. The ongoing
convective complex to our west may go through a diurnal decaying
process this morning. However, an outflow boundary will likely
provide a redeveloping focus later in the morning or this
afternoon as destabilization occurs to the east (where sfc dew
points will remain in the mid/upper 60s), and weak perturbations
eject northeast within broad southwest flow aloft. Bulk shear
should be sufficient to support some organized storms, with
multicellular the primary mode. A few storms containing hail and
damaging wind gusts cannot be ruled out. Believe at this time the
higher threat for isolated tornadoes will stay north of our
forecast area, closer to the warm front where helicity will be
maximized,

The actual cold front is still slated to approach the region
later Saturday/Saturday night. This will provide another focus
for showers/thunderstorms. Again, destabilization during the day
and bulk shear close to 40 kts could lead to a organized
development, with a few strong to severe storms possible in the
prefrontal environment as a stronger short wave rotates east from
the base of the upper trof. The Storm Prediction Center has
outlooked the entire region in slight risk ahead of the fropa. We
should finally get a break in the action Sunday as the front pulls
off to the east, and drier air works its way in from west to
east.

.LONG TERM...(Monday through Thursday)
Issued at 240 AM CDT Fri May 19 2017

Medium confidence in the extended with low confidence in the
forecast builder which would place the region in rain through most
if not all of the extended.

Models are in fair agreement with synoptic scale features in the
extended. However there are periods the FB places rain over us when
forecast sounding show little to no moisture below 400mb. I can only
imagine there is some climatology bleeding into the run which is
much wetter than previous run. So have attempted to dry some of the
extended a bit. Will wait and see if this can be collaborated with
surrounding FO`s. In a nutshell we will have high pressure over us
for the start of the week keeping us dry and cooler. Another
reinforcing front is poised to move through the area Tuesday but the
Gulf is cut off at all levels. This will be a limiting factor for
precipitation mid week. An upper level long wave will swing down
from Canada just north of the great lakes and into the lower Ohio
Valley. This will be the kicker that pushes the front through
tuesday with the mid to upper level low on its flanks Wednesday. The
main limiting factor for rain will be moisture. The only moisture
available for these systems. The main source of moisture will be
supplied by the system itself with no tropical connection. In
addition all the convective parameters are not conducive for
widespread thunder. CAPE is near Zero and Li`s are positive for the
most part. Mainly Tuesday morning parameters would permit a clap of
thunder. Even elevated instability is extremely limited with K index
values maxing out around 20c most of the time and showalters are
mostly positive. Finally with two fronts moving through and plenty
of cloud cover we will encounter well below normal temperatures.
Also any rain that does fall should be very light with no 6 hour
period yielding more than a tenth of an inch if any.

&&

.AVIATION...
Issued at 1249 PM CDT Fri May 19 2017

This is a convectively driven forecast. The TS near KCGI will
move east by 18Z, but there may be some isolated development near
KEVV and KOWB late this afternoon through sunset. Much of the
evening should be dry throughout the area, but the TS chances
increase overnight into Saturday morning. It appears that we will
most likely see an MCS move northeast through all or a portion of
the area 09Z-15Z, but there could be development ahead of it as
well, beginning as early as 03Z. Emphasized the early morning MCS
potential with a wind shift and VCTS at all sites except KOWB.
Kept it VFR for now, but IFR or lower conditions will be possible
if the MCS develops.

Southwest winds will be gusty this afternoon in the northeast,
but should calm down significantly by sunset and winds throughout
the area should back to the southeast for most of the night.
Winds Saturday morning will likely be muddled by thunderstorm
outflow.


&&

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

$$

UPDATE...DRS
AVIATION...DRS



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