Area Forecast Discussion
Issued by NWS Paducah, KY

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
677
FXUS63 KPAH 170055
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
655 PM CST Mon Jan 16 2017

.UPDATE...
Issued at 655 PM CST Mon Jan 16 2017

Updated aviation discussion.

&&

.SHORT TERM...(Tonight through Wednesday night)
Issued at 205 PM CST Mon Jan 16 2017

A cold front and associated H50 short wave will approach from the
west tonight, as surface low tracks northeastward through through
the Plains and into the Midwest. The slightly negative tilt to the
mid lvl short wave will lead to an area of enhanced upward motion,
especially as we heading into the night time hours. Still believe
the greatest upward motions will occur in the best H50 diffluence
region over wrn KY, and that is where the highest rain amounts
will be placed...on the order of 1/2 to 3/4 inch.

Turning to the thunderstorm potential with this system, the
strong/severe threat remains low given overall lack of
instability. Mixed layer MU CAPES are still expected to remain
limited...in the 100-300 J/KG range, with Showalter Index values
in the 0 to -2 range. More likely to be just a few isolated
storms here and there with some locally heavy downpours. Things
could change a bit if more than anticipated instability levels
were to work northeast into the region from AR. Currently, 60+
surface dew points are located just southwest of the forecast
area in northeast AR.

High pressure moving in behind this system will be of Pacific
origin, so should stay with above normal temps as we head into
Tue/Wed time frame. Will be a bit of a cool down from today, but
nothing drastic. Will at least get a nice break in the wet pattern
once precip ends later tonight/early Tuesday.

.LONG TERM...(Thursday through Monday)
Issued at 205 PM CST Mon Jan 16 2017

From a hemispherical perspective, the leading edge of progressive 500
mb zonal flow along the Northern Pacific moves well into the
intermountain region of the Western U.S.  At the same time, the
dominant ridging aloft along eastern Canada/U.S. serves as a
blocking mechanism for the progressive trough stretching from Texas
to the Upper Midwest/Northern Plains as of 6 am CST (12z) Thursday.

With the previous information in mind, this forces the closed low
and shortwave trough on the eastern side of the mean Central U.S.
trough to become negatively tilted and strong flow undercuts the
mean trough across the southwest quarter of the U.S.

With this more dynamic upper flow, stretched a plume of instability
in the form of a differential mention of thunderstorms over parts of
Southern Illinois and West Kentucky mainly during the afternoon and
evening hours on Thursday.

After that time, low amplitude ridging develops across the area
Friday and early Saturday, limiting any chances of precipitation.
Although Gulf of Mexico flow is open for moisture influx, the ECMWF
generates noticeable convection along the Gulf Coast, disrupting
the rich flow of moisture to the WFO PAH forecast area.

The more potent energy forecast by the 00z/12z ECMWF translates a
open wave over Nevada to an intensify low to middle level closed low
over the TX/OK panhandles around midnight Saturday night. This will
push the low in and near the WFO PAH forecast ares Sunday afternoon,
leading to a decent chance of convective activity on Sunday.

Although the Thursday and Sunday weather systems will initially have
some weak shear and instability from 0-3km, the Sunday system may
intensify somewhat, so will be worth watching in later forecasts.

With respect to temperatures, modified temperatures slightly from
the regionally blended numerical guidance initialization, adding a
30% influence of the deterministic ECMWF, NAM-WRF, SREF, European
and EKD MOS. This only modified the maximum/minimum temperatures by
1-2 degrees at most. No other significant changes made.

Forecast confidence has increased with preference toward the ECMWF
solution the past two days for the extended period.


&&

.AVIATION...
Issued 655 PM CST Mon Jan 16 2017

Sustained surface winds up to 12 knots will continue to veer with
the approach of a cold front this evening. Between midnight and
daybreak Tue, the front is expected to traverse the region from west
to east. Showers and isold tstms will continue to develop this
evening ahead of the front, and will gradually expand eastward. As
the lower trop moistens up this evening, MVFR and brief IFR vsbys
are possible in showers. The highest likelihood of a lightning
strike appears to be in the western half of the region due to
slightly more unstable conditions early on. Meanwhile, mostly VFR
cigs are expected to stay in the MVFR range in showers, then stay
MVFR in the post-frontal regime. Cigs may break up altogether over
parts of southeastern MO/western KY Tue morning, before returning
late in the TAF period.

&&

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

$$

SHORT TERM...GM
LONG TERM...Smith
AVIATION...DB



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.