Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 242345
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
645 PM CDT Fri Mar 24 2017

.UPDATE...
Issued at 644 PM CDT Fri Mar 24 2017

The AVIATION section has been updated for the 00Z TAF issuance.

&&

.SHORT TERM...(Tonight through Sunday night)
Issued at 210 PM CDT Fri Mar 24 2017

Considerable cloud cover but mild this afternoon with 30 to 40 mph
southerly wind gusts primarily SEMO, SRN IL, SW IN, far west KY.
Will keep an eye on the radar for isolated development through
early evening mainly along and west of the MS River. However, the
overall trend was to slow the arrival of the main convective band
a couple of hours overnight per model trends. Refer to the SPC
Day 1 outlook for severe probs. Overall, cannot rule it out.
However the chances do not appear too high. Mainly a strong wind
threat.

The chance of convection will continue Saturday, as the upper low
currently over the TX Panhandle moves east, ending up over MO by
18z Saturday. Expect bands of convective activity to rotate about
the low NNE across the area through the day. Best chances will
shift east Saturday night as the low takes on a more NE track
toward NCNTRL IL by 12z Sunday. PoPs for showers will lower Sunday
from south to north in response. After a short lull, convection is
forecast to spread NE and into the area after midnight Sunday
night ahead of the next s/wv trof forecast to approach the area
from the Plains.

Temperatures will continue to be a blend of MOS and existing
numbers. For a model preference, we used a blend of HIRes models,
transitioning slowly to a GFS/NAM blend tonight through Saturday.
After that, and even blend was used given adequate overall
CMC/GFS/EC/NAM agreement.

.LONG TERM...(Monday through Friday)
Issued at 210 PM CDT Fri Mar 24 2017

Wet period in the offing for the Monday through Friday time period
next week. A mean trough will be the dominant feature across the
central U.S., with dynamic shortwaves/closed lows expected to impact
the WFO PAH forecast area at least once every 48 hours, with
precipitation events expected within a 24 hour period on Monday,
Wednesday, and Friday of next week.

There will be little in the way of measurable surface cold air
advection with these systems. However, the dynamics (both thermal
and shear-wise) will be enough to generate copious amounts of
rainfall across the entire forecast area.

Glancing at the 00z Friday NAEFS (GFS/CMC Guidance), GFS, and ECMWF
Ensemble probabilities, most of next week`s weather systems will
remain within zero to two standard deviations of model norms with
respect to upper air temperatures, heights, and surface QPF
(precipitation) amounts.

Owing to decreased forecast certainty, the system on Monday,
especially late in the day, will have the highest QPF potential for
the week, with Friday having the second best rainfall potential for
the week.

Given the small windows for increased shear and thermal instability
associated with the passage of low pressure systems in and near the
WFO PAH forecast area, the probability for any widespread severe
weather will be extremely small. Cannot rule out an isolated strong
storm with the passage of these systems, but the greater focus will
be on rainfall amounts with next week`s systems.

The timing/spacing of accumulated rainfall starting this Saturday
and running through next Friday may have a greater impact on
producing a general rise on rivers and tributaries in the WFO PAH
forecast area. Where frontal boundary interaction and duration is
most persistent next week, there could be the potential for very
short duration overland flooding (e.g. urban and small stream
advisories) in isolated areas. However, drainage time between events
may be sufficient to avoid these concerns.

In conversation with other forecasters in the office, the signal for
showers and thunderstorms remains consistent, so there is high
confidence in its occurrence, including the timing of the convective
activity.  There may be some be some minor timing/coverage
differences in the start and end of precipitation during the Tuesday
and Wednesday time periods, but the ECMWF solution, which is
preferred (along with the regionally initialized model blend) is
reasonable. Believe the convective activity on Thursday into Friday
may be a little slow given the transition toward an open wave (from
a closed low), so have about a 40-50% forecast confidence on the
timing of the late week precipitation occurrence.

Went approximately one degree higher with dewpoints a degree lower
in the extended forecast period, but blended with surrounding
offices to reflect subtle differences.

Regardless, it will be a showery week for the WFO PAH forecast
area.

&&

.AVIATION...
Issued at 644 PM CDT Fri Mar 24 2017

Gusty winds are expected to subside quickly this evening. As the
low-level jet increases toward 06Z, LLWS will be a concern at all
locations for much of the overnight hours. As was the case last
night, at some point toward morning, winds will become gusty at
the surface and lessen the LLWS.

The initial band of convection is expected to reach KCGI around
08Z, but it will be weakening, and TS is not a given late tonight
and Saturday morning. The band of showers will likely reach KPAH
toward daybreak, but there is some potential for this band to
dissipate completely before reaching KEVV and KOWB. MVFR ceilings
and scattered to numerous showers will be possible at all sites
from late morning through the afternoon. TS is a good possibility
in the afternoon, but did not get specific with timing at any
location.

&&

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

$$

UPDATE...DRS
AVIATION...DRS



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