Area Forecast Discussion
Issued by NWS Paducah, KY

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274
FXUS63 KPAH 271746
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1245 PM CDT Thu Jul 27 2017

.UPDATE...
Updated aviation section for 18z taf issuance

&&

.SHORT TERM...(Today through Saturday Night)
Issued at 249 AM CDT Thu Jul 27 2017

Initial round of rain/thunderstorms impacting areas mainly north
of I-64 will eventually exit the FA early this morning as the
500mb short wave progresses east of the area. However, the pattern
is a bit complex and other showers/ thunderstorms over central MO
and IL will likely impact the northern parts of the FA this
morning as well. Otherwise the focus is on the 500mb short wave
producing the MCS over central MO early this morning. The SE
movement of this complex should put SE MO and SW IL in the path of
the showers/thunderstorms by late morning/ midday then developing
SE across the FA this afternoon.

In addition, new convection may fire today across the northern part
of the FA along outflow boundaries generated from storms overnight.
Bottom line is that with the cold front progressing southward, rain
chances will increase today, into this evening, given the
aformentioned factors. The front should be near I-64 by sunset
this evening. Thus will maintain likely POPs for this afternoon
across the north and further south tonight as the front continues
to progress southward. A low pressure center develops in the
vicinity of western KY and brings the greatest chances of rain to
western KY overnight and toward the TN border Friday morning.
Rain chances will diminish from north to south beginning overnight
and over the southern Pennyrile by early Friday afternoon as
northerly winds usher much drier...cooler air in behind the front.

Heavy rain appears to be the primary hazard due to the excessive
moisture content of the atmosphere as indicated by precipitable
water values increasing to 2 to 2.5 inches across the FA this
afternoon.

Per the latest SPC Day 1 outlook, a Marginal Risk of severe storms
exists for today/tonight. Deep-layer shear is relatively low yet
decent instability and lapse rates exist although air mass recovery
will be a factor in some areas given ongoing and forecast
convection. Any severe threat would primarily be damaging winds.

Heat indices for today may approach advisory criteria over mainly
SE MO and SW KY. Will consider a SPS to address this.

Northerly winds around 10 mph Friday into Saturday will bring the
major upcoming air mass change. High temps Friday should hold in the
mid 80s with unseasonable highs in the lower to mid 80s Saturday
amidst much less humid conditions. Guidance is averaging a degree
or so cooler for Saturday and Saturday night with lows Saturday
night forecast in the upper 50s to around 60 - quite rare for
July.

.LONG TERM...(Sunday through Wednesday)
Issued at 249 AM CDT Thu Jul 27 2017

The first part of the long term period continues to look quiet with
not much going on weather-wise in terms of precipitation. This could
change as we get deeper into next week.

Surface high pressure will be centered over the western Great Lakes
region at the start of the period. This sfc high will remain over
the Midwest for the start of the new work week. The major airmass
change that will take over on Saturday, will spill over into Sunday
as well. We are still looking for high temperatures only in the
lower 80s with dew points remaining in the upper 50s to near 60
degrees. This will result in continued pleasant conditions by late
July standards.

These dry conditions will linger into early next week as well.
However, we will see temperatures creeping back into the mid to
upper 80s by Monday through Wednesday. Dew points will also slowly
rise back into the mid 60s by the end of the period.

By midweek, the sfc high breaks down and some the upper level
pattern becomes much more relaxed. However, models are in pretty bad
agreement on what may be happening synoptically by Wed-Thu, so will
not get too carried away right now with the placement and degree of
POPs. This messy but typical summertime pattern has not been
resolved by the models for the past few days now but we shall see
some agreement as we get closer to next week.

&&

.AVIATION...
Issued at 1245 PM CDT Thu Jul 27 2017

Showers and thunderstorms are forecast to develop this afternoon
ahead of a cold front. The most unstable air is south of a line from
kmdh to kevv, where storms should be quite numerous and possibly
strong by late this afternoon. There is a good chance that the
relatively stable air in the kevv area will inhibit tsra, so there
is no mention of tsra there in the 18z tafs. Outside of storms,
widespread mvfr cigs have developed due to cumulus cloud formation.
These cigs should be persistent through the afternoon.

Tonight, mainly vfr conditions are expected early in the wake of
showers and storms. However, conditions are favorable for low
stratus and fog late tonight into early Friday. The low levels will
be very moist, and winds will be light. The low clouds and fog will
burn off later in the morning.

&&

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

$$

SHORT TERM...RLS
LONG TERM...CW
AVIATION...MY



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