Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 121901
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
101 PM CST Sun Nov 12 2017

.UPDATE...
Issued at 100 PM CST Sun Nov 12 2017

Made some minor adjustments to PoPs/Wx, clouds, and temps to account
for a slightly quicker end to the pcpn in the east (which is mostly
drizzle), and to account for temporary breaks in the low cloud deck
over parts of southeastern MO/western KY.

Updated aviation section for 18z taf issuance.

&&

.SHORT TERM...(Today through Tuesday night)
Issued at 230 AM CST Sun Nov 12 2017

A cold front over northwest Missouri early this morning will move
southeast, crossing the lower Ohio Valley this afternoon.
Moist southwest flow ahead of the front is generating a broad
area of stratiform cloudiness and pockets of light rain and
drizzle. The rather shallow depth of the moist layer is limiting
precip amounts to just a trace to a few hundredths of an inch. The
models indicate this will remain the case today. Therefore, pops
will remain in the chance category. The short-range model
consensus pops indicate precip chances will end from west to east
this morning, except lingering into the afternoon from sw Indiana
across the Pennyrile region of west KY. Highs today will range
from the upper 40s around I-64 to the upper 50s in the Ozark
foothills region, where partial clearing is forecast this
afternoon.

The prospects for clearing tonight are a little muddled. The
models indicate the low levels will be slow to dry out, and the
00z nam bufkit sounding for kpah holds onto low clouds all night.
We are getting into the time of year when low clouds are stubborn
to clear. The forecast will maintain an optimistic clearing trend
overnight, since there will be 15 to 20 knots of wind to keep the
clearing line moving.

On Monday, a good deal of sunshine is expected as surface high
pressure moves east across Illinois. The cool north to northeast
flow will keep temps a little lower than guidance indicated
yesterday. Highs will range from the upper 40s north and east of
kmdh to the lower 50s elsewhere.

On Tuesday, the cloud forecast again becomes muddled due to model
differences. The 00z nam generates early morning stratus clouds
that persist until higher clouds thicken ahead of the next system.
The 00z gfs indicates a dry column through the day. The forecast
will again go with a more optimistic gfs-weighted blend. Highs
will be mainly in the mid to upper 50s based on the sunnier
forecast. Clouds and showers will work their way into southeast
MO and southern IL Tuesday night.

.LONG TERM...(Wednesday through Saturday)
Issued at 230 AM CST Sun Nov 12 2017

By 12Z Wednesday, a frontal boundary will be draped from the
southern Panhandle of Texas, through Oklahoma, northwest Missouri
and up into Wisconsin. Convergence along the front weakens as the
front slowly slides southeast into the region during the day on
Wednesday. Highest chances for precipitation will be in the
northwestern half of the area during the morning, then shifts to
southern MO and western KY during the afternoon hours.

The ECMWF is the quickest ending precipitation during the evening
hours on Wednesday, while the GFS and Canadian hang onto rain at
least in the southern counties through the evening, then drying
things out overnight as surface high pressure presses in from the
north. Will hang onto some small chances in the far south even after
midnight given these timing differences. Glad to see the day shift
inserted some thunder chances as it does look like we could see at
least isolated thunderstorms with this system.

The frontal boundary will not go too far south of the area before
stalling out. The GFS is most aggressive in lifting the front back
north during the day on Thursday into Thursday evening. The ECMWF
and Canadian are behind and indicate a bit more of a delay in this
frontal return and indicate this push occurring Thursday evening
into the overnight hours. The differences in the models with the
front returning is tied to the timing of the upper level trough
moving east out of the Rockies and where/when a surface low develops
in the northern or central Plains states.

These differences bleed over into the forecast for Friday/Friday
night, with models indicating differing times of the cold frontal
passage. The GFS has slowed down a tad but is still the fastest and
brings the cold front through during the late afternoon and evening
hours on Friday, with the ECMWF/Canadian about 6 hours later.
Therefore, we will likely see POPs flipping and flopping during this
period (Wednesday night through Friday night) for a few more days
until models can settle down and offer up a more concise solution.
Will attempt to keep POPs from getting too high in any given period
due to the likely shift in higher POPs. There will be periods of
rain and embedded thunder and we should even have a time when we are
in the warm sector for a while as well with very little in the way
of precipitation.

Still keeping an eye on strong to severe storm potential with the
Friday/Friday night frontal passage. Decent southwesterly flow sets
up in the warm sector and dewpoints are progged to soar into the
upper 50s to lower 60s no matter what the speed of the front. Bulk
shear looks to be more than enough to get storm organization. The
amount of instability is a bit more in question but it does not take
much this time of year. We will continue to monitor.

Despite the timing differences, the weekend still looks dry.

&&

.AVIATION...
Issued at 100 PM CST Sun Nov 12 2017

A weak cold front will make its way through the region today. By
nightfall, surface winds under 10 knots will turn to the north or
northwest across the PAH forecast area. IFR cigs east of the Wabash
River and in the Pennyrile region of KY are expected to linger into
the mid-afternoon, along with some vsby-restricting drizzle.
Meanwhile, cigs west of there should stay mainly VFR, though some
temporary lowering could occur late this afternoon/ early evening
due to the passage of a mid level trof axis. Parts of southeastern
MO/western KY could see breaks in the clouds early this afternoon.
The cigs should go at least scattered after midnight.

&&

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

$$

SHORT TERM...MY
LONG TERM...CW
AVIATION...DB



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