Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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FXUS63 KEAX 290445
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1145 PM CDT Sun Sep 28 2014

.UPDATE...
Issued at 1006 PM CDT SUN SEP 28 2014

Latest observations show some light fog beginning to form in mainly
low lying and river valley areas. With light or calm winds forecast
and already low dewpoint depressions, have added patchy fog to our
river valley and low lying areas. Otherwise, forecast looks to be on
track.

&&

.SHORT TERM...(This Evening through Monday Afternoon)
Issued at 350 PM CDT SUN SEP 28 2014

Current satellite imagery shows the closed low, that has been parked
across the region for the last few days, is finally on the move out
of the area. This stubborn low will continue to bring a slight
chance of some isolated showers and t-storms through the afternoon
to parts of Central MO before departing the region tonight.

The large trough that has brought significant flood issues to the
Southwest US will very slowly move across the Great Basin and
towards the inter-mountain west. Another trough moving out of the
Gulf of Alaska towards the Pacific NW will help to get the Great
Basin trough moving a tad bit faster before finally merging Tuesday.
In response to the western troughs interaction, a ridge of high
pressure will be pushed eastward over the local region and allow for
a few more days of beautiful fall weather. Could see temperatures a
degree or two warmer tomorrow afternoon as that high builds into the
Central Plains. The aforementioned trough will begin to quickly
shoot northward as it moves out onto the Plains, with precipitation
chances increasing out ahead of the associated cold front. Northwest
MO will likely see showers and thunderstorms by Tuesday night with
increasing chances through the rest of the CWA by Wednesday morning.

.LONG TERM...(Tuesday Evening through Sunday)
Issued at 350 PM CDT SUN SEP 28 2014

Very challenging forecast period shaping up for the area...at least
early on as upper low pressure system currently over the Desert
Southwest and Great Basin ejects east with time. As this
occurs...expect increasing southerly flow which will allow low to
mid 60F dewpoint air to creep north from the Gulf. Models
continue to suggest precip across our western zones as early as
Tuesday afternoon/night...with renewed possibilities likely through
the remainder of the midweek as secondary upper trough starts
rotating through the central Plains. Its this secondary piece of
energy that will finally propel the main cold front through the area
during the day on Thursday.

With return flow reestablished...PWAT values quickly increase to
near 1.50" which is darn near close to two standard deviations above
normal for the early October. Main concerns early on may in fact be
moderate to heavy rainfall as secondary sfc low development
resulting from the next punch of mid-level energy digging southeast
across the Front Range/High Plains will likely create a temporarily
"holding pattern" as isallobaric response limits eastward
progression of main storm system. That said...model theta-e fields
suggest a weak pseudo warm front will be stretched from the
secondary low east through southern Missouri from Wednesday into
Thursday.  This feature will likely serve as a rain maker especially
during the overnight hrs when the low-level jet increases.
Fortunately much of the fcst region has been dry in recent weeks
which will hopefully limit hydro related issues. Regardless...this
system bears watching as we get closer.

Secondary threat from this system will be increasing chances for
severe weather from Wednesday into Thursday as main cold front
finally begins tracking east. Model trends this afternoon are much
different than yesterday with both the GFS and ECMWF suggesting
mid-level wind fields will be on the increase as the secondary
trough slowly approaches from the west. For now...both models agree
0-6km bulk shear magnitudes will be increasing to over 50 kts on
Thursday just in time for main fropa. Main questions right now is
whether bulk of activity will be elevated as position of pseudo warm
front to our south remains up in the air. If southerly flow is
strong enough to lift the front north...portions of the fcst area
could work into the warm sector which would result in greater
instability. Best chance for this would be across the southerly half
of the fcst area with decreasing chances for organized severe
north of the KC metro. For now it looks close...and hopefully model
trends will continue to iron themselves out as timing nears.

Main cold front to work through the area Thursday afternoon/evening.
Beyond this...much cooler air expected to filter into the region as
high pressure builds south from the northern Plains. In
fact...models in great agreement that a secondary cold front will
usher in even cooler air early Friday with 850-hPa temps forecast to
fall as low as 2C Friday afternoon. This will set the stage for what
appears to be another gorgeous fall weekend with moderating temps
expected through Sunday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
Issued at 1144 PM CDT SUN SEP 28 2014

VFR conditions are likely for most of the forecast. The exception
may be some light fog at the KC terminals, restricting visibility to
the MVFR range, and thicker river valley fog at STJ, resulting in IFR
restrictions. This should occur in the hours around sunrise.
Otherwise, skies should be clear tonight with few to scattered
diurnal clouds around 6K ft again tomorrow afternoon. Winds will be
light/variable or calm tonight with a trend to south or southeast and
still light tomorrow afternoon.


&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&

$$

UPDATE...CDB
SHORT TERM...PMM
LONG TERM...32
AVIATION...CDB






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