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

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FXUS63 KEAX 181118
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
618 AM CDT Tue Sep 18 2018

.Discussion...
Issued at 359 AM CDT TUE SEP 18 2018

The weather pattern is dominated by a zonal upper level pattern over
the northern plains with a leeward trough over the central plains
interacting with high pressure over the southeast CONUS.  This
interaction has caused warm southerly flow over the area with a warm
front extending from western KS up into northern IA leaving our area
in the warm sector for today.  Temperatures will remain above
average today in the lower 90s with heat indices into the mid to
upper 90s. Cloud coverage and potential precipitation this afternoon
will depend on the evolution of convection to the north and reaching
convective temperature. Some CAM guidance does indicate the MCS
forming over southern MN making it down into northern MO, but
propagation vectors would indicate it will go more SE and not make
it into our area so PoPs were not added for this feature. There is a
small window of opportunity for the convective temperature to be
reached late in the afternoon, but with little forcing in the lower
levels all showers and storms were left out of the forecast. As
the day progresses temperatures will need to be monitored to
determine if they will climb higher than expected or any CU
fields do form up in the afternoon. Any shower/storm development
would most likely be over northern MO in the late afternoon. An
upper level shortwave trough will begin to work its way into the
Rockies on Wednesday, building the upper level ridge and forcing
the warm front to move northward. This will allow a thermal ridge
to build over our area and increase temps a few degrees making
Wednesday the hottest day of the week, feeling more like July than
September.

As this upper level shortwave moves eastward the frontal boundary
over the northern plains will begin to shift southeast towards our
area. Ahead of this frontal boundary winds will increase along the
tighter pressure gradient, with gust up to 30 mph Thursday afternoon
possible over much of the area. Temperatures will decrease slightly
but still remain in the lower 90s for Thursday. Thursday night the
effects of this frontal boundary will start to make its way into NW
Missouri. A band of MLCAPE 2000-2500 J/kg, forcing along the
boundary, and 0-6km bulk shear 30-35kts will lead to a small
window of possible severe weather. The timing of the frontal
boundary will determine the level of severe weather with the
earlier the arrival the more likely for severe weather to occur.
There is still some uncertainty as to this timing, with the NAM
being slightly earlier and the GFS/ECMWF being a few hours behind.
If the front comes through closer to sunset then the threat of
severe weather will decrease, but strong elevated storms with hail
will still be possible. Guidance has continued to decrease the
QPF Thursday night into Friday progressing the front quicker
through the area. By Friday afternoon the boundary is now depicted
south of our CWA keeping most of Friday now dry with some slight
chances of rain over the southern CWA. While there may not be much
QPF with this boundary, cooler temperatures are looking likely
with temperatures in the low to mid 70s. Rain chances remain in
the forecast for Saturday morning, but guidance has started to
back off on the northern push of the boundary and some of this
precip is residual signals from previous models and the ECMWF. It
is likely that this may be reduced in up coming forecasts if the
drier trend continues. The seasonal temperatures will continue
through the weekend with the back edge of the surface high
pressure overhead. A southern return flow will start to develop
Monday as this high pressure moves eastward increasing
temperatures slightly, but remaining dry.

&&

.Aviation...(For the 12Z TAFS through 12Z Wednesday Morning)
Issued at 615 AM CDT TUE SEP 18 2018

VFR conditions are expected throughout the period. Winds will
slightly shift from southeast to southwest in the afternoon before
shifting back to southeast overnight. Some gusts up to 15-20kts
are possible in the afternoon timeframe. Isolated showers and
thunderstorms are possible in the region, but the uncertainty in
where they may develop is too high to add any mention in the TAFs.


&&

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

$$

Discussion...Barham
Aviation...Barham


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