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

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FXUS63 KEAX 182320
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
620 PM CDT Fri Aug 18 2017

.Discussion...
Issued at 250 PM CDT FRI AUG 18 2017

GOES-16 visible imagery showing a fair amount of clearing this
afternoon across western Missouri following this morning`s weak
shwr activity. Further north, agitated CU is noted just north of
the Iowa border, with this activity occurring directly in advance
of a cold front that is forecast to track south across our region
later this evening. As a result, forecast concerns this afternoon
remain fixed on possible severe storm development as the boundary
tracks south over the region later tonight. Latest SPC meso page
still shows some weak inhibition across our area, however this
will soon be eroded in response to an increase in solar heating.
Aloft, water vapor shows a positively-tilted trough axis tracking
across southern Minnesota and northern Iowa this afternoon, and
near term model guidance supports the idea that deep-layer shear
will continue increasing with time as secondary shortwave energy
dives southeast into eastern Iowa and northeast Missouri through
06z. Biggest caveat to the current forecast is just how far west
developing convection will extend and whether the Metro will be
impacted. For several hours the HRRR suggested the bulk of
activity would remain east, however the latest run has now shifted
west which is in better alignment with the NAMNest and RAP.
Isolated storms initially will be capable of large hail, but
models show activity congealing into a forward propagating MCS
before tracking south into central Missouri by 06z. As this
occurs, the main threats will likely transition more to a straight
line wind concern with gusts in excess of 50 mph possible,
especially east of the KC Metro.

Storm activity to quickly come to an end after midnight with clear
sky development expected during the predawn hours as high
pressure starts building into the area. There may be some fog
development during the predawn hours but the best potential for
such development may be east of the Metro where better rain
chances exist this evening. Despite the passage of a cold front,
southerly flow will return fast enough by Saturday afternoon to
allow temps to warm into the upper 80s to lower 90s across much of
the area. Another MCS is expected Saturday night early Sunday as
a shortwave in developing zonal flow tracks east from the Central
Plains. For now, chance pops appear reasonable until trends become
better established with later model guidance.

Beyond this, fcst guidance remains all over the place as we head
into early next week as several weak disturbances are expected to
impact the lwr Missouri Vly in the aforementioned zonal flow. How
this impacts/impairs viewing the solar eclipse remains up in the
air right now as model solutions remain all over the place (see
eclipse discussion below). What does seem certain is that MCS
activity will be possible across the region Monday morning with
additional convection possible Monday afternoon. Unsettled weather
to continue right through Tuesday with hints that conditions will
start improving by Wednesday following the passage of yet another
cold front. In fact the latter half of next week may be a tad
cool for mid/late August standards as strong high pressure extends
south from the upper Miss Rvr Vly.

&&

.Specifics for the Total Solar Eclipse on August 21st...
Issued at 250 PM CDT FRI AUG 18 2017

Uncertainty still remains with respect to Monday`s cloud cover
fcst as models continue to highlight overnight and early morning
convective activity across the Lwr Missouri Vly. As a result,
the prevailing idea that convective debris cloud cover will
remain in the area Monday morning appears likely once again this
afternoon, with additional concern also seen in the form of a
possible northward extending cirrostratus shield from the Southern
Plains into the upper Miss Rvr Vly. Unfortunately there remains
too many variables at play right now to really increase
confidence on where the best viewing potential will be, but
hopefully these questions will start being answered with
additional model runs in the coming days.

&&

.Aviation...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 619 PM CDT FRI AUG 18 2017

Storms currently moving through the KC area will be short-lived
and should only be impacting the terminals for another hour to two
hours as they move to the southeast. Once the storms pass, VFR
conditions are likely through the forecast with light winds. Will
monitor for potential for light fog late tonight to around sunrise
Saturday. But for now will keep things VFR.

&&

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

$$

Discussion...32
Aviation...CDB
Eclipse...32


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