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

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115
FXUS63 KEAX 181732
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1232 PM CDT Fri Aug 18 2017

.Discussion...
Issued at 401 AM CDT FRI AUG 18 2017

Short Term (Today through Sunday Night):

The main concern in the short term is the conditional threat for
severe weather late this afternoon into the evening hours. The
reason the threat is conditional is in relation to the ongoing
convection this morning. Two MCS`s, one in eastern Nebraska, and one
in central Kansas, are moving toward the CWA. Most models weaken
these complexes as they move toward the CWA however, the NAM does
try and bring some showers into northwest Missouri associated with
the Nebraska complex. Consequently, there may be some showers over
NW MO this morning. However, these complexes will introduce broken
mid-level cloud cover to the area. It is this cloud cover that may
act to limit instability somewhat as a surface trough approaches the
area later this afternoon. However, models are in fairly good
agreement that cloud will scatter out this afternoon allowing
conditions to become unstable on the order of 2000-2500J/Kg of
MLCAPE. Couple that with 0-6KM shear around 40kts and steep mid-
level lapse rate, and storms that develop along the surface trough
this afternoon could become severe. The initial threat would be for
large hail transitioning to a damaging wind threat as storms become
linear along the surface trough. These storms will progress
southeastward across the CWA tonight before exiting the area
overnight. High pressure will move into the area on Saturday
allowing for dry conditions and near normal temperatures in the mid
80s to near 90. Saturday night models develop a MCS, associated with
a upper level shortwave, over central Nebraska, which will roll
southeastward over night. The NAM keeps the MCS west of the CWA
where the GFS is a little further east with this feature and would
bring storms to the western forecast area Sunday morning. Additional
storm development may occur Sunday afternoon along outflow from
morning convection as a upper shortwave moves through the region.
Despite precipitation chances, highs on Sunday are expected to rise
into the upper 80s to near 90 as upper level ridging builds into the
region.

The Eclipse (Monday) : SEE BELOW

Beyond the Eclipse (Monday night to Thursday):

Monday Night an upper level trough will move from the northern
Plains into the Upper Midwest suppressing the upper level ridge
southward and forcing a cold front into the CWA bringing showers and
thunderstorms to the area. This front will be slow moving and will
provide for additional storms on Tuesday before finally shifting
south Tuesday night. Surface high pressure then builds into the area
for Wednesday and Thursday keeping conditions dry, less humid and,
comfortable with highs in the lower 80s.

&&

.Specifics for the Total Solar Eclipse on August 21st...
Issued at 641 AM CDT FRI AUG 18 2017

The only guarantees for Monday is that the sun is going to disappear
and that it is going to be warm with highs in the upper 80s to near
90. Unfortunately, the biggest reason the sun may disappear for
those of us in the KC local area is that of cloud cover (and
precipitation). The GFS and Canadian model solutions which have had
the most run-to-run consistency are both showing broken clouds with
a chance for showers and thunderstorms on Monday. Right now the
model blend of solutions produces a 20 to 40 percent chance of
precipitation with the larger percentages across northern Missouri
with lower percentages across central Missouri. However, the cloud
cover percentages are around 60 to 70 percent.

.Aviation...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1232 PM CDT FRI AUG 18 2017

Main item of concern with this afternoon`s package revolves around
potential impacts from developing convection later this afternoon
and evening as a cold front sags south over the region. Some
uncertainty as to whether developing activity will extend far
enough westwards to impact area terminals, but latest hourly
model guidance suggests it will. As a result, have included a
tempo group at STJ/MCI/MKC as these terminals stand the best
chance at seeing potential impacts. Otherwise, storms should
rapidly clear to the south and east late this evening with
clearing skies expected in their wake. Some potential once again
for developing VSBY restrictions at STJ during the predawn hours,
but fcst models suggest post frontal airmass may be too dry to
support such activity. In any event, will defer to later fcst
updates on early morning fog potential.

&&

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

$$

Discussion...73
Aviation...32
Eclipse...73



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