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

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KEAX 210802
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
302 AM CDT Mon Aug 21 2017

.Discussion...
Issued at 302 AM CDT MON AUG 21 2017

Complicating factors are abound for today`s eclipse in an active,
unstable pattern across the Plains. A convective complex which
formed in northwest IA this evening has begun to propagate south
southeastward as its cold pool strengthens, and will likely
continue to do so over the next several hours as the LLJ feeds
into the system. Evolution of this complex is once again handled
very poorly by high-res models, but Corfidi vectors and the
orientation of the instability gradient suggest the south to
south southeast development should continue. Have hand-edited
cloud cover upward as the anvil plume develops south and spreads
to the east across the northeastern quadrant of MO, and then
allowed higher cloud cover to dissipate and advect off to the east
as storms weaken by mid-morning.

An outflow boundary currently evident on radar pushing through the
Omaha area will continue to slide southward this morning, and
while the eastern extent of the of the outflow will continue to
push quickly to the south, the western edge may stall near the
NE/KS/MO border without strong evaporative cooling due north of
the boundary to reinforce its southward propagation. This pre-
existing boundary could serve as a focus for convective initiation
as early as 12PM in an already unstable atmosphere, complicating
the forecast for the eclipse even further. At the same time,
cirrus streaming northward from convection in the High Plains will
continue to approach the forecast area, and most models indicate
the thickest cirrus will push into the NE/KS/MO corner just after
noon. The cirrus is probably the least of the caveats to eclipse
viewing since it may remain thin and broken enough to view the
sun, but the potential for developing low-based thick cumulus is
much more concerning, particularly if the outflow boundary stalls
near the path of totality.

Any storms that develop this afternoon have the potential to
quickly become strong as MLCAPE increases to greater than 2000
J/kg, and while deep-layer shear remains questionable with a
weakness in the wind field around 600-500 hPa, decent 0-3 km
shear and enhanced helicity from remnant boundaries could add
organization to any robust storms that develop, and could even
result in a brief tornado in storms that root along a boundary.

This "questionable" shear profile will only serve to enhance the
potential for heavy rain this evening along and ahead of the cold
front as it pushes through the region. GOES-16 WV imagery finally
shows a break in the tropical connection between Hurricane Kenneth
and the desert southwest, but the damage has already been done as
very high PWATs continue to advect northeastward into the Plains.
The combination of multiple convection rounds, PWATs approaching
2.5 inches, very high warm cloud depths, a deeply saturated
profile, and an increasing low-level jet below weaker steering
winds will definitely set the stage for very heavy rain across
the majority of the CWA. Have kept the flash flood watch as-is,
but will also need to watch how much precipitation falls along the
MO/IA border early this morning, which could lower flash flood
guidance even further after yesterday`s storms and on top of
additional expected rainfall tonight.

Quieter conditions are finally expected once the front clears out
of the area early Tuesday morning, clearing out low-level moisture
and slashing high temperatures back into the upper 70s to low 80s
for Tuesday through the weekend.

&&

.Specifics for the Total Solar Eclipse on August 21st...
Issued at 302 AM CDT MON AUG 21 2017

Eclipse viewing in our forecast area will be limited by several
rounds of cloud cover this afternoon. Cirrus emanating from the
showers and storms over the High Plains will stream northeast into
the area by noon today, at least partially hampering the view of
the eclipse from southeast NE through northwest to central MO. Of
even greater concern is a complex of storms currently in southwest
through central IA, which will continue to drop southward through
the majority of the forecast area. Even if showers/storms do begin
to dissipate prior to arriving this morning, they will likely drape
an outflow boundary near the path of totality which could serve as
a focus for storms to develop as early as noon. Currently, the
most likely areas for possible viewing of the eclipse look like
central NE where cirrus will be present but remnant storms from
the IA complex are less likely, and south of the outflow boundary
in central to eastern MO. Much of this forecast will depend on how
far south the IA complex makes it this morning, so will continue
to update this information as the system progresses.

&&

.Aviation...(For the 06Z TAFS through 06Z Monday Night)
Issued at 1156 PM CDT SUN AUG 20 2017

Challenging forecast over the next 24 hours with a multitude of
items that could influence cloud cover and weather. First, an area
of storms in south central KS is moving toward the area. This
should weaken and dissipate through the remainder of the night
with only its cloud cover moving over. Second, the convection that
erupted in northeastern NE and northwestern IA will likely stay
to the east of the terminals. But it may throw a gust front
through that could potentially be a focus for afternoon storms in
the KC area. Third, storms are expected to develop during the late
afternoon/early evening over northeastern KS and northwestern MO
and track to the southeast through the terminals. Have added a
VCTS group starting at 00Z for this more likely thunderstorm
scenario. For the outflow boundary during the late morning and
early afternoon, have just added a scattered cumulus deck.


&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...Flash Flood Watch from this evening through Tuesday morning for
     KSZ025-057-060-102>105.

MO...Flash Flood Watch from this evening through Tuesday morning for
     MOZ012>016-020>024-028>032-037>039-043>045-053-054.

&&

$$

Discussion...Laflin
Aviation...CDB
Eclipse...Laflin


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.