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

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236
FXUS63 KEAX 210456
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1156 PM CDT Sun Aug 20 2017

.Discussion...
Issued at 401 PM CDT SUN AUG 20 2017

Short Term (Tonight through Tuesday):

The main concerns in the short term will be for the chance for
severe weather tomorrow evening as well as the chance for flash
flooding monday night into Tuesday morning.

This afternoon thunderstorms have persisted along an outflow
boundary north of I-70. These storms will continue to weaken through
late afternoon into the evening. Upper level ridging that has helped
to bring warm temperatures to the area today will be in place
tonight. A shortwave is expected to round to round the upper level
ridge and move through Iowa. A nocturnal LLJ will increase tonight
and nose right into central Iowa. A MCS is expected to develop
across Iowa tonight with the southern periphery affecting northern
Missouri. Tomorrow morning, the LLJ will weaken at begins to veer
into the local area. This may continue the chance for widely
scattered showers and thunderstorms through the morning hours.
Although a fair amount of cloud is expected tomorrow with southerly
flow and upper level ridging over the area, highs will still reach
the upper 80s to lower 90s.

Late tomorrow afternoon, an outflow boundary from the morning MCS
will be laid out across the CWA and may be the focus for afternoon
convection. NAM soundings suggest 2000-3000J/Kg of MUCAPE and
effective shear of 30-35kts. This would be supported of some severe
storms capable of large hail and damaging winds. Pinning down the
location for these storms will be difficult since much will hinge on
where outflow boundaries set up. Tomorrow night, a upper level
trough will move from the Plains into the Upper Midwest forcing a
cold front into the area. Extremely moist air will be in place as it
does as a Pacific monsoonal moisture plume will be rounding the
upper level ridge(it already is) and be focused on the local area.
Also, Monday night, the nose of a 40-45kt southwesterly LLJ will be
focused right over the Metro With PWAT values 3 to 4 standard
deviations above normal between 2.00"-2.30" in place. This may lead
to prolonged heavy rainfall over the area and as such a flash flood
watch has been issued for most of the CWA. On Tuesday morning the
LLJ finally veers off to the south of the CWA and precipitation
should weaken and shift south of the CWA as the cold front finally
moves through. Expect highs in the low to mid 80s behind the cold
front.

The Eclipse (Monday) : SEE BELOW

Long Term (Tuesday night to Saturday):

Beyond Tuesday, conditions look benign through the remainder of the
week as surface high pressure builds into the area Tuesday night and
remains entrenched over the area through Thursday night. High
Wednesday and Thursday will be in the upper 70s to lower 80s. Friday
we get a return to southerly flow as the surface high shifts
eastward. This will allow temperatures to warm a couple degrees into
the lower 80s. The next chance for storms won`t come until Saturday
will the next system approaches the area.

&&

.Specifics for the Total Solar Eclipse on August 21st...
Issued at 401 PM CDT SUN AUG 20 2017

Unfortunately, it continues to look like there will be broken to
overcast cloud cover from late morning through early afternoon. A
Pacific moisture plume is evident on the water vapor satellite
imagery today and this will continue into tomorrow bringing a cirrus
shield into the area. Also, with a weak low level jet impinging on
the area, there will be the chance for widely scattered showers and
thunderstorms during the late morning and early afternoon hours.
However, even if we remain dry a fair amount of mid-level clouds
will also be affecting the area. There will be some areas where the
sky will not be completely obscured however, they may be few and far
between.

&&

.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 Monday evening through Tuesday morning
     for KSZ025-057-060-102>105.

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

&&

$$

Discussion...73
Aviation...CDB
Eclipse...73



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