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

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000
FXUS63 KEAX 222046
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
346 PM CDT Fri May 22 2015

.DISCUSSION...
Issued at 346 PM CDT FRI MAY 22 2015

As has been discussed in recent days...main concern this afternoon
remains focused of potential heavy rains and renewed flooding over
the holiday weekend. Large scale upper flow this afternoon showing a
well-defined upper low spinning across the Desert Southwest with a
beautiful plume of Pacific moisture enroute to the Southern Plains
per latest water vapor and experimental layered precipitable water
product imagery
(http://cat.cira.colostate.edu/sport/layered/blended/lpw.htm). As
this feature continues to move inland...downstream ridging is
expected to strengthen across the American Southeast. The end result
will be a stagnant upper-level pattern and continued southwest flow
downstream across the Plains and lower Missouri Valley. Fcst models
this afternoon continue to suggest repeated disturbances traveling
across our region through the upcoming weekend...which combined with
PWAT values of up to 1.8" (2-3 standard deviations above
normal)...should lead to fairly efficient rainfall production through
the first half of the forecast period.

Before the heavy rain threat develops however...much of tonight looks
to be dry as subsidence on the backside of this morning/s shortwave
controls the weather pattern temporarily. Cannot rule out some pop-up
shwrs...but the majority of the night should be dry due to lack of
forcing. Precip chances look to increase through the day on Saturday
as the first in the series of upper disturbances approaches. For
now...fcst models continue to advertise very limited instability
through the day on Saturday which should keep any developing rains in
the lgt category. Regardless...best chances for rain through the day
will be along and west of Route 65...and highest pops have been drawn
accordingly.

Concerns really begin to rise Saturday night as models show a weak
warm front lifting through the area along with a strengthening low-
level jet. By then...the stagnant upper-level pattern will be well in
place across the Lower 48 and moisture advection from the Gulf will
increase through the period. Quick look at 925 and 850 moisture flux
convergence standardized anomalies shows a maximum over our region which
should translate to fairly decent rainfall production through the
period. The one saving grace remains the lack of instability which
should limit convective rainfall rates to some degree...and lessen
the overall flash flood threat minus urbanized locations. Of greater
concern will be the rainfall/s effect on area rivers and
streams...many of which still remain elevated due to last weekend/s
system. Latest WPC 24-hr QPF shows basin areal averages in the 2-3"
range across the western CWA which if realized...could significantly
impact river levels heading into early next week. To address the
possibility of renewed river flooding and the localized flash flood
treat over urbanized locations...have decided to post a flash flood
watch from Saturday night through Monday.

Moderate to locally heavy rains to continue on Sunday as main cold
front still remains well west of the area. Instability parameters look
marginally better on Sunday which could lead to better rainfall
efficiency from storms that do develop. Additionally wind fields
aloft look marginally better which may support an isolated strong
storm or two...but overall main concerns will likely remain focused
on hydro issues.

Conditions finally look to transition by Monday as main slug of
abnormally high moisture shifts east with time. Beyond
this...unsettled conditions will remain across the region through
much of next week as southwest flow prevails overhead. From this
vantage point...shwrs/storms look possible just about everyday
through the end of next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1206 PM CDT FRI MAY 22 2015

Precipitation to the west will cross through the area Friday
afternoon, while dissipating as it continues eastward. This will lead
to nearby showers for a few hours with continued VFR ceilings. Once
this activity moves out of the area, will likely see a dry period
through the evening and overnight hours. The next wave of activity
will come into play Saturday morning as additional precipitation
moves in from the west. Ceiling heights will lower at this time,
though should remain VFR through 18Z. Precipitation chances will
continue to increase after the forecast period.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...FLASH FLOOD WATCH from Saturday evening through Monday evening
     FOR KSZ025-057-060-102>105.

MO...FLASH FLOOD WATCH from Saturday evening through Monday evening
     FOR MOZ012>014-020>023-028>033-037>040-043>046-053-054.

&&

$$

DISCUSSION...32
AVIATION...Welsh





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