Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 230504
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1204 AM CDT Sat May 23 2015

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Saturday)
Issued at 339 PM CDT FRI MAY 22 2015

Light precipitation continue to move northeast from south central
Kansas into west central Missouri this afternoon. Light returns on
regional associated with the upper level trough axis from south
central Nebraska into south central Kansas. A period of subsidence
behind the tough axis will move across much of northeast Kansas
early this evening. Moisture transport vectors increase overnight
across north central and east central Kansas along with weak
isentropic lift and have gone with 20 to 40 percent chances of light
rain showers. Toward Saturday morning a shortwave will move north
out of Oklahoma as the main upper trough moves slowly across the
Rockies. This will initially increase the upward vertical motion
across central Kansas then as the day progresses another lobe of
energy ejects out into eastern Kansas in the afternoon hours with
another on it heels in Oklahoma. Cape remains on the low side
through the morning hours on Saturday then increases to a around 400
to 600 J/kg in the afternoon with weak to marginal shear. Expect
precipitation efficiency to increase later in the afternoon with
moderate rainfall from mid afternoon onward as ascent increases
ahead of the second wave moving north out of Oklahoma. Therefore
have precipitation chances increasing through the day with very high
probability of precipitation in east central Kansas in the 80
percent to 90 percent range.

.LONG TERM...(Saturday Night through Friday)
Issued at 339 PM CDT FRI MAY 22 2015

Concern is rising for periods of moderate to heavy rain for the
middle portions of the holiday weekend. Models continue to be in
good agreement with the upper trough making slow eastward progress
into the central ConUS into Memorial Day with deep southerly flow
resulting from the local area south through Texas. Heavy rain making
its way east into Oklahoma Saturday continues northeast through the
night with another stronger few rounds into at least Sunday
afternoon as embedded waves rotate through. 850mb winds through
these periods are fairly consistently around 40kt (stronger than
earlier projections) with precipitable water levels rising to around
1.5" (near the 90th percentile of the local sounding climatology),
warm cloud depths around 3500m, and periods of 700-850mb moisture
convergence local to upstream of the area, all supporting efficient
rainfall production. Somewhat drier air works east into central
Kansas late Saturday night into Sunday, keeping southern and eastern
locations in the greater concern for the heavier amounts. Widespread
amounts here look to be in the 1.5-3" range with heavier amounts
expected, with local amounts over 5" possible. Although a few dry
periods have occurred recently, still rather saturated ground
conditions and elevated river levels bring flood potential. Still
appears the greater concern will be from longer-lived moderate to
heavy precip versus quick but intense rain bursts for a greater
potential river/stream flooding. Will go ahead with a Flash Flood
Watch with increasing confidence in heavy rain. Hard to pin down
when individual gauges could reach flood levels, and have the watch
through Monday morning at this point.

As the trough pushes east, slightly cooler air moves in aloft with
moist southerly flow persisting near the surface for rapidly
increasing instability and decent deep-layer wind shear Monday
afternoon. Models begin to show differences with stronger waves
still passing around the trough, and surface features show little
convergence.  Will keep chance PoPs going but will need to watch
this period into Monday evening for severe weather potential.

Moderate west to southwest flow persists into the late week with at
least some chance for additional thunderstorms for most periods. At
this point the most likely dry periods look to be around Wednesday,
with longer wavelength troughing developing toward Friday.

&&

.AVIATION...(For the 06Z TAFs through 06Z Saturday Night)
Issued at 1201 AM CDT SAT MAY 23 2015

VFR ceilings currently in place will gradually lower as low level
moisture approaches TAF sites from the southwest. Expect MVFR
ceilings to build in before 12Z with a decrease to IFR after 12Z.
See a good chance for a few hours of IFR cigs before gradually
lifting toward 1500 feet by around 17Z. Scattered light showers
will be possible almost any time after 09Z, with an area of
heavier rain and thunderstorms likely to impact TAF sites closer
to 00Z, possible bringing IFR conditions once again.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH from this evening through Monday morning FOR
KSZ012-024-026-037>040-054>056-058-059.

&&

$$

SHORT TERM...53
LONG TERM...65
AVIATION...Barjenbruch





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