Area Forecast Discussion
Issued by NWS Topeka, KS

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386
FXUS63 KTOP 222346
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
646 PM CDT Mon May 22 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tuesday)
Issued at 250 PM CDT Mon May 22 2017

Observing several mid level impulses migrating south and east over
the central and western high plains this afternoon. The wave
currently over central KS has generated a cluster of showers and
isolated, non severe thunderstorms across the northern half of the
CWA this afternoon. Breaks in cloud cover across east central areas
has allowed sfc heating to commence with rising around 70 degrees.
Combined with dewpoints near 60, sfc cape has increased between 500
and 1000 J/KG. Effective shear is around 35 kts so will need to
watch the singular storms ahead of the main rain bands for the
possibility of small hail or gusty winds through late afternoon.
Otherwise focus for convection later this afternoon and evening lies
over southeast NE where the cold front is positioned. Short term
guidance continues to generate a line of showers and thunderstorms
by 00Z, entering the northern KS counties in our area. Atmosphere at
this time in north central KS is characterized by MUCAPE in excess
of 1000 J/KG while 0-6 km bulk shear is up to 30 kts. Lapse rates
are decent near the border, however decrease quickly as you head
south and east into the CWA. Current thinking is that convection
will be strongest initially over north central KS before gradually
weakening as the line dissipates and pushes southeast. The strongest
storms may produce marginally severe hail and gusty winds. Localized
heavy rainfall may also be of concern to area creeks and rivers,
especially across the northern tier of counties near the NE border
while highest qpf is forecast.

Residual showers with perhaps a few embedded thunderstorms are
expected to linger into Tuesday as the main upper low rotates slowly
southeast over Iowa. Precip coverage may increase towards the
afternoon hours where optimal chances for measurable precipitation
lie over the eastern half of the CWA. As a result, highs tomorrow
were lowered a few degrees with readings in the low to mid 60s.
Tightening pressure gradient behind the low increases sfc winds from
the north at 10 to 15 mph throughout the afternoon.

.LONG TERM...(Tuesday night through Monday)
Issued at 250 PM CDT Mon May 22 2017

Tuesday Night through Monday ...

By Tuesday night, the mid-level trough will be shifting east of the
CWA with a few lingering showers possible across far northeast KS.
Dry conditions are expected Wednesday into Thursday as a mid-level
ridge over the western U.S. advances eastward into the central U.S.
Highs on Wednesday will be in the mid 60s with highs reaching into
the mid/upper 70s by Thursday as surface high pressure shifts
southeast of the CWA and winds become breezy out of the south.

During the Thursday night through Sunday time frame, there will be
several chances for showers and thunderstorms as several
disturbances track across the central U.S.  A broad mid-level trough
will be in place across the northwestern U.S. on Thursday, with
models showing embedded waves along the southeastern edge of this
trough skimming across northern KS late Thursday night into Friday.
This passing wave will also push a warm front across the CWA, so
expect some scattered thunderstorms to develop along this frontal
boundary. These storms will likely be elevated, but with steep mid-
level lapse rates and 30-40kts of 0-6km shear, cannot rule out the
potential for a few strong storms to develop.

The next potential for showers and storms looks to be late Friday
night through Saturday night as another embedded shortwave within
the mid-level trough tracks across northern KS and helps to push
another warm front into the CWA.  Some strong to severe storms will
be possible across east central to southeast KS Saturday afternoon
into Saturday evening as model soundings show the cap being broken
with steep mid-level lapse rates supporting at least 2000 J/kg of
CAPE along with 40+ kts of 0-6km shear.  Precipitation chances may
extend into Sunday, however it will be dependent upon when the mid-
level trough axis finally shifts eastward over the CWA.  The
ECMWF/Canadian are more progressive in having the trough shift east
of the CWA by Sunday morning, resulting in dry conditions for the
day. However, the GFS is slower in tracking the trough axis over the
CWA Sunday into Sunday night, which would result in some scattered
showers and storms continuing across the region.

As for temperatures, high temperatures will range from the 70s to
low 80s from Thursday through Monday, with low temperatures in the
50s to low 60s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 640 PM CDT Mon May 22 2017

For the 00Z terminal forecast, showers should continue to move
east of the KTOP/KFOE terminals. A cold front continues to advance
toward the terminals and should slowly make its way to KMHK by the
07Z time frame and then around 08-09Z at the KTOP/KFOE terminals.
Right now, there is thunder with some storms along this line, but
they are expected to weaken as they continue into the terminals.
Therefore, have only inserted VCSH as instability looks to
stabilize before storms do make into the area. Will need to
monintor these trends over the next few hours. Do have winds
picking up behind the front and it is possible they may be a bit
stronger into the day on Tuesday.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Prieto
LONG TERM...Hennecke
AVIATION...Drake



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