Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 200005
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
705 PM CDT Fri May 19 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Saturday)
Issued at 258 PM CDT Fri May 19 2017

Late this morning a cluster of thunderstorms was moving along the
stationary boundary bisecting northeast Kansas from northeast to
southwest.  Early in the afternoon, a line of storms moving in from
the southeast moved into the forecast area.  These storms look to
stay elevated as they move across the area, although it is possible
some strong winds could mix down producing localized strong/damaging
winds.  If any storms can get rooted at the surface, they will have
between 30-40 knots of effective shear to work with which would
indicate supercellular convection.  The main limiting factor to
these storms is the low CAPE due to previous convection from the
night before. If any storms do become severe, with hail and damaging
winds being the main threats, the best chance is southeast of an
Emporia to Lawrence line.  Hi-res guidance suggests that after this
initial line of storms pushes through there will be a brief break in
precipitation before more showers and thunderstorms form as the
upper level trough continues to push east into the central plains.
The main hazard of today may actually be heavy rainfall leading to
flash flooding.  With the break now forecast between this leading
afternoon line and storms later in the evening, did go ahead and
lower QPF values slightly across the area.  Even so, an additional
half inch to 2.5 inches will be possible across the area tonight,
mainly in very eastern Kansas.  With the recent rain across
northeast Kansas causing river and stream flooding, have opted to
continue the flash flood watch throughout the entire area until 7am
tomorrow morning.  The surface low clears northeast Kansas tomorrow
morning bringing precipitation chances to an end.  Much cooler
temperatures are expected this evening, dipping down into the upper
40s in north central Kansas overnight.  Winds shift from the
northwest to west during the day tomorrow and high temperatures
range from the upper 50s in north central Kansas to the upper 60s in
east central Kansas.

.LONG TERM...(Saturday night through Friday)
Issued at 258 PM CDT Fri May 19 2017

The upper level low center will lift across central Nebraska on
Saturday. Northwest winds and cool advection will ease off during
the evening as surface high pressure builds into the local area.
This should be a good scenario for a very cool Sunday morning with
lows in the upper 30s north central to mid 40s east central KS.
Can`t rule out development of a bit of shallow fog too given
recent rains.

A new short wave trough vort max moves overhead early on Monday
within the west northwest flow pattern and should provide
substantial lift to support an area of showers and non-severe
thunderstorms. A stronger kicker wave will then quickly drop in
from the north with another round of rain and thunderstorms Monday
night. These again are most likely to be non-severe given limited
instability. After that point much of the week will be dry and
pleasant with a gradual warming trend. Upper flow will eventually
transition to a more zonal pattern and may become more active in
terms of thunderstorm chances by next weekend if low level
moisture can advect north into the forecast area by that time.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 653 PM CDT Fri May 19 2017

Expect MVFR CIG/VIS to transition to IFR CIGS at all terminals in
the next couple hours. Have VCTS in all TAFs as the trend is for
storms to begin to decay as they make further progression from the
west and southwest into the terminals. Still concerned enough
with mid level instability that have kept VCTS until around the
08-09Z time frame. IFR conditions lift back to MVFR around the 12Z
time frame and then as the low passes through, expect winds to
shift to a westerly component behind the low but still likely to
hold onto MVFR through most of the forecast period.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Saturday morning for KSZ008>012-
020>024-026-034>040-054>056-058-059.

&&

$$

SHORT TERM...Heller
LONG TERM...Barjenbruch
AVIATION...Drake



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