Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 261117

Area Forecast Discussion
National Weather Service Topeka KS
617 AM CDT Wed Jul 26 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 306 AM CDT Wed Jul 26 2017

Early this morning, elevated showers and thunderstorms were moving
eastward across Nebraska and northern Kansas towards the area. These
storms, aided by the low-level jet, are expected to move into north
central Kansas this morning and begin to weaken and dissipate
towards the late morning.  No severe activity will be seen with
these storms. Some hi-res guidance lingers these thunderstorms into
the early afternoon, which if this is the case, will play a big role
in how storms develop later along with greatly influencing high
temperatures for the day.

There may be some persisting cloud cover across the area this
morning, but overall, think there should be some clearing this
afternoon allowing for temperatures to rise into the 90s and low
100s.  The coolest temperatures will most likely be just along the
Kansas/Nebraska boarder where storms are most likely this morning.
Dewpoints in the upper 60s and low 70s will lead to heat indicies
between 103-108 for most of the area and, therefore, have continued
the Heat Advisory for today with the new addition of Cloud County.

This afternoon, the mid-level ridge flattens out and mean
westerlies are seen across the central plains with a shortwave
moving through the mean flow.  At the surface, a cold front will
drape across central Kansas early in the afternoon and move into
northeast Kansas by mid to late afternoon.  This front will be the
focus for afternoon and evening convection across the area, along
with any outflow boundaries lingering from morning convection.
Destabilization will occur with daytime heating and roughly 1000-
2000 J/kg of CAPE will be available, along with 0-6 km bulk shear
values between 25-35 knots, with the greatest values seen in far
northeast Kansas.  With this in mind, severe storms will be possible
this afternoon with strong winds and hail being the main hazards.
There is also a threat for very heavy rainfall and localized
flooding with any storms as the low level jet orients itself along
the boundary.  PWATS look to be about 2 inches across northeast
Kansas, with up to 2.5 inches seen in far northeast Kansas.  Storms
may form into more of a line later into the evening and continue to
move southeast through the overnight hours as the system works its
way southeast. Chances for precipitation continue into Thursday.

.LONG TERM...(Thursday through Tuesday)
Issued at 306 AM CDT Wed Jul 26 2017

For Thursday the cold front is expected to move south of the area
by the early afternoon. Have some small POPs in the forecast for
any lingering post frontal precip that may be slow to move out of
the area. Models prog clouds to remain over the area for much of
the day so high temps may be held down with weak low level cold
air advection and limited insolation. The forecast is for highs in
the lower and middle 80s.

For Friday through Tuesday, the general consensus is for the upper
ridge to retrograde to the west while an upper trough develops
over the eastern U.S. In this pattern, models have no obvious
shortwave interacting with the forecast area and any convectively
induced vorticity off the higher terrain remains generally to the
west of the forecast area. However the Canadian has thrown a
wrinkle into this idea by developing an upper low over the central
plains by Monday. In response an area of surface low pressure
develops over southwest KS and causes moisture to advect north
with precip chances for much of the first half of next week. This
is a significant departure from the previous Canadian run which
was more in line with the model consensus. With the 00Z GFS
ensemble and 00Z ECMWF maintaining more of the northwest flow
aloft with surface ridging at the surface, decided to not give
much weight the Canadian prog at this time and see if later
models reproduce this idea of a more pronounced low pressure
system developing next week. This also keeps continuity with the
prev forecast for dry weather into next week. Models don`t show
much of a change in airmass for Friday through Tuesday as surface
ridging centered over the upper Midwest keeps an easterly
component to the surface winds. Therefore with no obvious low
level warm air advection, lows should persist in the mid 60s
while highs remain in the mid and upper 80s.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 617 AM CDT Wed Jul 26 2017

Showers and thunderstorms this morning are expected to weaken and
dissipate by late morning.  Additional thunderstorms are expected to
develop near terminals between 22-23Z.  Kept only VCTS as the best
timing for storms is still uncertain due to this morning activity.
Models are hinting at MVFR ceilings moving in early tomorrow morning
after 09Z, but being so far into the period, have not included this
in this TAF issuance.


Heat Advisory from noon today to 8 PM CDT this evening for



LONG TERM...Wolters
AVIATION...Heller is the U.S. government's official web portal to all federal, state and local government web resources and services.