Area Forecast Discussion
Issued by NWS Topeka, KS

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41
FXUS63 KTOP 201759

Area Forecast Discussion
National Weather Service Topeka KS
1259 PM CDT Tue Jun 20 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 241 AM CDT Tue Jun 20 2017

A weak surface high pressure currently located over the Ozark
region is forecasted to gradually slide eastward during the day
today. A shortwave currently over northern MN will track over the
Great Lakes region today dragging a weak boundary southward, which
should reach the KS/NE state line this afternoon. High
temperatures will warm into the lower to mid 90s with dew points
in the lower 60s at peak heating. Ahead of the boundary deep
boundary layer mixing causes the LCLs to be around 700 mb
especially in northern and central KS. Mid level lapse rates are
expected to be on the order of 5.5-6.5 C/km therefore the mlcape
will only be as high as 1000 j/kg when the front arrives. Most of
forecast soundings agree that there will not be much of a cap in
place this afternoon and evening. Some convergence along the
boundary along with mid level isentropic lift should be enough
lift for initiation. So there is a chance high based showers and
possibly a few storms develop along this boundary. The best
chances for precipitation should be in north central KS with a
slight chance extending eastward into far northeast KS. Expect
that the coverage will only be isolated to scattered before the
chances diminish in the late evening. Given the forecasted
instability do not expect there will be enough precipitation
loading to cause sufficient sub-cloud evaporation for downbursts.
Although it may be enough for some gusty winds mainly across north
central KS. That boundary will quickly become diffuse as warm
advection increases ahead of another weak shortwave that will
track over the northern plains. Low temperatures tonight should
drop into the upper 60 to lower 70s.

.LONG TERM...(Wednesday through Monday)
Issued at 241 AM CDT Tue Jun 20 2017

For Wednesday and Thursday, models show a typical summer time
pattern with relatively weak flow aloft and a conditionally
unstable airmass. So precip chances generally depend on a surface
feature to focus low level convergence and provide some lift.
This seems to be the case in the model solutions with a surface
trough to the west of the forecast area on Wednesday and then a
cold front moving south through NEB on Thursday. For both days,
the stronger surface based instability develops along these
features with marginal 0-6KM shear. So this favors the idea of
storms developing in the heat of the day just outside of the
forecast area and impacting parts of it through the evening and
overnight hours. Temperatures look to be on the warm side with
most locations seeing highs in the lower and middle 90s. Lows are
expected to me in the lower 70s.

By Friday, most solutions bring the cold front through the
forecast area by the evening. So the forecast continues with
chance POPs for Friday and through the evening hours. The biggest
uncertainty in the forecast is whether this front will push all
the way through and bring dry cool air in for Saturday or if there
will be another frontal push with possible precip on Saturday. The
ECMWF continues to show this potential. And while not exactly
like the ECMWF, the Canadian brings a sharper shortwave through
the northwest flow on Saturday suggestive of some potential for
shower and thunderstorms. So have kept some chance POPs in for
Saturday and Saturday night until the models converge on a favored
solution. The main concern regarding temps are on Friday and
Saturday given the differences between the GFS and ECMWF timing
of the stronger push of high pressure. The forecast leans a little
cooler towards the GFS solution, but if indeed the initial front
on Friday is not that strong temps may be to cool.

Sunday and Monday look to be mainly dry with relatively cool
temps as surface ridging passes through the region. Some return
flow may set up for Monday night. So will include a slight chance
POP for the possibility of elevated storms heading into Tuesday


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1241 PM CDT Tue Jun 20 2017

For the 18Z TAFs, VFR conditions should hold. There is a period
late this afternoon into the early evening where TS potential does
exist mainly around the KMHK terminal. Have kept with VCTS as
eastward extent of storms could reach into the area. Largest
concern with any storms would likely be gusty outflow wind. LLWS
overnight is something to watch as a weak LLJ increases in
strength over the area. Winds may be stronger near KMHK also, but
have not included due to low confidence in the core of the winds
spreading far enough east into the terminals. Southerly winds
increase with mixing into the day Wednesday.




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