Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 292000
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
300 PM CDT Tue Jul 29 2014
.SHORT TERM...(This Evening through Wednesday)
Issued at 300 PM CDT TUE JUL 29 2014
19Z water vapor imagery continues to show mid level ridging over the
west with a broad trough over the eastern two thirds of the CONUS.
An area of vorticity can be seen in water vapor over UT and
beginning to turn east. The weak showers, formed from mid level
frontogenesis, continues to fall apart as the forcing weakens.
Surface obs show a broad area of highs pressure over much of the
The general model consensus is for the shortwave energy over UT to
remain mainly over the central Rockies and into the southern plains,
keeping the better forcing for precip to the west and south of the
forecast area. Additionally the suite of 12Z model guidance trended
to keep the QPF progs mainly southwest of the forecast area. This
is where the models also prog the deeper moisture to reside with no
obvious advection to the north or east. Because of this, have
shifted the POP gradient to the southwest with a 30-40 percent
chance from Minneapolis to Emporia and a dry forecast for Seneca and
Hiawatha. There are some signs of weak mid level frontogenesis that
may aid in a few showers developing late tonight, but that is about
it for forcing from the models. Mid level lapse rates remain
relatively shallow at 5 to 5.5 C/km. With this in mind, think
thunder will be hard to come by and maintained only a slight chance
wording in the forecast mainly along the southwestern portions of
the forecast area. As the mid level wave progresses south into the
southern plains on Wednesday, precip chances will diminish from
north to south across the area. Temps will again be highly dependent
on cloud cover and whether there is any precip. Have pretty much
kept the prev forecast in tact with lows in the lower 60s where
clouds are expected to remain thicker overnight. Think highs will
make the lower 80s from the KS river north where precip is less
likely and there could be some insolation in the afternoon. Highs
from Herington to Garnett should be around 80 or the upper 70s due
to limited insolation.
.LONG TERM...(Wednesday Night through Tuesday)
Issued at 300 PM CDT TUE JUL 29 2014
Any lingering precipitation with the recent system should be exiting
by sunset with drier air filtering in from the north. Still have some
concerns about fog development in mainly southern locations, but
guidance is similar with high clouds moving southeast into the area
by late evening and persisting through the night so radiational
setup is not looking ideal and not worthy of an inclusion of fog at
this range. Some slightly lower clouds move in on Thursday but
expect this period to remain dry with slightly warmer temps.
Both the NAM and GFS are similar with a very weak mid-level wave
coming south across eastern sections of Nebraska and Kansas Thursday
night into Friday, creating weak isentropic lift and some light
shower activity. At this point will leave this as something else to
be monitored for consistency and have no mention of precip.
The upper flow pattern of the Rockies ridge and eastern CONUS trough
breaks down early next week with modest zonal flow taking its place.
The opportunities for precipitation should increase by mid week next
week and will go ahead with small chances making their way east into
the area Monday night into Tuesday. Temperatures from the late week
into early next week should slowly moderate with limited flow and
weak wind fields.
.AVIATION...(For the 18Z TAFs through 18Z Wednesday Afternoon)
Issued at 1204 PM CDT TUE JUL 29 2014
The frontogenetical band of light showers appears to be falling
apart and should remain south of the terminals this afternoon.
Models show the deeper moisture and forcing overnight and into Wed
morning favoring precip across southern and western KS. A few
solutions still try to bring some light SHRA into MHK overnight.
Again with mid level lapse rates only around 5 C/km, impact to the
terminals would be minimal. With 12Z model guidance trending
southwest with their QPF, have removed the mention of VCSH from
TOP and FOE and left the mention in for MHK. Overall VFR
conditions should prevail even if -RA moves in due to no real low
level moisture advection anticipated.