Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 110445
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1145 PM CDT Wed Sep 10 2014
...Update to aviation forecast discussion...
.SHORT TERM...(This Evening through Thursday)
Issued at 319 PM CDT WED SEP 10 2014
On Wednesday afternoon, the cold front has passed entirely through
Kansas with widespread cold advection and cloud cover in its wake.
These north winds and cold advection will continue through tonight
and into Thursday. Patches of drizzle and a few light rain showers
were crossing east central KS, with possibly a few sprinkles moving
into northeast KS as well this afternoon. A patch of clearing was
developing into north central Kansas this afternoon, and will likely
expand a bit into the evening but seems pretty likely to fill back
in after dark. The expectation of widespread cloud cover and
continued winds should keep low temperatures from falling too low,
likely in the low to mid 50s. However, any areas able to keep clear
skies could end up 3-5 degrees cooler by morning. Thursday should
start out cloudy for much of the area but with gradual breakup to
partly cloudy skies by late morning. Winds will continue and even
with increased sunshine, the cooler airmass in place will only allow
highs to climb into the 60s...to perhaps 70 in east central Kansas.
By late in the day, a strong trough will be diving south toward the
area. A reinforcing cold front will approach the Republic county by
mid afternoon while southwest isentropic upslope flow near and over
the front increases in advance of the trough. Expect showers to
develop during the afternoon, although they should remain mainly NW
of the forecast area through sunset. Could see these showers
approach the Concordia and Marysville areas by early evening.
.LONG TERM...(Thursday Night through Wednesday)
Issued at 319 PM CDT WED SEP 10 2014
By Thursday night another decent upper level trough will be digging
into the central plains and upper Midwest. The area will be under
the influence of upper level divergence and PVA associated with the
trough both of which will provide the lift needed for widespread
rain. The best chances for rainfall will increase across north
central KS and spread to the southeast during the morning hours on
Friday. Instability during this time frame appears to be low which
will limit the potential for embedded thunder. Chances of precip
quickly diminish Friday afternoon as dry air overtakes the region
from the northwest. Behind the upper trough an expansive surface
high pressure will build southward from the northern high plains. As
the high pressure slides into the area a decent pressure gradient
develops causing an increase in wind speeds out of the north. Wind
gusts will approach 20 to 25 mph during the daytime hours. With the
fall like air mass in place temperatures will struggle to get out of
the 50s most of the day especially with the rain and cloud cover. As
the high pressure ridge settles directly into northeast KS
Friday evening the winds go calm and skies clear. This will set the
stage for an unseasonably cold morning and the potential for fog.
Saturday morning low temperatures range from upper 30s and low 40s.
Will have to continue to evaluate the potential for frost. As of now
we are not expecting widespread frost, but frost in isolated
locations is possible as dew points and temperatures approach 36 to
38 degrees mainly in north central KS.
Return flow quickly develops ahead of the next system, which is
forecast to clip the area on Sunday night. The models disagree on
the speed of the upper level trough therefore the pops continue
through Monday night. The GFS is much faster and develops return
flow rather quickly while the ECMWF is delayed. The pops for mid
week are associated with weak embedded waves within the northwest
flow aloft therefore did not make any changes to that portion of
the forecast. The instability does return as steep mid level lapse
rates spread over the region and dew points reach the low 60s. So
have kept the mention of thunder through mid week. Temperatures will
gradually warm through the extended although remain pleasant.
.AVIATION...(For the 06Z TAFs through 06Z Thursday Night)
Issued at 1145 PM CDT WED SEP 10 2014
MVFR conditions should dominate, and could persist throughout this
forecast. Moisture layer is rather shallow, and may be able
scatter out in peak heating. Have gone this route at this time.
Cannot rule out at least brief IFR cigs around 12Z but dewpoints
continue to fall with temps and believe this will continue to keep
spreads from shrinking.