Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 140004
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
604 PM CST Mon Nov 13 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tuesday)
Issued at 251 PM CST Mon Nov 13 2017

As of 20Z Monday afternoon, mid-level ridging continues to
overspread the central Plains. A broad fetch of Pacific moisture is
moving ENE towards the central Plains. Upstream of the ridge, a mid-
level trough was entering the Pacific northwest. An expansive
stratus shield stretched from west TX to northern IA. Due to the
minimal surface heating, high temperatures this afternoon will
remain in the upper 40s to near 50. Surface ridging across the
midwest continues its slow movement to the east. Southerly low-level
flow has returned on the western periphery of the surface ridge
across western OK and TX. This trend will continue through the short
term period with much of the CWA residing in low to mid 50 dew
points by Tuesday afternoon.

Tonight -- Low-level WAA will continue to overspread the CWA as a 30-
35kt southwesterly LLJ traverses the area. Isentropic lift will
increase in response to the strengthening low-level wind field. A
saturated boundary layer coupled with modest isentropic ascent,
expect drizzle to develop after 00Z. The most favorable locations
for drizzle look to to remain along and southeast of a Council Grove
to Hiawatha line. Visibility reductions appear likely as well with
the drizzle and low clouds/fog in the area. Expect visibilities to
hover in the 1 to 2 mile range for much of the overnight period.
There could be brief periods of lower visibilities. As far as low
temperatures go, WAA will tend to maintain temperatures in the mid
40s, if not slightly warming into the upper 40s overnight.

Tuesday -- Isentropic lift and boundary layer saturation look to
briefly lessen after 12Z Tuesday morning. As a result, expect
drizzle to become much more patchy across the area through the late
morning and afternoon hours. High temperatures look to warm into the
mid 50s Tuesday afternoon. Precipitation chances look to increase
once again after 00Z Tuesday as the main surface trough traverses
the CWA.

.LONG TERM...(Tuesday night through Monday)
Issued at 251 PM CST Mon Nov 13 2017

Models remain in strong agreement with low level moisture advection
increasing ahead of the deepening sfc low over the panhandles.
Initial drizzle in the early evening is expected to transition to
rain showers as elevated lift and convergence increase along the
frontal boundary overnight Tuesday. Rainfall amounts are generally
light and remain below half of an inch. Despite the decent shear
profiles on forecast soundings, elevated instability is very poor
and less than 100 J/kg. As a result, kept the mention for a slight
chance for a thunderstorm or two south of Interstate 70.

Strong subsidence behind the boundary should be enough to clear out
the persistent stratus deck Wednesday afternoon. The shallow airmass
in the boundary`s wake enables the warming trend to continue through
the week with highs rising into the middle 60s through Friday.

Similar setup to Tuesday occurs again Thursday night and Friday with
moist, southerly flow towards the sfc ahead of an incoming shortwave
trough/frontal boundary combination arriving during the afternoon on
Friday. While low level forcing is not particularly prevalent, a mix
of drizzle and rain is possible ahead and along the front.

Dry, northwest flow resumes for next weekend with slightly cooler
temperatures in the 50s. The better news however is the return of
sunny skies with northwest winds gusty at times in the afternoon up
to 25 mph.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 535 PM CST Mon Nov 13 2017

For the 00Z TAFs, CIG/VIS trends should continue to head from
mainly MVFR to IFR and gradually drop to LIFR into the overnight
period into the 12Z time frame. Do expect -DZ much of the
overnight period as radar trends continue to show an expanding
area of -DZ developing generally south of the terminals. Problem
with the timing of exact changes and how reduced CIG/VIS become is
low confidence. Expect this forecast will likely need a few
updates tonight.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Baerg
LONG TERM...Prieto
AVIATION...Drake



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