Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 110441
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1141 PM CDT Tue Oct 10 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Wednesday)
Issued at 245 PM CDT Tue Oct 10 2017

19Z water vapor imagery shows an upper low over northeast KS
lifting to the northeast. Another upper low was moving onshore
over the Pacific Northwest. At the surface, high pressure
stretched from the southern high plains to the upper Midwest.
Cloud cover and low level cold air advection continued into the
afternoon and temps have remains in the lower and middle 40s.

For tonight and Wednesday, the weather should remain dry. As the
upper low continues to lift northeast, subsidence should increase.
Combined with dry air advecting in with the surface ridge, there
is little chance of precip tonight or Wednesday. So focus shifts
to temps. Conditions for radiational cooling look favorable across
north central KS where the ridge axis is forecast to move into,
with skies clearing out. However the RAP and NAM hang onto the low
clouds over eastern KS through much of he night. So where skies
are forecast to clear out, lows should drop into the lower 30s
while cloud cover over eastern KS keeps temps in the mid 30s to
near 40. Based on this forecast, have issued frost advisories and
freeze warnings for north central KS and parts of northeast KS.
This forecast is heavily dependent on the cloud cover forecast, so
the evening shift will need to watch how the clouds clear out and
make any adjustments to the headlines as needed. Surface ridging
is expected to remain over the area through the day Wednesday. So
there is not expected to be a great deal of mixing and surface
winds maintain a light easterly component. So highs Wednesday are
expected to remain on the cool side. Mostly sunny skies by the
afternoon should help temps warm into the lower and middle 60s.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 245 PM CDT Tue Oct 10 2017

A gradual warming trend will set in for the latter part of the week
with the next major chance of showers and storms arriving on
Saturday.

Broad cyclonic flow will be in place over the western and central
CONUS at the start of the period, facilitating the return of warm
southerly winds. A northern stream wave will drag a cold front
southeastward across the Dakotas and Nebraska on Thursday. Lee
cyclogenesis will take place along the Front Range on Thursday
night and into early Friday with the cyclone gradually drifting
northeastward and reinforcing the decaying cold front. Highs on
Thursday will reach into the 70s across NE Kansas, but surge into
the low to mid 80s (upper 80s are possible) in areas ahead of the
boundary as ample WAA takes place. The upper level blocking
pattern breaks down late in the week with a sharp shortwave trough
ejecting ENE across the central plains.

The increase in kinematic support coupled with the strengthening Fg
forcing will fuel shower and thunderstorm development both late
Friday and again Saturday afternoon. The GFS/EC/GEM are in general
agreement with the position of the boundary and upper level
features, but there remain enough mesoscale differences to warrant
some degree of uncertainty. The CAPE-shear profiles ahead of this
boundary would be supportive of strong convective storms, but with
the mid to upper level steering flow parallel to the surface
boundary, it is likely that any storms will quickly grow upscale
into a linear line. GFS bufr soundings depict 0-1 km helicity values
of 200-300 m2/s2 with 0-3 km shear values of 30-40 kts. Thus, there
would exist a non-zero tornado threat should this scenario come to
fruition in addition to wind and hail. Heavy rainfall would be a
threat given PWATS of 1.5 to 2 inches and the possibility of
training cells, but the fast storm motions of 40 to 50 kts would
work somewhat against a flooding scenario.

This complex will quickly exit early Sunday with Canadian high
pressure and seasonal temperatures sliding southward to start next
week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1123 PM CDT Tue Oct 10 2017

MVFR ceilings at TOP/FOE continue to persist with most models now
hanging onto these until at least 12Z. Some hold on to this
feature even longer until 15Z, but predict this deck will slowly
slide eastward through the early morning hours clearing terminals
by 12Z. From here, VFR conditions are expected for the rest of the
period with only light winds to speak of.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 10 AM CDT Wednesday for KSZ010-022-035>037.

Freeze Warning until 10 AM CDT Wednesday for KSZ008-009-020-021-
034.

&&

$$

SHORT TERM...Wolters
LONG TERM...Skow
AVIATION...Heller



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