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Area Forecast Discussion (AFD)

Issued by Topeka, KS (TOP)

FXUS63 KTOP 171720

Area Forecast Discussion
National Weather Service Topeka KS
1220 PM CDT Tue Sep 17 2019


.SHORT TERM...(Today and tonight)
Issued at 311 AM CDT Tue Sep 17 2019

Upper ridge axis this morning continues to edge eastward into the 
Midwest region. Mid level moisture return continues today as several 
embedded perturbations are noted lifting towards the western high 
plains ahead of the mid level trough axis in Oregon. Despite the 
decent low level mixing and gusty south winds this afternoon, cirrus 
clouds should once again temper highs a few degrees to the low 90s. 
A secondary upper trough is progged to cross the Pacific Northwest 
coast this evening, shifting the first upper wave into the northern 
plains. Upper level forcing upstream of the wave focuses in vicinity 
of a front stretching across NE, with a cluster of thunderstorms 
progged to develop and shift through Iowa after midnight tonight. 
Moisture profiles from most guidance is more dry compared to 
previous evenings with weaker lapse rates over east central and 
north central areas. It remains possible that the storm cluster 
could clip far northeast Kansas so I kept the chance pops in aft 06Z.
Weak 0-6 km bulk shear does not support severe updrafts.

.LONG TERM...(Wednesday through Monday)
Issued at 311 AM CDT Tue Sep 17 2019

Guidance in the extended period is becoming more consistent with
the sfc front setting up from southwest KS through northeast NE. A
weak capping inversion may allow for scattered convection to
develop by late afternoon Wednesday. Coverage is of question with
the optimal upper forcing in Iowa, but have increased pops for the
late afternoon. Additional storms are again possible overnight as
the LLJ overruns the front in NE, perhaps reaching as far south as
northern Kansas. Thursday and Friday should be mostly dry with
increasing cloud cover as the main upper trough arrives into the
northern plains. The latest GFS and ECMWF continue to vary from
here on out as the front shifts southward into Kansas on Saturday.
The GFS is consistent with the faster solution on frontal timing
compared to the ECMWF that swings the front through the CWA early
Sunday morning. Thunderstorms now appear likely overnight,
especially over east central Kansas where both the ECMWF and GFS
maximize qpf values to around 1 inch. The front is expected to
slow in southern KS by Sunday with the potential for occasional
thunderstorms through Tuesday, particularly south of Interstate
70. The drier airmass will finally relieve the area from the hot
and humid conditions Sunday with dewpoints around 60 degrees and
highs in the low 80s into early next week.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1220 PM CDT Tue Sep 17 2019

VFR conditions should prevail with limited moisture in low levels.
Forecast soundings show a decent low level jet developing with a
steep low level inversion. Because of this will include a mention
of LLWS at MHK and TOP where sfc winds are likely to be lighter.
There is an outside chance for an elevated shower around sunrise
Wednesday. Probabilities appear to small at this time to include
and SHRA in the forecast.