Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 221119

Area Forecast Discussion
National Weather Service Topeka KS
519 AM CST Wed Nov 22 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 315 AM CST Wed Nov 22 2017

Frontal passage of yesterday has made it to the gulf coast early
this morning, with the center of the surface high moving over the
forecast area. Temperatures have fallen into the teens over north
central Kansas to the lower 20s in the east central, which is 5-10
degrees below climatology for this time of year.  Good news will be
that the cold temperatures are generally short lived, as by the end
of the day today southerly surface winds and warm advection spread
their way across eastern Kansas.  Highs out west should approach 50
by later this afternoon, while areas in the east slowly rise toward
the middle 40s.  A weak front passes overnight Wednesday night and
should mainly act to keep boundary layer with some mixing, with
overnight lows in the 30s.

.LONG TERM...(Thursday through Tuesday)
Issued at 315 AM CST Wed Nov 22 2017

Late this week, a shortwave trough is forecast to track eastward
and undergo slight amplification across the northern states and
southern Canada -- embedded within the northern branch of a
multi-stream midlevel flow pattern. A speed maximum accompanying
this perturbation will glance the forecast area on Friday, while
separating from a secondary vorticity banner and related speed
maximum flanking an amplifying western states ridge. In response
to these developments, a broad area of surface low pressure will
become established from the southern Canadian Prairies to the
central U.S. from Thursday into Friday, with an increase in the
surface pressure gradient across the region. Related low-level
warm advection and diurnal heating amid a dry air mass will
encourage warmer surface temperatures for Thursday and especially
into Friday ahead of a cold front associated with deepening low
pressure. The front is expected to move southeastward across the
region Friday afternoon into the evening. The primary impacts from
these features will be elevated fire-weather conditions on Friday,
addressed below.

Relatively cooler conditions are expected in the wake of the front
for this weekend, as a surface ridge moves across the region. Medium-
range model guidance suggests that the aforementioned midlevel ridge
could break down early next week, as height falls preceding a
trough spread across the western states. While confidence in the
evolution of this pattern is limited, the primary impacts would
be enhanced gradient winds related to trough-preceding surface
cyclogenesis and perhaps the eventual passage of a moisture-
lacking cold front.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 518 AM CST Wed Nov 22 2017

VFR conditions are expected through the period. Light and variable
winds are expected this morning. Winds will become southerly this
afternoon and gradually veer to the southwest and west-southwest
through tonight, with speeds around 5-7 kt.


Issued at 315 AM CST Wed Nov 22 2017

On Friday, elevated fire-weather conditions will be possible. Much-
above-normal temperatures are expected ahead of the front (into
the lower 70s) for Friday afternoon. Present indications are that
diurnally enhanced vertical mixing on Friday will manifest
strong flow aloft related to the tightened pressure gradient at
the surface as gusty winds. Furthermore, any substantive influx of
moisture will be inhibited by northerly flow west of an evolving
surface trough over the middle and east Gulf of Mexico. As a
result, elevated fire-weather conditions may affect the region on
Friday, and an abrupt wind shift to the northwest to north is
anticipated with frontal passage Friday afternoon into the




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