Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 211133

Area Forecast Discussion
National Weather Service Topeka KS
633 AM CDT Wed Mar 21 2018

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 303 AM CDT Wed Mar 21 2018

Early this morning satellite imagery showed the back-edge of the
stratus lingering over far northeast Kansas, but expect this cloud
cover to finally exit east of the area by around sunrise this
morning.  The combination of mostly clear skies, light surface
winds, and low-level moisture from the recent rainfall is conducive
for fog development early this morning. However, with stronger winds
noted just above the surface, it may limit fog development mostly to
low-lying areas.  As a result, have kept the mention of some patchy
fog in through just after sunrise.

The region will remain under northwesterly flow aloft as a mid-level
ridge steepens over the western U.S. today and tonight.  Surface
high pressure will continue to dive further southward into the
central U.S. today and gradually shift east of the CWA by this
evening.  So with the center of the high passing over the area
through the day, expect light northwesterly winds to back to the
south through the day.  Short-range guidance shows this shift to
southerly winds occurring across central KS by mid/late morning, but
not mid/late afternoon across far eastern KS.  The timing of this
wind shift will have an impact on the amount of WAA that will occur
today, so expect highs to range from the mid 50s to low/mid 60s from
east to west across the CWA.

As the mid-level ridge continues to build just west of the region,
models show the potential for a very weak embedded wave to develop
within the northwesterly flow aloft tonight.  This passing wave will
bring some mid-level clouds into the area through the overnight
hours.  The combination of this cloud cover with southerly surface
winds will result in slightly warmer conditions tonight with lows
only dropping into the upper 30s/near 40 degrees.

.LONG TERM...(Thursday through Tuesday)
Issued at 303 AM CDT Wed Mar 21 2018

On Thursday a mid/upper level ridge will build eastward over the
plains allowing warmer temperatures to spread into our area. There
will also be modest lower tropospheric moisture advection likely
contributing to partly cloudy skies. Highs are expected to reach
the lower to mid 70s with deep boundary layer mixing. The low-
level pressure gradient is not expected to be particularly strong
therefore wind gusts should remain below 20 mph with the exception
of far southeast KS. This is where the diurnal heating will
allowing mixing into the low-level jet veering over the mid MS
valley. These conditions may cause elevated fire danger, but
certainly not extreme. On Thursday night a midlevel shortwave
tracks over the central Rockies and the lee-side trough deepens.
This should reinforce the low-level moisture return beneath a
strengthening EML. Some models are suggesting some isentropic lift
within this moisture may result in light rain or drizzle across
portions of eastern KS Friday morning.

During the day Friday the shortwave ejects out over the Central
Plains and steers a surface cyclone into Central KS. Models are
hinting at modest MUCAPE and substantial shear Friday afternoon.
Although a stout EML should keep all surface convection capped.
On Friday evening the GFS is showing almost 0.50" of QPF along and
north of I-70, which does not make much sense conceptually with
the EML in place. A majority of the other model solutions place
the higher QPF north and east of the area. This makes more sense
where a weaker cap could erode as the wave approaches. Drizzle
seems more like a possibility in our area with increasing lift
below the EML. Another weaker shortwave lifts northeastward over
the plains on Sunday night perhaps forcing warm advection showers.
On Monday a deepening longwave trough over the Rockies increases
the meridional flow over the central US. The poleward flux of
moisture will encounter a baroclinic zone in the vicinity and
steep lapse rates aloft. The juxtaposed instability, shear, and
lift could contribute to more widespread precipitation. Strong
convection and heavy rain is possible with this set up Monday into
Tuesday. There are still some temporal and spacial difference
among the models so the details are uncertain at this point, but
something to watch moving into next week.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 627 AM CDT Wed Mar 21 2018

For the 12z TAFs, current observations and short-range guidance
continue to trend away from reduced visibilities from patchy fog
development, so have VFR conditions prevailing through the period.
As surface high pressure gradually progresses eastward across the
outlook area, light winds will back from northwest to south this
afternoon into this evening. Models show a LLJ tracking over the
TAF sites early Thursday morning which could potentially produce
some borderline LLWS concerns. However, confidence is too low to
warrant a mention in the TAFs at this time.




SHORT TERM...Hennecke
LONG TERM...Sanders
AVIATION...Hennecke is the U.S. government's official web portal to all federal, state and local government web resources and services.