Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 140515

Area Forecast Discussion
National Weather Service Topeka KS
1115 PM CST Wed Dec 13 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Thursday)
Issued at 335 PM CST Wed Dec 13 2017

As of 20Z Wednesday afternoon, the stagnant mid-level pattern
continues across the entire CONUS. Two of the three mid-level
features of interest reside with two shortwave troughs descending
southeast along the western periphery of the broad, mid-level
trough. The first shortwave of interest has pushed into the Great
Lakes region. Its associated surface trough pushed through the CWA
early this morning, veering winds to the northwest. A surface
pressure gradient on the order of 4-5 hPa across the CWA, coupled
with a well mixed BL to H85 yielded sustained winds near 30 MPH
with gusts upwards of 40-50 MPH earlier this afternoon. As the
aforementioned surface cyclone progresses eastward, the pressure
gradient will continue to weaken. Wind speeds have already
responded to the weakening gradient, therefore the wind advisory
has been allowed to expire.

Tonight: Increasing cloud cover is expected overnight in response
to wrap around moisture from the system in the Great Lakes, and a
secondary shortwave across the Continental Divide. With the
increased cloud cover, temperatures should remain near 30

Thursday: The third clipper system of note will translate
southeast within the northwest flow toward the central Plains
tomorrow evening. Guidance continues to shear the compact
shortwave as it approaches the area. That being said, forecast
soundings continue to suggest the potential for scattered snow
showers along the surface trough after sunset Thursday into the
early overnight hours. ARW/NMM/NAM/GFS all suggest 0.01 to 0.02
inches of liquid QPF. This translates to minimal snowfall with
most areas being limited to a light dusting. High temperatures
look to range from the low to middle 40s.

.LONG TERM...(Thursday night through Wednesday)
Issued at 335 PM CST Wed Dec 13 2017

The remainder of the period looks to consist of above normal
temperatures with another chance for light precipitation Saturday
night into Sunday. The aforementioned mid-level shortwave across
the Continental Divide will become cutoff across the Baja region
by weeks end. Transitioning into the weekend, the cutoff low will
eject into the southern Plains and mid-Mississippi Valley Saturday
night and Sunday. Quality moisture looks to remain southeast of
the CWA. That being said, thermal profiles would support a rain
and/or snow mix across the area. Again, QPF amounts look to remain
less than a tenth of an inch for much of the area. Any lingering
precipitation would transition to all rain by the day time hours
on Sunday as temperatures warm well above freezing. Otherwise, the
remainder of the period looks quiet with no notable clipper
systems traversing across the central Plains.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1115 PM CST Wed Dec 13 2017

Little change to the previous TAF forecast. Models still vary
slightly on ceiling heights tomorrow afternoon, but the consensus
looks to keep broken to overcast VFR ceilings. Northwest winds
decrease under 5 knots after 00Z.




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