Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 131714

Area Forecast Discussion
National Weather Service Topeka KS
1114 AM CST Tue Feb 13 2018


.SHORT TERM...(Today and tonight)
Issued at 254 AM CST Tue Feb 13 2018

Shortly after midnight, areas of patchy sleet/graupel had moved
east of Kansas leaving conditions dry for today and tonight. A
closed mid-level low is noted off of the southern California coast
with southwest flow persisting over northeast Kansas. A weak
disturbance within this flow skims Kansas late tonight, but any
precipitation looks to remain southeast of the area. Cloud cover
early this morning will decay from the south with sunny skies
expected by the afternoon hours. Winds veer through the day,
remaining from the south by late morning. Diurnal heating along
with southerly flow will help warm things up a bit today with
highs from the mid 40s to low 50s expected. Clouds return tonight
from the south as the aforementioned disturbance moves near the
area. Lows tonight range from the low to upper 30s, which is above
climatology for this time of the year.

.LONG TERM...(Wednesday through Monday)
Issued at 254 AM CST Tue Feb 13 2018

Spring-like variations in temperatures will be the main theme for
the rest of the week and into the weekend with little chance of
any widespread precipitation.

A cutoff low/trough over the Sierra Nevadas will keep WSW zonal
flow over Kansas for Wednesday with a +12 C downslope=modified
H850 airmass spreading into the Central Plains as H300 ridging
amplifies downstream of the cutoff low. At the same time, a lee
cyclone pulls off the Front Range and meanders eastward into
western Kansas by late in the day on Wednesday. A weak warm
frontal boundary begins to manifest itself ahead of the low along
the KS/NE border and have likewise maintained a gradient in the
temperature field near the position of the front for Wed and
leaned on the higher side of the guidance envelope for highs to
the south of the front. Given the lack of upper level support, the
trailing surface trough will remain nearly stationary through 21Z
Thu before a reinforcing shot of cold air plunges southward with
a 1034 mb Canadian high. The broad surface westerly flow in place
before the cold air arrives will keep highs in the 50s and 60s on

The push of continental polar air will increase baroclinicity
along the boundary and likewise increase the potential for
precipitation. However, it appears that the best chance of precip
will be just south of the CWA Thu afternoon. A tight 25 ubar/km
pressure gradient will bring strong winds to NE Kansas Thursday
night and harken the arrival of the cold air. Forecast soundings
show a well-mixed boundary layer all night with winds at the top
of the layer pushing 30 kts. H850 temps fall to -8 C by midday
Friday and surface temps will struggle to reach the mid 30s for
daytime highs. With the breakdown of the cutoff low late in the
week, a more progressive northern stream pattern sets in for the
weekend. The surface high slides east of the CWA by Saturday
morning and allows return southerly flow to bolster temps back
into the 50s for the weekend, only to be followed by another cold
front late Sunday.

Model solutions are in generally good agreement with this setup,
though the NAM surface temperature fields for Wed/Thu were
discounted due to its problematically cool PBL as of late, and
significant disagreements begin creeping into the 13.00Z
GFS/EC/GEM mass fields after the passage of the high over the
weekend. A few stray GEFS members and the 13.00Z GEM bring precip
before the end of the weekend, but for the most part no widespread
QPF appears in the forecast until early next week at the soonest.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1114 AM CST Tue Feb 13 2018

Main concern is the potential for fog and stratus moving north
overnight. Models show the low level warm air advection pattern
continuing with increasing dewpoints. With most guidance
saturating the boundary layer, there is some potential for fog.
However forecast soundings maintain some mixing at least in the
top of the boundary layer and the low level moisture does not
appear to be to deep. So am not sure how far north and west the
fog or stratus may go. Will include only some MVFR VSBY at TOP and
FOE for now and monitor trends.




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