Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 062315
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
515 PM CST Wed Dec 6 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Thursday)
Issued at 231 PM CST Wed Dec 6 2017

An elongated region of H925-H850 Fg forcing was wrapping
southward along the upstream flank of an H500 trough axis early
this afternoon. Light to moderate snow has been reported across
central Nebraska and western Iowa with this forcing band with
visibilities of a mile or less in a few locations. CAA behind this
line coupled with large T/Td spreads and wet bulb temps near
freezing has allowed SN to be reported despite surface temps near
40 degrees. The HRRR has done a decent job depicting this region
of forcing and continues to weaken it through the afternoon.
RAP/NAM model along with the 12Z TOP RAOB depict a wedge of dry
air over SE Nebraska and NE Kansas under the precip generating
layer with surface Td depressions of 10 to 15 C. Thus, leveraged a
compromise in the precip forecast for the rest of the afternoon,
trending upwards in coverage and intensity in the far northern
counties while at the same time decaying the band rapidly from 22
to 01Z. Likewise increased cloud cover through the evening hours
for the passage of the band--which clears out quickly before 06Z.
Surface ridging builds for the day on Thursday with and -12 C
H850 thermal trough overhead and keeping surface temps around the
freezing mark.

.LONG TERM...(Thursday night through Wednesday)
Issued at 231 PM CST Wed Dec 6 2017

The extended pattern will be characterized by continued NW flow due
to a strong synoptic block anchored over the west coast. Multiple
weak perturbations will drop southward during this time, but with
minimal forcing and moisture to realize, the sensible weather
effects will be minimal. A downslope airmass will translate
southeastward into the region starting on Friday, with increasing
H850 temps through the weekend. By late Sunday, H850 temps will be
above +10 C with corresponding surface temps in the upper 50s to
near 60. A second push of cold air will arrive for early next week
and drop temps back to near average. The next decent chance of
precip may not be until next Monday has the H500 wave/vort max
drops through, along with some very low chances of
flurries/sprinkles attendant to synoptic jet dynamics on Friday
and Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 514 PM CST Wed Dec 6 2017

VFR conditions are expected throughout the period. There is a
slight chance for some flurries at sites for the next couple
hours, but with such scattered coverage of precipitation have left
this mention out of the TAF.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Skow
LONG TERM...Skow
AVIATION...Heller



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