Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 190537

Area Forecast Discussion
National Weather Service Topeka KS
1137 PM CST Wed Jan 18 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Thursday)
Issued at 144 PM CST Wed Jan 18 2017

Early afternoon water vapor satellite imagery shows an elongated
upper level low situated along the front range with multiple
embedded vort maxes. This cutoff low will move only a few hundred
miles to the east by the end of the period on Thursday evening,
placing it nearly directly over the CWA. A thin altostratus deck
has been eroding as it enters the southern CWA this afternoon and
this trend is expected to continue through the evening before low
level moisture overspreads the region from the south around 06Z.
There is some uncertainty with whether we will see advection fog,
low stratus, or a combination of the two overnight. RAP/GFS/NAM
soundings show this moisture trapped between the surface and 800mb
with a southerly flow of around 5 kts through the night. Thus
leaned towards a compromise of stratus and fog but kept dense fog
wording out of the forecast. Pushed highs down several degrees
close to the CONSRAW guidance given the persistent cloud deck
through the day on Thursday and only weak WAA/surface flow. Lift
through the BL is not terribly impressive during the day with
omega values in the -2 to -4 ubar/sec range in the western CWA,
but continued to maintain slight chance drizzle wording along and
west of the HWY 75 during the day.

.LONG TERM...(Thursday night through Wednesday)
Issued at 144 PM CST Wed Jan 18 2017

Pattern becomes a bit unsettled in the extended, but overall a
mild forecast early with chances for precip every few days, with
perhaps a larger system mid week.

Low chances for drizzle or light rain across mainly the eastern
and northern forecast area on Thursday night and into Friday as
the next system makes an approach and lifts the warm front
northward. This should keep lows up in the 30s and 40s, with
highs reaching from the upper 40s to middle 50s. The upper low
then lifts quickly out of central Kansas into the upper midwest
through Saturday, leaving us mild and dry for the early weekend.
Next shortwave low in the stream moves quickly out of the southern
Rockies and across Oklahoma, bringing rain chances into southern
Kansas, although latest NAM splits the trof and brings precip
across the eastern half for late Saturday with the leading wave.
Keeping the generally dry forecast, save the far southern
counties. Highs cool off a bit on Sunday as cooler air comes south
behind the southern wave, but is quickly lifted back north as next
wave approaches. The EC splits this one, with initial wave late
Monday and second piece on Wednesday - while the GFS brings the
system through as one piece late Tuesday into Wednesday.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1132 PM CST Wed Jan 18 2017

Moisture will continue to advect northward towards the terminals
this morning. This will result in IFR and LIFR ceilings developing
at KTOP and KFOE after 10Z and will probably continue through 18Z.
Advection fog may drop visibilities down to around 1 mile betweeen
12Z and 15Z with some patchy drizzle possible. KMHK terminal may
only see MVFR to IFR ceilings developing after 10Z and lasting
through 18Z. The low IFR ceilings will redevelop across the
terminals after after sunset and last through Wednesday evening.




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