Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 191718

Area Forecast Discussion
National Weather Service Topeka KS
1218 PM CDT Thu Oct 19 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 227 AM CDT Thu Oct 19 2017

Forecast for the next 24-30 hrs remains warmer, dry and
uneventful as far as sensible weather impacts are concerned.
Currently, northern PFJ remains well north of the area with a
quasi-zonal pattern in place. Closed low and amplified trough in
Canada now advancing into the Hudson Bay region with lobe of
energy extending back into the Great Lakes region. Southern extent
of the weak boundary that made its way into northern counties
near the KS/NE border has been slowly washing out. Winds have
decoupled and went calm over the area mainly along and north of
I-70. Therefore, some very patchy fog has begun to form in
valleys. Temps have dropped to the upper 40s and low 50s which
should be good for the overnight lows as well.

Into the day today, upper pattern will transition gradually in
response to a major shortwave as it digs into the Pacific Northwest
and Intermountain West regions.  This will place the Central Plains
under a broad but more highly amplified ridge.  Heights should rise
through the day as a result and with increased H85 temps into the
18C range, will push surface temps into the low 80s for much of the
area.  Winds increase as well due to a lee trough acting to tight
pressure gradient over the area with southerly to slightly
southeasterly winds in place.  Should see some winds out west near
central and north central KS push up near the 20 kt range for a
period of time in the afternoon.

.LONG TERM...(Friday through Wednesday)
Issued at 227 AM CDT Thu Oct 19 2017

Leading shortwave trof still forecast to traverse across eastern
Kansas through Friday. This will bring both breezy conditions with
sustained winds near or over 20 mph and gusts in the 30s, but also
a boost in moisture in the boundary layer, with dewpoints starting
the day in the low 50s and ending the day toward 60. Highs rise to
the upper 70s and aren`t expected to fall very far overnight as
southerly winds continue, with lows in the middle 60s. Could see
some isolated elevated storms if they can get started on the nose
of the LLJ as it lifts northward overnight.

By mid morning Saturday, next front and upper trof are making
their way across western into Central Kansas, ahead of which a
plume of 1-2K J/kg of instability develops. Also a respectable
amount of wind in the column, with 60kts or better around 10kft by
the early evening hours, and would make all modes of severe
weather possible with the front as it passes later in the
afternoon into the evening. Also with 1.5 inches of PW also in
the column, and flow out of the southwest possibly training storms
along the front for a short window of time before becoming a more
well developed squall line, will need to watch for locally heavy
rainfall as well. System pushes eastward quickly with most precip
out of the forecast area by 09z.

Behind this wave is drier and cooler weather, with Sunday highs
in the middle 60s. As surface winds turn westerly ahead of the
next boundary progged to move in for Tuesday, may get highs back
into the 70s on Monday before dropping into the lower 60s on
Tuesday. Also will get breezy north northwesterly winds with this
front, and as cold advection continues into Wednesday, current
forecast in the low 60s could be too warm.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1215 PM CDT Thu Oct 19 2017

VFR prevails at terminals with main concerns being LLWS aft 03Z at
KMHK and 04Z at KTOP/KFOE as a strong low level jet at 1000 feet
increases to near 40 kts per the latest forecast soundings from
high resolution guidance. The shallow nature of the sfc inversion
layer should preclude any fog from reforming at KTOP. Expect
gusty, south winds above 10 kts sustained aft 14Z Friday.




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