Area Forecast Discussion
Issued by NWS Topeka, KS

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013
FXUS63 KTOP 301138
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
638 AM CDT Sun Apr 30 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 251 AM CDT Sun Apr 30 2017

Strong mid level low pressure is currently located over the TX
panhandle and is forecasted to lift northeastward directly over
the area tonight. At the surface there was a low pressure was
located in far northeast OK, and it is forecasted to drift into
central KS slightly deepening in the process as the main low lifts
out. Some mid level drier air has moved over the area, which
explains the change over to drizzle. That moisture should start to
fill in over the next few hours as the main low approaches from
the southwest. A majority of the guidance shows showers developing
and spreading across the area later this morning. Steeper mid
level lapse rates could allow the cape to increase enough to
support some thunderstorms as well. The synoptic dry slot then
moves over the area this afternoon. Showers will continue to
linger through the evening with steep lapse rates near the surface
and no inhibition, but there should not be enough instability for
thunder. In north central KS strong frontogenesis, moisture, and
large scale lift will support the trowal on the northwest side of
the main low. Current radar shows that there is significant
banding taking place across western KS and central NE. This is
most likely caused by some CI and CSI, which makes it difficult to
nail down where a band may set up. If the CSI becomes weaker than
a more widespread area of precipitation should take place within
in the trowal. Therefore there is a better chance of a more steady
rain in north central KS during the morning and early afternoon.
Soundings are suggesting that RH in the dendritic ice layer will
not be sufficient enough for ice in the cloud unless a band can
form, but overall it appears limited. Therefore the chances for
snow are very low so have removed from the forecast. An additional
half to one inch of rain is expected across the area by sunrise
tomorrow morning with the highest amounts in north central KS
within the trowal.

.LONG TERM...(Monday through Saturday)
Issued at 251 AM CDT Sun Apr 30 2017

Relatively quiet weather is on tap for the upcoming work week
with a chance for rain midweek, followed by drier and seasonal
weather. The stacked low responsible for our wet and dreary
weekend will be over SW Iowa/NW Missouri on Monday morning. Monday
will start cool and cloudy with some isolated showers in far NE
Kansas in the early morning given the proximity of the low.
Despite the rapid clearing Monday midday depicted by the GFS/NAM,
the continued cyclonic flow over the region (and cutoff nature of
the H500 low) would lend credence to the cloud cover possibly
hanging on longer than the models depict. Any clearing, however,
would exacerbate wind gusts which will already be pushing 30 kts
given the tight pressure gradient behind the departing low. These
winds will decrease throughout the afternoon as the low pull
further NE and ridging begins to build along the Front Range.

Tuesday will see the surface ridge slide through with moderating
temperatures. However, with a col developing just north of the
area, we will see little to no return flow before our midweek H500
wave arrives from the NW. The surface-H850 warm front looks to
barely reach far SE Kansas, and model soundings likewise show
little to no instability over NE Kansas as this wave moves
through. Thus kept thunder out of the forecast for the duration of
the event. The upper level pattern amplifies once again as a
potent omega block builds across the western CONUS by late in the
week and parks itself over the central CONUS for the weekend--
spelling a longer period of dry and seasonal conditions.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 633 AM CDT Sun Apr 30 2017

A line of storms will move through the taf sites at the beginning
of the period. Then isolated to scattered showers will develop
this afternoon and evening. During this time the visibility and
ceilings should improve although remaining MVFR. Behind the
departing system low IFR stratus is forecasted to move back into
the taf sites. There are a few models that improve to VFR late
this evening.

&&

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

$$

SHORT TERM...Sanders
LONG TERM...Skow
AVIATION...Sanders



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