Area Forecast Discussion
Issued by NWS Topeka, KS

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660
FXUS63 KTOP 251149
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
649 AM CDT Wed Apr 25 2018

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 308 AM CDT Wed Apr 25 2018

Early this morning, water vapor imagery showed increasing cloud
cover spreading eastward across the CWA as a mid-level low and
shortwave trough were diving southward into northern KS.  Areas of
isentropic lift just ahead of this wave were supporting widespread
rain showers across central and south central KS. As of 08z, some
shallow low-level dry air was still present over far eastern KS, but
expect the advancing shortwave and increasing isentropic lift to
support light rain finally reaching the ground by around sunrise.
Models show the mid-level closed low within the shortwave trough to
track southward over central and eastern KS today, with an
increasing vorticity maximum developing along the southern edge of
the closed low as it tracks across central to southeast KS.  As a
result, this ample forcing combined with sufficient moisture will
allow for widespread rain showers across the entire CWA today, and
have continued to trend a bit higher with QPF amounts.  Latest model
guidance shows approximately 0.5" to 0.75" of rain possible across
much of northeast and east central KS, with around or less than 0.5"
over north central KS.  With models showing little to no instability
present, do not anticipate any thunderstorms. By tonight, the mid-
level low will progress southeast of the area, with surface high
pressure gradually advancing into the area today through tonight
behind this system. As a result, rain showers should exit from west
to east mid-afternoon through early evening.

As surface high pressure shifts further eastward across the outlook
area today, model soundings show conditions gradually drying out
aloft to aid in the diminishing precipitation. However, some short-
range model guidance also is suggesting that enough dry air will
advect into north central KS to scatter cloud cover out enough for a
brief late-afternoon warm-up in temperatures. With early morning
temperatures currently ranging from the mid 40s to low/mid 50s from
west to east over the CWA, the overcast skies will hinder much of
the daytime heating. But if the cloud cover scatters out enough by
late this afternoon, short-range guidance suggests temperatures
could quickly and briefly rise into the mid 50s.  This temperature
forecast will likely be the biggest forecast challenge for today, so
will need to closely monitor conditions this afternoon. Cloud cover
should diminish across the entire outlook area tonight, with decent
radiational cooling supporting low temperatures tonight plunging
into the mid/upper 30s, which could potentially result in some
patchy frost development by Thursday morning.

.LONG TERM...(Thursday through Tuesday)
Issued at 308 AM CDT Wed Apr 25 2018

Precipitation chances with the weaker wave Thursday are waning
with much weaker forcing and more limited moisture than today`s
system. Could see some sprinkles at times, but at this point will
convey little opportunity for wetting rains and remove any precip
mention. Cloud cover diminishes in the evening with a weak
modified Canadian ridge moving in. Winds will likely be light for
much of the overnight hours and temperatures could drop into the
mid 30s in the northwest. Will mention some frost here but a
widespread frost looks unlikely.

Modest winds, clear skies, and moderating temps dominate the
Friday through Saturday night periods under northwest flow.
Subsequent periods bring fairly steady breezy/windy south to
southwest winds as the upper trough off the west coast comes
inland. Have high confidence in warmer temperatures as well, but
much remains to be seen in how the wave behaves with the ECMWF
much more progressive than the GFS and GEFS. Both operational runs
suggest at least some capping to deal with and only a slow
increase in moisture quality. Will precip chances quite limited
for these periods dry but a the potential for a more robust and
widespread convective event will need to be monitored.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 631 AM CDT Wed Apr 25 2018

For the 12z TAFs, widespread light rain showers are expected
through much of today, with MVFR cigs/vis gradually overspreading
the TAF sites this morning. These low-end MVFR cigs may drop to
IFR conditions at times late this morning into early this
afternoon before conditions gradually start to dry out late
afternoon through early this evening.


&&

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

$$

SHORT TERM...Hennecke
LONG TERM...65
AVIATION...Hennecke



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