Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 270441
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1141 PM CDT Wed Apr 26 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Thursday)
Issued at 256 PM CDT Wed Apr 26 2017

A sharp H300 meridional trough centered over the central CONUS will
progress E/NE over the next 24 hours with a more zonal flow upper
level pattern settling in across the base of the broad upper trough
by tomorrow morning. At the surface, a N-S elongated ridge axis will
build east across eastern Kansas by tomorrow morning, with light
winds and temperatures dropping into the low 30s north to mid/upper
30s south. Low stratus/stratocumulus should erode from west to east
this evening. though there is some uncertainty as to how long it
will take the clearing to manifest itself in the east, with the
RAP/HRRR about 3-5 hours faster than the NAM. In either case it does
appear that frost will remain a concern over the north and have
continued the going frost advisory and expanded it slightly SE,
using CONSMOS as the basis for min temps tonight.

Southerly return flow sets up ahead of the next subtle shortwave
propagating through the mean longwave trough. Modest isentropic
upglide sets up ahead of the next surface low attendant to this
trough, but if the latest 12Z NAM/GFS soundings are any indication,
the deeper moisture won`t arrive until late in the afternoon and
have pushed POPs back to better align with this consensus.

.LONG TERM...(Thursday night through Wednesday)
Issued at 256 PM CDT Wed Apr 26 2017

Thursday Night through Wednesday...

The active and cool weather pattern continues through the upcoming
weekend. Rain chances will increase from south to north late
Thursday evening and Thursday night as an embedded shortwave within
the longwave trough traverses the CWA. MUcape values possibly as
high as 100-200 J/KG Thursday night/Friday morning may result in a
few rumbles of thunder along with the rain showers. As the shortwave
exits the area Friday morning, expect the best rain chances to push
northeast of area. Large scale ascent will return to the area late
Friday into Saturday as the CWA will be positioned within the right
entrance region of an upper level jet. A secondary weak embedded
shortwave will traverse the CWA once again. Therefore, have chance
to likely PoPs returning.  The main upper level system will eject
into the Southern and Central Plains throughout the day on Sunday.
As the upper low approaches the area, H850 temperatures will plummet
to near 0C Sunday morning, especially in north central KS. For that
reason I can`t rule out a few snowflakes mixing in. However, surface
temperatures will remain well above freezing (upper 30s). Elsewhere,
I expect widespread rainfall, possibly moderate to heavy at times.
As the upper level low passes just to the east of the CWA Sunday
evening/night, expect a band of moderate to heavy rainfall in
response to the deformation zone. Any lingering shower activity will
push northeast of the CWA Monday morning. With the multiple rounds
of rainfall resulting in widespread 1-3" of accumulation, the threat
of flooding and river flooding will increase throughout the weekend.

As for next week, another long wave trough will be taking shape in
the northwestern US. Primarily dry conditions are expected for much
of the week. Rain chances may increase Wednesday as the upper level
trough traverses the Plains. Temperatures will be slowly warm back
into the 60s and 70s by midweek.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1141 PM CDT Wed Apr 26 2017

Clouds just above limiting levels more stubborn to exit, but VFR
should still dominate through the bulk of this forecast. Showers
should increase quickly after 21Z, with some lean toward an
earlier onset in warm air advection scenarios such as this.
Lower ceilings and at least brief limitations in precip becoming
more likely toward 06Z Thursday, but should stay MVFR at worst.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 8 AM CDT Thursday for KSZ008>012-020>024-
034>036.

&&

$$

SHORT TERM...Skow
LONG TERM...Baerg
AVIATION...65


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