Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 211720
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1220 PM CDT Thu Sep 21 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 255 AM CDT Thu Sep 21 2017

Storms continue to back build into northwestern MO early this
morning, with the potential for a few storms to make it into very
northeast Kansas this morning mainly before sunrise.  For today,
northeastern Kansas remains under the influence of mid-level
southwest flow as the main upper level, positively tilted trough,
digs into the western US. This will act to increase the pressure
gradient over the area today allowing for southerly winds to be near
20 mph sustained, with gusts up to 30-35 mph.  Hot temperatures will
be seen with highs ranging from the upper 80s to mid-90s across the
area as the front lifts north by mid-morning.  The windy conditions
continue into the evening, especially in central and north central
Kansas keeping low temperatures nearly 20 degrees warmer than
climatology, in the mid and lower 70s.  Some models do want to
develop convection later Thursday evening most likely associated
with the LLJ, but overall consensus is for a dry forecast period
(minus the storm potential early this morning).

.LONG TERM...(Friday through Wednesday)
Issued at 255 AM CDT Thu Sep 21 2017

This weekend a longwave trough will deepen over the western US. This
will set up a front across the plains that stretches from ND to CO.
Ahead of the boundary strong southerly flow will remain established
across the area. This will keep temperatures warm and dew points
relatively high. Heat indices on Friday afternoon will be in the mid
to upper 90s. Conditions will also be breezy with wind gusts as high
as 30 mph. Most locations appear to remain dry until Sunday night
when the main shortwave trough begins to lift out of the central
Rockies. The front will slowly progress eastward on Monday and
Tuesday causing widespread showers and storms. The models are now
showing additional shortwave energy entering the longwave trough
from the west and possibly cutting off in the southwest US. The
northern stream flow and ejecting wave should still push the front
through the entire forecast area by Tuesday night. More seasonable
temperatures return as high pressure builds southward behind the
front. There are some model discrepancies as to the evolution of the
cut off low pressure across the southwest.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1219 PM CDT Thu Sep 21 2017

Cu field is once again developing in the warm humid boundary layer
this afternoon and should continue through the daylight hours.
Expecting LLWS overnight as the inversion forms, then gets breezy
again in the morning as mixing resumes. Still south winds
overnight but lose gustiness this evening.

&&

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

$$

SHORT TERM...Heller
LONG TERM...Sanders
AVIATION...67



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