Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 122017

Area Forecast Discussion
National Weather Service Topeka KS
317 PM CDT Tue Sep 12 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 316 PM CDT Tue Sep 12 2017

Remnants of Irma were located over the Lower Mississippi Valley this
afternoon. Main effect for eastern Kansas has been high cirrus clouds
and north to northeasterly winds which have kept temperatures cooler
across the area. Temperatures early this afternoon were in the upper
70s to lower 80s. Tonight through Wednesday Irma will move slowly
northeast into southern Indiana. An upper level low will move off
the eastern Pacific and into southern California tonight while the
upper level ridge builds back into the Plains. Tonight temperatures
are expected to cool into the mid to upper 50s. Forecast soundings
show dry air in the lower boundary layer so left out patchy fog.
Highs on Wednesday will be warmer with the return of southerly winds
as low pressure tough deepens in the lee of the Rockies and the
surface high moves eastward. Expect highs to warm to near 90 in
north central and central Kansas with readings in the mid 80s in
east central Kansas.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 316 PM CDT Tue Sep 12 2017

By Wednesday night, the remnants of Irma will be situated near the
Ohio River Valley with a broad SW to NE oriented mid-level ridge
stretching across the central U.S.  Both the ridge and Irma remnants
will shift further east through the end of the week as a strong mid-
level trough develops and dives southward toward the Four Corners
region.  As Irma remnants shift into the New England region, a broad
area of surface high pressure will settle in across the eastern U.S.
 The advancing trough will push surface low pressure just east of
the Rockies, with the surface low deepening by late week.  With the
CWA wedged between these surface features, expect the pressure
gradient to gradually increase each day ahead of the frontal passage
late Saturday afternoon through Saturday night.  As a result, have
increased the winds/wind gusts during the Thu.-Sat. time period.
These breezy southerly winds also will support warm-air advection,
with high temperatures rising into the upper 80s to mid 90s Thu.
through Sat.  While models show the potential for some embedded
waves to develop along the lee-side of the trough late week, most of
the scattered precipitation chances look to stay northwest of the
CWA.  However, there is a slight chance for precipitation from a
nearby shortwave to clip north central KS early Friday morning, with
another chance across northeast KS Saturday morning.  In both cases
there looks to be a decent amount of dry air still in the low/mid-
levels, so it may be challenging to get precipitation from these
weak embedded shortwaves. Precipitation chances increase by Saturday
night as models show post-frontal showers and thunderstorms
developing across much of the forecast area.  This cold front looks
to be south of the CWA Sunday morning, but models show this front
potentially lifting northward over the area as a warm front into
early next week. However, there are notable timing differences with
this warm front movement, resulting in high uncertainty with
precipitation chances into early next week.  It is worth noting that
the GFS is continuing to pick up on a tropical system near the Baja
peninsula on Sunday, and then showing this system getting ingested
into the mid-level flow and bringing precipitation chances to the
area on Tuesday.  The ECMWF/Canadian models however keep this
tropical system in the Pacific and, thus, have only isolated
precipitation chances by Tuesday.  Temperatures behind the front
will be slightly cooler with highs in the 80s and lows back in the
low/mid 60s.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1221 PM CDT Tue Sep 12 2017

VFR conditions are expected through the period. Forecast soundings
do not show saturation near the surface so have left any mention
of fog out of the forecast.




LONG TERM...Hennecke
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