Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 221716
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1216 PM CDT Sun Apr 22 2018

...AVIATION UPDATE...

.SHORT TERM...(Today and tonight)
Issued at 357 AM CDT Sun Apr 22 2018

As of 08Z Sunday morning an upper low was centered across south-
central KS/northeast OK. The best divergence aloft and associated
vertical motion exists just east of the upper low. This corresponds
quite nicely with radar and observations with scattered rain showers
predominately south of a line from Abilene to Ottawa. At the surface
an inverted trough extended from Omaha, NE to western LA.

For the rest of today, the upper low will continue pivoting eastward
into AR. While doing so, the axis of vertical motion and mid level
moisture will shift southeast of the CWA. As a result expect rain
shower activity to end from northwest to southeast through the
morning and afternoon hours. Additional QPF amounts will remain
confined to areas along and southeast of I-35 where up to two-tenths
is possible. In regards to temperatures, cooler temperatures
expected across the southern counties with warmer temperatures
across the northern counties. HRRR/RAP/NAM forecast soundings for
areas north of I-70 suggest BL mixing heights between H85 and H8.
H85 temperatures ranging from 2-3C would result in mid 60s for areas
north of I-70. Thicker cloud cover and more shallow BL mixing
heights south of I-70 should keep temperatures in the upper 50s to
near 60. A decent pressure gradient on the backside of the inverted
trough -- on the order of 6 mb across the CWA -- will setup this
afternoon, yielding northeasterly winds from 10-20 MPH. As the upper
low and surface trough continue their progression away from the CWA
tonight, expect decreasing cloud cover and winds. Low temperatures
look to range from the low to middle 40s.

.LONG TERM...(Monday through Saturday)
Issued at 357 AM CDT Sun Apr 22 2018

Dry conditions are expected for the start of the work week as
surface high pressure advances into the area behind the exiting
surface low.  Some lingering mid-level cloud cover may still be
present over eastern KS on Monday, which may have an impact on
temperatures depending upon how quickly these clouds scatter out. At
this time, models show cloud cover diminishing enough to support
afternoon high temperatures reaching into the upper 60s/low 70s.

Further west, models show a shortwave trough moving into the
Northern Rockies on Monday and deepening as it tracks into the
Central Plains Tuesday into Wednesday.  This advancing trough will
result in northwesterly flow aloft setting up over the central U.S.,
with models showing this flow persisting through the end of the week
as a second shortwave tracks into the area by late week.  There are
still model discrepancies with this first shortwave as the GFS is
more progressive (compared to the ECMWF/NAM/Canadian) and quickly
pushes light precipitation across the CWA Tuesday into Tuesday
evening. Because of the orientation of the shortwave trough in the
slower solutions, they actually shift the better moisture and
forcing just south of the CWA, which would result in limited
precipitation chances over the CWA.  Due to these uncertainties,
have only slight to low-end chances PoPs in the forecast for
Tuesday/Tuesday night. Slightly cooler conditions are expected by
Wednesday behind this first wave with highs in the low/mid 60s.
Models show the second embedded shortwave trough diving from Canada
into the Northern Plains by Thursday, however there are notable
differences in the timing/tracking of this trough and any associated
precipitation across the Central Plains. The more progressive
GFS/Canadian model solutions keep conditions dry across the CWA as
the better moisture and lift look to stay just north and east of the
area.  In contrast, the slower ECMWF extends the trough axis (and
associated moisture and lift) further south into the central U.S.,
resulting in better chances for precipitation across the CWA.
Northwesterly flow behind this second shortwave trough should keep
Friday high temperatures in the low/mid 60s with temperatures
warming to near 70 degrees by the weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1216 PM CDT Sun Apr 22 2018

Moisture rotating around the northwest side of the low pressure
system is expected to keep clouds and some light rain or sprinkles
over east central KS into the evening. However relatively dry low
levels should keep VFR conditions prevailing at the terminals.
There may be a brief drop to MVFR as seen over the last couple
hours at FOE. But this looks to be transient with little
predictability. Therefore will maintain a VFR forecast expecting
that to be the most dominate condition. The overall trend should
be for improving CIGS through the night as the upper low drifts to
the east and south.

&&

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

$$

SHORT TERM...Baerg
LONG TERM...Hennecke
AVIATION...Wolters



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