Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 132309 RRA
AFDTOP

Area Forecast Discussion...DELAYED
National Weather Service Topeka KS
609 PM CDT Sun Aug 13 2017

...AVIATION UPDATE...

.SHORT TERM...(This evening through Monday)
Issued at 253 PM CDT Sun Aug 13 2017

Broad troughing aloft this afternoon centered over the plains region
with the axis centered over eastern ND. Sfc high influencing the
area continues to shift eastward shifting and increasing southerly
winds around 10 mph. Lee troughing builds over the western high
plains with the frontal boundary centered over northwest NE. These
areas to our west and north are once again the focus for scattered
convection this afternoon with the forecast uncertainty if these
storms hold together to impact north central areas in the late
evening. Southerly low level flow increases somewhat tonight,
advecting low level moisture into the region. Enhanced isentropic
lift around 305K interacting with the warm front over Nebraska may
allow a few scattered storms to reach far northern KS midnight
onward. The elevated nature of the convection however may be
difficult to overcome the drier air aloft so have only mentioned
slight chances.

Monday morning starts off overcast, with the insulating cloud cover
dropping overnight lows to the middle 60s. The front is fairly
consistent between short term guidance being over central NE during
the day. Differences lie however in areas of embedded upper lift
along and south of the front, generating scattered showers and
thunderstorms in the afternoon. Seeing the NAM and 4 KM WRF
solutions developing activity in the afternoon and given the
instability and minimal inhibition in place, maintained slight
chances for thunderstorms in the afternoon over far northern KS.
Much of the area becomes mostly sunny with forecast highs warming to
the upper 80s as temps at h850 increase to near 20C amid the deeper
mixing.

.LONG TERM...(Monday night through Sunday)
Issued at 253 PM CDT Sun Aug 13 2017

The biggest takeaways from the extended period are continued
shower and thunderstorm chances along with high temperatures
remaining in the 80s! By Monday evening, a low amplitude mid level
ridge will continue inching towards the central Plains. A surface
cold front will attempt to enter the northern areas of the CWA,
although the vast majority of guidance keeps the front just north
of the KS/NE border. All models have a shortwave traversing the
central Plains during the early morning hours of Tuesday. However,
subtle difference exist amongst placement. GFS/Canadian keep the
bulk of precipitation north of the area, while the NAM/EC/ARW/NMM
bring thunderstorms across northern KS. As we transition into
Tuesday, a surface low will deepen across western Kansas as a mid
level trough across the western US deepens as well. The
aforementioned cold front will retreat northward as a warm front
into northern NE. The mid level trough will push across the
Rockies during the day on Tuesday, pushing the front southward
during the evening and overnight hours. Expect widespread
thunderstorm development across the area late Tuesday
night/Wednesday morning. Modest mid level lapse rates near 6 C/KM
will yield MUcape values approaching 2000 J/KG. Effective shear
values are expected to approach 30 knots as well, therefore
organized convection is possible with large hail and damaging
winds the primary hazards. Heavy rainfall and flash flooding will
once again be possible as warm cloud depths are expected to be
near 15k feet with Pwat values near 2 inches. Behind the cold
front on Wednesday, drier weather is expected. The central Plains
will reside in zonal flow through the remainder of the work week.
Weak perturbations within the flow could spawn a few showers and
storms Thursday/Thursday night. A stronger system looks to
approach the area next weekend, continuing the wet and cool
pattern.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday)
Issued at 608 PM CDT Sun Aug 13 2017

Models continue to show the low level moisture axis over the
region through Monday. With forecast soundings continue to support
at least MVFR CIGS, only change to the forecast has been to move
up the timing when MVFR CIGS should develop. There is some
potential for fog as well. But think reasonable mixing within the
boundary layer will favor stratus over fog. As for precip chances,
models show mixed signals for and against storms moving south from
NEB. Will keep forecast dry for now and monitor trends.

&&

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

$$

SHORT TERM...Prieto
LONG TERM...Baerg
AVIATION...Wolters



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