Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 171805
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
105 PM CDT Fri Apr 17 2015

...Update to aviation forecast discussion...

.SHORT TERM...(This Afternoon through Saturday)
Issued at 714 AM CDT FRI APR 17 2015

Isolated showers and embedded thunderstorms continue to move slowly
to the north across our northern counties this morning, while a
broader area of showers and storms extends across much of western
into central Kansas at this hour.  Seasonably nice night with lows
and dewpoints across the area in the 50s.

Anticipate showers and storms to be slowly on the increase through
the morning then into the afternoon hours as the series of systems
moves out of the southwest and across Eastern Kansas through
the late afternoon. By early afternoon models suggest a freely
convective atmosphere as the second wave comes in, and will
therefore keep higher pops for the afternoon as a result. Another
round is forecast late this evening and overnight with another
impulse rotating around the upper low and across eastern Kansas,
and given additional lift from closer upper wave and a boost from
the low level jet, think overnight is probably when the highest
QPF will move through. Severe chances today and tonight are
highlighted for Slight in the far eastern counties, where shear is
a little better for hail to be the primary threat, although an
isolated tornado can`t be ruled out.

.LONG TERM...(Saturday Night through Thursday)
Issued at 714 AM CDT FRI APR 17 2015

On Saturday morning convection from the overnight hours will still
be lingering across portions of eastern KS as the main mid/upper low
finally begins to track over the plains. Do not expect much in the
way of organized storms as the instability will be limited, and the
deep layer shear still remains rather low. During the day Saturday
the models forecast an increase in the cape ranging from 1500 to
2500 j/kg. Although, any morning convection or shower activity could
have an impact on this recovery. As the main mid/upper low
progresses eastward it will gradually weaken into an open wave. In
the process it will still provide enough shear for severe storms
Saturday afternoon and evening given the instability increases. The
better chances for this to occur should be in central KS closer to
the better shear and forcing. Most of the models indicate little to
no CIN during this time frame so any localized focus for lift could
generate storms. Similar to Thursday the focus for lift could be
anything from diffluence aloft with localized low level convergence
to a remnant MCV or established cold pool. High temperatures
Saturday should generally be in the low 70s.

Saturday night and into Sunday the main shortwave tracks over
eastern KS bringing a cold through the forecast area Sunday. A
sharp pressure gradient behind the front supports northwest
surface winds increasing to 15 to 20 mph with gusts as high as 30
mph. Ahead of the front instability looks to increase across east
central KS as the wave passes overhead. The deep layer shear
around 30 to 40 kts may support some organized convection along
the front Sunday afternoon and evening. Behind this wave temps
cool into the 30s Monday and Tuesday morning. NW flow aloft is
forecast to become more zonal mid week as a shortwave moves over
the SW US and Rockies. The GFS develops showers and storms in the
area as early as Tuesday, but may be slightly aggressive with the
moisture return. The GFS is also aggressive with the instability
and shear as it advertises multiple rounds or strong to severe
storms. Confidence in that scenario is low at this point.

&&

.AVIATION...(For the 18Z TAFs through 18Z Saturday Afternoon)
Issued at 105 PM CDT FRI APR 17 2015

VFR conditions are expected through the period outside of
convection. Expect isolated tsra this afternoon and evening then a
better chance of more widespread shra and isolated tsra after 08Z
through the end of the period. MVFR vsbys are expected along with
brief reductions of cigs into the mvfr category. Winds remain east
southeast through the period generally less than 10 kts.

&&

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

$$

SHORT TERM...67
LONG TERM...Sanders
AVIATION...53






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