Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 190107

807 PM CDT Sat Apr 18 2015


Issued at 805 PM CDT SAT APR 18 2015

Storms currently in a north to south line from Marysville to
Parkerville are slowly moving north.  Outflow from this line aiding
in storm development, but the environment storms are moving into has
become increasingly unfavorable throughout the day due to previous
morning to mid-afternoon convection.  CAPE values across the area
range from 500-750 J/kg as indicated in the 00Z Topeka sounding with
647 J/kg, and shear in north is almost nonexistent.  Low and
mid-level lapse rates also do not support the rapid updraft
development needed for severe storms.  Interestingly, effective bulk
shear of 35 kts is nosing its way into our southern CWA ahead of the
line.  Stronger reflectivities with storms moving into Morris county
are seen due to this increased deep shear.  Expect storms to stay
below severe criteria tonight due to the lack of modest instability
and shear, however, if stronger storms were to develop they would be
in the very most southern counties.


.SHORT TERM...(This Evening through Sunday)
Issued at 321 PM CDT SAT APR 18 2015

20Z regional radar loop shows an MCV moving north northeast across
western Miami county. Broad area of showers continued over northeast
and east central Kansas into northwest Missouri aided by upper level
diffluence and the above mentioned MCV. Expect the precipitation to
gradually work its was northeast out of the CWA early this evening.
Further west across central and south central Kansas thunderstorms
where thunderstorms developed along a outflow boundary from this
mornings convection and were moving north across central Kansas.
Expect the activity to spread east into the areas west of a
Belleville to Salina line through 22Z. Have increased precipitation
chances there. SBCAPE of 1000-2000 J/kg and 0-6km shear of 30 to
40kts so expect a few storms to produce hail and some strong gusty
winds. Further east subsidence behind the MCV should keep most areas
dry for late afternoon and part of the evening hours. Short term
models move the area of showers and thunderstorms northeast later
this evening and overnight across much of the area, given the mean
850mb-300mb flow from the south expect storms to continue to move
north through early evening, but slowly build eastward. Have
increased precipitation chances west of a Council Grove to Manhattan
to Marysville line through the evening then spread east through the
night. The upper low is expected to start moving east into the
Plains and phase with a northern stream shortwave trough which was
moving across Saskatchewan into Montana at late afternoon, and phase
late tonight and then progress eastward on Sunday. A cold front will
move into north central Kansas by early Sunday morning with the from
moving southeast across the remainder of northeast and east central
Kansas by early afternoon Sunday. Expect an area of showers and
embedded thunderstorms to be ongoing then precipitation chances
diminishing after the frontal passage. With the upper trough still
to move through and steep lapse rates expect an area of showers post
frontal for a few hours. Lows tonight mainly in the 50s. Highs
Sunday will range from the lower to upper 60s.

.LONG TERM...(Sunday Night through Saturday)
Issued at 321 PM CDT SAT APR 18 2015

By 00 UTC on Monday, all of the 12 UTC models were showing that the
cutoff low will be opening up as an open wave as it phases with the
northern stream upper trough. As the upper trough axis passes, the
precipitation will exit the area late Sunday afternoon or evening as
subsidence and cold advection takes over.  Soundings are showing
strong winds below 850 mb and a high percentage of the wind should
get transported to the surface given the steep low-level lapse rates
and subsidence.  This should result in wind gusts above 30 mph
during the evening.

Northwest upper flow on the southwest side of a large upper low will
be the rule early next week over the central plains. A well mixed
boundary layer with deep mixing is expected on Monday so expect
breezy and cool conditions.  A weak surface ridge will be over
northeast Kansas Tuesday morning with lows in the mid to upper 30s
with some frost possible.

A split flow pattern is in place for midweek and beyond with the
deep upper low over the great lakes region and an active southern
stream across the southern plains.  The 12z GFS/ECMWF both push
Canadian high pressure into the central plains late in the week with
the bulk of the cold air to the northeast of northeast Kansas.
Shortwave energy should be moving through the southern plains
providing some precipitation chances from time to time during the
extended.  Northeast Kansas should be in the cool air thus any
shower and thunderstorm activity should be elevated in nature.  At
this point, the timing and strength of the shortwave energy and the
depth of the cool air over northeast Kansas is uncertain. Will
forecast some precipitation chances and below normal temperatures
during the extended.


.AVIATION...(For the 00Z TAFs through 00Z Sunday Evening)
Issued at 632 PM CDT SAT APR 18 2015

Convection over north central Kansas is lifting northward and has
pushed an outflow boundary that may impact KMHK between 00Z and
01Z with a shift to westerly winds. Otherwise differences between
short term models has lead to somewhat lower confidence on timing
of convection for tonight. MVFR conditions may impact KMHK as
early as 02Z while KTOP/KFOE may not reach MVFR until 04Z. Through
the overnight period, more widespread showers and thunder will
gradually lower closer to IFR near sunrise. Improving conditions
anticipated by mid morning with activity shifting eastward and a
strong cold front approaching from the northwest, expected to
impact sites in the afternoon. Gusts over 20 kts are likely
through 00Z. Another round of showers with isolated thunder and
MVFR conditions are also likely along and behind the front.




LONG TERM...Johnson
AVIATION...Bowen is the U.S. government's official web portal to all federal, state and local government web resources and services.