Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 212253
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
553 PM CDT Tue Apr 21 2015

.UPDATE...
Issued at 553 PM CDT TUE APR 21 2015

Surface obs have shown the weak surface convergence in the winds
has shifted further south over the last couple hours. Additionally
visible satellite shows the CU field diminishing across east
central KS. Therefore think thunderstorm chances may be
diminishing as well. Will likely make some adjustments to the POP
forecast for this evening a little closer to sunset. There is
still the potential for elevated shower activity as a weak
perturbation rotates around the base of the closed upper low.
However limited moisture and weak forcing overall suggests that
any precip may only amount to some sprinkles. In general, there
does not appear to be any major concern weather wise this evening
once humidity levels begin rising.

&&

.SHORT TERM...(This Evening through Wednesday)
Issued at 333 PM CDT TUE APR 21 2015

Upper level low remains over the Great Lakes region inching its way
eastward tonight and tomorrow.  Showers are already popping up just
south of our forecast area and in southern MO where a line of
convergent winds is located.  The threat for storms this afternoon
and evening is limited to a line south of northern Lyon county to Franklin
county. where the best moisture/instability lies.  Effective bulk
shear of 35-40 KTS (mainly unidirectional) is seen just nosing into
our area in the south along with a narrow band of MLCAPE of 500
J/kg.  This instability, along with current dry air at the surface
will allow any storms that do develop to produce strong winds and
hail.  A small disturbance moves down the western flank of the upper
level low into Iowa this evening helping to push a cold front
through our region. With this frontal passage, winds will veer north
and high pressure will begin to nose in ending chances for
additional storm development.  Temperatures fall behind the front
with lows reaching the mid 30s in our most northern counties.  Have
taken frost out of the grids this evening due to lacking low level
moisture and higher winds, even though skies will be mostly clear.

Tomorrow, high pressure moves just east of the area and allows for
clearer skies and northerly winds.  Highs will be much cooler than
today topping out in the upper 50s/low 60s. Dry conditions remain
throughout the day.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 333 PM CDT TUE APR 21 2015

Dry conditions are expected Wednesday night through Thursday as
surface high pressure slides just east of the area. Being on the
western edge of the surface high, surface winds will shift to the
southeast by Thursday. However, the combination of northwesterly
flow aloft and increasing cloud cover through the day from the next
approaching system will limit high temperatures to slightly below
the seasonal normals in the low/mid 60s.

Models show a mid-level trough lifting from the Baja Peninsula area
toward the Four Corners region Thursday into Thursday night with a
few weak embedded shortwaves possible along the lee-side of the
trough. These shortwaves should move into western Kansas Thursday
night and advance into north central Kansas by Friday morning, so
have increased PoPs over that area during the overnight period.
Models are in pretty decent agreement with the timing and tracking
of the mid-level trough over the region late Friday afternoon
through early Saturday morning. At the surface, the associated warm
front may lift as far north as into east central Kansas Friday night
before the low exits to the east Saturday morning. With the
increased model consistency, have likely PoPs in for the entire
forecast area Friday and Friday night. With the warm front in the
vicinity, model soundings show that there is the potential for
storms to become surface-based for a few hours late afternoon into
early evening. Models show MUCAPE values of 500-1000 J/kg with
strong 0-6km bulk shear (55-65 KTS) extending northward into east
central Kansas late afternoon/early evening so cannot rule out the
potential for some strong to severe storms.  The better potential
looks to be just south of the area, but it will be dependent upon
where the warm front sets up.  With overcast skies and no real
cold-air advection with the passing system, expect temperatures to
stay near-normal Friday and Saturday with highs in the 60s and lows
in the 40s to low 50s. Expect precipitation to exit from west to
east on Saturday with dry conditions Saturday night.

There is model uncertainty with whether or not there will be the
potential for showers on Sunday as models show another mid-level
trough developing over the Rockies but are inconsistent with how
quickly it advances eastward into the area. Have slight to chance
PoPs in for Sunday night, but the GFS is much faster with the
eastward progression of this trough while the ECMWF/GEM have the
trough slowly traversing eastward into early next week. While models
are inconsistent with the mid-level pattern for early next week,
have gone with a dry forecast Monday through Tuesday as surface high
pressure should build into the region with highs in the mid 60s to
low 70s.

&&

.AVIATION...(For the 00Z TAFs through 00Z Wednesday Evening)
Issued at 553 PM CDT TUE APR 21 2015

Limited moisture is expected to keep VFR conditions prevailing
through Wednesday. There could be a few sprinkles this evening
with CIGS around 10 KFT, but should not amount to much of an
impact for the terminals.

&&

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

&&

$$

UPDATE...Wolters
SHORT TERM...Heller
LONG TERM...Hennecke
AVIATION...Wolters






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