Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 190437
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1137 PM CDT Sat Apr 18 2015

...Update to aviation forecast discussion...

.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 06Z TAFs through 06Z Sunday Night)
Issued at 1127 PM CDT SAT APR 18 2015

Sct showers continue to develop ahead of the main cluster of
showers of isolated thunder between KMHK and KTOP/KFOE. Initial
MVFR conditions that accompanied a westerly wind shift improve to
VFR until the main cluster arrives near 08Z at KTOP/KFOE.
Conditions may temporarily fall to MVFR within the heavier rain bands
however trends show cigs improving to VFR as activity weakens and
becomes more scattered. With the cloud deck lifting to near 10 kft
behind the showers, a saturated sfc with light winds aft 09Z are
trending towards patchy fog developing at sites. Will need to
monitor since multiple factors may contribute to visibility being
lower in the IFR category. May see a brief period of VFR
conditions by mid morning before another round of showers and
isolated thunder forms along and ahead of a cold front, falling
back to MVFR in the afternoon. Northwest winds become gusty in
excess of 25 kts late afternoon through the evening.

&&

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

$$

SHORT TERM...53
LONG TERM...Johnson
AVIATION...Bowen






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