Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 250448
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1148 PM CDT Mon Apr 24 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tuesday)
Issued at 337 PM CDT Mon Apr 24 2017

Windy conditions across northeast Kansas this afternoon. Lee
troughing over the CO Rockies has induced a strong pressure gradient
across the entire state, resulting in strong south winds at 20 to 35
mph sustained. Gusts in the CWA have peaked at 45 mph today. These
winds are expected to calm around 10 to 15 mph this evening,
allowing the wind advisory in effect to expire at 3 PM. As the sfc
trough lifts northeast overnight, the warm front is forecast to push
north through the CWA. With the exception of the HRRR, guidance
lifts warm, moist air over the boundary, producing enough lift for
the possibility of scattered showers. Mid level instability is
fairly weak (less than 200 J/KG of MUCAPE) so perhaps an isolated
thunderstorm. Kept the slight chances in place as there is still an
ample amount of dry air in forecast soundings and the window of
favorable lift is brief.

Tuesday is a bit tricky forecast wise as the mid level shortwave
trough shifts a bit further east into the western high plains. In
turn a 500 mb jet streak rounds the southern periphery, entering
southern KS by late afternoon. Towards the sfc, the cold front is
positioned from southwest to northeast at this time over north
central Kansas. Ample sfc instability develops across east central
KS with sfc CAPE near 2000 J/KG. Meanwhile, bulk shear values
increase in upwards of 50 kts by 21Z. Limiting factor for any
convection in the afternoon with the front is the strong inhibition
in place. All guidance holds convection at bay until perhaps the
early evening. Have mentioned chances for thunderstorms by 21Z, with
the higher probabilities shifting further southeast thereafter. Main
hazards with any afternoon convection will be large hail and
damaging winds. Highs were lowered a few degrees based on the
thicker cloud cover and cold front moving through. Currently have
mid 60s in north central KS, to the mid 70s in the Emporia and
Garnett areas.

.LONG TERM...(Tuesday night through Monday)
Issued at 337 PM CDT Mon Apr 24 2017

For the mid range forecast into Tuesday late afternoon evening time
frame, a broad upper level trough with its main axis will be
situated over the intermountain west into the Desert Southwest
region. Several impulses of energy will be ejecting out ahead of
this upper level system. A shortwave is progged to pull out of the
Southern and Central Rockies and develop a lee side low which
will make its way into northeastern Kansas by Tuesday night
drawing down a cold front trailing to the southwest of the low.
During this time do expect a favorable dynamically forced pattern
to develop deep layer shear profile along and ahead of the front
in excess of 40- 50kts parallel to the frontal system. Problem may
be with the quality of moisture along and ahead of the front.
GFS, EC keep weak instability in place, but the NAM does suggest
higher instability will develop before the cap breaks. Given that
there will be a strong cold front developing, still expecting
areas along and southeast of I-35 corridor to see the potential
for some severe storms at least early in the evening. The main
threats continue to be severe hail with some strong outflow winds.
Hold onto post frontal showers into Wednesday morning over mainly
eastern portions of the CWA.

Cooler temperatures expected behind the front on Wednesday with
patch frost possible over night into Thursday morning mainly over
northwestern portions of the CWA likely from points northwest of a
line from Abilene to Manhattan to Marysville areas.

For Friday through the weekend time frame, much uncertainty still
exists, but periods of rain and thunderstorms will continue to be
off and on as lead waves work out ahead of the main trough still
positioned to the west of the area.  Isentropic lift increases into
friday morning with the best chance of showers and perhaps elevated
thunderstorms mainly in the morning time frame into the early
afternoon.  Best severe chances for the day appear to remain south
of the area as the warm front is stretched across northern OK into
the Ozark region.  Saturday and Sunday will also see off and on
periods of showers and isolated storms work through the area before
the main trough finally moves through the region into Monday
morning.  In general, there are slight differences in the guidance,
but the general trend points to more southerly tracks for the
surface features which should help keep both heavier precip and
severe weather off to the south and east of northeastern KS and
vicinity.  In general, expecting high temps to range from the 50s to
lower 60s with lows mid to upper 30s and 40s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1148 PM CDT Mon Apr 24 2017

LLWS is still forecast at all terminals until 13Z.  Have continued
the mention of SHRA at TOP/FOE where soundings look the most
favorable for showers tonight associated with a warm frontal
boundary.  MVFR ceilings are expected to move into northeast Kansas
tomorrow although confidence in timing is still low.  Have included
these lowered ceilings at MHK at 22Z, and TOP/FOE after 00Z.

&&

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

$$

SHORT TERM...Prieto
LONG TERM...Drake
AVIATION...Heller



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