Area Forecast Discussion
Issued by NWS Topeka, KS

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
000
FXUS63 KTOP 240839
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
339 AM CDT SUN APR 24 2016

.SHORT TERM...(Today and Tonight)
Issued at 338 AM CDT SUN APR 24 2016

A closed upper low was located over southern WY per the 08Z water
vapor imagery, and a shortwave was rotating around the base of the
upper low across the CO/NM state line. A surface low pressure system
was gradually deepening over southwest SD. This has allowed
southerly winds to remain up through the morning which continues to
advect moisture from the Gulf of Mexico north. An area of elevated
showers and thunderstorms have developed just west of the forecast
area within an area of isentropic assent.

For this morning, the HRRR/RAP/NAM solutions seem to be handling
the elevated precip fairly well so far. The showers should fall
apart during the mid to late morning hours as the isentropic lift
weakens. The main concern for today remains the potential for severe
storms later in the afternoon and early evening. Models prog the
shortwave currently over the CO/NM state line to be lifting through
north central KS by the late afternoon. Models also show the dryline
setting up across north central KS with increasing low level
convergence along the boundary. Moderate instability around 2000
J/kg may develop just ahead of the dryline as mid level lapse rates
steepen to 7.5 or 8 C/km. With forecast soundings showing a mainly
unidirectional profile and deep layer shear sufficient for supercell
storms, there is the potential for splitting storms and some very
large hail. Initially low level winds remain veered to the SSW and
as a result low level shear parameters are not that impressive for
tornadoes. So it appears that any tornado risk will be dependent on
whether local effects can cause surface winds to back. With a slower
progression to the boundary, Think storm initiation could occur just
to the west of the forecast area between 2 and 5 pm. The forecast
shows increasing POPs into the evening hours anticipating a broken
line of storms to move across northern KS.

Along with the thunderstorms this afternoon and this evening, south
winds should become strong by this afternoon with gusts between 30
and 40 MPH possible. Models show a strong pressure gradient setting
up along the turnpike. Because of this, think there could be a few
hours that sustained winds near 30 MPH with gusts over 40 MPH
through the flint hills and will be issuing a wind advisory for
Morris, Wabaunsee, Lyon, Osage and Coffey counties to account for
this potential.

With the morning showers expected to fall apart by the late morning,
think there should be enough insolation along with decent mixing of
the boundary layer for temps to warm into the upper 70s or around 80
this afternoon. There should be a pretty good gradient in lows temps
as models hang the boundary up across the forecast area. With some
dryer air moving in behind the boundary, lows are forecast to fall
to around 50 across north central KS, while northeast and east
central KS stay in the warm moist air with temps around 60 by Monday
morning.

.LONG TERM...(Monday through Saturday)
Issued at 338 AM CDT SUN APR 24 2016

By Monday morning the frontal boundary is progged to be over far
east central Kansas with any residual showers and thunderstorms
dissipating at this time. There is a slight chance for storms to
redevelop in the afternoon and early evening over east central
Kansas given the weak convergence along the front, however with the
subsident air aloft associated with weak upper ridging, most areas
should remain dry. Dewpoints rise to the upper 50s/lower 60s coupled
with lighter winds around 10 mph, conditions will feel warm and
muggy with highs near 80 degrees.

On Monday evening, the upper trough axis is centered over the
southwest CONUS, with the lee trough beginning to form over eastern
Colorado. The ECMWF and NAM runs respectively continue to develop
light qpf amounts near the boundary (generally south of Interstate
70) with some isentropic lift increasing as moisture return builds
northward. The ECMWF runs have seemed overdone with the amount of
precipitation so have sided closer to the NAM with a slight chance
mention through the morning hours.

A stout EML builds northward into the area as the warm front lifts
dewpoint temps into the lower 60s in the late afternoon Tuesday.
Both the NAM and GFS are signaling higher dewpoints, temperatures
near 80 degrees, therefore the amount of sfc CAPE in the 3000-4000
J/KG range in the late afternoon seems probable. Weakening CIN as
the capping inversion erodes could trigger an isolated storm or two
within the warm sector or just ahead of the dryline across north
central Kansas by late afternoon. Sfc winds back to the southeast at
this time while a 55 kt southerly mid level jet streak enters
central Kansas. Effective bulk shear is fairly similar across the
models at 45 to 50 kts. Low level helicity from 0-1 km shear
increase to near 30 kts by 00Z as the low level jet enhances and the
main upper low pushes into the area. All guidance is pretty robust
in developing scattered convection in the 7 PM to midnight time
frame over northeast Kansas. Optimal low level and mid level shear
parameters, ample instability, and lowering LCL heights pose a
tornado threat, in addition to the large hail and damaging winds.
Only major change to the forecast in this period was to increase
pops to a definite probability after 00Z Wednesday.

As the low pressure system phases over the central plains Wednesday,
speed of the low slows lingering showers and thunderstorms through
portions of the day Wednesday. With the high moisture profiles in
the area and the slowing system, it is possible we could have
isolated flash flooding issues especially for areas near the
Nebraska border. Severe storms are not expected on Wednesday. The
system is progged to exit Wednesday evening as northerly winds and
cool advection increase on Thursday. Thursday may be the only dry
day of the week with highs in the 60s and clearing skies.

The next slow moving upper low builds over the southwest CONUS
before ejecting over the southern and central Plains Friday into
Saturday. Placement of the trough axis still varies from the GFS to
ECMWF, however both are signaling multiple rounds of thunderstorms,
with some potential for strong to severe convection on Saturday
evening.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday Night)
Issued at 1146 PM CDT SAT APR 23 2016

VFR conditions should be the rule for this forecast. Convective
trends to the west suggest a bit earlier potential for high-based
precip at MHK. Persistence and timing of convection here is
challenging both early and late in the period and no doubt
alterations will be needed in subsequent forecasts.


&&

.TOP Watches/Warnings/Advisories...
Wind Advisory from noon today to 7 PM CDT this evening for
KSZ037-038-054-055-058.

&&

$$

SHORT TERM...Wolters
LONG TERM...Bowen
AVIATION...65



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.