Area Forecast Discussion
Issued by NWS Topeka, KS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 46 47 48 49 50

000
FXUS63 KTOP 240449
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1149 PM CDT Wed Apr 23 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Thursday)
Issued at 326 PM CDT WED APR 23 2014

Scattered showers with isolated thunder associated with mid level
isentropic lift will continue across north central KS and along the
NE border for the next few hours. Given the afternoon mixing and low
level dry air can not rule out a brief wind gusts associated with
the isolated showers. Southerly winds have increased in response to
the tightening pressure ahead of the next system. Those winds will
diminish early this evening as the front approaches the area from NW
KS and SC NE. Thunderstorms are still expected to develop along this
boundary later this afternoon as a shortwave moves out of the
Rockies. These storms should congeal into a linear system in NW KS /
SC NE and move eastward along the NE border. An area of surface
convergence has developed just west of the forecast area near the
frontal zone, and will be the area for initiation in the next few
hours, which is supported by the latest high res models. As this
line reaches the far NW forecast area instability will be on the
order of 500 to 1000 j/kg as well as decent deep layer shear. This
is the most likely area for damaging winds and possibly quarter
sized hail around 01-03Z. Low level bulk shear appears to be around
30 kts, which could favor more upright convection and localized
enhanced downdrafts along the line. Could not rule out the
development of a mesovortex capable of a weak tornado in Republic
and Cloud counties as the line impacts the area. Forcing will most
likely be cold pool driven as the line manages to advance ahead of
the front, which the models still indicate will have a slower
progression tied to the shortwave trough. Models also indicate
instability and shear decreasing as the line progresses into
northeast KS therefore expect a weakening trend with these
particular storms. The main mid level trough lifts into KS overnight
as the front sweeps through the area therefore expected a more
widespread area of showers and thunderstorms early tomorrow morning.
This precip should persist until mid day tomorrow as the front
pushes east into MO. Winds increase tomorrow starting mid morning
behind the front out of the northwest and persist through the
afternoon. Clouds also clear out of the region from west to east
mainly during the afternoon so high temps should reach low to mid
70s.

Sanders

.LONG TERM...(Thursday Night through Wednesday)
Issued at 326 PM CDT WED APR 23 2014

Friday into Saturday will be warm with increasing moisture through
Saturday as upper ridging builds into the Plains states in advance
of a strong storm system entering the southwest CONUS. By late
Friday night, a warm friend is likely to be lifting north into
Kansas with moisture streaming northward over the boundary on a
strong low level jet focused over central Kansas. The nose of this
LLJ will veer slightly after 06Z with focused convergence in eastern
Kansas in conjunction with steepening lapse rates aloft. If the
moisture content within the jet is sufficient, stronger elevated
instability could develop with potential for elevated hail storms
early Saturday morning. This activity should push east of the area
by sunrise or shortly thereafter, and is dependent upon the eventual
strength of instability.

Saturday and Sunday pose the potential for a multi-day, possibly
significant, severe weather event with all hazards possible. While
many ingredients are coming together for severe weather across the
region, the details and intricacies of what will certainly be a very
complex storm system are not particularly clear cut, and will
certainly have an impact on the severe weather details of the event.

By Saturday afternoon, the warm front...which has continued to trend
north in recent model runs...will likely be situated across northern
Kansas with strong to extreme instability in place across the warm
sector. There are some indications that a lead short wave trough
will be crossing central Kansas by late afternoon, enhancing the mid
level wind speeds and providing ascent over the region. There has
also been a persistent suggestion amongst various model guidance
that the dry line will bulge east across north central KS in
conjunction with this wave. CINH across the entire warm sector will
be low by mid afternoon and the wave in conjunction with the dry
line, perhaps the warm front itself, and/or any low level convergent
zones in the warm sector should be sufficient to initiate
thunderstorms. These storms will likely quickly take on supercell
characteristics given the strong instability and deep shear of 35 to
50 kts. While LCL`s may be relatively high in the afternoon despite
dewpoints likely in the mid 60s, the low level shear should be
rather strong and increasing through the evening as the LCL
decreases. Thus expect potential for tornadic storms along with very
large hail and some damaging winds. The greatest uncertainty lies in
where these storms develop initially, and how they evolve through
the overnight hours as the severe threat may persist well into the
evening.

By Sunday morning, the dry line is likely to retreat well west into
western Kansas as the upper low and surface low will still be
located well west of the area. There is some indication that low
level moisture quality will be a bit lower on Sunday and shunted to
the east, but with the resurgence of south to southeast flow, this
may be more a function of a strange post-convective feedback.
Regardless, expect cooler temps due to clouds and also colder temps
aloft as the upper low approaches to allow instability to remain in
place and LCL`s fairly low. As the upper low approaches along with
a very strong mid level jet streak, expect widespread thunderstorm
development along and perhaps ahead of the dry line as it surges
back east through the afternoon. The wind profiles are much more
northerly in the mid/upper levels on Sunday, but with backed low
level winds the potential still exists for fast moving storms with
all hazards possible should they remain rooted in the warm sector.
The dry line should push all the way through the forecast area
late Sunday evening, thus ending the severe weather threat.

On Monday, the slow moving upper low will move directly overhead
with very cold mid/upper level temperatures. This will be a time
frame to watch closely for potential isolated severe weather as can
occasionally happen with this type of system despite the cooler
surface temperatures and dryer conditions. Then on Tuesday, a piece
of energy pinwheels around the back side of the main low and brings
resurgence of precipitation to the region. This will likely be in
the form of rain, but it should be noted that the ECMWF...which has
had a cold bias at times this winter...would perhaps support a rain
snow mix at times. It will be quite a bit cooler on Tuesday
regardless. Expect things to dry out by Wednesday, although the
upper trough remains in the vicinity and could support some light
precip if it is close enough. For now have gone with a dry forecast
for Wednesday.

&&

.AVIATION...(For the 06Z TAFs through 06Z Thursday Night)
Issued at 1148 PM CDT WED APR 23 2014

Several hours of limitations continue to be anticipated. Backed
off TSRA timing a bit based on latest trends. Still looks like
MVFR conditions should dominate with brief IFR possible. Improving
conditions still on track around 15Z with drier air moving in.

&&

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

$$

SHORT TERM...Sanders
LONG TERM...Barjenbruch
AVIATION...65





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