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 022021
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
321 PM CDT Tue Jun 2 2015

.SHORT TERM...(This Evening through Wednesday)
Issued at 227 PM CDT TUE JUN 2 2015

Skies have began to scatter out this afternoon from west to east,
allowing temperatures to reach the lower 80s in the west to upper
70s more east where clouds still persist. With more scattered
cloud cover tonight and persistent southeasterly winds, expect
lows to drop into the mid- 60s. The main feature of the night will
be an MCS developing across Nebraska as short wave energy moves
across the upper level northern ridge axis.

The general consensus is that this system will begin to move into
our northern counties just before 12Z and and track SE across the
NE portion of the CWA, exiting by the afternoon. With the best
instability focused west of our area, this complex is expected to
weaken as it moves into NE Kansas. Have started bringing slight
chances into our area by 08Z with chances focused mostly to the
north and northeast by late morning. It should be noted that some
of the hi-res models had this complex fizzling out before reaching
NE Kansas. How this system plays out during the overnight hours
will have an impact on weather during the afternoon tomorrow.

One solution is that if the MCS does transverse part of the area,
residual boundaries left over from the morning convection could
initiate afternoon thunderstorms. With afternoon dewpoints in the
upper-60s, upwards of 1500 J/kg of CAPE, and shear between 25-30
kts, any storms that do develop would be likely organized
multicells. If the MCS does not create any boundaries for
afternoon storms, the atmosphere would continue to destabilize
ahead of an MCS forming to the north on Wednesday afternoon. Have
kept PoP chances mainly limited to the northern half of the CWA
tomorrow afternoon.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 227 PM CDT TUE JUN 2 2015

Many of the details of the mid and long term forecast period will
be largely driven by mesoscale and storm scale processes which may
not be well resolved until the actual day of the forecast. With
that in mind, there are some strong signals for the weather in
several periods of the forecast so will try to present a most
likely scenario while remembering that significant changes are
possible.

By Wednesday evening, expect the airmass across the forecast area
to be moderately to strongly unstable with minimal inhibition in
northern Kansas. Even into the overnight hours, expect at least
moderate MUCAPE to persist with lifted parcel levels within the
lowest 2000 feet AGL and minimal elevated inhibition...easily
lifted by any decent cold pool. Additionally, an east- west
oriented frontal boundary will likely be in place across southern
Nebraska late Wednesday. All of this is important because it
points to a likelihood for ongoing thunderstorms in Iowa and
southern Nebraska to congeal and develop toward the south and even
southwest into the CAPE axis and LLJ during the evening and
overnight. Furthermore, while parts of this MCS may tend to
forward propagate with damaging wind potential, there are also
indications that western edges of the MCS will effectively back
build into the low level jet. If this occurs, it would be a
favorable set up for heavy rain and flooding. Several models agree
in setting up a heavy rain area across the forecast area with a
main focus near and north of I-70. Wednesday night into Thursday
morning. This activity would likely wane with the weakening LLJ on
Thursday morning.

Outflow boundaries from these storms are likely to significantly
impact the Thursday and Thursday night forecast. Wherever the
outflow boundary / effective front sets up on Thursday afternoon
is likely to become a focus for strong thunderstorms given
likelihood for the return of strong instability near and south of
the boundary and convergence along it. There are indications that
0-6 km wind shear could be a bit stronger late Thursday,
especially with any storms interacting with the outflow boundary.
This suggests at least a window for better storm organization
before generally merging into another MCS. Current indications are
that this development would occur near or just north of the NE/KS
border before spreading south and east. However, do not want to
get too deep into the details of possible evolution through the
day on Thursday as there are also hints by the NAM/NMM/ARW of a
mid day MCS moving along the NE/KS border which, should it
develop, would complicate the afternoon scenario. The bottom line
is that another round (or rounds?) of storms is likely across
parts of the area (especially northern KS) with potential for
hail, damaging winds, and very heavy rainfall.

For Friday and beyond, the forecast picture remains rather
unclear. The upper level flow pattern remains at least similar
across the region with moderate flow and occasional short wave
trough passages aloft, interacting with a surface front and/or
outflow boundaries. There are several more chances for
thunderstorms through the long term period but much will depend on
the day-to-day variations in mesoscale features. The presence of
quality boundary layer moisture, decent lapse rates, and
associated instability will allow at least the potential for
periods of strong storms and heavy rain, but the details are fuzzy
at best.

Temperatures through the period will also be dependent upon any
frontal/outflow locations and cloud cover...but generally expect
highs in the 80s with humid conditions, and could flirt with 90
where the afternoon sun shines through (especially in central KS
Thurs and Fri).

&&

.AVIATION...(For the 18Z TAFs through 18Z Wednesday Afternoon)
Issued at 1215 PM CDT TUE JUN 2 2015

Clouds are expected to stay VFR throughout the period varying
between BKN and SCT.  Tomorrow morning after 12Z, there is a slight
possibility that weakening storms will move into the area.
Confidence is low on timing and if these storms make it south enough
to reach terminals, so have not included it in this TAF package.


&&

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

$$

SHORT TERM...Heller/Sanders
LONG TERM...Barjenbruch
AVIATION...Heller





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