Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 200449
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1149 PM CDT Sat Apr 19 2014

.SHORT TERM...(This Evening through Sunday)
Issued at 357 PM CDT SAT APR 19 2014

An upper level trough across the desert southwest will slowly lift
northeast into the southern and central plains before phasing with
an upper level trough within the polar jet moving east across the
northern plains into the upper Midwest.

Thunderstorms will probably develop later this afternoon across
western KS and north of a surface cold front across northwest KS and
central NE. These showers and thunderstorms will move northeast and
may expand southward into north central KS later this evening and
through the night. The cold front across northwest KS will become
stationary or move northward across southwest NE while the surface
dryline retreats towards the CO border.

As the stronger ascent ahead of the upper level trough spreads
across the state of KS Sunday afternoon, more numerous showers and
thunderstorms should develop across the western CWA and then spread
northeast across the eastern counties of the CWA during the late
afternoon hours. The upper level trough will be filling as it lifts
northeast across the central and southern plains. SBCAPE is forecast
to be about 500 to 1200 J/KG across the CWA Sunday afternoon, though
the effective 0-6KM shear will be less than 20 KTS, and the vertical
wind shear will be weakening through the afternoon. Areas that may
destabilize could experience pulse storms with small hail and gusty
winds Sunday afternoon.

Southerly winds Tonight will keep overnight lows mild, with lows
only dropping down into the mid 50s to lower 60s. Southerly winds
with potentially some breaks in the cloud cover will help
temperatures to warm into the mid to upper 70s.

.LONG TERM...(Sunday Night through Saturday)
Issued at 357 PM CDT SAT APR 19 2014

Precipitation chances increase Sunday night into Monday as the
mid-level low currently over the southwestern U.S. lifts
northeastward into the Central Plains and merges with the northern
stream of the mid-level flow. This approaching mid-level wave
combined with a surface cold front that will track eastward across
the forecast area overnight through late Monday morning will
provide enough forcing to support the development of showers and
thunderstorms. However, with the loss of daytime heating, expect
these storms to become elevated during the evening hours. Soundings
show modest lapse rates in place through the overnight hours,
however 0-6km bulk shear continues to look extremely weak at less
than 20kts, so do not anticipate severe weather. However, model
soundings show a deep saturation layer present through much of the
overnight hours into Monday morning with PWAT values reaching
upwards of 1.5 inches, so could receive some decent rainfall amounts
from this system. These showers and thunderstorms will gradually
exit the area from west to east on Monday with dry conditions by
Monday night. Overcast skies and southerly winds Sunday night will
limit radiational cooling and help to keep lows mild in the
mid/upper 50s. Skies will clear through the day on Monday behind the
frontal passage but winds will become breezy out of the north.
However, there doesn`t look to be much in the way of cold air behind
this system, so have Monday highs ranging from the upper 60s to mid
70s. A brief dry period is expected Monday night through Tuesday as
a mid-level ridge moves into the central U.S., along with surface
high pressure.

Focus then shifts to the mid-level trough that begins to develop
across the Pacific Northwest on Tuesday and progresses eastward into
the Northern and Central Plains from mid to late week. Models are
continuing to highlight the potential for a few embedded shortwaves
to develop along the southeastern edge of the trough, with enough
mid-level lift to potentially support the development of some
scattered showers and thunderstorms. However, model soundings show
that if anything were able to develop it would be very high based as
conditions remain quite dry up to at least 700mb. While confidence
remains low with this activity, have kept slight to low-end chance
PoPs in for Tuesday night into Wednesday due to the consistency
amongst the models. High temperatures for Wednesday should soar
several degrees above the seasonal normals as strong southerly flow
helps to advect warmer air into the region. Have continued to trend
upward with temperatures, with highs in the mid 70s to low 80s.

Wednesday night into Thursday, models show the large mid-level
trough swiftly tracking across the Rockies into the Northern and
Central Plains, which will help to push an area of surface low
pressure into the area along with an associated cold front. The 12z
GFS has started to trend more toward the consistently progressive
ECMWF solution, however there are still minor differences with the
exact timing of the frontal passage. The ECMWF has the cold front
tracking east of the area by mid morning while the GFS has it moving
through by early afternoon. Models show showers and thunderstorms
developing generally along and behind the cold front and in the
vicinity of the dryline, but with the progressive nature of this
system precipitation may quickly track across the area through the
day, drying out from west to east during the afternoon hours. On
Thursday, while there looks to be decent 0-6km shear (40-50kts),
MUCAPE may be limited to less than 700 J/kg. Will continue to
fine-tune the details with future forecast updates, but have gone
ahead and gone dry for Thursday night with the trending faster
solutions. Expect slightly cooler conditions behind this system for
the end of the week into the weekend with high temperatures dropping
into the mid 60s to low 70s. Another weak wave may clip the region
on Saturday, but have only slight chance PoPs in due to model
uncertainty this far out in the forecast.

&&

.AVIATION...(For the 18Z TAFs through 18Z Sunday Afternoon)
Issued at 1148 PM CDT SAT APR 19 2014

VFR conditions should continue to dominate. Will go ahead with
LLWS mention given radar and higher resolution model data. Still
not highly confident in TSRA timing and coverage, but enough
uptick in activity expected to warrant VCTS during peak heating,
with likely slow movement and high water content leading to IFR
visibilities in any storm at the terminals.

&&

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

$$

SHORT TERM...Gargan
LONG TERM...Hennecke
AVIATION...Gargan





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