Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 241144
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
644 AM CDT Fri Mar 24 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 338 AM CDT Fri Mar 24 2017

An upper level low was located across extreme southeast CO early this
morning with a trough axis extending south-southwest across south
central NM. A 100 KT H5 jet max was lifting northward into southwest
KS ahead of the upper low. The upper low is forecasted by all the
numerical models to track east-southeast across north central and
northeast OK through Tonight.

Today, as the upper low tracks east-southeast into northern OK a
surface low will deepen across northwest OK with a surface trough
extending northeast across central KS by Noon. Stronger ascent ahead
of the upper low, along with isentropic lift within the zone of
stronger moisture advection across extreme eastern KS and western
MO, will cause scattered to numerous elevated thunderstorms to
develop across the extreme eastern counties of the CWA during the
late morning and early afternoon hours. These elevated storms will
shift east into MO during the early to mid afternoon hours as a
700mb dry slot advects northward to the east of the upper low across
the CWA. We may even see breaks in the cloud cover especially across
western and central counties. The NAM and WRF solutions show about
600 to 1200 J/KG of ML CAPE developing within the warm sector
across the CWA during the mid and late afternoon hours. A cold front
extending from the the surface low over northwest OK, northeast
across central KS will begin to push east and cause scattered
thunderstorms to develop. The better 0-6 KM shear will be shifting
east of the eastern counties of  CWA  and into MO through the
afternoon, especially as mid and upper level winds begin to back on
the north side of the upper low across northern OK. The low-level
vertical shear looks rather weak as well. The best chance for a few
low top supercells to develop may be across the western half of the
CWA during the afternoon hours. Any thunderstorm that can track
along this surface front without moving north of the boundary may
ingest baroclincally generated vorticity along the boundary in a
stream-wise fashion to be tilted and stretched within the storm`s
updraft. This could intensify the storms enough for large hail or
perhaps a stronger thunderstorm downdraft. I cannot rule out an
isolated weak tornado but overall the low-level vertical windshear
looks weak and would not be the type of environment conducive for
tornadic supercells. Eventually a line of storms will develop along
the front as it pushes southeast across northeast and east central
KS into the early evening hours. A weak dryline may also push
northeast across northern OK into south central and southeast KS.
Thunderstorms may develop along this weak dryline and push northeast
across the southeast counties of the CWA. But the 0-1KM SRH only
increase to around 100 J/KG by 00Z SAT but the 0-6 KM effective
shear is bit higher in our southeast counties with 30 to 50 kts,
thus any storms that move into the southeast counties may have a
better chance of becoming strong to severe with the primary hazard
being large hail with any storm that maintains a mid level rotation
or damaging wind gusts. The 850mb winds will veer to southwest by 3Z
SAT and the deeper moisture will shift east of the CWA, thus any
strong to severe thunderstorms along the front will weaken through
the mid evening hours.

Highs Today will reach the lower to mid 70s. If the cloud cover
holds across the eastern counties of the CWA then highs may be
slightly cooler. If the western counties see a bit more insolation
then highs may reach the upper 70s to around 80.

Through the night wrap around moisture will keep the showers
continuing through the night behind the front. The better rain
chances will be across the eastern half of the CWA through the
night. The upper low will slowly move east across northeast OK by
12Z. Lows will be the 40s.

.LONG TERM...(Saturday through Thursday)
Issued at 338 AM CDT Fri Mar 24 2017

Saturday brings slowly drying conditions as the upper system slowly
pushes northeast. Subsidence should steadily end precip chances from
west to east, though temperatures remain tricky with modest cold
air advection being offset by some potential for insolation in the
afternoon. Kept diurnal ranges in the 10-15F range. Next upper
system in the split flow enters the area late Sunday with lapse
rates aloft increasing ahead of it. Could see some elevated
thunderstorms Sunday night though instability looks too weak for any
severe weather. Given GFS Ensemble agreement, have gone on the
higher side with precip chances Sunday afternoon, though best
chances look to be during the night, ending by midday Monday. Monday
night and Tuesday still looking dry with next system in similar
regime coming into the region late in the mid week. Models showing
more spread with timing and track of this one, but likely PoPs still
seem in order in southern areas for much of Wednesday and Thursday.
Could have some thunder again, but potential currently looks even
lower than the previous system. Temperatures look mainly near to
slightly above normal through the end of next week in split flow.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 640 AM CDT Fri Mar 24 2017

The 12Z forecast period remains in flux weather wise. Early, all
terminals will hold on to southerly gusty winds up into the mid
20s. Due to well mixed low levels, have left out WS mention. Lower
confidence in TS this afternoon has led to keeping only VCTS with
best chances for KTOP/KFOE. Into the evening showers wrap around
the low system moving through with most guidance hinting at lower
CIGS but still some increase in winds, so VIS probably not to
degraded with stratus moving in. Some indications remain that
stratus could dip into IFR category, but too low confidence to
go below MVFR at this time.

&&

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

$$

SHORT TERM...Gargan
LONG TERM...65
AVIATION...Drake



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