Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 230453
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
1153 PM CDT SUN MAY 22 2016

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Monday)
Issued at 334 PM CDT SUN MAY 22 2016

20Z water vapor imagery shows a shortwave ridge from the Red River
valley into MN and WI with the upper trough over the western states.
A closed low was noted north of MT and another shortwave seen moving
across northern UT into WY. At the surface, a trough of low pressure
along the lee of the Rockies and ridging over the central MS river
valley have combined to funnel low level moisture north with mid 60s
dewpoints now in central KS.

Objective analysis suggests there remains some weak convective
inhibition across north central KS while the best low level
convergence remains over the TX panhandle and western KS. Since
there isn`t much indication of a shortwave or other forcing imminent
across central KS, think the afternoon and evening hours are likely
to remain dry. And really the biggest unknown is what will actually
force convection late tonight and Monday as there remains no real
obvious synoptic scale forcing from the models. At best there may
be inferred a subtle wave in the 500MB pattern by Monday morning, but
this is far from a clear forcing mechanism. Nevertheless most if not
all guidance is showing convection developing through the pre dawn
hours and continuing through the morning. Think that it should not
take much forcing for storm development given the potential
instability and the models lake of inhibition to convection. Maybe
all it will take is a weak MCV from the convection out west. Have
trended POPs down slightly given the lack of an obvious forcing
mechanism and to better collaborate with neighboring offices, but do
not feel comfortable lowering POPs much more since models have shown
a consistent signal for precip Through the day Monday.

Regarding severe potential, 0-6KM shear is progged to improve to
between 30 and 40 KT by Monday afternoon and a weak surface trough
is expected to set up just to the west of the forecast area. So
given the moist airmass and improving shear profile, there remains
the potential for severe storms. Thinking is that there may be
elevated storms through the morning and then the better chances for
severe storms could be late in the afternoon with potential
development along the surface trough axis if the airmass is able to
recover. Low level veering of winds with height favor a reasonable
curved hodograph with low LCL heights so there is some potential for
a tornado if storms redevelop. Large hail will likely be the most
likely hazard with any storms.

Given the uncertainty in how convection evolves over the next 24
hours, think that there could be some reasonable insolation
tomorrow. Because of this have adjusted highs up into the upper 70s
and around 80. Lows tonight should be mild due to continued
southerly flow and moisture advection. The forecast has lows in the
lower and middle 60s.

.LONG TERM...(Monday Night through Sunday)
Issued at 334 PM CDT SUN MAY 22 2016

Thunderstorm potential remains the main challenge through the
extended periods. Southwest flow aloft with southerly low level flow
continues to dominate much of these periods. There is also little if
any suggestion of strong capping building over the warm and moist
low levels, keeping unstable conditions intact. Forcing for
convection is the primary issue, and there are not many obvious
features for when chances will considerable greater or lesser. Weak
front should be laying up to the northwest of the area Monday night
into Tuesday, though precip could be ongoing Monday evening with
some moisture convergence allowing for continuation into these
periods. Models vary with push of dryline east across Kansas Tuesday
but tend to keep it well west. The 850-925mb layer also stays rather
moist all day and may keep destabilization in check. There is a
fairly consistent suggestion of a weak mid-level wave passing
through Tuesday night for somewhat greater storm potential. Drier
air moves in aloft behind this wave Wednesday with dryline possibly
having more luck moving this way, but capping potential with the
drier air loft does keep precip chances/coverage somewhat more
limited Wednesday and Wednesday night. The main upper trough finally
rotates into the area Thursday into Friday night, with timing
differences and the potential for multiple larger-scale waves in
this trough bringing questions on when the best storm potential will
be. Precip chances still look to linger into the weekend with
instability remaining and southwest flow/moisture returning.

Severe weather potential for much of these periods remains, largely
based on moderate to high instability as shear parameters are not
very impressive. Winds do look to increase aloft with the main trof
in the late week and could present the strongest overall potential
depending on timing of the waves. Heavy rainfall and flooding
chances continue with some chance of multiple rounds of convection,
though exactly where and when remains well uncertain.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
Issued at 1152 PM CDT SUN MAY 22 2016

Challenging forecast with timing of ceilings and convection this
period.  With the low level jet moving east over the area tonight,
model soundings have been hinting at LLWS at all terminals. Believe
this may be more on the marginal side, but have kept persistence
with previous forecasts to leave in this potential.  Overnight,
storms are expected to move in from the west impacting terminals
between 13-14Z.  Along with storms, ceilings will also deteriorate
to MVFR at the same time.  From here, lingering storms could be seen
through early afternoon before a brief break is seen in
precipitation.  Exact timing is still being worked out, but a
clearing from roughly 22-23Z to 01-02Z is possible before storms
move through again tomorrow night.

&&

.TOP Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Wolters
LONG TERM...65
AVIATION...Heller



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