Area Forecast Discussion
Issued by NWS Topeka, KS

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938
FXUS63 KTOP 301107
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
607 AM CDT MON MAY 30 2016

...AVIATION UPDATE...

.SHORT TERM...(Today and Tonight)
Issued at 256 AM CDT MON MAY 30 2016

08Z water vapor imagery shows little chance to the overall pattern
from 24 hours ago. There is still an upper low over southern CA and
an upper trough moving across the northern Rockies leaving somewhat
zonal and relatively weak flow over KS. At the surface, high
pressure remains over the southern MS river valley with low
pressure along the lee of the Rockies. This is allowing for a moist
airmass to remain over the central plains.

A conditionally unstable airmass is expected once again this
afternoon with temps warming into the lower and mid 80s while
dewpoints remain in the mid 60s. This should be good for CAPE values
around 2000 J/kg. However 0-6 KM shear remains weak given the weak
synoptic flow over the region. So once again the weather will be
driven more by mesoscale features, and confidence of where exactly
forcing or lift for storms will come from is low. With this in mind,
have 30 to 40 percent POPs through the afternoon for possible
scattered convection. If storms are able to form, they will once
again pose a risk for hail as there looks to be plenty of
instability (although the NAM looks to be overdone with dewpoints
and hence the CAPE prog). But organized severe storms would be
limited by the weak deep layer shear. Highs this afternoon are based
on the RAP and NAM forecast soundings mixing the boundary layer to
around 800MB and yesterdays highs making the upper 80s in some
locations. If cloud cover is limited to the afternoon, the forecast
could again be a degree or two on the cool side.

Any afternoon convection should fall apart this evening with the
stabilization of the boundary layer. Although models show a
shortwave and frontal boundary moving into north central KS during
the early morning hours Tuesday. The addition of some dynamics to
the moist airmass should only increase chances for precip. And with
most guidance showing showers and thunderstorms along the frontal
boundary, the forecast has increasing POPs after 06Z from northwest
to southeast across the forecast area. There does not appear to be a
significant wind shift with any cold air advection until after 12Z
Tuesday. Therefore lows are expected to be mild as southerly low
level flow maintains a moist airmass. So have lows in the lower and
middle 60s. The one caveat would be if a decent cold pool formed
from convection with the front. This could cause lows to be several
degrees cooler. Later shifts can look at this again.

.LONG TERM...(Tuesday through Sunday)
Issued at 256 AM CDT MON MAY 30 2016

On Tuesday, the mid level shortwave trough enters the western high
plains. A cold front extending southward will push east through the
region, providing the convergence and lift for widespread convection
throughout the day. Timing from guidance still varies somewhat
similar to yesterday`s model trends. The NAM appears to be the slow
outlier and the ECMWF/GFS in similar agreement with the heaviest
rainfall being in the afternoon. Ample moisture in place with PWAT
values near 1.65 inches is about 150 percent of normal for this time
of year. Moderate rainfall is likely at times which may produce a
quick inch of rain, in addition to localized flooding and river
flooding. Mid-level winds are not particularly strong, suggesting
this boundary may move a bit slower, increasing the flood potential
especially for north central areas. While shear profiles remain weak
at 15-20 kts, ample instability with steep mid level lapse rates
will support updrafts capable of producing large hail and damaging
wind gusts through early evening.

There may be lingering showers and thunderstorms over east central
Kansas on Wednesday, but these should clear out as dry northwest
flow enters the region. Highs will fall back Wednesday and Thursday
into the 70s with lower humidity values and more comfortable
conditions. Overnight lows will generally be in the 50s under clear
skies. The upper ridge over the western CONUS begins to amplify by
late week, essentially trapping the southern plains under a closed
low and continual rainfall. Dry northwest flow centers over
northeast Kansas where Gulf moisture is cutoff by the southern
system. A mid level trough is progged to track south and east
towards the Great Lakes during this time, dropping another cold
front through for next weekend. Models are still inconsistent on
available moisture and lift as the boundary comes through so have
continued with dry pops.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
Issued at 607 AM CDT MON MAY 30 2016

Have a VFR forecast with no mention of TS for now since there is
low confidence in where afternoon convection might occur. The
patchy ground fog is expected to quickly dissipate this morning
leaving VFR conditions for the rest of the day. Models are hinting
at some possible BR after midnight tonight. The NAM has a tendency
to overdo the boundary layer moisture, so will let later shifts
see if models continue to show low level saturation tonight.

&&

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

$$

SHORT TERM...Wolters
LONG TERM...Prieto
AVIATION...Wolters



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