Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 032330
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
630 PM CDT Sun May 3 2015

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Monday)
Issued at 328 PM CDT SUN MAY 3 2015

Zonal but weak flow aloft continues over the Central Plains
between northern and southern branches with a few weak waves
moving through. Appears moderate mid-level isentropic lift
combined with one of these waves to spark overnight convection,
with another wave keeping isolated showers going in eastern Kansas
into the early afternoon. High- based nature of this activity
keeping much precip from what there is in check however. Water
vapor imagery suggesting a stronger wave rotating northeast out of
eastern New Mexico with convection firing ahead of it into
southeastern Colorado. Cold front was from northwestern Kansas
into northeastern Nebraska early this afternoon with a few cumulus
along it in central Nebraska. Dewpoints have dropped to around 40F
in southwest Kansas with thermal ridge ahead of front pushing temp
at CNK to near record levels.

Precipitation chances remain the main challenge through Monday
afternoon. Recent HRRR and RAP runs continue to attempt to produce
convection along the front, but have been too fast to do so. With
low levels rather dry to the west, the main player with convection
to the west and south could be via the New Mexico wave, or other
convective-induced waves from eastern Colorado. Isentropic upglide
looks less impressive than this morning but some is again present
and could be enough to continue or even produce convection into east
central Kansas late this evening and into much of Monday. Other
prime scenario for convection seems to be with eventual convection
generated in eastern Nebraska sinking south into northeast Kansas on
decent 850mb moisture convergence as a moderate low level jet veers
with time. This could linger well into Monday morning, and with the
earlier possibilities as well, have kept chance PoPs going into the
morning Monday, with lesser confidence in precip in the northwest
counties nearer the drier low level air. Details in precip activity
Monday afternoon will be largely impacted by the earlier activity,
but models increase low level moisture further, though NAM likely a
bit aggressive again, with CAPE possibly near 2000 J/kg ahead of any
outflow or front/effective front. Shear values again look meager to
support much severe weather but some potential remains. Have kept
highs cooler than today with more cloud/precip/moisture anticipated.

.LONG TERM...(Monday Night through Sunday)
Issued at 328 PM CDT SUN MAY 3 2015

Models continue to show an active pattern for Monday night through
Sunday as they dig another closed low into the southwestern U.S. by
the end of the work week. This causes mid level flow to remain
from the southwest while gulf moisture continues advecting north.
So there looks to be plenty of moisture available with occasional
forcing mechanisms passing overhead such that there is a chance
for precip in every period of the forecast. The one period with
the lowest chance for precip remain Tuesday. There seems to be
agreement among the models that shortwave ridge will propagate
over eastern KS with some relatively dryer air moving in.
Therefore have a dry forecast for northeast and east central
KS. North central KS may be close enough to shortwave energy
lifting north through the high plains that have kept a small
chance for the western counties for Tuesday.

The best chance for showers and thunderstorms appears to be late
Tuesday night and Wednesday as a well defined shortwave is progged
to lift across northeast KS. There are some minor differences in
timing of the vort max lifting out. Nevertheless with little or no
inhibition to convection expect showers and thunderstorms to
overspread the area and have increased POPs into the 70 to 80
percent range.

Wednesday night through Saturday does not look like it will be
constant precip, but the pattern makes it difficult to say when
chances are better than not. With occasional low amplitude waves
within the southwest flow and a moist airmass remaining in place,
the forecast has a chance for precip each day. There are even some
signs of a weak frontal boundary moving into the forecast on
Friday which may help focus moisture and provide some lift.
Otherwise think chances could be on the increase for Saturday
night and Sunday as the upper low begins to lift out of the
southern Rockies. Because the GFS is a little further north and
doesn`t have as much shortwave energy rotating through the
southern plains, have kept POPs in the chance category for now.

There should not be any big swings in temps through the period due
to the persistent pattern. If anything there may be a slight cool
down for Wednesday expecting cloud cover and precip to limit
heating. Otherwise temps should be seasonable with lows around 60
and highs in the mid 70s to near 80

&&

.AVIATION...(For the 00Z TAFs through 00Z Monday Evening)
Issued at 625 PM CDT SUN MAY 3 2015

There is a chance for scattered showers and storms tomorrow
morning around sunrise as an outflow passes near the area. Trying to
pin down the location and timing of this possible outflow is very
difficult therefore did not add any mention at this point. Like
the past few days the cloud bases appear to be high and will most
likely not affect the flight conditions.

&&

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

$$

SHORT TERM...65
LONG TERM...Wolters
AVIATION...Sanders





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