Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 132319
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
619 PM CDT Sun Apr 13 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Monday)
Issued at 326 PM CDT SUN APR 13 2014

20Z water vapor imagery shows a shortwave lifting across eastern
KS as another wave digs south towards the four corners region.
This initial wave has sparked a line of thunderstorms to form
along a cold front that is surging southeast through the forecast
area. Much of the short range guidance is pointing towards the
convection to be east of the forecast area by 7 pm, which fits in
with current radar trends. Therefore have lowered pops for this
evening and removed mention of thunder. There is a band of snow
across NEB. The HRRR and RAP suggest the tail end of this precip
may move east along the NEB state line through the evening as the
first shortwave lifts northeast. Precip accumulations with this
should be fairly light as the better mid level frontogenesis stays
mainly to the north. However as the second shortwave comes out of
the Rockies late tonight and through the morning Monday, this
frontogenetical band redevelops south and most guidance is
pointing at a band of snow moving over east central KS. The
frontogenesis looks strong enough for a decent band of snow and
possible accumulations around an inch through late morning Monday.
This will be highly dependent on the intensity of the snowfall
however since ground temps remain relatively warm. If the band
produces higher snowfall rates, some parts of east central KS
could see accumulations a little higher.

In between the convection this afternoon and the frontogenetical
precip overnight, think there will be a lull in the precip and
have tapered pops down this evening. Models show saturation in the
lower levels hinting at the possibility for some drizzle which
could be freezing depending on surface temps. However the
conditions for drizzle do not look to persist for long as some mid
level drying occurs before the next shortwave moves in and
saturates the column. Overall am not to excited about the
prospects for drizzle but can`t rule out the chance so will
include a mention in the forecast.

Lows tonight should fall into the lower 30s due to strong cold air
advection behind the front. Temps in central NEB have already
fallen into the upper 20s suggesting my lows may not be cool
enough. In any case, freezing temps look likely tonight and will
issue as freeze warning as we have entered the locally defined
growing season. Cold air advection persists through the morning
Monday so highs are not expected to warm much. However think
clouds will eventually clear out by the afternoon so some
insolation may help to warm highs into the 40s.

.LONG TERM...(Monday Night through Sunday)
Issued at 326 PM CDT SUN APR 13 2014

Monday night through Wednesday looks dry as the central plains see
dry northwest flow develop ahead of the next wave expected to dig
into the plains by Thursday. The medium range models seem to be in
some agreement with timing of the next wave therefore have trended
pops up for Thursday and Thursday night. There does not appear to
be much instability with this system as warm moist are is slow to
return. However there does appear to be another shot of cold air
moving in Thursday night which could cause a brief change over to
snow before the precip comes to an end. Therefore have maintained
a mention of rain and snow for Thursday night.

While less certain, there are indications of a southern stream
wave trying to phase with a northern stream wave over the area
Sunday. Confidence is low since the GFS struggles to advect
moisture this far north. However with the ECMWF breaking out some
QPF, will insert some low (20-30%) POPs Saturday night and Sunday.

A hard freeze looks likely Tuesday morning as skies clear out and
surface ridging moves over the region. Therefore have continued
with lows in the lower to middle 20s and will post a freeze
warning through Tuesday morning too. Southerly flow returns for
Wednesday helping to moderate the cool temps before the next cold
front moves in Thursday and knocks temps back down into the 40s
and 50s for Thursday and Friday. With a split flow for the weekend
and the northern stream remaining north, temps should moderate
into the 60s for the weekend.

&&

.AVIATION...(For the 00Z TAFs through 00Z Monday Evening)
Issued at 613 PM CDT SUN APR 13 2014

MVFR conditions should persist through for the remainder of
tonight. A band of snow will develop over south central KS early
tomorrow morning and move northeast towards the taf sites. Have
adjusted the timing slightly from previous forecast. There could
be a brief period of moderate to heavy snow that would cause IFR
vis but confidence for that occurring is low at this point.
Conditions should improve to VFR after the snow band exits the
taf sites.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
FREEZE WARNING from Midnight tonight to 10 AM CDT Monday FOR
KSZ008>012-020>024-026-034>040-054>056-058-059.

FREEZE WARNING from 11 PM Monday to 9 AM CDT Tuesday FOR
KSZ008>012-020>024-026-034>040-054>056-058-059.

WIND ADVISORY until 9 PM CDT this evening FOR KSZ008>010-020-021-
034.

&&

$$

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





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