000
FXUS63 KTOP 070539
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1139 PM CST Thu Mar 6 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Friday)
Issued at 252 PM CST THU MAR 6 2014

Increased mixing through the boundary layer has gradually scattered
out the stratus deck noted on the visible satellite. As a result of the
lingering cloud deck, high temperatures were much cooler in the
upper 30s while ample sun peaked highs in the 40s, near 50 degrees
in east central Kansas.

For this evening, the surface shortwave trough gradually shifts
southward, maintaining southerly flow through the period. Ridging at
500 MB keeps the winds weak while a decent inversion from 950-900 MB
develops after sunset. Uncertainty as to how strong winds within
the boundary layer remain through the evening resulting in another
band of stratus and/or fog re-developing. Latest short-term guidance
shows height falls over western Kansas increase winds over the area
near 40 kts within the boundary layer off the surface. This would
keep the surface mixed with speeds around 10 mph, preventing a
widespread fog potential and indicating more low stratus instead.
North central and portions of northeast Kansas see the best chance
of this occurrence with the southerly winds advecting weak warmer
air northward. Could also see a similar scenario to this morning
with fog and stratus so have mentioned patchy fog possible after
midnight for the aforementioned areas.

On Friday, all guidance is on similar track in bringing the cold
front southeast through north central Kansas by mid afternoon, and
near the I 70 corridor by early evening. Decent warm advection ahead
of the boundary results in highs from the 50s to near 60 over east
central Kansas. Dependent on how fast the lingering stratus clears
out, highs may be too warm over north central Kansas. Have upper 40s
to low 50s for the area, however similar to this afternoon may be
cooler if the low stratus does not clear in the morning. In terms of
precip, post frontal frontogenetical forcing increases over Nebraska
during the afternoon as the upper trough passes over the central
Rockies. Have kept the slight chances for rain over far north
central Kansas as the main wave approaches. It is worth noting the
latest GFS/ECMWF hints at a stronger and smaller vort max ahead of
the main wave, developing rainfall during the late afternoon.
Meanwhile most high resolution models including the GEM indicate a
much weaker wave with the main precip occurring after 00Z.

.LONG TERM...
Issued at 252 PM CST THU MAR 6 2014

Saturday night through Sunday...Next in the series of waves
moving in off the west coast comes into the area late Friday into
Saturday morning. Cold air coming in behind this wave not nearly
as cold as the past few, and will see a slow fall toward freezing
near midnight. Precipitation type coming in associated with the
wave and front appear at this time to be rain or snow depending on
surface temperatures, although could be an outside chance for some
sleet as the cold surface air undercuts the warmer air aloft for a
brief time. Have brought a rain/snow mix across the forecast area
into Saturday morning, transitioning to light snow north as it
gets colder. Appears as though surface temperatures across the
east central counties will stay warm enough to keep type as rain
for the warmer afternoon hours and will carry a slight chance
there as well. Rain/Snow clears north to south with much of the
northern half dry by the afternoon. After lows in the middle 20s
to near 30 with the front passage Friday night, temperatures
should climb near the upper 30s low 40s expected for highs on
Saturday.

Subsidence and clearing skies Saturday night dries out precipitation
and lows fall back into the 20s, but with an upper ridge moving
overhead for Sunday along with a thermal ridge near 850MB of 10-12C,
highs should reach middle 50s east and near 60 west.

Monday through Thursday...Models bring another shortwave
through the flow with a front passing through the forecast area on
Tuesday. There remains considerable uncertainty as the ECMWF is
more amplified and develops a deep cyclone over the Ozarks while
the GFS and GEM remain weaker and more progressive with the
system. In fact the GEM and GFS show quite limited moisture with
the system keeping the better saturation north across NEB and IA.
Due to the uncertainty have continued with some 20 to 30 percent
chance POPs for Tuesday and Tuesday night. By Wednesday even the
stronger ECMWF shows the surface front well south and east of the
forecast area with northerly winds bringing in dry air. With this
in mind have removed POPs from Wednesday and Wednesday night. Am a
little concerned that Temps for Tuesday and Wednesday morning are
not cool enough based on progged thicknesses and cold air
advection. But until models come into better agreement, have only
made minor adjustments cooler from the consensus blend.

Temps on Monday and Thursday appear to be mild as good low level
warm air advection is progged by both the GFS and ECMWF. Would not
be surprised is a few locations in north central KS reach 70
degrees on Monday. The model consensus gives high in the mid 50s
for Thursday. But if 925MB temps in the lower teens pan out this
is likely to be to cool for highs Thursday.

&&

.AVIATION...(For the 06Z TAFs through 06Z Friday Night)
Issued at 1130 PM CST THU MAR 6 2014

Vfr conditions will persist at all terminals through 18z with only
high clouds expected and south winds 7-13 kts...although some
brief mvfr vsbys in hz/br are possible at the KTOP terminal.
As a cold front moves in from the north aft 22z mvfr cigs will
overspread the terminals as winds switch to the north by 00z/08
with some gusts aoa 20kts through the remainder of the fcst.

&&

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

$$

SHORT TERM...Bowen
LONG TERM...67/Wolters
AVIATION...63