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000
FXUS63 KTOP 021750
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1150 AM CST Mon Mar 2 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 325 AM CST MON MAR 2 2015

Mid level heights rising this morning over northeast Kansas as
water vapor imagery highlights the progressive upper trough
dropping southward over the Pacific Northwest. This wave will
allow the persistent and broad west coast trough to lift northeast
across the region later this evening.

In the meantime for today, scattered mid level clouds increase
through the afternoon as the surface high pushes eastward with lee
troughing developing at 850 MB. This will induce the higher winds
from the south over central Kansas at around 15 mph sustained, while
further east, southeast winds around 10 mph are more common. Weak
warm advection commences aloft by late afternoon as much warmer
temps and moisture lifts northward. While highs warm into the upper
30s today, temperatures thereafter may drop briefly to the lower and
middle 30s before increasing to near 40 degrees by Tuesday morning
as strong southerly winds advect a warm and moist air mass into the
CWA. Expect wind speeds to increase as well between 15 and 20 mph
after midnight with gusts near 30 mph.

In terms of precip, track of the upper trough axis focuses the
synoptic lift further north and east, placing most of the area (with
exception of east central areas) in the dry slot. However, adequate
strong low level lift with the warm air advection should develop
scattered light precip for much of the area, primarily after 6 PM
through sunrise. Uncertainty in forecast lies in the strength of
the warm air advection and subsequent timing which brings the
possibility of freezing precip, especially in the 00Z to 06Z time
frame where boundary layer is able to cool near freezing before
winds increase and temps warm. Dry air in the 850-600MB layer also
plays a factor in drizzle forming as well. Currently, NAM is the
cooler yet persistent outlier while the GFS is in between the warmer
ECMWF, GEM, and initial runs of the RAP. Forecast focused a bit on
the warmer side for areas south of Interstate 70 where a mix of
drizzle, rain, and perhaps brief freezing rain will be possible
through midnight. With the freezing precip being brief, would not
expect any accumulation. Further north where warmer air arrives
closer to midnight, drizzle or freezing drizzle transitions to a
light freezing rain and sleet mix. Accumulations are very light to
nonexistent here as well. After midnight all precip should switch to
light rain or drizzle with best chances east of highway 75.

.LONG TERM...(Tuesday through Sunday)
Issued at 325 AM CST MON MAR 2 2015

For Tuesday, models continue to show the mid level dry slot
working its way through the forecast area while the better forcing
associated with a shortwave lifts northeast towards the great
lakes. Therefore think chances for precip remain rather limited.
Have some chance POPs across eastern KS through the morning for
any light rain or drizzle that may be ongoing. However as the day
progresses, POPs should diminish as the dry slot moves in. The
main uncertainty in the forecast is timing the frontal passage and
its affects on temps. The GFS has remained the most aggressive in
bringing the front through during the late morning and early
afternoon, but it is only slightly faster than the model
consensus. Therefore am fairly confident that daytime highs will
occur early in the day with temps falling through the afternoon.

Tuesday night and Wednesday morning may still see some light snow
as models bring some mid level saturation across the area with a
band of frontogenesis. Since the GFS is faster moving the front
through, it is also pushing the frontogenesis south of the area by
12Z Wednesday. However the new ECMWF has trended in hanging this
weak forcing across east central KS through part of the morning
similar to the NAM`s solution. With this in mind, have held onto
some slight chance POPs through Wednesday morning. By the
afternoon, think the increasing dry air with the surface ridge
will cause precip chances to diminish. At this time, any snowfall
looks to be light with a dusting to a couple tenths accumulation
since the models prog the frontogenesis to be rather modest and the
ageostrophic response to the forcing is not very strong.

The main upper trough axis is expected to finally pass east of the
area Wednesday night with northwest flow redeveloping. Since there
is not much in the way of moisture advection within this pattern
the forecast is dry from Wednesday afternoon through the weekend.
However there are some signs from the ECMWF late in the period
that a shortwave may move through the flow and bring a chance for
precip. Confidence in this is pretty low so will make a note of it
and watch later runs to see if there is any continuity. Wednesday
and Wednesday night look to be the coldest temperature wise due to
the arctic high pressure system passing through. Tweaked lows
Thursday morning down a couple degrees thinking that a favorable
set up for radiational cooling could develop as the center of the
surface ridge moves into northeast KS. By Friday temps should
moderate and become a little more closer to normal as models only
suggest a couple modified pacific fronts pass through the area.
With 925 MB temps between +5C and +10C, think highs in the lower
50s is reasonable.

&&

.AVIATION...(For the 18Z TAFs through 18Z Tuesday Afternoon)
Issued at 1149 AM CST MON MAR 2 2015

For the 18z TAFs, VFR conditions are expected through this
afternoon. As the next system approaches the region, areas of
drizzle and possibly light rain will be possible tonight into
Tuesday morning. However, there is uncertainty with regards to how
widespread or prevailing this light precipitation will be, as models
seem to be trending downward with the available moisture. MVFR and
some periods of IFR cigs will be possible. Expect winds to increase
overnight into Tuesday, veering from south to northwest with the
passage of a cold front.

&&

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

$$

SHORT TERM...Bowen
LONG TERM...Wolters
AVIATION...Hennecke