Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 281744
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1244 PM CDT Sat Mar 28 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 411 AM CDT SAT MAR 28 2015

Early Saturday morning, a weak trough evident in surface pressure
analysis and implied in WV imagery was moving south across eastern
Nebraska. West-to-east isentropic upslope flow in the mid levels was
being enhanced in advance of this wave, and was resulting in
increasing radar returns across southeast NE and eastern KS. The
reflectivity patterns also indicate that the lift was being enhanced
by weak convective instability on the west edge of this precip and
CSI in far northeast KS and northwest MO. Dry air in the lowest 5000
feet AGL (evident in the 00Z TOP RAOB) was inhibiting much of this
precip from reaching the ground, but decreasing dewpoint depressions
and radar reflectivity noted lower in the vertical suggests that
pockets of sprinkles or even light snow showers may be reaching the
ground in eastern KS. The enhanced reflectivity is also training
over the same areas which will help continue to saturate down and
expect slightly increased coverage of light showers in the near
term. However, subsidence will take over as the weak trough passes,
and expect this light activity to come to an end shortly after
sunrise with decreasing cloud cover through the morning. Winds will
become southerly through the day and sunshine should bring temps
into the middle 50s east and middle 60s in central KS.

A fairly strong short wave trough, currently coming on shore in the
NW CONUS, will track across the northern Plains into the upper
Mississippi Valley by early Sunday morning. This system will aid in
developing a strong LLJ overhead with persistent isentropic ascent
tonight. Additionally, a surface front will enter the forecast area
on Sunday morning. Currently expect to have weak elevated
instability above the LLJ moisture advection as mid level
temperatures cool near sunrise. This should result in scattered
shower development, and while a thunderstorm is not totally out of
the question have not included it in the forecast at this time given
rather weak instability. Overnight low temperatures will be a bit
warmer with persistent southerly winds and some warm advection.

.LONG TERM...(Sunday through Friday)
Issued at 411 AM CDT SAT MAR 28 2015

Models continue to show a mid-level shortwave trough tracking across
the Northern Plains and into the Great Lakes region on Sunday, which
will help to push a weak cold front into north central Kansas Sunday
morning and exit the area Sunday afternoon. While the models are in
good agreement that the better moisture and lift will be focused
further north and east, there is still some uncertainty with how far
into the forecast area the light rain will extend. Have kept low-end
chance PoPs in far northeast Kansas as they should be clipped by
some showers, but have dry conditions by the afternoon hours.
Despite the shift to northwesterly winds behind the frontal passage,
there doesn`t look to be much in the way of cold air advection and
have high temperatures reaching into the mid/upper 60s.

Dry and mild conditions are expected for early next week as surface
high pressure advances into the area Sunday night and progresses to
the southeast by Monday. As a result, southwesterly surface winds
are expected and will lead to decent warm air advection through the
early half of next week. Have continued to trend on the warmer side
of guidance with Monday highs in the low/mid 70s and Tuesday highs
in the mid/upper 70s. The 00z model runs have continued with the
slower progression of the next storm system. Models show a mid-level
trough advancing eastward over the Rockies on Wednesday which will
help to push a low-pressure system and associated cold front
eastward across the CWA Wednesday night rather than on Wednesday (as
the previous 00z model runs were showing). As a result, continued
southwesterly flow on Wednesday should keep high temperatures warm
in the mid/upper 70s. While most of the moisture and forcing will be
focused along and behind the cold front, some models are suggesting
that some lift will be present ahead of the boundary to promote some
light scattered precipitation Wednesday afternoon over east central
Kansas, so have slight chance PoPs in for much of the area with
chance PoPs over north central Kansas as thunderstorms may develop
as early as late afternoon. The GFS shows a stronger system than the
ECMWF with decent enough CAPE and bulk shear values to suggest the
potential for some severe weather, so will need to continue to
monitor this potential for some strong to severe thunderstorms
Wednesday evening.

Models become much more inconsistent Thursday into Friday as the GFS
is much more progressive with the passage of the cold front and
clearing precipitation out of the area Thursday morning.  While both
the GFS and ECMWF show a trough developing over the Rockies Thursday
night, the trough is much more pronounced from the ECMWF while the
GFS simply shows a weak shortwave. As a result, the ECMWF brings a
stronger wave into the area Thursday night into Friday. The
discrepancies in the strength of this next system has led to
uncertainties in temperatures as well as precipitation chances. Due
to the low confidence in this part of the forecast, decided to stay with
the model consensus for the Thursday/Friday forecast.

&&

.AVIATION...(For the 18Z TAFs through 18Z Sunday Afternoon)
Issued at 1244 PM CDT SAT MAR 28 2015

VFR conditions will persist through at least 02Z, with increasing
chances for limiting ceilings thereafter. Confidence is not high
in the cloud, but pattern suggests at least decent MVFR potential. Will
continue with gusts developing after 06Z, with some wind shear
potential if they are not persistent. Cold front and any SHRA
should pass around 16Z.

&&

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

$$

SHORT TERM...Barjenbruch
LONG TERM...Hennecke
AVIATION...65






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