Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 171726
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1226 PM CDT Wed Sep 17 2014

...AVIATION UPDATE...

.SHORT TERM...(Today and Tonight)
Issued at 323 AM CDT WED SEP 17 2014

The low level jet has becomes focused directly over the forecast
area and showers/storms are now developing in response to the
isentropic lift. The instability above this lift is around 1000 j/kg
with effective bulk shear near 40 kt. Given the environment can not
rule out a storm capable of producing hail likely under quarter
sized. Expect this activity to increase in coverage as it moves
eastward the next few hours. The low level jet will continue to veer
as it noses more into western MO and isentropic lift becomes better
focused there. A majority of this morning activity should stay
mainly south of interstate 70, and clear out of the area around
sunrise or shortly after. Short term models are suggesting a
potential for fog centered around sunrise especially in north
central KS. Soundings show that any fog and low level stratus will
begin to lift and scatter out from west to east. There are some
indications that the stratus could hold on longer in spots across
east central KS into the afternoon hours. By the afternoon a warm
front should be located from near Salina to Emporia or just south of
there. This is where the cap is weak and surface convergence is
present. The only limiting factor will be no mid/upper level support
to enhance the lift. With steep mid level lapse rates in place the
surface based cape will approach 3500 j/kg. Hodographs will also be
impressive with decent turning with height within the northwest flow
aloft and southerly surface flow. Deep layer shear of 35 to 40 kt
means any storm that is able to develop near the front could quickly
become strong to severe around the 21-01Z time frame. Have kept
slight chances along the southern border of the forecast area
through the evening hours. Further north of the front stratus tries
to linger as a fairly strong cap remains in place so do not expect
any development in those areas. Later in the evening the front
retreats south of the area and southerly flow increases over the
stable air mass. Elevated convection will again be possible, which
should hold off until around 03-06Z. This mornings temperatures will
remain steady with the expansive cloud cover. Highs today should
reach the mid to upper 80s in central KS, and low 80s in northeast
KS if the clouds lift as forecasted.

.LONG TERM...(Thursday through Tuesday)
Issued at 323 AM CDT WED SEP 17 2014

Thursday, scattered to isolated elevated thunderstorms will be
ongoing into the morning hours across the eastern and southern
counties of the the CWA. An upper level ridge across the high plains
will amplify through day. A stronger EML will overspread the area by
Thursday afternoon and the elevated thunderstorms across the
southeast counties should dissipate. Skies will begin to clear from
west to east across the CWA during the afternoon hours. Highs will
vary dependent on afternoon insolation. The southwest counties will
warm into the mid 80s while the eastern counties may keep cloud
cover longer through the afternoon hours and only see highs in the
upper 70s.

Thursday night through Friday night, The upper level ridge axis will
shift east across the central and southern plains into to the the
mid and lower MS river valley by Friday night. The remnants of Odile
will lift northeast around the upper ridge axis across NM into
western KS Friday night. Rain and thunderstorms will slowly spread
northeast across western KS through the night but remain west of the
CWA. Friday highs will be warm with the upper level ridge across the
southern and central plains. Highs Friday afternoon will reach the
mid to upper 80s and it will feel more humid with deeper gulf
moisture in place.

Saturday into Saturday Night, The remnants of Odile will begin to
phase with an upper level trough digging southeast across the
northern plains and upper Midwest. Rain and thunderstorm chances
will increase from west to east across the CWA during the day on
Saturday. The 6Z run of the ECMWF is slower and would bring the
heaviest rain across the CWA Saturday night. The GFS and GEM models
are more progressive in the speed of the upper trough digging
southeast across the northern plains into the upper Midwest. Both
models show the remnants of Odile remaining south of the CWA across
OK and southern KS. ATTM, I`m leaning more towards the ECMWF which
will phase the remnants of Odile with the the northern plains H5
trough during the late afternoon hours across central KS then move
both systems east-southeast across eastern KS during the evening
hours. The ECMWF forecast QPF of 1 to 3 inches rainfall Saturday
into Sunday along and south of I-70, with only a quarter inch of
QPF along the NE border. The other operational models keep the
heavier rainfall south of the CWA with half inch of QPF south of
I-70 and only about a tenth of an inch of rainfall across the
northern counties of the CWA.

Sunday Afternoon through Tuesday, If the 6Z ECMWF solution verifies
the rain and thunderstorms may continue through the morning hours
of Sunday but should end by Sunday afternoon. It looks dry into
early next week, as the H5 trough across the upper Midwest digs
southeast into the Great Lakes and amplifies. The coldest airmass
will remain east of the CWA. Highs will generally be in the mid to
upper 70s with overnight lows in the 50s.

&&

.AVIATION...(For the 18Z TAFs through 18Z Thursday Afternoon)
Issued at 1226 PM CDT WED SEP 17 2014

The terminals are expected to remain within a northeast to
easterly low level flow through the period with little or no dry
air advection at the surface. Confidence in when the stratus will
burn off is marginal, but there are signs from satellite and
recent obs that it is starting to erode. Initally based the timing
of improvements to CIGS on the RAP forecast soundings but adjusted
them to hold onto the CIGS slightly longer since there seems to be
a expansive deck of clouds still to the east and northeast.
Models have backed off on elevated precip overnight. Think this
may be due to some dry air in the 900MB to 700MB layer seen in the
isentropic surfaces. With models shearing out the upstream
vorticity or keeping the vort max to the northeast of the
terminals, think it is more likely to remain dry overnight at the
terminals and will not insert a mention of precip at this time.
MOS guidance also wants to redevelop fog (possibly dense) for
Thursday morning. However forecast soundings from the RAP and NAM
suggest any moisture will be very shallow and that 925MB winds of
15 to 20KT should keep some dry air mixing into the boundary layer
through the night. Additionally models show some possible mid
level clouds moving overhead limiting the radiational effects for
ground fog. Because of this, I`m not ready to put IFR VSBY in the
forecast.

&&

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

&&

$$

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






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