Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 201732
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1232 PM CDT Wed May 20 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 331 AM CDT WED MAY 20 2015

Mid/upper level trough currently lifting northeastward over SD and
NE, and will eventually merge with energy tracking over the upper
Midwest. An expansive area of light to moderate rain will move
across northeast KS early this morning, which is supported by upper
level forcing associated with the trough and low level
frontogenesis. Most of the forcing is forecast to continue eastward
and mainly exiting the area around 12Z. There are indications that
light rain showers and or drizzle could linger through the early
afternoon hours after the mid/upper levels dry out. Both RAP and NAM
soundings show steep low level lapse rates coinciding with
saturation along with weak lift. This could be enough to generate
these light showers and or drizzle. Although these models also
suggest isentropic downglide on the backside of the wave so very
little precip accumulations are expected after 12Z. Clouds will
stick around most of the day and northerly flow will keep
temperatures from warming up much, therefore highs will generally be
in the mid 50s. Surface high pressure will build into the region
tonight and clouds may begin to scatter out as the drier air filters
southward. As surface winds begin to lighten and temperatures cool
there is a chance fog could develop especially given the recent
rainfall. Temperatures are expected to drop into the low to mid 40s
with a few isolated locations in the upper 30s.

.LONG TERM...(Thursday through Tuesday)
Issued at 331 AM CDT WED MAY 20 2015

Thursday through Thursday night, A surface ridge of high pressure
over eastern KS will shift east into MO by Friday morning. An upper
level trough will move onshore across southern CA. Expect mostly
sunny skies on Thursday with highs reaching the mid 60s. Thursday
night will be a bit warmer as the center of the surface ridge moves
east into MO, allowing light winds to become southerly. Lows Friday
morning will only drop into the mid to upper 40s. High and mid level
clouds will increase late Thursday night.

Friday through Monday, The upper trough over southern CA will slowly
drift northeast into western CO and slowly fill. Southwest flow
aloft across the central Rockies will cause a surface lee trough to
deepen across the central and southern high plains. Deeper gulf
moisture will gradually be advected northward into the southern
plains Friday afternoon. The resulting isentropic lift ahead of the
deeper moisture return combined with any ascent from minor H5
troughs embedded within the southern stream of the H5 jet will
provide an increasing chance for showers and isolated thunderstorms
during the day Friday and into the Friday evening. The ECMWF shows a
brief amplification of the main H5 trough across AZ. This may
amplify a downstream H5 ridge across the southern plains which may
provide a break from the showers and thunderstorms across eastern KS
on Saturday. Due to cloud cover and increasing rain chances on
Friday, highs will only reach the mid 60s. If we see more insolation
on Saturday highs will reach the lower 70s.

Saturday night through Sunday night, the Upper trough will fill as
it lifts northeast into western CO. The southern stream H5 ridge
will shift east across the Gulf coast states. Embedded shortwave
trough combined with deeper moisture advection will cause periods of
showers and thunderstorms to develop. The mid level flow will weaken
below 40 KTS. The weaker vertical wind shear should prevent
organized storms updrafts. Also, the instability may be lower due to
the cloud cover. I don`t expect severe thunderstorms this weekend.
The primary hazard may be occasional heavy rainfall. Highs on Sunday
will reach the mid 70s

Monday (Memorial Day), The ECMWF and GEM forecast a slightly more
amplified H5 trough to move northeast from southwest TX into central
OK. The better ascent ahead of this trough will be across northern
TX and southern OK. Both models do not forecast much in the way of
QPF during the day. The showers and thunderstorms may increase
Monday night as the H5 trough lifts northeast into western MO. Highs
on Monday should reach the mid 70s

Tuesday, the H5 trough across western MO will lift northeast into
eastern IA and IL. We may see a break in the precip. The GFS is
slower moving the H5 trough northeast across MO and forecast higher
QPF across eastern KS on Tuesday. Looks a bit warmer on Tuesday as
16 to 18 degree C 850mb temps advect northeast across the CWA. Highs
should reach into the upper 70s to around 80.

&&

.AVIATION...(For the 18Z TAFs through 18Z Thursday Afternoon)
Issued at 1232 PM CDT WED MAY 20 2015

Expect slight improvements to rather frequent IFR cigs in next few
hours given typical diurnal trends and upstream obs, though
confidence is not high. Timing of stratus exit also difficult, but
guidance similar with a delayed exit from earlier expectations. Am
not too worried about FG development around 11Z at this point
with some boundary layer mixing occuring.

&&

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

$$

SHORT TERM...Sanders
LONG TERM...Gargan
AVIATION...65






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