Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 242332
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
632 PM CDT Thu Jul 24 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Friday)
Issued at 245 PM CDT THU JUL 24 2014

Upper flow pattern this afternoon continues to show the region
influenced by upper ridging while another embedded shortwave trough
shifts eastward from CO into NE.  A stronger upper trough tracking
eastward over the Pacific Northwest will alleviate this persistent
pattern later this evening.

Main forecast concern in the short term period is the heat returning
for tomorrow. Surface high pressure currently to our east will exit
the region tonight as a surface trough deepens east over the high
plains. High clouds increase over north central areas while a low
level jet increases up to 50 kts at 850 MB. The boundary layer
should stay fairly mixed through the evening as an h85 thermal axis
reaches 27C over north central KS. Low temps were raised a few
degrees into the mid and upper 70s, while low 70s are seen
elsewhere. Any convection that is able to develop over NE should
remain north and west of the CWA.

Mid level flow becomes zonal on Friday due to the passing upper wave. In
its wake, a cold front will dive southward through the plains. A
pretty strong capping inversion at h85 should preclude any
convection over north central KS during the late afternoon. Moisture
pooling ahead of the front maximizes dewpoints from the mid 60s to
low 70s across east central KS during peak heating hours. Combined
with strong downward mixing of the 27-29C thermal axis over the CWA,
expect highs to peak in the upper 90s and low 100s. Heat index
readings are expected to reach near or at advisory criteria in the
103 to 109 degree range. A heat advisory has been issued for
tomorrow afternoon. Strong southerly winds may gust in excess of 30
mph during this time.

.LONG TERM...(Friday Night through Thursday)
Issued at 245 PM CDT THU JUL 24 2014

For Friday night through Saturday night, a lot will depend on the
timing and location of a cold front progged to move through the
area. In short it appears as the the NAM solution is a fast outlier
in bringing the front into east central KS by Saturday afternoon.
With this in mind the forecast follows the consensus of having the
boundary closer to the NEB state line through Saturday afternoon.
Models show that there may end up being a decent elevated mixed
layer (EML) at least ahead of the boundary capping the boundary
layer from convection within the warm sector. Since there does not
appear to be a strong signal of forcing from the models, decided
to keep a slight chance going Saturday afternoon and Saturday
night as the boundary moves across the area. The main adjustment
to the previous forecast was to trend temps warmer given a slower
frontal progression and 850 temps from the models suggest triple
digit heat is probable along and south of the KS river. So it is
conceivable that we will need a heat advisory through Saturday as
well. However confidence in the frontal timing casts enough doubt
that felt is prudent to hold off an advisory and see what later
model solutions show.

Cooler weather should move into the area by the end of the
weekend, however the new ECMWF and GFS are a little slower in
bringing the cooler low level temps south and wait until Sunday
night and Monday for the stronger cold air advection. Models
indicate a weak shortwave should round the upper ridge to the west
and move through the central plains Tuesday through Wednesday
morning. Therefore have some 20 to 30 percent chance POPs going
with better chances likely across central KS.

Kept the forecast dry after Wednesday in spite of the ECMWF
developing QPF over the area. With broad surface ridging over
eastern KS through the end of the period, there is not expected to
be much in the way of moisture advection. Additionally there is
some uncertainty in the thermal profile from the ECMWF given its
limited vertical resolution so think it may be over doing diurnal
convection. Wont say precip chances are nil since there could be
some weak waves within the flow aloft. Temps should remain mild
through the end of the forecast with the upper ridge remaining
over the southwestern U.S.

&&

.AVIATION...(For the 00Z TAFs through 00Z Friday Evening)
Issued at 629 PM CDT THU JUL 24 2014

Expect VFR conditions through the next 24 hours. Winds will become
southwest after sunrise and increase to 14 to 18 KTS with gusts of
24 to 28 KTS through the day Friday. May see some moderate
windshear late tonight as 925 MB winds increase to 45 KTS from the
southwest between 8Z and 13Z FRI

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
HEAT ADVISORY from Noon to 7 PM CDT Friday FOR KSZ008>012-
020>024-026-034>040-054>056-058-059.

&&

$$

SHORT TERM...Bowen
LONG TERM...Wolters
AVIATION...Gargan





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