Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 191121
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
621 AM CDT Sat Aug 19 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 250 AM CDT Sat Aug 19 2017

The weak surface trough that was moving through the area yesterday
has become rather diffuse, and is expected to lift northward today.
Light to calm surface winds and clear skies is supporting decent
radiational cooling. Therefore ground fog development is possible
between now and sunrise especially in the low lying areas. Today
skies remain mostly sunny and winds relatively light with highs in
the 90s. These temperatures in combination with dew points in the
60s will cause heat indices to reach the mid to upper 90s this
afternoon. Later today storms are expected to develop along the
deeper surface trough or dry line across northwest KS and western
NE. The are indications that these storms clusters could form into
an forward propagating MCS. The models are indicating a very subtle
shortwave that lifts out of WY, which could support this scenario as
well as ample low level moisture and a low level jet. Although the
models differ on the exact location and coverage of the possible
convection later this evening, but the consensus of the latest
guidance is tracking a possible MCS near the KS/NE state line. As
typical with these systems strong to severe wind gusts will be
possible if this MCS can materialize and maintain strength as it
progresses east-southeastward through the late evening and early
morning. There is some agreement between the HRRR and WRF ensembles
with tracking something into north central KS, while the NAM
slightly further north. A few of the HRRR ensembles even bring the
MCS into portions of eastern KS. Both the EC and GFS do not show
much convection after midnight let alone anything reaching our area
with the exception of far north central KS.

.LONG TERM...(Sunday through Friday)
Issued at 250 AM CDT Sat Aug 19 2017

Will keep small precip chances going for much of Sunday with some
potential for overnight convection to linger. Southerly winds bring
dewpoints above 70 in the eastern counties with little inhibition
for afternoon storms. Deep shear looks limited but could see a
strong storm or two given ML CAPE above 3000 J/kg. This moisture
will contribute to heat index values peaking around 100 for the
bulk of the area. Will keep small precip chances going into the
night with deep moisture increasing from the southwest.

Not much change in thinking for Monday`s forecast. Models are
consistent with a weak wave over the Gulf of California this
morning meandering into the state late Sunday night into Monday
with significant mid and upper moisture. These features keep a
chance for showers and thunderstorms in the forecast. Have
increased cloud cover somewhat, in kind with most model guidance,
but there remains some opportunity for breaks in the cloud
cover. High temps may back off a bit in the increased cloud but
apparent temps will still reach the 90s to around 100.

Best precip chances come late Monday night into Tuesday as a
stronger cold front passes through. Timing of this feature keeps
severe weather concerns limited. A modified southern Canadian
airmass in place for Tuesday night through Friday keeps these
periods mainly dry.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 608 AM CDT Sat Aug 19 2017

Ground fog will be possible at TOP/MHK for the next few hours
with VFR conditions expected after that. A complex of storms may
move towards the taf sites tonight mainly after midnight. Some
strong wind gusts may be possible with these storms although the
chances are low at this point.

&&

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

$$

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



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