Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 192317
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
617 PM CDT Mon Jun 19 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tuesday)
Issued at 257 PM CDT Mon Jun 19 2017

This afternoon, northeastern KS remains under northwest flow aloft
with a weak embedded wave slowly pushing mid level clouds through
into the Mid MS Valley region.  A broad ridge remains centered over
the Desert Southwest into the Inter-Mountain West.  Dewpoints are
mainly in the 50s and some lower 60s over southern portions of the
forecast area.  These dewpoints have helped set up a very pleasant
day with sounding profiles showing mixing up to around the 800mb
level and 850mb temps around 15C.  Therefore, expect afternoon high
temps to top out in the mid 80s.

Return flow should begin tonight with weak WAA helping to keep
overnight low temps into the mid 60s.  There could be some very
shallow ground fog in low lying areas (primarily along the Kansas
River valley through the Topeka area), but enough mixing and a
mostly dry low level airmass will allow for a clear night.  Into the
day Tuesday, return flow around the surface high pressure ridge
should increase into the afternoon as it slowly retreats off to the
east/southeast. Weak embedded waves through the northwesterly flow
aloft will be traversing through the Northern Plains into the Mid MS
Valley helping to push a weak cool boundary into southern NE by late
afternoon time frame.  The afternoon should stay dry over the area
as it doesn`t appear that isentropic upglide associated with WAA
will cause enough lift, along with instability developing throughout
the day, to form high based showers and storms until after the 6pm
time frame.  Therefore, have only kept slight chance POPs over
northern counties near the KS/NE border.  Highs in the afternoon
likely to be a bit warmer than today with mid 90s over western
portions of the area especially west of Manhattan.

.LONG TERM...(Tuesday night through Monday)
Issued at 257 PM CDT Mon Jun 19 2017

An upper level anticyclone over the southwest CONUS will gradually
break down over the course of the week, with a PV lobe breaking off
a Gulf of Alaska low and diving south and deepening into a broad
longwave trough across the Northern Plains for the weekend. NE
Kansas will linger under broad westerly flow with multiple
perturbations working through the flow over the course of the week.
A cooler, northwesterly flow pattern will ensue for the weekend and
early next week as the trough dives southeastward.

For Tuesday night into early Wednesday morning, increasing 310K
isentropic lift upstream of an H850 Southern Plains high, coupled
with a modest mid-level EML, will likely result in shower and
thunderstorm development across western/central Kansas in the late
afternoon and evening hours. Effective shear profiles are weak and
unidirectional with height, which will likely result in poorly
organized storm structures--and a low severe weather threat. Forcing
wanes quickly into eastern Kansas closer to the H850 high, thus any
storms will be confined to the western CWA.

A cold frontal boundary will slide ESE from the High Plains into
west-central Kansas by late in the afternoon on Wednesday with
return flow ahead of front pushing highs into the 90s Tuesday
through Thursday. Dewpoints on Wednesday and Thursday ahead of the
boundary will rebound into the upper 60s to low 70s, which will push
heat indices close to 100 on both days. This front be the focus for
convective development late in the afternoon with MLCAPE values
around 1500 to 2000 J/kg ahead of the front with modest deep shear.
The environment rapidly becomes less favorable into eastern Kansas--
thus while residual thunderstorms may persist into the night in NE
Kansas, the threat for severe weather is low.

Model confidence decreases towards the end of the week and the
weekend with the various medium range guidance struggling to resolve
the timing of the PV lobe ejecting off the Gulf of Alaska low. At
this point, expect the chance for strong to possibly severe
thunderstorms both Thursday and Friday afternoon/evening in eastern
Kansas, with favorable thermodynamic/kinematic profiles to support
wind and hail threats at a minimum. Canadian surface high pressure
builds southeastward for the weekend and early next week and will
keep temps seasonably cool in the upper 70s to low 80s for highs.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 617 PM CDT Mon Jun 19 2017

VFR conditions are expected throughout the period. Scattered
showers near TOP/FOE should move east by 02Z. There is a chance
for some shallow fog in the early morning near 12Z around low
lying areas, but have left this mention out of the TAF.

&&

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

$$

SHORT TERM...Drake
LONG TERM...Skow
AVIATION...Heller



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