Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 191127
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
627 AM CDT FRI AUG 19 2016

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 231 AM CDT FRI AUG 19 2016

Lead shortwave over the upper Midwest is dragging a cold front into
portions of NE early this morning. This front currently stretches
from northeast NE into northwest KS, and will continue moving
southeastward through out the day. The models also depict a weak
shortwave over northern CO that will move over the NE/KS state line
later today. This wave along with the front will support shower and
storms across the forecast area this afternoon and overnight. The
front is forecasted to arrive in north central KS between 1 and 4
pm. Surface based storms are expected to develop around noon in
central KS before moving eastward. Models are showing MLcape should
reach 2000 to 3000 j/kg, and deep layer shear around 20 kts. This
shear will be mostly parallel to the front therefore promoting cold
pool development. These cold pools along with possibly bowing
segments will cause the storms to move ahead of the front and into
eastern KS. The storms will be capable of producing damaging wind
gusts, but the threat should stay fairly localized. The 0-3 km wind
shear is forecasted to be around 20 kts, which favors a slightly
cold pool dominate environment. Therefore a widespread severe wind
event seems less likely at this point. The better chances for
damaging wind gusts will be locations west of a line from Holton to
Emporia between 4 and 10 pm. Later in the evening the storms should
begin to weaken with the loss of daytime heating, and a relatively
weak low level jet. The line of storms is forecasted to reach far
eastern KS between 10 pm and 3 am.

Ahead of the line of storms will be an uncapped environment later in
the day. Therefore models are developing isolated to scattered
convection across the eastern half of the forecast area this
afternoon. There is not an obvious signal for forcing besides the
model generated surface convergence. There is a slight chance for
elevated showers and storms in southeast KS this morning. Perhaps
this is causing the models to generate precip later in the
afternoon. The high res models are showing widespread rainfall
between 0.5 and 1 inch, with localized amounts up to 2.5 inches.
After the initial round of storms it is uncertain if redevelopment
will take place along the front as well as post frontal. There may
be some showers that linger into until sunrise especially across far
eastern KS.

.LONG TERM...(Saturday through Thursday)
Issued at 231 AM CDT FRI AUG 19 2016

By Saturday morning, area should be on the back side of the upper
trof, clearing skies from northwest to southeast and bringing a
period of gusty winds through on Saturday morning as it passes.
Once the gradient relaxes toward the afternoon, may need to think
about a chance for fog Saturday night but will depend on how much
rain falls Friday and amount of decoupling early Sunday. Southerly
surface flow starts to move back into the western counties by late
Sunday afternoon. High temperatures in the middle to upper 70s on
Saturday may feel a little cooler given the northwesterly winds,
while highs rise to near 80 on Sunday. Lows rise from middle 50s
Saturday night to around 60 on Sunday night.

General model guidance is for rain to hold off until later on
Tuesday, with highs rising back into the low/middle 80s both days.
Larger scale upper flow pattern swaps back from northwesterly to
southwesterly as early weekend trof moves east, and next pair of
trofs takes shape over the northern Rockies and across the Great
Basin states. Smaller embedded waves ejecting northeast out of the
Southwest trof are initially the ones responsible for
precipitation chances and timing, and are therefore subject to
more uncertainty. Better chances currently are Wednesday into
Wednesday night, and diminish in coverage from north to south
into Friday. However larger upper trof over the northern rockies
is consistent between guidance and would suggest a front over the
Central States to focus rain chances on. Highs may drop into the
lower 80s late week depending on position of the front and
associated precip chances.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday Morning)
Issued at 618 AM CDT FRI AUG 19 2016

Low level moisture in the form of IFR/LIFR stratus is moving
towards TOP/FOE. The HRRR has captured this stratus and keeps it over
the sites until a few hours after sunrise as it may take some
time to lift and scatter out. There is a chance for a line of
storms later this afternoon and evening. Damaging wind gusts are
possible along with heavy rainfall. There may be visibility
restrictions for brief periods. There is a slight chance of
isolated storms ahead of the main line in the afternoon as well.
MVFR stratus is possible behind the front towards the end of the
period.

&&

.TOP Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Sanders
LONG TERM...67
AVIATION...Sanders



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