Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 251749
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1249 PM CDT Thu May 25 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 350 AM CDT Thu May 25 2017

An upper level trough across the Pacific northwest and south central
Canada will dig southeast across the northern high plains and
central Rockies. A lead upper level trough across southwest CO will
lift out into the central plains ahead of the main trough axis this
digging southeast across the central Rockies this evening.

Today, There will be some mid level clouds this morning and perhaps
a few elevated showers across the northern counties. I placed in 10
to 14 percent pops across the northern counties through the mid
morning hours. Late this morning skies will become be mostly sunny
across much of the CWA. As west-southwesterly mid-level flow
increases across the central Rockies, lee surface trough will deepen
across eastern CO and western KS. The deepening lee surface trough
across the high plains will cause south-southeast winds to increase
across the CWA through the afternoon hours. Southerly surface winds
will be 15 to 20 MPH with gusts to around 30 MPH. High temperatures
will warm into the mid to upper 70s with some 80 degree readings
across the southwest counties.

Tonight, during the late afternoon and early evening hours a complex
of thunderstorms will develop ahead of a surface front and dryline
across western KS. Most models show this complex of storms becoming
a forward propagating MCS or QLCS. This complex of storms will begin
to weaken as it heads into more stable air across north central KS.
Most models show MUCAPES dropping below 1,000 J/KG across north
central KS by 3Z. However, if an organize complex of storms can
maintain its intensity moving into north central KS during the mid
and late evening, then there could be a risk of damaging winds
before the complex weakens and becomes elevated. I suppose some of
the more intense updrafts may provide a chance for quarter or larger
size hail across the far western counties this evening. All the
numerical model solutions show this complex of storms dissipating as
it moves east across north central KS into northeast and east
central KS after midnight. Overnight lows will drop into the upper
50 to lower 60s.

.LONG TERM...(Friday through Wednesday)
Issued at 350 AM CDT Thu May 25 2017

Precipitation chances remain to be the main forecast challenge. Weak
forcing and increasing model differences continue to keep confidence
reduced.

Weak inverted trough northwest of surface low in southeast
Kansas/northeast Oklahoma lingers near I-35 Friday afternoon.
Capping inversion aloft looks fairly strong, but could be enough
convergence for a few storms here in the late afternoon. Low level
wind fields are not impressive, but could be enough shear with good
CAPE for pulse severe storms. Increasing CIN should this activity
early in the evening, but will then watch for convective activity
moving into the area from the west overnight as a shortwave digs
into the High Plains. Elevated CAPE near 1500 J/kg and a modest low
level jet could support a few strong storms with hail into the local
area. Any of this activity should generally weaken through the
morning with weakening wind fields, but coverage may increase as the
wave weakens and passes through. Models continue to suggest a
potential warm front developing over the far southern counties
Saturday afternoon, though daytime convective trends could keep it
farther south in this weakly-forced regime. If some insolation can
occur, ML CAPE values could breach 2500 J/kg, with enough mid-level
wind for some storm organization. The front should push southeast by
early evening as the upper flow veers ahead of the larger-scale
upper trough beginning to push southeast through the Northern
Plains. Another area of convection moving out of the Front Range
with another shortwave may impact mainly southern areas Saturday
night into early Sunday but deepening northwest flow brings more
stable air in through the day. Have kept Sunday afternoon through
the remainder of the holiday periods dry, with little agreement in
waves rotating around the Great Lakes upper low. Mid level moisture
return brings better precip chances back around Wednesday.

Have kept Friday temps mainly in the lower 80s though am somewhat
concerned with backed winds and some low cloud potential. Northern
locations likely cooler with more precip and cloud for Saturday.
Modified northwest flow suggests keeping temps fairly steady into
the midweek.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1238 PM CDT Thu May 25 2017

For the 18z TAFs, southeast winds will remain breezy this
afternoon with gusts of 20-25kts. Models continue to show the
potential for some scattered thunderstorms developing near KMHK as
a cold front tracks into north central KS. However, there is
still too much uncertainty with the coverage and tracking of any
storms. As a result, have not included any mention of storms in
the TAFs at this time. By Friday morning, winds will back to the
north with model soundings showing the potential for ceilings to
drop to MVFR conditions. Currently have cigs improving to VFR by
late morning, however it is worth noting that some models are
keeping MVFR cigs in place into early Friday afternoon.


&&

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

$$

SHORT TERM...Gargan
LONG TERM...65
AVIATION...Hennecke



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