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Area Forecast Discussion (AFD)

Issued by Topeka, KS (TOP)

                            
000
FXUS63 KTOP 211744
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1244 PM CDT Sun Apr 21 2019

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 337 AM CDT Sun Apr 21 2019

A broad upper level trough was located across the western US early 
this morning. A lead H5 shortwave trough was lifting northeast across 
southeast CO and the OK and northern TX PNHDL. This lead H5 trough 
will lift northeast across western and central KS this morning. The 
ascent combined with isentropic lift may develop a few rainshowers 
during the morning hours across the western half of the CWA. These 
showers will end by mid morning, as the H5 trough lifts northeast 
into southern NE, and the DAVA on the west side of the H5 trough axis 
provides an area of subsidence across central and eastern KS during 
the afternoon hours. A second H5 trough will then lift northeast 
from the southern high plains into southwest KS and northwest OK by 
00Z SUN. DCVA ahead of the H5 trough will help to deepen a lee 
surface low across southwest KS and erode the capping inversion. A 
surface front will push southeast across the central high plains 
into northwest KS by 00Z MON. A surface dryline will extend 
southward from the front (triple point) across west central KS, 
south-southwestward into the eastern TX PNHDL. Several of the 
numerical models including some CAM models show isolated to 
scattered thunderstorms developing across west-central KS, ahead of 
the surface front and dryline between 22Z SAT-02Z SUN, as surface 
convergence along with ascent ahead of the H5 trough lifting 
northeast across the TX PNHDL and western OK into southwest KS. 
MLCAPE is forecasted to be between 1500-2000 J/KG from west central 
KS, east into the western counties of the CWA after 00Z. The 
effective shear look rather weak with only 20 to 25 KTS of shear. 
Thus thunderstorms will probably not be well organized but given the 
instability there could be pulse severe thunderstorms with large 
hail and damaging wind gusts across west central KS. As the surface 
front pushes southeast into north central KS, some of the 
thunderstorms that developed across west central KS during the early 
evening hours will move northeast into north central KS after 3Z MON 
and potentially other surface based storms may develop along the 
cold front. There may be a chance for isolated strong to severe 
thunderstorms across north central KS during the mid and late 
evening hours. The severe thunderstorms will be capable of producing 
large hail and isolated damaging wind gusts. The chances for severe 
wind gusts will diminish through the late evening hours, as 
temperatures cool and the inversion strengthens. The WRF CAMs show 
that forecasted Zr decreases as storms move into north central KS 
after 3Z.  The WRF solutions also show a cluster of thunderstorms 
developing across south central KS near the triple point, west of 
ICT between 00-03Z, and moving northeast but weaken as they reach 
the TOP CWA.  Through the remainder of the night the surface cold 
front will move southeast across the entire CWA. There may be 
sufficient isentropic lift north of the front for showers and a few 
elevated thunderstorms. These storms will not be severe northwest of 
the surface front.

As the lee surface low deepens through the day across west central 
and southwest KS, southerly winds will increase through the mid 
morning and through the afternoon hours to 15 to 25 MPH with gusts 
of 30 to 40 MPH. The corridor of strongest surface winds will be 
across the south central and southeast counties with some sustained 
wind speeds approaching 30 MPH. The PBL will mix up to 850mb across 
much of the CWA allowing for air parcels at 850mb at 17-20 deg C to 
mix down dry adiabatically, allowing highs to reach the lower to mid 
80s, with some upper 80s across the southwest counties of the CWA 
this afternoon.

Overnight lows will occur behind the front with mid 50s across north 
central KS and lower 60s across east central KS.

.LONG TERM...(Monday through Saturday)
Issued at 337 AM CDT Sun Apr 21 2019

The extended portion of the forecast looks fairly quite with just a 
few opportunities for rain.

On Monday, a large upper level closed low will be located over the 
desert southwest. At the surface, an area of low pressure will be in 
place over Iowa with a cold front trailing to the southwest through 
northeast KS and into central OK. The cold front will continue to 
move through northeastern KS during the afternoon with a few showers 
possible along the front, especially late in the day in east-central 
KS. The next batch of rain that could impact the area will arrive 
Tuesday as a piece of energy and associated area of ascent ejects 
northeastward ahead of the closed low and moves into south-central 
KS. As of right now, it looks like the best chance for measurable 
rainfall will occur over the southeastern half of the CWA during 
the daytime hours Tuesday. Generally, around 0.25" of 
precipitation looks possible.

The upper low will pass to the south of the region on Thursday with 
associated precip also remaining to our south. Northwest flow will 
set up aloft into the end of the workweek as a surface ridge builds 
into the area. Return flow could become re-established over the area 
on Saturday. Warm advection associated with the return flow could 
boost temperatures back to near 80 degrees with dewpoints also 
increasing on Saturday. Some long range models are hinting at 
another chance for rain and storms for the first half of the weekend 
given lift associated with the warmer, more moist airmass moving in, 
especially if another surface low develops near the area. Will 
continue to monitor model trends for next weekend as we get
closer. 

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1237 PM CDT Sun Apr 21 2019

Gusty south winds will continue through the afternoon and early
evening hours. As the nocturnal inversion builds in after 00Z
wind gusts should decrease, although LLWS conditions are likely
after 01Z as a 40-50 LLJ near 1.5 kft remains overhead through
09-11Z. Thunderstorms are expected to traverse portions of 
northern KS late this evening into the overnight. There is still 
uncertainty whether the terminals will be impacted. At this point
MHK looks to have the greatest potential for -TS conditions, 
especially between 05-07Z. Have not mentioned any TS at the Topeka
terminals as confidence in storms impacting these sites is too 
low at this time. In addition, MVFR stratus is possible after 11Z,
especially at the Topeka sites. 

&&

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

$$

SHORT TERM...Gargan
LONG TERM...Teefey
AVIATION...Baerg