Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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773
FXUS63 KEAX 191743
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1243 PM CDT Wed Apr 19 2017

.Discussion...
Issued at 301 AM CDT WED APR 19 2017

Main concern for this forecast is the potential for severe storms
this afternoon and evening across northeastern KS and northwestern
MO.

Early morning convection developed along the stalled cold front
and ahead of lead shortwave trough moving across KS. This activity
should move through northwestern MO this morning. The stalled
front should lift north as a warm front and help to produce a
greater tornado risk north of the forecast area as winds back to
the southeast in the vicinity of the front, enhancing helicity
values. For us though, our chances will be tied to the advancing
cold front as the main upper trough moves east. With the area
fully in the warm sector, it`ll be warm, humid and windy through
the day. But this may lead to capping inversion as soundings in
northwestern MO show throughout the day. As the upper system
approaches, this inversion weakens and convergence along the front
should initiate convection in southeastern NE late in the
afternoon. By this time there will likely be 1500 to 2000 J/kg of
CAPE ahead of the front. Wind shear will be impressive with 40 to
50 kts of 0-6km shear. There is also good turning in the low level
hodographs suggesting there is some potential for a tornadoes,
despite winds being veered to the southwest. Overall, the strong
shear and steep midlevel lapse rates suggest large hail and
damaging winds would be the most likely hazards. But with 0-1km
helicity values ranging from ~ 100 to 200 m^2/s^2, tornadoes are a
real possibility in NW MO and NE KS. The main caveat is how
quickly the instability wanes after sunset. Models suggest the
instability weakens considerably after sunset so feel the greatest
potential for severe storms will be in far northeastern KS and
northwestern MO. Storms should weaken as the front moves southeast
late in the evening and overnight.

Cooler and drier conditions will move into the region behind the
front, which only pushes as far south as central OK and AR. By
Friday afternoon, another upper level system will be approaching the
area. This lead to a surface low developing over OK and then
tracking to the east. This more southerly trend is quite a
difference from the previous two nights which had the low further
north. The more northern track favored more widespread heavy
rainfall through much of the forecast area. With a trend further
south, the heaviest rain now looks to be south of I-70 and more
likely across southern MO/northern AR. Another difference is that
the precipitation looks to be ending earlier on Saturday than
previously expected, perhaps during the afternoon, rather than late
in the evening or even overnight.

High pressure traversing the area on Sunday should help to start to
dry things out. The forecast through Tuesday looks relatively quiet
at this point. But models are pointing to another strong storm
system for the middle part of next week.

&&

.Aviation...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1234 PM CDT WED APR 19 2017

Thunderstorms still expected to move into the terminals late this
evening from northwest to southeast. Expected timing is a bit
slower than previous forecast so have moved the timing a bit
later. Once the cold front pushes into and through the terminals
MVFR CIGs are expected at least right behind the front. Models
indicate very thin saturated layer around FL025, so MVFR CIGs
could scatter out to MVFR earlier than the anticipated late
morning or early afternoon on Thursday.

AMD NOT SKED still written into the KSTJ forecast due to delivery
of observations at KSTJ being unreliable. Reliability in delivery
should be restored by the end of the week.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&

$$

Discussion...CDB
Aviation...Leighton



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