Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO
FXUS63 KEAX 271724
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1224 PM CDT Wed Aug 27 2014
Issued at 900 AM CDT WED AUG 27 2014
Quick update this morning to account for latest radar and satellite
trends. Radar showing ongoing convection across northern
Missouri...with a secondary round inbound from northeast Kansas.
Meanwhile...outflow from this morning/s convection continues to race
south of the metro with decent northerly winds (gusts in the low 20
kt range) found in its wake. As alluded to below...very complicated
fcst today as models continue to struggle with convective trends.
That said...have increased pops south into the KC metro this morning
to account for activity across northeastern KS which continues
tracking east. Fairly efficient rainfall this morning thanks to PWAT
values close to 2" (validated on TOP and OMA 12 RAOBs). Concerns
heading into tonight will be for the potential for redeveloping heavy
rain as stalled front begins to lift north as leeside cyclogenesis
takes shape across the Colorado and Kansas High Plains. A modest low-
level jet feeding into the boundary coupled with a few passing
shortwaves aloft will likely support an active radar scope during the
early morning hrs. Main questions are just how far east will this
activity get...and whether any precip hits areas that received heavy
rain this morning /4+ inches in Atchison Co. MO/. May need to
consider a flash flood watch for portions of our northwestern zones
Issued at 403 AM CDT WED AUG 27 2014
Challenging forecast on tap for today mainly in regards to
precipitation chances. Early this morning...a stationary front is
analyzed from Springfield, Illinois to Sedalia to south of Topeka. A
modest 20-25KT southwesterly LLJ has develop across central Kansas
and is overriding this stationary front allowing elevated convection
to develop across southwestern Iowa through extreme northwestern
Missouri and back into northern Kansas. This may allow for training
for precipitation across northwestern Missouri this morning and with
PWAT values near 1.75" precipitation may be heavy. These storm are
progged to move eastward across northern Missouri this morning. This
afternoon however, is more nebulous as some operational models
(GFS/EC) play the stationary front as the focus for afternoon
convection. However, with little convergence to speak of this
solution is not preferred. The 00Z NAM is more focused on an area of
isentropic ascent along the 310K surface sparking convection over
the KC Metro late this morning and then moving precipitation sewd
across the CWA this afternoon. Hi-res models are pointing toward
pop-up type convection this afternoon south of the boundary in the
warm sector. Also, it develops additional convection across
northwestern Missouri later this afternoon and evening in response
to better upper level support in the form of a lead shortwave
ejecting out from the main upper trough back across the Great Basin.
It is this solution that is preferred an as such have higher POPs
for today across the northern CWA to account for morning convection
and additional convective development this afternoon. Also have
slight POPs further south to depict afternoon pop-up convection.
Cloud cover and height falls later in the day especially across the
north will lead to highs in the lower 80s to the north and to the
lower 90s across the south.
Also, during the day today, the upper level trough over the Great
Basin will move eastward into the Eastern Rockies. Lee cyclogenesis
will develop across the western high Plains and a surface low will
develop and begin to move northeastward during the evening. This
will help pull the surface boundary northward across the forecast
area. Another nocturnal LLJ will develop albeit west of the area.
Thunderstorms are again progged to develop and move into the
northern portion of the CWA north of the front...so how far south
precipitation makes it will hinge much on the frontal position.
Consequently, have chance POPs across the northern CWA sloping to
slights further south.
Outside of morning convection Thursday...it appears conditions will
remain dry as the area should be firmly in the capped warm sector.
this will allow for warmer temperatures in the mid 80s to mid
Thursday night the aforementioned upper level trough moves into the
central Plains forcing a cold front into eastern Kansas. This will
allow thunderstorms to move into the western CWA Thursday night. The
front will then move slowly across the area Friday and Friday night
as the upper level trough slows and weakens as it moves into the
eastern Plains. Highs Friday will be in the 80s. The upper level
trough finally moves through on Saturday continuing thunderstorm
For the extended period...Sunday looks to be the dry day of the
holiday weekend in the wake of the upper level system. Expect highs
in the 80s. Models are in agreement that on Monday an upper level
trough will bring another round of thunderstorms to the area. Where
they are different is in the strength of the and placement of the
trough. The EC is much stronger and further north than the GFS. Both
push a cold front into the area Monday however, the EC pushes it
through the area by Tuesday night whereas the GFS which depicts a
much weaker and flatter trough stalls the front across the CWA. This
front then becomes the focus for a prolong period of precipitation.
As such have opted to keep the ALLBLEND solution which keeps chance
POPs over the area from Monday through Tuesday and slight chance
POPs into Tuesday night.
.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1224 PM CDT WED AUG 27 2014
Ongoing shwr/storm activity now lifting northeast of area terminals
as southerly flow reestablishes itself aloft. Overall...current fcst
calls for dry conditions this afternoon as main outflow boundary
from this morning/s convection remains south.
Overnight...shwrs/storms expected to redevelop after 3z as low-level
strengthening and stalled front to our south begins lifting north. For
now...have offered a VCTS mention at all terminals starting between
2/3z...with a tempo TSRA mention at STJ...which stands the best
chance at realizing impacts from developing overnight convection.
Conditions should improve after sunrise as front retreats north.
Weak easterly winds between 5-10 kts expected through the period.