Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO
FXUS63 KEAX 182326
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
626 PM CDT Mon Aug 18 2014
.SHORT TERM...(This Evening through Wednesday Night)
Issued at 252 PM CDT MON AUG 18 2014
There are several things working for and against getting convection
through the forecast area tonight and that is leading to a relatively
high level of uncertainty for a 6 to 12 hour forecast. Working for
the potential for storms tonight is a weak upper wave noted on
afternoon water vapor imagery in western South Dakota and Nebraska.
The other positive for storms tonight is strong isentropic ascent
around 310K from a strongly veered low level jet. A stronger upper
wave was noted in eastern North Dakota and that may drag a cold front
southward into northwestern Missouri and northeastern Kansas which
could provide enough low level ascent to realize the modest to strong
instability present in the region. However, there is a stout cap in
place and the features previously mentioned are nebulous and weak so
it doesn`t seem like a really good probability for storms tonight.
Have generally kept the chances in the 40 percent range but felt the
strong and moist isentropic ascent would be enough to get some
showers and storms going so have PoPs as high as 50%. If this occurs,
shear is strong enough, probably on the order of 35 to 40 kts in the
0-6KM layer, to lead to some organization as any storms propagate
south/southeastward. *If* we`re able to get storms, there is the
potential they could produce strong and gusty winds as well as
marginally severe hail given the stronger shear working into the
Tuesday - Wednesday:
Tuesday will likely be very hot and humid across the southwestern
two-thirds of the forecast area, where the warmest temperatures
aloft will be located. We should also see a decreasing trend for
convection through the day. But there is a different story at night.
It appears the elevated mixed layer will be straddling the forecast
area. Models are pretty good agreement depicting a northwest to
southeast corridor of precipitation associated with this temperature
demarcation and shows up well as an area of strong theta-e
convergence. Strong and moist isentropic ascent in the 305K to 310K
surface will help to initiate showers and storms. Shear may be
marginal for severe convection leading to a marginal risk for hail.
Rather, precipitable water values approaching 2" in the area will
likely lead to pockets of heavy rain during the overnight period.
Otherwise, daytime temperatures look to return to the upper 80s and
lower 90s on Tuesday and the the lower to middle 90s for Wednesday.
With high humidity in the area, afternoon heat indices will climb
into the 100 to 103 range for much of the forecast area.
.LONG TERM...(Thursday through Monday)
Issued at 252 PM CDT MON AUG 18 2014
The end of the week will feature above normal temperatures as upper
ridge buckles northward over the region in response to troughing
over the eastern and western US coast. Strengthening low level
southwesterly flow should boost H8 temperatures into the +20C to
+24C range by Thursday continuing into the weekend. Surface
temperatures in the lower and middle 90s combined with increasing
low level RH should produce heat index values near or slightly above
Nocturnal convection could brush far northern Missouri along the
periphery of the upper ridge during this time period, but chances
appear to be fairly low at this time. Better chance for
precipitation looks to hold off until early next week when some
flattening of the upper ridge occurs and a surface boundary works
southward into the region.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 626 PM CDT MON AUG 18 2014
VFR conds will cont thru midnight. However, after midnight, the
operational models are dvlpg ts acrs nern KS and nwrn MO btn 06Z-08Z.
There is some uncertainty in thunderstorm dvlpment though since the
short range hi-res models are not dvlpg thunderstorms tonight. With
dvlpment uncertain have contd VCTS mention in the TAF affecting the
terminals btn 08Z-12Z. Otherwise conds should remain VFR with clr
skies tonight giving way to sct-bkn clouds btn 5-6kft after midnight.
Thru the day tomorrow expect sct mid lvl clouds. Winds tonight will
be light out of the south before becmg lgt and vrb tomorrow.