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Area Forecast Discussion (AFD)

Issued by Wichita, Kansas (ICT)

                            
000
FXUS63 KICT 151829
AFDICT

Area Forecast Discussion
National Weather Service Wichita KS
129 PM CDT Thu Aug 15 2019

.MESOSCALE DISCUSSION...
Issued at 112 PM CDT Thu Aug 15 2019

Complex and challenging short term forecast. Models struggled 
with storms this morning, which were partially or substantially 
elevated convection across Nebraska. Outflow from these storms is
just north of the forecast area at this time, and suspect there 
will be only minor movement of boundary during the afternoon given
increasing south flow on south side of the boundary, good heating
and lack of convection north of boundary. Satellite and SPC meso 
page suggest airmass is still strongly capped and may remain that 
way for much of the afternoon.

The current thinking is for storms to develop on this boundary
closer to 23-00 UTC and then move south into instability axis. 
Initially discrete storms should form into a cluster and/or line 
as it heads south. Initial large hail/wind threat should 
transition to more of a wind threat as the storms move across 
south central KS, probably in the 03-06 UTC time frame. An
isolated tornado cannot be ruled out, but does not appear to be
the primary threat. -Howerton

&&

.SYNOPSIS...
Issued at 327 AM CDT Thu Aug 15 2019

There will be several opportunities for strong to severe
thunderstorms over the next few days. Not everyone will see severe
weather, but many areas will have a chance. In addition to any
severe weather, heavy rain and flooding will be a threat as well.
Temperatures will be close to normal for most areas over the next
few days, although thunderstorms could keep temperatures from
getting too warm for some. Heading into the weekend and,
especially, next week, hot and drier weather look to return.

&&

.SHORT TERM...(Today through Saturday night)
Issued at 327 AM CDT Thu Aug 15 2019

The stage is set for multiple opportunities for thunderstorms over 
the next few days, some of which will be strong to severe. The 
challenge will be attempting to resolve day-to-day convective 
evolution, with each day potentially being impacted by convection as 
far back as 24-48 hours prior (as has been seen over the past 
couple of days). While short term model guidance (CAMS) can 
resolve some of these features, and very well at times, their 
solutions can also be vastly different than what actually plays 
if any boundary or low-level feature, for example, isn't handled 
well. For those who use model data, it is recommended to keep all 
of that in mind. I'll try to cover the potential scenarios below.

THE SETUP - Early this morning, a seasonally strong s/w was 
dropping SE through the Northern Rockies/Northern High Plains. 
Ahead of this wave, ongoing, and organized, convection extended 
from the Wyoming Front Range eastward into northern Nebraska. This
appears to be driven by WAA ahead of the Northern Rockies wave. 
Corfidi Vectors suggest a continued SE movement into the Central 
Plains through the morning hours. At the same time, a baroclinic 
zone arcing SE from Wyoming into southern Kansas may tend to shift
ever-so- slightly north and east through the day ahead of the 
Northern Rockies' shortwave. 

SCENARIO #1 - Convection over Nebraska propagates southeast across
northeastern Kansas, possibly clipping northern sections of
central Kansas with strong, gusty winds and heavy rain later this
morning or early afternoon.

This scenario would likely lay out an outflow boundary that could
become the focus for redevelopment this afternoon/evening across
parts of our area, especially in the vicinity of a more deeply 
mixed airmass emanating out of SW KS (leading to enhanced 
convergence). This scenario appears to be the "worst-case" so to 
speak as any convection that forms along the outflow boundary this
afternoon would occur in the presence of steep to very steep 
lapse rates (8-9 C/km), seasonally strong deep layer shear 
(40-50kt), strong instability (3000-4000 j/kg MLCAPE), and
good veering with height (higher effective SRH). While convection
developing along the outflow boundary may tend to grow upscale
with time into a forward-propagating MCS, any discrete or semi-
discrete cells would have the potential to become supercellular, 
posing a large to very large hail threat in addition to 
gusty/damaging winds, and very heavy rain. Given the potential 
combination of steep low- level lapse rates, convergence along 
residual boundaries, and strong instability/enhanced stretching, 
a tornado risk cannot be ruled out in in this 
scenario...especially with any initial discrete cell. This 
scenario could also tend to focus the severe threat further south 
on Friday, depending on how far south any MCS/outflow can get.

SCENARIO #2 - Convection over Nebraska propagates with a bit more
of a southward motion (compared to southeastward), moving across a
larger portion of our CWA later this morning/afternoon. 

In this scenario, storms upstream could reach part of our area
during peak heating, leading to an increased risk of becoming more
SFC-based (if they aren't already). In this case, the threat may
tend to be more of a wind concern, with isolated large hail.
Should this occur, the atmosphere could be worked over enough to
delay additional thunderstorm development until late tonight as
the Northern Rockies' shortwave glances the area. If the
environment is worked over sufficiently enough, the 2nd round of
storms may tend to stay north of our area. While this scenario
certainly poses a severe risk as well, the threat of discrete
cells and a few tornadoes may tend to be lower. This, in turn, 
could allow the severe weather threat on Friday to cover more of 
our CWA (compared to scenario #1). 

The main takeaways here are that severe weather is expected for at
least parts of our CWA over the next couple of days, but it cannot
be stressed enough how much the evolution of ongoing, upstream
convection may play into the threat/outcome. Stay tuned for
continued updates.

Martin

.LONG TERM...(Sunday through Wednesday)
Issued at 327 AM CDT Thu Aug 15 2019

Late in the weekend and into next week, the mid/upper jet should 
begin to lift back north as an upper level ridge attempts to build 
north out of the southern/southwestern US. This would favor the 
return of hot conditions, with dangerous heat indices once again 
possible. This may also tend to suppress convection.

Martin

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 112 PM CDT Thu Aug 15 2019

Challenging aviation forecast due to uncertainty with convection.
Current thinking is storms will develop in the vicinity of 
outflow boundary in central KS late this afternoon in central KS 
and then develop south during the evening. Limited to VCTS for now
given lower probability of occurrence and timing issues. Models 
have been struggling with so far with ongoing convection. 
Potential for MVFR ceilings in the wake of the storms in central 
KS in the predawn hours. -Howerton 

&&

.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT    91  70  93  73 /  20  60  20  30 
Hutchinson      92  68  91  71 /  20  60  20  40 
Newton          89  68  90  71 /  20  60  20  40 
ElDorado        88  70  91  72 /  10  60  20  30 
Winfield-KWLD   90  70  94  74 /  10  50  20  20 
Russell         95  65  88  66 /  30  40  10  30 
Great Bend      94  66  90  69 /  20  50  10  30 
Salina          90  67  89  70 /  30  50  20  40 
McPherson       90  67  89  70 /  20  60  20  40 
Coffeyville     89  73  92  73 /   0  50  10  20 
Chanute         87  71  90  71 /  10  50  20  40 
Iola            86  70  89  71 /  10  50  20  50 
Parsons-KPPF    88  72  91  73 /  10  50  20  30 

&&

.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

MESOSCALE...PJH
SYNOPSIS...RM
SHORT TERM...RM
LONG TERM...RM
AVIATION...PJH