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Area Forecast Discussion (AFD)

Issued by Kansas City/Pleasant Hill, MO (EAX)

                            
000
FXUS63 KEAX 210440
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1140 PM CDT Fri Sep 20 2019

.Discussion...
Issued at 331 PM CDT FRI SEP 20 2019

The main concerns through the forecast period will be the potential 
for heavy rain and flooding as well as the potential for severe 
storms Saturday night through Sunday. This afternoon moisture from 
the remnants of Imelda are streaming into the southern CWA bringing 
light showers to the area. These showers should subside this 
evening. However, late tonight a low level jet will become focused 
over the area as a lead mid-level shortwave ejects out ahead of the 
main upper level trough which will be over the western High Plains. 
This will allow scattered showers and thunderstorms to develop over 
the area generally after midnight. The low level jet become more 
diffuse as we move into the day on Saturday however, it continues to 
nose into the area with continued lead mid-level shortwave moving 
through the region. This should continue scattered thunderstorm 
activity through the day on Saturday. As we move into Saturday 
evening the aforementioned upper level trough over the northern High 
Plains will move into the northern Plains forcing a cold front into 
the area. Storms with heavy rain will be possible out ahead of this 
front Saturday evening across northwestern Missouri and northeastern 
Kansas. This will be our window for severe weather on Saturday 
evening also it will be conditional on how scattered the storm 
activity is during the day on Saturday. The main threat will be for 
isolated damaging winds. 

The bigger threat will come Saturday night into Sunday in the form 
of flash and river flooding. This will occur as the front becomes 
stationary across the CWA and a nocturnal LLJ develops Saturday 
night. This will lead to several rounds of heavy rainfall. PWATs at 
this time will be between 2.00-2.25" which is 200 to 250 percent of 
normal for this time of year. Sunday the front will sag slowly south 
by heavy rainfall will continue until the upper level trough finally 
pushes through the Upper Midwest Sunday evening and force the cold 
front south of the CWA. Models are consistent in painting widespread 
2 to 4 inches of precipitation across the CWA with a possible band 
of higher amounts somewhere between Interstate 70 and Highway 36. As 
such, a flash flood watch is in place for the entire CWA from 
Saturday night into Sunday night.  

Conditions are expected to finally dry out Sunday night into Monday 
as high pressure builds into the region with more early Fall like 
temperatures expected Monday and Tuesday. By Tuesday afternoon, the 
upper level flow becomes more quasi-zonal with several shortwaves 
continuing precipitation chances through Thursday with the best 
chance occurring on Friday as a strong upper level trough moves 
through the region forcing a cold front through the area.

&&

.Aviation...(For the 06Z TAFS through 06Z Saturday Night)
Issued at  1132 PM CDT FRI SEP 20 2019

Expect cigs to drop to IFR conditions at all terminals after
06-07z. Otherwise spotty light rain/drizzle may reduce visibility
to 5-6 miles but winds should stay above 10kts all night so
visibility should not be an issue. Winds continue to gust near
20kts and will increase after sunrise. Cigs will increase to MVFR
around midday and could go VFR by afternoon but not enough 
confidence so did not introduce into TAFS. Thunderstorms expected
to develop between 09-12z and again in afternoon hours, but
confidence not high for afternoon storms. Expect a line of storms
to develop across NW MO ahead of cold front and push south and 
affect terminals tomorrow evening.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...Flash Flood Watch from Saturday evening through Sunday evening 
     for KSZ025-057-060-102>105.

MO...Flash Flood Watch from Saturday evening through Sunday evening 
     for MOZ001>008-011>017-020>025-028>033-037>040-043>046-053-
     054.

&&

$$

Discussion...73
Aviation...Christensen