Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 220839
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
339 AM CDT Sat Apr 22 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 339 AM CDT Sat Apr 22 2017

One wave of rain will move out of the area around 10z while the next
wave moves into central MO. Previous forecast has a decent handle on
the situation however have had to manipulate the pops a bit to try
and match the movement. Temperatures will be quite cool today, but
have raised the highs just a bit for most areas. The upper system
finally moves out late tonight from 06 to 12z Sunday. Rain will end
this evening hanging on the longest across the southeast. Plenty of
dry air, sunshine, and warmer temperatures for Sunday.

JPK

.LONG TERM...  (Sunday through Friday)
Issued at 339 AM CDT Sat Apr 22 2017

After a chilly start to Sunday morning strong April sunshine under a
mostly clear sky should kick temperatures back up into the upper 60s
and low 70s in spite of continuing weak north-northeast flow and cold
advection.  Tranquil weather continues Sunday night through Monday
night with temperatures warming well into the 70s on Monday as warm
advection ramps back up ahead of a trof of low pressure over the
Great Plains.

The cold front associated with this trof will move into southeast
Nebraska or northwest Missouri on Tuesday.  There`s some
discrepancies between model guidance on the timing and strength of
the system as it pushes further east through Missouri on Tuesday
night.  It does look like we`ll see some thunderstorms Tuesday night
across the area.  GFS has MUCAPE over 500 J/Kg all the way up into
west central Illinois at 06Z with showalter index around -3...though
the greatest instability will stay south of I-70 across southeast
Missouri and southwest Illinois with MUCAPE in excess of 1000 J/Kg.
0-6km shear is 40-50kts and the greater instability across the
Ozarks suggests there could be some strong to severe storms. However
the ECMWF is has even less CAPE than the GFS and would suggest that
severe potential would be very limited if any at all Tuesday night.
The ECMWF is also quite a bit faster pushing the front through and
would basically have us in dry/cold advection all day Wednesday
while the GFS pushes the front through our area during the morning
and early afternoon on Wednesday and therefore has much more
precipitation over us.  Tuesday continues to look warm ahead of the
front int warm advection. Think upper 70s and low 80s is easily
attainable in southwest flow. Wednesday should be cooler whether due
to clouds and precip or due to cold advection.

The GFS drops another strong longwave trof of low pressure over the
Rockies on Thursday.  The ECMWF handles this trof differently with
an initially weaker shortwave and then the stronger longwave
developing late in the forecast on Friday.  Either way, the weather
on Thursday and particularly Friday looks unsettled although
confidence is low due to the model differences that far out.

Carney

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1147 PM CDT Fri Apr 21 2017

Waves of light rain are expected overnight with a trend to more
continuous rain along a KCOU-KSTL axis after 10Z. This more
continuous rain would then last through Saturday morning, ending
in the early afternoon across far eastern MO/southwest IL.
VFR flight conditions will prevail initially with the rain,
however as the rain becomes more continuous in the predawn hours
there should be a trend for predominately MVFR flight conditions
until the rain ends. Gusty northeast winds will also develop
overnight and continue through Saturday.

SPECIFICS FOR KSTL:

Waves of light rain are expected overnight with a trend to more
continuous rain between 10-12Z, with the rain continuing until
early Saturday afternoon. VFR flight conditions will prevail
initially however as the rain becomes more continuous in the
predawn hours there should be a trend for predominately MVFR
flight conditions until the rain ends. Gusty northeast winds will
also develop overnigh and continue through Saturday.

Glass

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     55  43  72  48 /  90  20   0   0
Quincy          58  40  71  45 /  20  10   0   0
Columbia        54  40  70  44 /  80  10   0   0
Jefferson City  53  41  70  43 /  90  10   0   0
Salem           54  43  68  44 /  80  30   0   0
Farmington      49  42  68  42 /  90  40   0   0

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



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