Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 292041
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
341 PM CDT Fri May 29 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 340 PM CDT Fri May 29 2015

Complex of showers and thunderstorms ahead of an MCV over E OK will
slowly translate north and eastward overnight. Main threat with this
feature looks to be the potential for localized heavy rainfall due to
long/narrow CAPE profiles with high PWAT values and slow
translational speed of convection. Best bet right now of where
heaviest axis of rainfall would be across south-central Missouri
extending toward the Missouri River between KCOU and KSUS where
1.00-1.50"+ of rain is likely. Threat of widespread severe weather
continues to look low as low-level atmosphere nocturnally stabilizes
through the evening hours along with weak deep-layer shear.
However...cannot rule out an isolated strong wind gust or two in any
heavy precipitation core.

Another seasonably mild night should be in store ahead of synoptic cold
front which will move into northwestern sections of the are very late
tonight. Lows are expected to be in the 60s.


Gosselin


.LONG TERM:  (Saturday through Next Friday)
Issued at 340 PM CDT Fri May 29 2015

(Saturday-Saturday Night)

Front will slowly progress south and east on Saturday clearing the
CWFA by late afternoon per latest model guidance. Showers and
thunderstorms along and ahead of the front along with post-frontal
showers as UL jet streak backbuilds. A few storms across southeast
Missouri and southwest Illinois may be strong to severe with CAPE
values of 1000-1500 J/kg and 0-6km shear on the order of 20 knots or
so. Isolated severe wind gusts along with small hail look to be the
primary threats. A cooler day compared to this afternoon is also
expected due to copious amounts of cloud cover...precipiation...and
cold advection commencing to the northwest of the low-level
baroclinic zone. Coolest conditions will be across portions of
northeast Missouri with highs only in the mid 60s with warmest highs
near 80 degrees toward KFAM and KSLO.

Cold/dry advection begins to really amplify and take hold late
Saturday night as low-level anticyclone slides southeast toward the
Great Lakes. Chances of showers should wane overnight from north to
south as the drier/more stable air filters in from the north and
east. A cool night for very late May should be in store just from
the strength of the cold advection as clouds look to linger across
the area. Look for lows to range from the upper 40s to mid 50s from
north to south across the bi-state area.


(Sunday-Friday)

The Sunday through Friday timeframe will be marked by mostly dry
weather along with moderating temperatures. Cool day still appears
to be in store on Sunday with highs likely failing to hit 70 degrees
across the area. Upper-level low as previous forecaster mentioned
looks to get stuck beneath/to the south of building ridge axis
across lower Mississippi Valley. This should yield fairly
tranquil/dry weather through much of next week with highs warming
back above normal by Wednesday. Next chance of showers/storms still
appears to be on Thursday though large model disagreements do exist
between the GFS/ECMWF with the European solution continuing the dry
trend while the GFS brings the area some showers/storms.


Gosselin

&&

.AVIATION:  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1227 PM CDT Fri May 29 2015

There are 2 main areas to watch for precipitation this afternoon.
The first is from central MO into west central IL including KCOU
and KUIN. These terminals will be impacted by a large area of
showers that is lifting northeastward and should consist of
predominatly VFR flight conditions. The other region is from south
central MO through St. Louis and points east where scattered
showers and thunderstorms will prevail. KCPS appears to have the
greatest thunder potential in the short term and thus have a TEMPO
group. There should be a lull of precipitation from the late
afternoon into the very early evening then a large area of showers
and thunderstorms originating in Eastern OK/Southeastern KS/Southwestern
MO should spread across the area and dominate much of the evening
into the overnight hours. Predominately MVFR flight conditions are
expected with this precipitation tonight. A cold front will then
move across the region on Saturday bringing a northwest wind shift
and MVFR cigs.

Specifics for KSTL:

Tough call on direct impacts this afternoon. In the near term it
appears that any thunder threat will be just to the east of KSTL.
However, scattered showers and thunderstorms will dot the area
thru mid afternoon but confidence is not great enough for more
than VCTS at this time. Will monitor closely and AMD if conditions
change. There should be a lull of precipitation from the late
afternoon into mid evening then a large area of showers and
thunderstorms originating in Eastern OK/Southeastern KS/Southwestern
MO should spread across the area and begin impacting the terminal
late this evening and dominate through the overnight hours.
Predominately MVFR flight conditions are expected with this
precipitation tonight. A cold front will then move across the
region on Saturday with FROPA near midday bringing a northwest
wind shift and MVFR cigs.

Glass

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     68  76  54  66 /  90  80  30   5
Quincy          64  67  47  65 /  80  60  10   0
Columbia        64  69  51  66 /  90  30  20   5
Jefferson City  64  71  49  66 /  90  40  20   5
Salem           70  77  54  67 /  60  70  40  10
Farmington      67  76  54  65 /  70  70  30  10

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX





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