Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 160832
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
332 AM CDT Thu Apr 16 2015

.SHORT TERM:  (Today and Tonight)
Issued at 331 AM CDT Thu Apr 16 2015

Shortwave ridging will develop and amplify aloft today and tonight,
providing the area with warmer and drier weather than the past few
days.  Forecast soundings show us mixing up to around 900mb this
afternoon, so used a healthy dose of mix-down temperatures for highs
today, blended with MOS guidance.  This yielded highs at or just
slightly above warmest MOS guidance.  With ridging holding in
tonight, don`t expect much if any precip...although some of the
high-res WRF members do spit out some sprinkles.  Again...this seems
unlikely given the subsidence provided by the ridge aloft.  As a
result, stuck with a dry forecast for tonight.  It looks like
mid-high clouds may be increasing toward morning, and therefore some
decent insulation so I used a blend of guidance which ended up
producing lows close to the warmer end of MOS numbers across the
area.

Carney

.LONG TERM:  (Thursday through Next Wednesday)
Issued at 332 PM CDT Wed Apr 15 2015

There is a slight chance of lingering showers across southwest IL
on Thursday morning ahead of the lifting and weakening short wave
trof with large scale subsidence overspreading the entire region
in its wake. The big unknown on Thursday is the extent of cloud
cover and impact on temperatures. My present thinking is there
will be extensive clouds at the start of the day given the weak
overall flow aloft and rather moist 925 mb RH progs. I think
clouds will gradually clear/thin west to east during the day, in
part due to the shallow nature of the moisture and high sun angle
and this should allow temps to rise into the 70s.

Thereafter weak surface high pressure slowly retreating into the
OH Valley will produce easterly surface winds and delay southerly
low level return flow. This should allow for a dry period into
Friday morning and potentially longer. The overall trend in the
new forecast is to slow down the eastward spread of pops/precipitation
from the previous one. Present indications are that ridging aloft
will delay the eastward moisture transport and hence the arrival
of precipitation until sometime Saturday. The threat of precipitation
should ramp up on Saturday and into Saturday night as the western
U.S. upper low/trof advances into the Plains bringing south/southwest
flow aloft, embedded disturbances aloft, and deeper moisture
transport into the region. Sunday and Sunday evening look wet as
well with the migration of the main upper trof and associated cold
front.

In the wake of the cold front, a cooler than normal pattern will
persist through the first half of next week thanks to a rather
strong upper low centered north of the Great Lakes and accompanying
broad trof. Several disturbances within the cyclonic west-northwest
flow could bring additional showers from late Tuesday night into
Thursday.

Glass

&&

.AVIATION:  (For the 06z TAFs through 06z Thursday Night)
Issued at 1055 PM CDT Wed Apr 15 2015

Shortwave exiting region, so chances of precipitation have moved
out. VFR clouds will linger across the region for most of the
forecast period. SREF and NARRE model probabilities shows some low
level moisture advecting north towards taf sites, though best
chances of MVFR cigs/vsbys will be just east of metro area. For now
kept tempo MVFR cigs from 09z to 13z Thursday for these tafs.
East winds to become light and variable for remainder of forecast
period.

Specifics for KSTL:
Shortwave exiting region, so chances of precipitation have moved
out. VFR clouds will linger for most of the forecast period. SREF
and NARRE model probabilities shows some low level moisture
advecting north towards region, though best chances of MVFR
cigs/vsbys will be just east of metro area. For now kept tempo MVFR
cigs from 09z to 13z Thursday for STL. East winds to become light
and variable for remainder of forecast period.

Byrd

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     75  59  78  60 /  10   5  10  10
Quincy          72  54  76  56 /  10   5  10  10
Columbia        74  57  78  59 /  10   5  10  30
Jefferson City  75  57  77  59 /  10   5  10  30
Salem           72  56  76  56 /  20   5  10  10
Farmington      73  54  76  57 /  10  10  10  10

&&

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

$$

WFO LSX






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