Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 172035
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
235 PM CST Fri Feb 17 2017

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 234 PM CST Fri Feb 17 2017

The main item of interest over the next 24-30 hours will be the
threat of any rainfall associated with the lifting upper low
currently located over the southern Plains.  Model consenus shows
the upper low lifting east-northeast tonight to the vicinity of the
NW AR/SW MO border by 12Z Saturday, and then into the TN Valley by
early Saturday evening. The increase in clouds with this system will
contribute to mild temperatures tonight with most locations only
experiencing lows in the 40s, and some record high mins will be
possible. The unseasonably warm temperatures (+20 to +25 degrees
above average) will continue on Saturday as well, however the
greater cloud cover should temper the max temp readings back a bit
from those experienced the last few days.

Rainfall is a little more iffy. Weak large scale ascent associated
with the upper low spreads into southeast MO and southern IL
overnight and persists to varying degrees on Saturday morning. The
low levels however are quite dry and moisture will be largely
confined to the mid-upper levels. I prefer the RAP depiction of this
and thus some scattered rain showers seem the most probable scenario
across parts of southeast MO and southern IL, with the probability
diminishing and shunting east in the afternoon with the progression
of the upper system.

Glass

.LONG TERM...  (Saturday Night through Next Friday)
Issued at 234 PM CST Fri Feb 17 2017

Upper ridge to build into region Saturday night, so will see dry and
above normal temperatures through the rest of weekend and into early
next week. Near record highs Sunday and Monday in the upper 60s to
mid 70s.

By Monday, upper ridge begins to move off to the east as next
weather system approaches. So will see low level moisture on the
increase as well as decent instability for our area. But still have
the issue with split flow aloft, models continue to lift the
northern stream wave out faster through the Great Lakes region,
while southern stream closed low tracks eastward slowly. However,
12z model runs are a bit more optimistic with two streams phasing
together, giving us better chances for rain early Monday morning
through Tuesday morning. Could see scattered/isolated thunderstorms
Monday afternoon/evening, mainly over central/northeast MO, as well
as west central IL, so added thunder mention there.

Weak boundary washes out over region for mid week with zonal flow
aloft, so will see slightly cooler highs in the mid 60s to low 70s.

Next system to approach area on Thursday with strong cold front
moving through Friday. This is when we will have our best chances of
showers and a few thunderstorms. Highs will dip down into the low
50s to mid 60s by Friday, but still above normal for this time of
year.

Byrd
&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1131 AM CST Fri Feb 17 2017

VFR flight conditions will prevail at the terminals through the
forecast period. Occasionally gusty southwest winds will continue
this afternoon and then diminish at sunset. An upper level system
will bring an increase in mid-high clouds beginning tonight and
thickening on Saturday. Present indications suggest that any
chance of showers with this system will be south of all the
terminals across southeast MO and southern IL.

SPECIFICS FOR KSTL:

VFR flight conditions will prevail through the forecast period.
Occasionally gusty southwest winds will continue this afternoon
and then diminish at sunset. An upper level system will bring an
increase in mid-high clouds beginning tonight and thickening on
Saturday. Present indications suggest that any chance of showers
with this system will remain south of KSTL.

Glass
&&

.CLIMATE...
Record Highs

 2/17  2/18  2/19    2/20
STL: 77/1911  74/1971  77/2016  78/2016
COU: 74/2011  71/1930  76/1930  76/2016
UIN: 70/2011  68/1971  71/1930  72/2016


&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     50  68  49  75 /  10   5   0   0
Quincy          45  66  45  71 /   0   0   0   0
Columbia        47  67  47  73 /   5   5   0   0
Jefferson City  47  68  46  74 /   5   5   0   5
Salem           48  64  47  70 /  10  10   0   0
Farmington      48  66  47  71 /  30  30   0   0

&&

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

$$
WFO LSX



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