Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 252011

Area Forecast Discussion
National Weather Service Saint Louis MO
311 PM CDT Wed Apr 25 2018

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 311 PM CDT Wed Apr 25 2018

Upper level LOW currently centered over southeast Kansas continues
to move slowly southeastward early this afternoon and has helped to
overspread a large area of light rain across the western and central
sections of Missouri.  Skies were otherwise cloudy across our region
with a light northerly flow, resulting in temperatures being largely
stagnant this afternoon, with readings in the 65 to 70 range for
areas around Saint Louis and further S and E, and upper 50s and
lower 60s elsewhere.

Models continue to track the center of the upper LOW to the
intersection of MO/AR/OK/KS by early this evening and then pivot
the LOW more to the east overnight tonight to near Memphis by
12z/Thu and further east from there.  This will pivot the light rain
as well, allowing it to overspread into much of central and
southeast MO and far southern IL tonight while leaving areas near
Saint Louis and sections of IL near I-70 near the northern edge or
gradient. Believe the likelihood of pcpn is high for many of these
areas, but realized rainfall will be only a few hundredths for much
of the area, except southeast MO where up to a half inch will be
possible, mainly tonight.  Areas around Quincy and towards central
IL will miss out on this rain opportunity.  Rain is then expected to
exit southeastern Missouri by late Thursday morning with decreasing
clouds during the day on Thursday.

The approach of another shortwave is now expected to be uneventful
with the main strength of this diving well south of our area, and
with limited moisture and a shear axis sliding thru, will be
difficult to produce much in the way of sensible wx.

Min temperatures tonight will largely be in the 40s, with many sites
not getting there until late as clouds clear in the north, with a
preference for slightly above MOS in the south where clouds will
hold and slightly below MOS in the far north where clearing is
expected.  Max temperatures should recover well on Thursday for an
unusual "average" temperature day with afternoon peaks around 70 for
many locales.


.LONG TERM...  (Thursday Night through Next Wednesday)
Issued at 311 PM CDT Wed Apr 25 2018

Northwest upper flow will prevail thru Sunday.  One final shortwave
will slide thru at the start of this period on Thursday night, but
as mentioned in the SHORT TERM section, is not expected to result in
any precipitation and has been trending lower on PoPs the past
couple of days.

Friday thru Sunday should otherwise be a dry period with
temperatures within 5 degrees of average for this time of year.

A big pattern shift is then anticipated with passage of the upper
RIDGE axis late Sunday and a deepening of the western CONUS TROF
early next week, setting it up for warmer and active wx to dominate
the middle and latter part of next week.  Dry weather should prevail
until the combo of moisture and lift from shortwave disturbances
ejecting from the main TROF reach here, which looks to begin on
Tuesday afternoon.  Max temps are expected to rise into the lower
80s for parts of the area on Monday thru Wednesday.



.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1220 PM CDT Wed Apr 25 2018

VFR conditions are expected to prevail at the TAF sites for much
of the valid period. Only exception is anticipated to be a small
area of MVFR CIGs located just NE of STL metro slowly advecting to
the SW in the ambient light N-NE flow. This area is now expected
to impact STL and CPS for up to a few hours this afternoon and
will be monitored if it will affect SUS. Otherwise, look for light
N-NE surface winds to back more N-NW by Thursday. A period or two
of very light rain should affect COU later this afternoon and this
evening, and could affect STL metro sites mainly this evening and
have added in VCSH to primarily account for.

SPECIFICS FOR KSTL: Clump of stratocumulus clouds with MVFR CIGs
just NE of the terminal currently and should affect the terminal
early this afternoon. Otherwise, VFR and mainly dry. A period of
very light rain could affect the terminal this evening but is not
expected to result in wet runways at this time due to the
anticipated very light intensity.



Saint Louis     47  69  48  70 /  50   0   5   0
Quincy          41  69  44  67 /   0   0   5   0
Columbia        44  69  45  69 /  50   0   5   0
Jefferson City  44  69  45  69 /  60   0   5   0
Salem           44  66  46  68 /  20   0   5   5
Farmington      47  65  46  69 /  90  10   5   0




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