Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 070912

Area Forecast Discussion
National Weather Service Saint Louis MO
412 AM CDT Sun Jun 7 2020

.SHORT TERM...  (Through Late Tonight)
Issued at 411 AM CDT Sun Jun 7 2020

High pressure over the Great Lakes and Ohio Valley will continue to
provide east-southeast flow today, and the upper level ridge will
also help to keep the mid Mississippi Valley warm and dry.  Mass
fields on short term models are hinting that there will a bit more
cool/dry intrusion into our area today than there was on Saturday,
so I don`t think it will be quite as hot today.  That being said,
looking at the consensus of guidance, and considering the strength
of the upper ridge as well as strong insolation with little or no
cloud cover, I leaned toward the bias corrected temperatures which
are a few degrees warmer than traditional MOS temperatures today.
This yielded highs ranging from the upper 80s in central Illinois to
the low 90s in central, east central, and southeast Missouri.

Tonight continues to look quiet for the mid Mississippi Valley
underneath the upper level ridge.  Easterly surface flow actually
looks like it will increase a bit as the pressure gradient increases
between the high which will be trying to nose south into the Mid
Atlantic States and TS Cristobal. The easterly flow should push the
cooler and drier air over the Ohio Valley east into the mid
Mississippi Valley.  This will produce slightly cooler lows for
tonight, particularly across the eastern Ozarks and rural east
central Missouri.  The more urban St. Louis Metro Area will likely
be a few degrees warmer due to the heat island effect.


.LONG TERM...  (Monday through Saturday)
Issued at 411 AM CDT Sun Jun 7 2020

The upper level ridge moves east allowing TS Cristobal to slide
north through the lower Mississippi Valley on Monday.  The forward
speed of the system has increased slightly, and the consensus of
guidance now brings the leading edge of the rain shield into
southeast Missouri before 00Z Tuesday.  However, GEFS QPF plumes and
WPC guidance still shows the lion`s share of the rain falling
between 06Z and 18Z Tuesday.  Speaking of GEFS plumes, there is
still a wide range of storm total amounts among the members.  The
lowest QPF amount at KCOU is 0.58 inches and the highest is 3.91
inches, at KIRK the range is 0.07 to 4.35 inches, and at KSTL it`s
0.24 to 2.73.  There also seems to be very little clustering in the
plumes, so we can continue to infer a large amount of uncertainty in
the QPF.  However, the consensus of guidance does have the heaviest
QPF on the western side of the storm track which would put the the
highest amounts over central Missouri.  Continued to stick with WPC
guidance for the official forecast which yields 3-4 inches of rain,
primarily between 06Z and 18Z Tuesday.

Rain should be tapering off to scattered showers on Tuesday night as
Cristobal moves into the upper Mississippi Valley.  The trough which
picks up Cristobal moves east Wednesday and pushes a cold front
through the Midwest bringing us some cooler and drier weather.  That
trough phases a larger trough over eastern North America and the
pattern becomes highly amplified.  Medium range guidance has the
Midwest in northwest flow by the end of the week with temperatures
at or below normal.



.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1218 AM CDT Sun Jun 7 2020

VFR flight conditions are expected to prevail across the area for
the rest of the night with light east-southeast flow. There may be
some fog in river valleys again like last night, but temperatures
are a little warmer, so I don`t think it`s going to be as
widespread or as dense tonight. Any river fog that does develop
should dissipate quickly after sunrise. VFR conditions are
expected to continue through the remainder of the forecast period.



Saint Louis     92  68  91  73 /   0   0   5  60
Quincy          87  66  88  71 /   0   0   0  40
Columbia        92  68  89  70 /   0   0   0  60
Jefferson City  93  68  91  71 /   0   0   5  70
Salem           88  65  91  73 /   0   0   5  40
Farmington      90  63  88  69 /   0   0  20  80




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