Area Forecast Discussion
000
FXUS63 KLSX 180250
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
950 PM CDT Thu Jun 17 2021
.SHORT TERM... (Through Late Friday Night)
Issued at 215 PM CDT Thu Jun 17 2021
(Through Tonight)
Activity that fired up over portions of southeast Missouri this
morning, has moved south of forecast area. Otherwise, as clouds
thinned out temperatures warmed up into the upper 80s to 90s.
For tonight, very mild conditions are still forecast as winds pickup
from the south to southwest across the mid-Mississippi Valley. So
lows tonight are expected to be in the 70s areawide, which are about
10 degrees above normal for this time of year.
(Friday)
***Record-breaking Temperatures Are Likely Friday***
Very little change to the temperature forecast on Friday, as the
conditions remain nearly ideal for a very hot day. There will be
plenty of sunshine, favorable southwest to west winds, 850mb
temperatures between +20 and +24C, and very dry soils. So very
high confidence that highs will be in the upper 90s to low 100s,
thus the record highs at KSTL/KCOU (100F/1953) are in jeopardy.
Still some uncertainty with heat index values, but with the
southerly flow returning, seeing 70+ dewpoints advecting into
southern portions of Missouri today, so raised dewpoints on
Friday a bit with heat index values in excess of 105 degrees for
a number of locations now. Therefore, will issue a heat advisory
for a large portion of the forecast area, including metropolitan
St. Louis.
Otherwise, will begin to focus on precipitation chances with a
frontal boundary that approaches region late Friday afternoon.
Majority of the deterministic and ensemble models are a bit slower
with the boundary, having it stall out further north, more over
northeast MO and west central IL. So better chances of showers and
storms will be just north of forecast area Friday night. The threat
for severe storms remains conditional Friday night in this area,
depending on when storms develop as the strong CAP weakens through
the evening hours and forcing increases near the boundary. Some of
these storms could produce localized wind damage or hail given
strong instability and sufficient deep-layer mean wind speeds.
Byrd
.LONG TERM... (Saturday through Next Thursday)
Issued at 215 PM CDT Thu Jun 17 2021
(Saturday - Sunday)
The focus for the weekend is the location of the frontal boundary in
relation to our forecast area. Latest model trends have the boundary
stalling out either along the MO/IA border or closer to the I-70
corridor Saturday through Sunday. So will go with a blend, thus a
further north solution with lower precipitation chances across the
region through this period. With the lower chances of precipitation
and front further north, will have warmer temperatures both Saturday
and Sunday, in the 90s.
With the warmer temperatures, dewpoints in the 60s, and decent
mixing both days, heat index values should stay mostly in the mid to
upper 90s, though values approaching the century mark appear
possible in/around the St. Louis metro area each afternoon.
(Sunday Night - Thursday)
Still some uncertainty on speed and location of the frontal boundary
as there are varying solutions among the deterministic models. The
GFS remains the strongest and fastest with the boundary exiting the
forecast area by Monday morning, with some lingering post frontal
precipitation and decent CAA. So highs by Monday would be in the
60s. On the other end of the spectrum, the ECMWF is slower with the
precipitation chances not ramping up til later in the day on Monday.
Thus highs could top out in the 90s once again. For now will stick
with the NBM solution with upper 70s in northeast Missouri to mid
80s in southeast Missouri and southwest Illinois.
Otherwise, cooler weather will return to the region for the
remainder of the work week.
Byrd
&&
.AVIATION... (For the 06z TAFs through 06z Friday Night)
Issued at 938 PM CDT Thu Jun 17 2021
A cold front extending from northwestern Wisconsin southwest into
southwestern Nebraska will sag southward to near the Missouri and
Iowa border Friday afternoon. Showers and storms associated with
this front may move into UIN Friday evening. Otherwise and
elsewhere mainly just high level cloudiness through the period. A
southwesterly low level jet across northern MO late tonight may
produce LLWS conditions in UIN with southwest winds around 1500
feet in height near 45 kts late tonight and early Friday morning.
South-southeast surface winds will become more southwesterly late
tonight and Friday morning.
SPECIFICS FOR KSTL: A cold front extending from northwestern Wisconsin
southwest into southwestern Nebraska will sag southward to near
the Missouri and Iowa border Friday afternoon. Showers and storms
associated with this front will likely remain north of STL,
although they may get close to STL by late Friday night. Mainly
just high level cloudiness through the period. South-southeast
surface winds will become more southwesterly late tonight and
Friday morning.
GKS
&&
.CLIMATE...
Issued at 258 PM CDT Wed Jun 16 2021
Record Highs:
Thu 6/17 Fri 6/18
STL 99(1944) 100(1953)
COU 101(1918) 100(1953)
UIN 103(1918) 99(1913)
&&
.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 79 102 78 97 / 0 10 30 20
Quincy 76 96 72 90 / 5 20 50 20
Columbia 74 98 72 95 / 0 5 20 20
Jefferson City 76 100 75 97 / 0 5 20 20
Salem 76 98 74 94 / 0 10 30 40
Farmington 73 96 72 94 / 5 5 5 20
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory from 1 PM to 7 PM CDT Friday for Audrain MO-Boone
MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
Jefferson MO-Lincoln MO-Marion MO-Moniteau MO-Monroe MO-
Montgomery MO-Osage MO-Pike MO-Ralls MO-Saint Charles MO-
Saint Francois MO-Saint Louis City MO-Saint Louis MO-Sainte
Genevieve MO-Shelby MO-Warren MO-Washington MO.
IL...Heat Advisory from 1 PM to 7 PM CDT Friday for Bond IL-Calhoun
IL-Clinton IL-Fayette IL-Greene IL-Jersey IL-Macoupin IL-
Madison IL-Marion IL-Monroe IL-Montgomery IL-Pike IL-
Randolph IL-Saint Clair-Washington IL.
&&
$$
WFO LSX
NWS LSX Office Area Forecast Discussion
