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fxus63 klsx 272355 
afdlsx

Area forecast discussion...updated aviation
National Weather Service Saint Louis MO
555 PM CST Mon Feb 27 2017

Short term... (through late Tuesday afternoon)
issued at 306 PM CST Mon Feb 27 2017

Unseasonably warm weather will continue tonight and Tuesday. A band
of showers and a few storms was moving northeastward through
southwestern MO this afternoon. This current convection may weaken
some as it moves closer to our forecast area, but should have at
least a few showers into portions of central and southeast MO
already by early evening. More elevated convection is expected for
late evening and overnight as a warm front lifts northward through
the region and a southwesterly low level jet brings increasing
temperature and moisture advection to the area. Could not rule out
small hail with a few of the storms late this evening and overnight,
especially across southeast MO. Most of this convection should
shift east of our forecast area by Tuesday morning, followed by the
low level cloudiness breaking up. At least partial sunshine along
with a relatively strong and gusty southwest wind will lead to
record or near record high temperatures on Tuesday. May see the
redevelopment of convection by late Tuesday afternoon, particularly
across northeast MO and west central Illinois as a strong cold front
approaches, although the atmosphere should be initially capped over
the warm sector. Still some uncertainty as to where and when
convection will initially fire south of the cold front Tuesday
afternoon into the evening with varying model solutions. Better
coverage of convection will hold off until Tuesday evening.

Gks

Long term... (tuesday night through next monday)
issued at 306 PM CST Mon Feb 27 2017

All guidance continues to point to an active period on Tuesday night
and Wednesday. A frontal boundary with attendant low pressure in
southern Iowa will just begin to push into the area Tuesday night.
Models are in pretty good agreement about convection along the front
after 0z but timing issues still exist convective evolution further
south away from the front. There is some solutions pointing to
initiation as early as 01z in the southern part of the cwa, while
others point convection firing as late as 06z. The boundary will be
entering a broad warm sector over the region.

The combination of diabatic heating, sufficient moisture, and
steep lapses rates. This will be coupled with deep layer shear of
60 to 80 knots and continuing of winds aloft and sb cape values
of 750 to 1100 j/kg will lead quite a favor environment for semi
discrete and discrete supercells during the late afternoon and
evening hours. Any discrete or semi-discrete supercells will
likely grow upscale and congeal into a severe squall line. The
severe weather threat will end west to east through the overnight
hours before ending just after sunrise Wednesday. Main hazards
will be large hail, damaging winds, and a few tornadoes with
perhaps a strong tornado or two possible.

High pressure will build into the area from the Central Plains. This
will dry weather and near seasonal temperatures through the end of
the work week before temperatures trend. The weekend could see a few
showers and thunderstorms over NE MO and wc Illinois with a short wave
passing over the area.

Kelly
&&

Aviation... (for the 00z tafs through 00z Tuesday evening)
issued at 540 PM CST Mon Feb 27 2017

Warm front to continue lifting northward through forecast area
this evening. So could see some scattered rws/trws, thus kept
vcsh/thunderstorms in the vicinity mention through 10z-11z Tuesday. Otherwise, dry VFR
conditions expected for most sites during the day Tuesday with
gusty south winds. Could see MVFR for a time during the morning
hours at KUIN since they will be closer to warm front. Next round
of storms to move in with cold front Tuesday afternoon/evening,
timing hard to pin down, so just have thunderstorms in the vicinity mention.

Specifics for kstl:
warm front to continue lifting northward through forecast area
this evening. So could see some scattered rws/trws, thus kept
vcsh/thunderstorms in the vicinity mention through 11z Tuesday. Otherwise, dry VFR
conditions expected during the day Tuesday with gusty south
winds. Next round of storms to move in with cold front Tuesday
afternoon/evening, timing hard to pin down, so have vcsh mention
from 20z Tuesday to 00z Wednesday, then predominant tsra after 00z
Wednesday.

Byrd
&&

Climate...
record temperatures for Tuesday 2/28

Record highs record high lows

Stl 80/1972 stl 54/1895
cou 75/1972 cou 52/1895
uin 68/1932 uin 40/1987

&&

Lsx watches/warnings/advisories...
MO...none.
Illinois...none.

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