Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 230543
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1143 PM CST SUN NOV 22 2015
Issued at 935 PM CST Sun Nov 22 2015
Forecast on track this evening with area of mid level cloudiness
edging thru the northern and northeastern forecast area and should
be out of the area shortly after midnight. Elsewhere, clear skies
Weak warm front has mostly slid thru our region and the main
effect is to slow down cooling with its S-SW flow. A surface TROF
will then move thru late tonight and veer winds further from the W
where they will continue into Monday. Min temps will seem "mild"
compared to last night with most locales remaining in the 30s.
Sneak peak at Monday shows sunny skies for many areas and thanks
to W flow, should see decent mixing heights to where max temps
will continue their warming trend into the low-mid 50s, save in
the far north and northeast part of the region where mid-upper 40s
.SHORT TERM: (Through Late Tonight)
Issued at 344 PM CST Sun Nov 22 2015
Expect another dry and cold night with clear skies. Winds will
remain light tonight has high pressure moves off to the east. Have
stayed on the cooler side of the temperature guidance because of the
strong radiational cooling.
.LONG TERM: (Monday through Next Sunday)
Issued at 344 PM CST Sun Nov 22 2015
(Monday through Wednesday)
Monday and Tuesday will remain dry as weak upper ridge moves across
the area before upper flow eventually turns out of the southwest and
a weak shortwave trough moves across the area on Wednesday. This
weak trough will bring enough moisture and ascent to warrant
adding a slight chance of showers to the forecast on Wednesday.
Temperatures will moderate during this period as winds turn out of
the west and southwest. With mixing into the 925mb layer, highs
will recover into the 40s/50s by tomorrow and will be all in the
50s by Tuesday.
(Thanksgiving through Sunday)
This will be a more active period as the ECMWF and GFS both agree
that precipitation will develop over the area ahead of deep upper
over the western CONUS. By Thanksgiving, Gulf moisture will begin
to stream northward ahead of a cold front that will move across the
area on Thursday night and early Friday. Given that amount of
moisture moving northward and the amount of progged low level
convergence/mid level ascent, there could be a decent amount of
rainfall with this front.
Uncertainty begins to enter the forecast by next weekend as the
ECMWF shows the upper low moving into Colorado while the GFS keeps
it farther west over Idaho/Nevada/Utah. The ECMWF is showing better
continuity with it`s solution so have followed it. While
precipitation out of the area on Saturday, it will begin to move
back into the southern parts of Missouri and Illinois next Sunday as
large scale ascent increases ahead of the upper low in the Plains.
Temperatures during the period will go from above normal to below
normal as the cold front passes through the area and 850mb
temperatures fall from +10C to around 0C which will make allow for
some of the precipitation with this system to fall as snow behind
the cold front.
.AVIATION: (For the 06z TAFs through 06z Monday Night)
Issued at 1137 PM CST Sun Nov 22 2015
VFR flight conditions will continue to prevail through Monday
evening across the region. Wind will veer from the south-southwest
to the west by mid morning as a trof of low pressure moves
through. Model guidance continues to show a 30-40kt low level jet
at about 1000 FT, and AMDAR soundings from KSTL confirm increasing
wind aloft. Went ahead and included LLWS at KCOU, KSTL, KSUS, and
KCPS for most of the rest of the night. Shear should diminish with
the passing of the trof.
Specifics for KSTL:
VFR flight conditions will continue to prevail at Lambert Monday
evening. Wind will veer from the south-southwest to the west by
mid morning as a trof of low pressure moves through. Model
guidance continues to show a 30-40kt low level jet at about 1000
FT, and AMDAR soundings from KSTL confirm increasing wind aloft.
Went ahead and included LLWS to the TAF `til 11Z. Shear should
diminish after the trof passes.