Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 232150
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
350 PM CST Fri Jan 23 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 349 PM CST Fri Jan 23 2015

Stratus continues to dissipate over our eastern counties, so it
appears that overnight cloudiness will come from two main
concerns...a final gasp of some mid and high clouds clipping our
southeast counties this evening (on northern fringes of system
working its way through the southeast U.S.), with another band of
mid level cloudiness dropping southeast across the area overnight as
surface trof/weak cold front drops into the region.  There are some
very weak echoes showing up with this band of mid clouds over Iowa,
but given the very dry low level air will maintain a dry forecast
for now.   Lows should be in the upper 20s to lower 30s, with clouds
and mixing preventing any big temperature drop.

Truett

.LONG TERM:  (Saturday through Next Friday)
Issued at 349 PM CST Fri Jan 23 2015

Above normal temperatures are expected for Saturday as the surface
winds back around to a southwesterly direction, along with plenty of
solar insolation particularly across central and southeast MO.  The
latest model runs were a little stronger and deeper with the
northwest flow, clipper type upper level trough/low and associated
surface low dropping southeastward through the northern Plains
Saturday night and into the Ohio Valley region Sunday afternoon or
evening compared to previous model runs.  The GFS model appears too
far southwest with the low track and is an outlier compared to the
other models.  Prefer the NAM and ECMWF solutions which have the low
dropping southeastward through Iowa and central IL, although the NAM
looks too deficient with its qpf across our forecast area.  The
models were also trending colder on Sunday with a non diurnal
temperature trend likely.  The temperature will likely fall during
the day on Sunday across much of our area as cold air advection
strengthens on the backside of the surface low.  The best chance of
rain will occur late Saturday night across northeast MO and west
central IL, then across west central and southwest IL on Sunday
mainly along and left of the track of the low.  Surface temperatures
should be warm enough that most of the precipitation falls as liquid
rain, although could not totally rule out a brief period of light
snow or a few flurries across portions of northeast MO and west
central IL especially if the storm system were to track a little
further southwest or be a little stronger.  At this time it appears
that any snow accumulations should remain northeast of our forecast
area.  The precipitation should shift east of our forecast area by
Sunday evening with colder temperatures for Sunday night.  Another,
weaker northwest flow shortwave will drop southeastward through the
Great Lakes region on Monday, but it appears that any measurable
precipitation should remain north and east of our forecast area,
although could not rule out sprinkles or flurries well east of the
Mississippi River.  Warmer temperatures are expected by Wednesday as
an upper level ridge moves eastward through the region, and as
surface winds become southerly on the backside of the surface ridge
shifting east of our area.  A cold front will drop southeastward
through our region Wednesday night and Thursday.  There may be a
little rain along and just ahead of this front, but it appears that
most of the precipitation will be north of our forecast area closer
to the shortwave and surface low.

GKS

&&

.AVIATION:  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1149 AM CST Fri Jan 23 2015

Stratus deck will continue to erode as sun and westerly winds
break up the thin layer of moisture supporting the cloud deck.
Based on the latest satellite pics, diurnal "pop" of clouds at
KCOU will be going scattered shortly, with cigs also scattering
out shortly at KUIN. In the STL metro, all TAF sites should lose
their ceiling no later than mid afternoon. After the stratus
erodes, it appears VFR conditions will hold the remainder of the
forecast period with a weak front pushing through the area during
the predawn hours. There are hints of post-frontal SC in some of
the soundings on Sat, but this deck is currently up in n MN and low
level winds would suggest the bulk of this cloud deck remaining NE
of our TAF sites. For now have kept some scattered clouds 3-4kft
going in the TAFs along the Mississippi River for now.

Specifics for KSTL: MVFR cigs should go scattered no later than
mid afternoon, and once this cloud deck breaks up VFR conditions
are expected for the remainder of the forecast period. As
mentioned in the primary AFD discussion, not totallyl sold on post
frontal SC suggested by soundings at this point, and for the time
being have gone with scattered clouds 3-4kft on Saturday morning.

Truett

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX





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