Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

FXUS63 KLSX 101149

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
549 AM CST Tue Jan 10 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 337 AM CST Tue Jan 10 2017

Main concern in the near term will be the wind.  Will be issuing a
wind advisory for most of the area.

Latest analysis showed a warm front moving into southwest Missouri
with a tight pressure gradient across Missouri and Illinois.  This
pressure gradient was causing the winds to stay up overnight. Latest
RAP is showing this tight gradient remaining over the area into at
least early afternoon with some mixing allowing stronger gusts to
mix down.  Think this will be enough to justify a wind advisory
across all but the far northern part of the CWA today.  Sustained
winds will be around 30 mph with gusts to around 40 mph before they
rapidly fall later this afternoon and this evening once the pressure
gradient relaxes.

There will be a chance of showers today as a weak shortwave moves
across the Midwest.  The attendant cold front will move from
northwest to southeast across the area today as well.  We are
already well above January temperature normals, and we will see a
non diurnal trend as temperatures fall behind a bit behind the
front.  Highs over most of the area today will reach the upper 50s
to around 60 which is supported by the MOS temperatures. Dry weather
is expected tonight in the wake of the upper trough. Temperatures
should fall back into the 30s according the GEFS mean 2m


.LONG TERM...  (Wednesday through Monday)
Issued at 337 AM CST Tue Jan 10 2017

Primary concern for the longer term forecast remains the potential
for periods of wintry precip starting late Wednesday night and
continuing through the weekend.  After one more mild day on
Wednesday a cold front with an Arctic airmass behind it will move
into the area late Wednesday night and sag south through Thursday.
This will be a shallow airmass, and southwest flow will continue to
prevail aloft, the upper dynamics supporting the southward push of
the front will stay well north of the area across the Upper Midwest
causing the front to stall over Arkansas and Tennessee Thursday
night.  850mb high pressure aloft off the southeast coast of the
U.S. will keep warm/moist southerly flow pointed directly at the
boundary providing excellent isentropic lift for precipitation over
the cold air at the surface.  Precipitation types and accumulations
for the duration of this storm will be highly dependent on very
small changes in temperature, and guidance has been varying from run-
to-run and model-to-model over the past few days.

While there I have moderate to high confidence in periods of wintry
precipitation across the area, my confidence is not very high yet on
how much wintry precip will fall, and what form it will take at any
given time due to uncertainties in the temperature forecast.
Forecast soundings across the area suggest that the primary precip
type to begin with on Friday will be freezing rain across the
eastern Ozarks and southwest Illinois, with a mix of freezing rain
and sleet from central to east central Missouri and into south
central Illinois. Precipitation will overspread much of the area by
Friday night and looks likely to continue on-and-off through Monday.
The persistent low level southerly flow over the Mississippi Valley
should slowly push the shallow cold airmass northward Saturday and
Sunday.  Expect any remaining sleet to change to freezing rain by
early Saturday morning, and for temperatures to rise above freezing
as far north as the I-70 corridor in eastern Missouri and Illinois.
Temperatures should warm enough by Sunday afternoon to end the
freezing rain across the entire area ahead of the next shortwave and
frontal system which will move through the area Monday.



.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 548 AM CST Tue Jan 10 2017

Current MVFR ceilings will move out of the terminals this morning.
Southerly surface winds between 15-30kts with higher gusts will
veer to the west by early this afternoon as a cold front moves
across the area. The winds will diminish quickly after 00Z. Isolated
showers will be possible, however coverage will be limited enough
to not mention in any of the terminals at this time.

SPECIFICS FOR KSTL: Ceilings are expected to gradually rise to VFR
by late morning. Southerly winds early this morning will gradually
veer westerly by this afternoon. This will cause crosswinds for a
time from mid morning into afternoon as winds will be sustained
between 20-25kts with higher gusts. Winds will diminish quickly
after 00Z with dry and VFR conditions expected.



Saint Louis     60  35  59  45 /  30  10  20  50
Quincy          53  28  52  29 /  30   5  30  40
Columbia        58  32  60  35 /  20   0  10  40
Jefferson City  61  33  63  37 /  10   0  10  40
Salem           57  31  58  52 /  40  10  30  50
Farmington      61  36  61  54 /  40  10  30  40


MO...Wind Advisory until 6 PM CST this evening for Audrain MO-Boone
     MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Lincoln MO-Madison MO-Moniteau MO-
     Montgomery MO-Osage MO-Pike MO-Ralls MO-Reynolds MO-Saint
     Charles MO-Saint Francois MO-Saint Louis City MO-Saint
     Louis MO-Sainte Genevieve MO-Warren MO-Washington MO.

IL...Wind Advisory until 6 PM CST this evening 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 IL-Washington IL.



WFO LSX is the U.S. government's official web portal to all federal, state and local government web resources and services.