Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 161222
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
722 AM CDT Sun Mar 16 2014
.SHORT TERM: (Today through Tuesday Night)
Issued at 316 AM CDT Sun Mar 16 2014
(Today - Tonight)
Potent vorticity maxima was located just to the south and east of KOUN
as of 0600 UTC. Given its vigorous appeal in water vapor imagery...it appears
that the stronger GFS/ECMWF captured this feature better than the NAM
comparing 6-hr forecasts from each model`s respective 0000 UTC runs.
Therefore...relied on the GFS/ECMWF for track of this feature and used a blend
of their QPF forecasts. NAM QPF was once again largely discounted due to the
its trouble handling the strength of the aforementioned vort max.
This yielded mainly subtle/cosmetic changes for snow/sleet amounts. Main
changes were to shift >= 1.0" total accumulations just a bit further to the
south as well as increasing gradient just to the north of Interstate 70.
Totals will likely really be cut into north of this area as upper-level
forcing is not sufficiently strong enough to overcome the persistent cold/dry
low-level advection associated with northeasterly flow.
Going winter weather advisory looks good as these areas across southeastern
Missouri and southwest Illinois should still receive 1-3 inches of total
snow and sleet as well as a light glazing of ice possible.
Precipitation shield should weaken and move off to the east/southeast by late
this afternoon with decreasing cloudiness and slackening winds expected.
Should be an unseasonably cold night with lows for the most part in the
mid to upper teens areawide...10-20 degrees below normal for mid March.
Areas which may get appreciable snow cover...i.e., eastern Ozarks/portions
of southwestern Illinois may even observe low temperatures a bit cooler
if enough snow falls and winds become light/variable.
(Monday - Tuesday Night)
Dry weather is expected on Monday with sunny skies. Temperatures will remain
well below normal with highs in the 40s. Went above guidance on Monday due
to expected sunshine.
Winds will veer to the south Monday night as sfc ridge axis passes and moves
into the southeast United States. Return flow ramps up on Tuesday ahead
of next weather system. Moisture return ahead of this feature looks very poor
attm and with best upper-level forcing well to the north...expect main impacts
on Tuesday/Tuesday night to be an increase in cloudiness as a dry fropa is
expected. For Tuesday`s highs...a nice warmup is forecast with highs in the
60s and leaned aoa warmest guidance.
.LONG TERM: (Wednesday through Saturday)
Issued at 316 AM CDT Sun Mar 16 2014
(Wednesday - Saturday)
The medium range will be dominated by quasi-zonal flow aloft and
temperatures near or just a skosh above normal. The tail end of a
strong shortwave aloft will be moving through the Midwest on
Wednesday with the surface reflection moving from Wisconsin
northeast across the Upper Peninsula of Michigan. The associated
front should be east of our area by 12Z Wednesday morning. With
weak cold advection occurring, Wednesday will likely be the coolest
day of the period. ECMWF is printing out a bit of post-frontal
precip, but the atmosphere looks pretty dry behind the front so have
opted to stay dry for now. Weak ridging builds overhead for
Thursday with south-southwest low level flow and warm advection
pushing temps above normal into the mid 50s to low 60s. A weak
shortwave moves across the Upper Midwest on Friday pushing the
associated cold front into our area with a chance for some rain.
Temperatures south of the front should be warm in the mid 60s with
readings falling into the 50s behind the front. GFS and ECMWF
differ somewhat on Saturday with the EC having a deeper trof aloft
over the East Coast and therefore allowing a Canadian airmass to to
infiltrate deeper into the Mid and Lower Mississippi Valley. GFS is
almost perfectly zonal which would suggest that cooler air will stay
bottled up over the Upper Midwest. This far out a compromise seemed
reasonable so went with temperatures near climatological normal.
.AVIATION: (For the 12z TAFs through 12z Monday Morning)
Issued at 642 AM CDT Sun Mar 16 2014
Tracking two areas of precipitation this morning. The first across
northeast Missouri and west central Illinois stretching southwest
into west central Missouri. This band is producing snow and a
little sleet according to surface observations and media reports.
Additionally low MVFR/IFR flight conditions are being reported
with this band. KIRK briefly reported a visibility of 1/2SM in
moderate snow. Short range guidance is indicating this band will
weaken over the next few hours and dissipate by 17-18Z. The second
area of precip is south of the I-70 corridor and is producing
rain and primarily MVFR flight conditions. Expect this rain to mix
with sleet and eventually turn to snow this morning from north to
south as cold air deepens. Ceilings and visibilities should drop
as well as the precipitation changes. Expect low MVFR and IFR
with the change over. Precipitation should end from northwest to
southeast from 18-00Z this afternoon. Sandwiched between these two
areas of precipitation is a wedge of dry air and VFR conditions.
Don`t think the northern edge of the southern area of precip will
make it too much further north than I-70, so this area of dry air
may stay VFR all day; but I think it`s more likely that MVFR
ceilings will develop later this morning as cold air deepens over
the area. Ceilings will improve to VFR before scattering out from
northwest to southeast this evening. Strong and gusty northeast
wind will diminish through the late afternoon into early evening.
Specifics for KSTL:
Lambert will be on the northern edge of an area of precipitation
this morning into early afternoon. Expect light rain or sleet to
change over to snow by mid morning. Think MVFR flight conditions
will prevail after the change over...though am not confident in
the ceiling forecast since a slightly more northerly shift in the
precip will likely bring ceilings down to IFR category.
Precipitation will end from northwest to southeast late this
morning or early this afternoon and expect MVFR flight conditions
to continue to prevail until early evening. Strong and gusty
northeast wind will produce nearly a direct crosswind on the main
runways today. Wind will diminish early this evening.
.PRELIMINARY POINT TEMPS/POPS:
Saint Louis 34 19 47 33 / 70 5 0 5
Quincy 33 16 44 31 / 50 5 0 5
Columbia 33 17 50 34 / 80 5 0 5
Jefferson City 33 18 50 34 / 80 5 0 5
Salem 34 20 46 32 / 70 10 0 5
Farmington 35 19 47 31 / 100 10 0 0
MO...WINTER WEATHER ADVISORY until 7 PM CDT this evening FOR Crawford
MO-Franklin MO-Gasconade MO-Iron MO-Jefferson MO-Madison MO-
Osage MO-Reynolds MO-St. Francois MO-Ste. Genevieve MO-
IL...WINTER WEATHER ADVISORY until 7 PM CDT this evening FOR Clinton
IL-Marion IL-Monroe IL-Randolph IL-St. Clair IL-Washington