Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 261208
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
608 AM CST Thu Feb 26 2015
.SHORT TERM: (Through Late This Afternoon)
Issued at 308 AM CST Thu Feb 26 2015
Shortwave digging over northeast Missouri and associated cold front
now moving through the I-44 corridor will continue to produce light
snow through the first part of the morning. Have also had a few
reports of freezing drizzle back in central Missouri, but not sure
how long this will last so have opted not to mention in the forecast
at this time. Will continue to monitor and update if freezing
drizzle ends up persisting. Both NAM and GFS show some decent low
level frontogenetical forcing back on the cold side of the front
before 12Z this morning...but the forcing quickly diminishes between
12Z and 15Z. Mesoscale models do keep light snow going for a few
hours this morning, but really back off the precip by 15Z like the
operational models. Both NSSL and NCEP 4km WRF models pop up what
look like instability snow showers this afternoon, so have kept
chance PoPs going into the afternoon primarily along and east of the
Mississippi River. Total accumulations of 1 inch or less look
likely along and south of the I-70 corridor with 1-3 inches north
and northeast of St. Louis...primarily across west central and parts
of southwest Illinois. Will continue headlines as they are this
morning. Stuck close to the cold side of guidance for temperatures
today as the cold Arctic high moves in behind the cold front.
.LONG TERM: (Tonight through Wednesday)
Issued at 527 AM CST Thu Feb 26 2015
Arctic high builds overhead tonight into Friday. Doesn`t look like
we`ll set any record lows Friday morning, however widespread
temperatures near or below zero can be expected from central and
northeast Missouri into west central Illinois with single digits
elsewhere. With the cold start to the morning, it`s likely
temperatures will struggle to make the teens on Friday. Southerly
flow develops Friday night into Saturday and while it should be
warmer, temperatures will still be well below normal.
Looks like an active weather pattern coming up for late Saturday
into next week. The persistent ridge over the western CONUS/eastern
Pacific that we`ve been dealing with for the past several weeks is
breaking down and it looks like we`ll get into a southwest flow
regime by late Saturday and into Sunday. While this means we will
most likely see warmer temperatures, it also looks like a much
wetter pattern than we`ve had recently. Have several periods of
likely PoPs headed out into the medium range beginning late Saturday
continuing into Saturday night and Sunday in a warm advection
pattern. Precipitation types are difficult to pin down at this time
with the receding Arctic airmass potentially causing a wintry mix.
Another bout of warm advection precip develops on Monday night and
continues into Tuesday. Again, low level temperatures will likely
dictate what falls, but there may be more liquid rain than wintry
mix, especially into Tuesday with good southerly flow developing at
the surface. Regardless, this will be a challenging forecast due to
the mixed precip types and inherent difficulty in forecasting
shallow layers in the medium range.
.AVIATION: (For the 12z TAFs through 12z Friday Morning)
Issued at 608 AM CST Thu Feb 26 2015
Snow continues to track southeast through forecast area this
morning. Snow to taper off from north to south. Otherwise, IFR
conditions to improve to MVFR as heavier snows shift south and
east of taf sites by 14z. Gusty north winds to persist through the
day before diminishing late this afternoon/early this evening.
Cigs to scatter out this evening.
Specifics for KSTL:
Snow continues to track southeast through metro area this
morning. Otherwise, IFR conditions to improve to MVFR as heavier
snows shift south and east of metro area by 14z. Gusty north winds
to persist through the day before diminishing by 22z Thursday. Cigs to
scatter out after 06z Friday.
MO...WINTER WEATHER ADVISORY until 9 AM CST this morning FOR Knox MO-
Lewis MO-Marion MO-Monroe MO-Ralls MO-Shelby MO.
IL...WINTER WEATHER ADVISORY until 9 AM CST this morning FOR Adams IL-
Brown IL-Pike IL.