Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/18/20
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
830 PM CST Fri Jan 17 2020
.UPDATE...
Issued at 827 PM CST Fri Jan 17 2020
Surface temperatures have been inching upward so far this
evening. The latest obs from 02z show locations at freezing are
become less uniformly distributed along and south of I-70 and
temps range from 32-35F. A recent AMDAR sounding into KSTL at
0150z is also showing a warming environment with a 7 kft deep
elevated warm layer, peak warm layer temperature near 7degC, and a
shallow and shrinking surface-based cold layer less than 2 kft
deep. These thermodynamic profiles would suggest a rather
inefficient freezing rain/icing scenario. Locally at the WFO there
has been little if any ice accretion since 22z. With this in mind
and given the trends of increasing surface and low level
temperatures this evening, I plan to let the southern-most winter
weather advisory expire on target at 900 pm. This is fully
realizing there may be spots within this expiring advisory still
at that hour at 32F however with the expectation it will be short-
lived and impactful ice accretion is done. The northern winter
weather advisory for northeast MO and west-central IL still looks
on target to expire at 06z as warmer air advances northward. Even
within this region temperatures are warming with current temps of
31-32F, and conditions for ice accretion are becoming less
favorable and becoming largely confined to elevated surfaces. This
northern area is also where we continue to see the greatest
impacts - both hazardous travel and scattered power outages.
Glass
&&
.SHORT TERM... (Through Late Saturday Night)
Issued at 330 PM CST Fri Jan 17 2020
This afternoon, the strong storm system of interest was centered
over southern Colorado with a lesser storm system over northern
Idaho. Flow aloft was from the southwest over our region with
several upper level disturbances being thrown our way in a
broadscale WAA regime. These disturbances have resulted in the
outbreak of widespread precipitation, whose backedge is now moving
through far western Missouri. At the surface, a warm front was laid
out across far southern Missouri and into western Kentucky, with
temperatures surging into the 40s and winds from the south. For
areas to the north of it, including the entirety of the forecast
area, temperatures were hanging tough in the upper 20s and lower
30s, fueled by cold and dry air originating from a 1045mb high
pressure centered over the eastern Great Lakes thanks to winds from
the east-southeast. Precipitation types at this point have
transitioned to all liquid across the forecast area, with only the
32F surface isotherm delineating freezing rain from rain.
The TROF axis of the strong storm system is not expected to pass
through until Saturday morning, a slight slowdown from what was
exhibited 24 hours ago. This will end precipitation with its
passage, but due to this slowdown will effectively maintain a
limited precipitation threat into Saturday morning for some areas.
Fortunately, at this point, much of the precipitation looks to be
all rain.
In the meantime, airmasses will be on the move this evening, with
the cold high pressure to our east accelerating away, allowing the
warm front and approach of a surface wave to push it north more
quickly: to just south of I-70 around 00z/Sat and north of the
forecast area by 06z/Sat. This will result in surface temps warming
above freezing and into the upper 30s and 40s at one point, ending
the freezing rain threat and melting any existing ice shortly
thereafter. As a result, we feel confident enough to expire the
Winter Weather Advisory by 9pm for areas near and south of I-70 and
maintain the existing midnight expiration for areas to the north.
The flooding threat continues for potential for widespread
nuisance/minor flooding for much of the forecast area with a
widespread one inch of precipitation forecast with isolated
approaching two inches. If thunder materializes this evening, it
will give more merit to the two inch potential.
Dry weather is then expected after Saturday morning, but still
plenty of things going on. A strong surface cold front will make
its push through our region late tonight and Saturday morning
followed by strong CAA. Max temps are expected to be hit early with
a steady fall through the day into the teens and 20s. Wind chills
are expected to be in the single digits and teens thanks to strong
west winds gusting to 35-40mph at times. The temperature fall
continues into Saturday night with min temps in the single digits
and teens expected with diminishing winds. Nevertheless, wind
chills approaching 10 below are expected for portions of northeast
MO and west-central IL.
TES
.LONG TERM... (Sunday through Next Friday)
Issued at 330 PM CST Fri Jan 17 2020
Very cold conditions will continue for Sunday and Sunday night with
northwest upper level flow, and as a strong 1040-1045 mb surface
high centered over the northern Plains drops slowly southeastward
into our area. Highs on Sunday will be about 15 to 20 degrees below
normal. Although wind speeds will be decreasing Sunday night the
wind chills will be quite low due to the very cold low temperatures
forecast for Sunday night. The wind chills may be as cold as 10 to
15 below zero across parts of northeast MO and west central IL late
Sunday night and early Monday morning. A northwest flow shortwave
will drop southward through our area on Monday. At this time it
appears that the lower levels of the atmosphere will likely be too
dry for any measurable snow associated with this feature. Will begin
to see the start of a warming trend by Tuesday afternoon due to
rising upper level heights, and as the surface wind becomes
southerly as the slow moving surface ridge finally shifts east of
our area. Increasing low-mid level warm air advection along with
southwest flow shortwaves will result in a chance of precipitation
across northeast and central MO on Wednesday. The chance of
precipitation will gradually increase and shift eastward through the
entire forecast area by Thursday as a deepening upper level
trough/low approaches from the Plains. The chance of precipitation
continues through Friday as the upper level low and associated
surface low move eastward through our area. The operational GFS
model is further north with the track of the upper level and surface
low which would favor a precipitation type of mainly liquid rain,
but the ECMWF model is further south with the low which could lead
to a wintry mix.
GKS
&&
.AVIATION... (For the 00z TAFs through 00z Saturday Evening)
Issued at 531 PM CST Fri Jan 17 2020
Flight conditions will continue to deteriorate from west to east
across the area this evening as CIGS lower to IFR and rain
persists. The freezing rain should end at KCOU and the St. Louis
metro terminals by 02z as temperatures rise above freezing.
Freezing rain will continue longer into the evening at KUIN with
temperatures not rising above freezing until around 05z. In
addition to the rain and poor flight conditions expected tonight,
an intensifying southerly LLJ will result in LLWS conditions
overnight. The rain is expected to have moved east of all the
terminals by 12-14z as a cold front drives across the region. The
cold front will result in west-northwest surface winds gusting
25-30 kts and flight conditions improving to MVFR.
SPECIFICS FOR KSTL:
Flight conditions will continue to deteriorate this evening as
CIGS lower to MVFR and then IFR, accompanied by persistent rain.
The freezing rain should end by 02z as temperatures rise above
freezing. In addition to the rain and poor flight conditions
expected tonight, an intensifying southerly LLJ will result in
LLWS conditions overnight. The rain is expected to have moved east
of the terminals by 12-14z as a cold front drives across the
region. The cold front will result in west-northwest surface
winds gusting 25-30 kts and flight conditions improving to MVFR.
Glass
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch until 6 AM CST Saturday 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-Reynolds MO-Saint Charles MO-
Saint Francois MO-Saint Louis City MO-Saint Louis MO-Sainte
Genevieve MO-Warren MO-Washington MO.
Winter Weather Advisory until 9 PM CST this evening for Boone MO-
Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
Iron MO-Jefferson MO-Madison MO-Moniteau MO-Montgomery MO-
Osage MO-Reynolds MO-Saint Charles MO-Saint Francois MO-
Saint Louis City MO-Saint Louis MO-Sainte Genevieve MO-
Warren MO-Washington MO.
Winter Weather Advisory until midnight CST tonight for Audrain
MO-Knox MO-Lewis MO-Lincoln MO-Marion MO-Monroe MO-Pike MO-
Ralls MO-Shelby MO.
IL...Flood Watch until 6 AM CST Saturday 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.
Winter Weather Advisory until 9 PM CST this evening for Bond IL-
Clinton IL-Fayette IL-Madison IL-Marion IL-Monroe IL-
Randolph IL-Saint Clair IL-Washington IL.
Winter Weather Advisory until midnight CST tonight for Adams IL-
Brown IL-Calhoun IL-Greene IL-Jersey IL-Macoupin IL-
Montgomery IL-Pike IL.
&&
$$
WFO LSX