Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/31/19
Area Forecast Discussion
National Weather Service Huntsville AL
827 PM CDT Wed Oct 30 2019
Issued at 827 PM CDT Wed Oct 30 2019
Low clouds, drizzle and a few showers are still occurring in between
MCSs. The northern extent of the next MCS in MS will produce light
to moderate rain in northwest AL shortly. Have removed thunderstorms
and added drizzle through 06Z. Stronger thunderstorms in central and
southwest MS have been progged to lift northeast into west central
and north AL after 08-09Z. This as a low level jet of 40-50kt
develops within the RRQ region of the upper jet that begins to pivot
with the upper trough into the lower OH/MS valleys late tonight.
This will aid a mesolow associated with the convection in southwest
MS to develop and ride northeast along the cold front. Earlier
convection has lowered convective instability over central and north
AL for the time being. However, southerly flow increasing later
tonight will advect dew points around 70 northward into the area.
This may enable a nose of 300-500 j/kg CAPE to reach north AL and
southern middle TN very late tonight as the mesolow and QLCS
approach. Several successive HRRR runs have indicated a stronger
cell or cell cluster with the mesolow moving with the low into north
central or northeast AL from 10-12Z. This as 1km SRH values increase
again to above 300 m2/s2. Thus, will maintain the risk of damaging
wind or even a tornado in our HWO and impact graphics.
.SHORT TERM...(Thursday through Friday)
Issued at 250 PM CDT Wed Oct 30 2019
A strong to severe thunderstorm in extreme northeastern Alabama
cannot be ruled out just after daybreak around 8 or 9 AM, but
otherwise just expecting lingering rainfall behind the front. With
cloud cover lingering and cold air advection behind the front,
temperatures will likely only not move much on Thursday due to the
effects of cloud cover and cold air advection.
Cloud cover should finally move east out of the area in the late
afternoon or very early evening hours on Thursday. With light winds
expected behind the front overnight and dewpoints dropping into the
upper 20s to around 30 degrees, widespread frost or freezing
temperatures between 28 and 32 degrees look possible by Friday
morning. Therefore, have issued a Freeze Watch that is in effect for
all of our northern Alabama and southern middle Tennessee counties
from 12 AM midnight on Friday through 9 AM.
With this much colder start to the day and some continued weak cold
air advection, highs will be much colder despite abundant sunshine
only reaching the lower to mid 50s.
.LONG TERM...(Friday night through Tuesday)
Issued at 250 PM CDT Wed Oct 30 2019
A strong ridge of high pressure centered across the Deep South
region will reinforce a much cooler and dry air mass this weekend.
This will result in mostly sunny, but cool, crisp days with highs
peaking in the mid to upper 50s to kick off the month of November.
Clear nights with calm winds will allow for good radiational cooling
and potentially additional nights with a light freeze (with lows in
the 28 to 32 degree range), with widespread frosts each morning. The
upper-ridge will gradually slide to the northeast into the Mid
Atlantic region by Monday and Tuesday. This will help develop a SE/S
flow off the Gulf of Mexico which will help to advect some moisture
back into the region. We`ll also see an uptick in temperatures as
highs climb back into the 60s during the day. A few isolated showers
may be possible Tuesday afternoon and evening as a weakening front
approaches the area. However, most locations will remain dry for much
of this period and the upcoming week ahead.
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 639 PM CDT Wed Oct 30 2019
An active overnight and early morning period in store for both
terminal locations. Shower activity is expected to pick up near the
KMSL terminal within the next couple of hours, and by midnight at
KHSV. Vsbys and cigs remain a challenge, and amendments may be needed
as several fluctuations are likely through the overnight hours. Both
terminals could drop as low as LIFR vsbys, which has already occurred
for a short period of time at KHSV. Expect the heaviest shower and
thunderstorm activity to occur before or right around sunrise, and
these storms could be accompanied by strong winds. Expect strong
gradient winds behind the frontal passage tomorrow, with sustained
winds of 15kts and gusts up to 25kts beginning around sunrise and
lasting through the end of the TAF period. Expect MVFR/IFR cigs to
clear by sunset on Thursday.
AL...Freeze Watch from late Thursday night through Friday morning for
TN...Freeze Watch from late Thursday night through Friday morning for
For more information please visit our website
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
1004 PM EDT Wed Oct 30 2019
Strong low pressure will travel through the Ohio Valley today
through Thursday, bringing widespread showers. Colder
temperatures and strong winds will follow the storm system
Thursday night. Dry and chilly weather is forecast for Friday
and continuing through the weekend under high pressure.
.NEAR TERM /THROUGH THURSDAY/...
Steady rain is moving off to the east for now, with patchy
showers and drizzle expected through around 08Z, before
additional steady rain begins to move in from the southeast.
With this part of the forecast roughly behaving as expected,
attention was primarily given to fog potential overnight.
Along a corridor including several counties on either side of
the KY/IN border, stretching as far northeast as Oxford OH,
visibilities have been dropping below 1SM. This is currently
being handled quite well by HRRR visibility projections, in an
area where low-level theta-e is pooling on the warm side of a
frontal boundary. This front is somewhat ill-defined in terms
of wind flow, but those light and variable winds are certainly
one factor helping the fog to develop. However, it remains
somewhat unclear just how dense this fog will get -- with a
pretty solid expectation of visibilities in the 1SM-3SM range,
but not as much confidence in any prolonged period of 1/2SM or
below. The trend on the HRRR has been to gradually shift the
worst of the visibilities eastward with time, keeping the far
northwestern ILN CWA generally out of the worst of it, and
moving the lower visibilities into central Ohio by 06Z. Still
very possible that a dense fog advisory may be needed, but it
would be good to make sure that it isn`t going to be a situation
where an observation site begins improving again after just an
hour or two.
A quick look was also given to wind gust potential tomorrow
afternoon/evening. There is certainly some support (especially
from the GFS) for winds approaching advisory criteria near/north
of Interstate 70, but enough uncertainty from a few other models
to not want to go out with a headline until a full run of 00Z
products becomes available.
Previous discussion >
The cold front that slowly moved through last night has begun
to stall as pressure falls over the Ohio Valley are promoting
increased easterly flow. Along the front, moisture advection
from the southwest and a subtle wave of low pressure are
resulting in periods of showers this afternoon and these will
continue into the evening hours. With the wave exiting to the
northwest late this evening, a few hours of dry weather during
the overnight are expected. Additional pressure falls occur over
the Ohio Valley overnight with a deepening trough moving in
from the east. Moisture increases once again, resulting in
additional showers Thursday morning as the cold front moves
The main concern within the short term period will be
associated with the stationary front moving back to the
northwest overnight. While the rain may cease for a time, low
cloud ceilings and enhanced surface moisture favors the
development of areas of fog by as early as this evening. How
dense the fog will ultimately be and how widespread is still
quite uncertain. As of 2 PM, observations in Dayton and
surrounding ares are observing limited visibility as convergent
winds and saturated air results in fog/haze. Light to moderate
rain is also a contributing factor but confidence is increasing
that the fog will not clear after the rain has cleared. Highest
confidence is currently from Cincinnati through Dayton metro
areas along the front. A dense fog advisory may be required as
early as this evening depending on how quickly conditions
worsen. Further southeast, fog is also expected to develop but
it may not be quite as dense.
After temperatures reach their peak this afternoon,
temperatures will struggle to fall overnight with the battle
between warm air to south and cooler air to the north. Temps
will vary in relation to the boundary with the forecast to range
from the low 50s northwest to the low 60s southeast.
.SHORT TERM /THURSDAY NIGHT/...
Showers are likely overspreading the area once again Thursday
morning ahead of an approaching cold front. A deepening area of
low pressure over the southern Great Lakes moves northeastward
throughout the afternoon, providing active weather during the
short term period. High temperatures for the day occur during
the morning hours as the warm sector covers much of the forecast
As the low deepens and reaches Northwest Pennsylvania, showers
will diminish in coverage with the cold front moving eastward.
Strong winds will develop in the very tight pressure gradient
following the low. Latest guidance shows gusts over 30 knots
late Thursday afternoon as direction shifts from south to west
behind the low.
The west winds will usher in sharply colder temperatures
Thursday afternoon. Late Thursday night, wrap around moisture
presents a brief opportunity for rain/snow showers, primarily
north of I-70. With warm surface temperatures, no accumulation
is expected at this time. Temperatures continue to drop into the
upper 20s Friday morning, with a Freeze Watch currently in
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
High pressure will be building in from the southwest on Friday as
zonal flow aloft slowly becomes southwest as a deepening l/w trough
in the central U.S. deepens Friday night. The surface high crosses
east of the Ohio Valley late Friday and southwest flow will bring a
slight return to warmer air but probably have a hard time scouring
out the cooler air entrenched at the surface overnight. Friday will
be the coolest day of the forecast with readings in the mid to upper
40s. The slight southwest flow expected overnight will warm things
slightly for daybreak Saturday off of Friday morning lows, but only
marginally with readings still expected to drop below freezing
Saturday will be similar to Friday but could reach near 50 in parts
of KY and the lower Scioto Valley. Increased cloud cover with the
l/w trough crossing the region during the day will inhibit any real
warming, and the brief flow from the south will then turn west.
Sunday will see another high settle south-southeast of the region
with northwest flow aloft keeping the region under a cool advection
pattern. The upper flow turns more westerly overnight and then a
gradual increase in temperatures will be found for next week.
The next real chance of precipitation will be found Tuesday as a
weak cold front crosses the region as an upper low digs into the
upper midwest. Temperatures will be below normal until the work week
starts and then hover near climo values.
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Steady rain will likely come to an end over the next hour or
two, with occasional periods of showers or drizzle expected to
continue through the rest of the night. Winds are also expected
to become lighter as the evening turns into the overnight. There
is high confidence that low ceilings (IFR/LIFR) and fog (IFR)
will develop at all TAF sites, with some chance of dense fog
(1/4SM) especially at KDAY/KILN/KCVG/KLUK. This TAF update will
largely retain the pessimistic forecast through the overnight
hours and into tomorrow morning.
A very gradual improvement in ceilings is expected tomorrow,
though IFR ceilings should persist for a while, becoming MVFR
later in the day. Another period of showers (potentially heavy)
is expected late morning / early afternoon, followed by drier
conditions after that. Winds will be one of the main stories
tomorrow, and they will pick up more markedly after the rain has
ended, with gusts into the 30-35 knot range at all TAF sites.
This is slightly higher than the previous forecast, and there is
still a chance that these gusts may need to be increased again
in future forecasts.
OUTLOOK...MVFR ceilings may continue into Thursday night. Gusty
west winds will also continue Thursday night, diminishing by
Friday morning. MVFR ceilings are possible again Saturday night.
OH...Freeze Watch from Thursday evening through Friday morning for
KY...Freeze Watch from Thursday evening through Friday morning for
IN...Freeze Watch from Thursday evening through Friday morning for
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
918 PM CDT Wed Oct 30 2019
918 PM CDT
Somewhat of a complex forecast tonight into Thursday with mid-
latitude cyclone developing/strengthening as it moves across the
Strong mid-upper level jet nosing northeast from the southern high
Plains into the mid-Mississippi Valley with evening RAOBS sampling
135kt at 250mb and 100kt at 500mb. Regional WSR-88d mosaic shows
developing warm conveyor belt of precip beginning to blossom from
southeast MO north into northwest IL. This development trend is
likely to continue tonight as forcing strengthens and begins
spread east taps into the northward surging moisture.
This evening into the overnight hours anticipate this band of
precipitation to increase in coverage and gradually move across
the area. Precip type is tricky with a somewhat convective nature
to the precip combined with lack of ice nuclei outside of the
heavier precip likely to lead to hodge podge of precip types
overnight. In the heavier showers, will likely see snow and some
sleet over northwest portions of the CWA with mainly rain eastern
CWA. Outside of the heavier precip elements, lack of ice nuclei
will probably lead to more of a drizzle and snizzle as dominant
Developing dry slot over MO will likely nose into the area late
tonight into early Thursday morning, with again a loss of ice
likely leading to a period of mainly drizzle/very light rain.
Unfortunately, NAM and particularly RAP cross sections would
support a period of potential freezing drizzle later tonight into
early Thursday morning in the dry slot over portions of northern
IL. Reluctant to make the forecast too complicated, but given the
potential impacts of FZDZ think its probably worthy including in
the updated forecast this evening. A lot will hinge on placement
of sfc freezing line, but looks like the best FZDZ threat will be
west of I-355 into north central IL, with mainly just drizzle east
into heart of Chicago metro and rest of eastern IL and points
Developing/strengthening deformation zone is then forecast to
sweep across the area in the wake of the dry slot. Model forecast
ascent within this deformation band is respectable, but nothing
too extreme and unlike mainly mid-latitude cyclones, guidance
suggests it will be relatively stable with rather weak lapse rates
in the dry slot. Cross sections do show a bit of saturated
negative EPV, but overall doesn`t appear to be a set up that
really favors intense banded precipitation, but rather a 4-6 hour
window of light to moderate snow. Surface temps will be falling
during the day, especially western and central CWA where best
accumulations look to be setting up and most impactful snow is
expected. Snow will be fighting a bit with the high October sun
angle to accumulate during the afternoon when the heart of the
deformation band is over the Chicago area.
Thermodynamically, conditions do appear moderately favorable for
lake enhancement to the snowfall over northeast IL near the lake
and does appear as though high res models are picking up on this
and depicting a heavier band of snow in the simulated
reflectivity. That heavier lake enhancement to the precip should
help somewhat offset the unfavorable diurnal timing to the
snowfall in northeast IL, though the milder temps near the lake
will also tend to cut down on accumulations. Weighing all these
potential factors and possible complications it really appears the
going forecast has a good handle on potential accumulations and
not planning any headline or meaningful changes to forecast
accums this evening. The potential factors above certainly do
highlight the possible factors which could result in forecast
snowfall amounts being off, either too high if sun angle, marginal
temps, lake warming are a bigger factor, or potentially locally
higher amounts into NE IL if lake enhancement is more robust.
Finally, do want to mention that I am a bit concerned about the
potential magnitude of the lakeshore flooding into Chicago.
Already seeing 7ft waves at the Wilmette Buoy and with northeast
to north winds forecast to continue overnight through Thursday
morning and strengthening further, expecting waves on the IL shore
to build with waves probably peaking in the 10-12ft range. Really
hard to know what magnitude of impacts 10-12 foot waves will have
at these near record high lake levels given the lack of a solid
historical database. Am concerned that lakeshore flooding could be
worthy of warning, but given the unknowns will pass this concern
to oncoming mid shift to watch.
328 PM CDT
Through Thursday night...
We have issued a winter weather advisory for much of northern IL
for tonight through much of Thursday for some accumulating snow.
While we are quiet right now across the area, attention has turned
to our west, where the main upper level storm system is now
beginning to shift over the central High Plains of CO and western
KS. This storm system is expected to shift eastward over the mid
and lower Missouri Valley tonight. As it does so, surface low
pressure will begin to consolidate over the Ohio Valley into early
It still appears that the orientation of the upper trough will
gradually shift from a positive tilt (southwest to northeast
orientation) to more of a neutral tilt (north to south) as it
shifts over our area on Thursday. As a result, large scale
dynamics with this storm system will be in the beginnings of
ramping up as it moves over our area Thursday. This should support
a more organized deformation zone over the area on Thursday as
the lower level circulation begins to develop. For this reason,
it appears that we will be in for some more accumulating snow for
The precipitation should onset over north central IL this evening,
and while it could start as a mix of rain and snow, it will
quickly transition over the snow. Snow should occur for much of
the night over north central IL, with accumulations of 2 to 3"
inches by early Thursday morning. Farther east towards the western
Chicago suburbs the precipitation will onset as rain, but we will
see a gradual change over to snow from west to east tonight. The
western and northern suburbs of Chicago could see the change over
to snow by midnight, but in the City the snow change to snow will
likely hold off until around daybreak Thursday due to lower near
surface temperatures. Areas over northwestern IN are likely not
see the transition to snow until mid to late Thursday morning. Once
we transition to snow expect periods of light to moderate snow
to continue into Thursday afternoon before it gradually ends from
west to east during the mid to late afternoon.
Total snow accumulations still look to be the highest over north
central IL, where some totals could push close to 6". These
amounts should tapper off towards the western suburbs of Chicago
into the 2 to 5 inch range, and likely down to an inch or less in
the city itself and into northwestern IN.
Winds will also become gusty up to 35 mph from the north-northwest
during the day Thursday, and this could result in some blowing
snow in open areas. Otherwise, lake shore flooding continues to be
a concern later tonight and on Thursday as waves build to around,
or just above 10`.
328 AM CDT
Friday through Tuesday
In the wake of this system, expect a hard freeze (temps falling
into the upper 20s) area-wide into Friday morning. Otherwise,
below average temperatures are likely to continue through the
weekend as another upper trough and surface cold front brings a
reinforcing shot of cool air to the area. Some clipper type
systems could result in some changeable temperatures and on and
off again small chances for precipitation going into next week.
However, at this time no changes were made to the general blended
For the 00Z TAFs...
648 PM...Multiple forecast concerns including...
Light rain through early morning...chance of snow/sleet.
Period of moderate snow mid Thursday morning/early afternoon.
Ifr cigs through Thursday afternoon.
Strong northerly winds tonight shifting northwest Thursday.
Pockets of light and drizzle this evening will transition to a
more widespread light rain with scattered heavier showers and
these will likely have heavier precipitation rates allowing for
precipitation to mix/changeover to snow and perhaps have some
sleet mixed in. Precip is likely to change over to all snow for
northwest IL and rfd by late evening with light snow already being
reported in parts of eastern IA. While confidence is low...there
may be a lull in the precip prior to daybreak for the Chicago
terminals where prevailing precip may remain light rain or
drizzle. But there is good agreement among the most recent models
of a band of snow slowly moving across all of northern IL Thursday
morning...ending from west to east during the early afternoon.
Confidence is increasing that there could be a period of snow
across much of the area with visibilities below 1sm and possibly
into the 1/2sm range for at least a few hours. But only medium
confidence at this time and opted to only tempo 3/4sm for the
Chicago terminals. Changes to both lower vis and cigs are possible
with later forecasts. The snow will taper off during the early/mid
afternoon and should be finished by sunset for ord/mdw.
Prevailing ifr cigs are expected to continued through late
Thursday afternoon when cigs will lift to mvfr and then scatter
out. Ifr cigs will spread back across northern IL and rfd later
this evening. Its possible there could be some lifr cigs with the
North/northeast winds currently will turn northerly this evening
and then turn north/northwesterly overnight with gusts into the
lower/mid 20kt range. Winds will slowly turn more northwesterly by
Thursday afternoon. Speeds and gusts likely to increase during
the late morning with gusts into the 30-35kt range possible from
early afternoon through early evening with speeds/gusts quickly
diminishing by mid evening as winds turn more westerly. cms
331 PM CDT
Winds expected to steadily increase this morning through this
afternoon and tonight, as low pressure lifts across the Ohio
Valley and into the central Great Lakes. The current northeast
winds of 10 to 20 kt are expected to increase to 20 to 25 kt this
afternoon and then to 30 kt tonight. These strengthening onshore
winds and building waves will produce hazardous conditions for
small craft, with an extended period of these similar conditions
expected into Thursday night. As the low draws near tonight into
Thursday morning, it is appearing that gales will develop across
the southern half of the lake and nearshore waters, and have
updated the Gale Watch to a warning for Thursday into Thursday
evening. It`s quite possible that these gales start a little
sooner for the IL shore, and then possibly last longer into
Thursday night for the IN shore.
IL...Winter Weather Advisory...ILZ006-ILZ012-ILZ019-ILZ020-ILZ021-
ILZ032...midnight Thursday to 6 PM Thursday.
Lakeshore Flood Advisory...ILZ006-ILZ014...1 AM Thursday to 4 PM
Winter Weather Advisory...ILZ013-ILZ014...3 AM Thursday to 6 PM
Winter Weather Advisory...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-
ILZ011 until 4 PM Thursday.
IN...Lakeshore Flood Advisory...INZ001-INZ002...10 AM Thursday to 1
LM...Gale Warning...LMZ740-LMZ741-LMZ742...10 AM Thursday to 7 PM
Small Craft Advisory...nearshore waters
until 10 AM Thursday.
Gale Warning...LMZ743-LMZ744-LMZ745...10 AM Thursday to 10 PM
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
923 PM CDT Wed Oct 30 2019
Issued at 923 PM CDT Wed Oct 30 2019
At 9pm, surface temperatures have fallen a bit quicker than
originally anticipated, with sub-freezing temperatures around 30
degrees for much of Knox, Shelby, and Lewis counties. KUIN has
fallen to 32F and KCOU to 34F. It is for this reason, along with
light precipitation already occurring, that the Winter Weather
Advisory was moved up to begin early this evening.
IR satellite imagery has been helpful at evaluating cloud ice
potential through sampling of cloud top temps, and indeed cloud
tops have cooled to below -10C for many areas N and W of the STL
metro area thanks to at least a partial seeder-feeder effect from
cold cloud tops advecting from OK this evening. This has resulted
in snow onset a bit earlier for KUIN and likely in central MO
imminently, but will probably only be temporary, as these colder
cloud tops are expected to move out by 04z. At that point, the
original cloud ice forecast still looks mostly on track.
Colder surface temps and a period of colder cloud tops will result
in a bit more snow forecast than earlier and less icing from
freezing rain--with the biggest change occuring in portions of
northeast MO where amounts approaching 3-4 inches of snow will be
possible with little or no ice accretion. Elsewhere, the forecast
largely remains on track for snow and ice amounts. It needs to be
emphasized that the snow forecast is for grassy surfaces with
roads expected to receive less. The current Advisory area still
looks good taking into account the road consideration.
Another notable thing is the blustery conditions that will develop
later tonight and continue into Thursday with sustained winds of
15-20 mph and gusts to 30-35 mph at times. For areas that receive
a few inches of snow in northeast MO and west-central IL, this
could create additional issues with regard to blowing and drifting
snow especially on rural roads.
Finally, the RAP shows an area of modest 100-200 MUCAPEs south of
STL metro, with this expanding into southwest IL this evening
before exiting. Sure enough, a CG or two have been seen thus far
in this area. An isolated thunderstorm will be possible in these
.SHORT TERM... (Through Late Thursday Night)
Issued at 336 PM CDT Wed Oct 30 2019
This is a complex forecast over the next 12 -18 hours across the
area. The expectation is for light rain to breakout by early this
evening as a midlevel disturbance ejects eastward out of the lee of
the Rockies. The precipitation will eventually changeover to snow
from northwest to southeast overnight into early Thursday morning as
the temperature profile rapidly cools in the 700-800 hPa layer.
However, there likely will be at least a brief period of time where
there is a lack of cloud ice nuclei aloft and surface temperatures
drop below freezing. This situation would produce light freezing
rain, with a light glaze expected. This is most likely this evening
across portions of northeast Missouri where upstream infrared
satellite imagery depicts cloud top temperatures mostly in the -5 to
-10C range. These cloud top temperatures likely will not be cold
enough to support the introduction of ice.
The light snow should wind down late tonight and into the
early morning hours with lingering flurries possible for several
hours. Snowfall accumulations will take place mostly across the
northwestern third of the CWA with the heaviest accumulations (1-3")
from near Kirksville ENE toward Canton. Have issued a winter weather
advisory for these locations as there is expected to be several
hours of light snow falling with temperatures falling through the
upper 20s. Therefore, travel conditions may deteriorate as road
temperatures fall toward the freezing mark.
The other story is the anomalously cold conditions. Widespread near
or below freezing temperatures are expected tonight so no changes
made to tonight`s freeze warning. Temperatures through midday will
likely remain steady, with only a slight rebound in the afternoon.
Highs should only be in the mid to upper 30s, which is about 25-30
degrees below normal! In fact, all three of our climate sites are
likely to break daily record low maximum temperatures for Halloween.
Please see the CLIMATE section for more details.
A clearing sky will greet the region late Thursday afternoon into
the evening hours from west to east. A surface ridge will quickly
slide southeastward across the area into the mid south and Ohio
Valley. Southwesterly return flow around this surface ridge will act
to help keep temperatures up a bit, with steadying or even slowly
rising temperatures late Friday night for parts of the area.
Consequently, raised low temperatures a few degrees for northwestern
sections of the forecast area. That being said, very cold
temperatures are still forecast areawide. Lows should range from the
mid to upper 20s across the bi-state area.
.LONG TERM... (Friday through Next Wednesday)
Issued at 336 PM CDT Wed Oct 30 2019
A broad long wave trof will dominate much of NOAM during this
period. Short waves of varying intensity translating across the
region within the mean long wave trof will be responsible for
several frontal passages and any precipitation threat along with
helping modulate temperatures.
We are in between short waves on Friday in the wake of Thursday`s
departing trof and just in advance of the next prominent trof.
Low level WAA will be in full force in the wake of the retreating
surface high pressure system and this along with an initial lack
of clouds should allow for much warmer temperatures than
Thursday`s chill. Still highs will remain below normal for the
beginning of November. This upstream short wave trof will then
amplify and dig into the Mississippi Valley Friday night into
early Saturday driving a cold front through the region. The cold
front itself will bring a reinforcing shot of cold air and keep
temperatures well below normal. Any real question with this system
is the potential for any post-frontal precipitation. The NAM is
the sole model showing any potential into our CWA with the
southern edge of a post-frontal band clipping northeast MO and
west central IL between 06-12z Saturday. This band would be the
result of low-mid level frontogenetic forcing and weak large
scale forcing associated with the digging upper trof, and thermal
profiles on the NAM would suggest largely snow. If this occurs it
looks like a quick round with very minor accumulations less than
an inch. The good news is that all of the other deterministic
guidance and SREF and GEFS suggest this precipitation will remain
north of the CWA, and that is the course of the current forecast.
Otherwise brisk northwest winds and typical post-frontal
stratus/stratocu is expected to accompany the front.
Fast cyclonic upper flow accompanying the broad long wave trof will
keep things zipping along and the surface high that moves into the
region in the wake of the cold front moves quickly to the east on
Sunday. This results in the return of low level WAA and moderating
temperatures again Sunday-Monday, with highs approaching normal on
Like yesterday we begin to see some differences with the
deterministic model solutions and within members of the GEFS late
Monday into midweek with the handling of short waves moving within
the mean long wave trof. It still appears we will see a cold front
move through the area Monday night into Tuesday. Whether or not it
is accompanied by any precipitation depends on the amplitude of
these aforementioned short waves and the resulting low level
forcing. The ECMWF and GEFS mean are beginning to support a
precipitation threat Tuesday into Tuesday night which should
largely be rain at this point.
.AVIATION... (For the 00z TAFs through 00z Thursday Evening)
Issued at 650 PM CDT Wed Oct 30 2019
Band of wintry precipitation extending from eastern IA into
eastern KS through northern MO, will gradually translate eastward
tonight and Thursday morning, affecting all of the TAF sites with
wintry precipitation types at some point as colder air spills in.
This is expected to occur at KUIN around 02z and KCOU around 05z
and involve a brief period of FZRA before becoming all SN. For the
STL metro sites, this is expected to occur around 09z and should
involve precipitation going straight to SN. This will intersect
with the SN then tapering to flurries and ending during Thursday
morning. The biggest runway impacts will likely be at KUIN where
wintry precipitation will occur the longest but could also impact
all the other TAF sites as well, becoming less likely towards the
STL metro sites. Otherwise, look for IFR CIGs to persist for all
TAF sites tonight and then clear out late Thursday morning or
in the afternoon. N surface winds will back to NW and become gusty
to 25-30kts later tonight and continue for much of Thursday.
SPECIFICS FOR KSTL: Rain or drizzle will be the main
precipitation-type until around 09z with a few hour window of
potentially accumulating snow before it backs off to flurries by
around 12z. FZRA probs during the transition looks too low to
mention at this time. Otherwise, IFR conditions to prevail until
Thursday morning with improvement to VFR and clearing during the
Issued at 326 PM CDT Tue Oct 29 2019
Record low max temperatures for Thursday October 31st
St. Louis 41 (1993)
Columbia 39 (1993)
Quincy 36 (1951)
Record low temperatures on Friday November 1st
St. Louis 26 (1954)
Columbia 16 (1895)
Quincy 23 (2014)
MO...Freeze Warning from 1 AM to 10 AM CDT Thursday for Audrain MO-
Boone MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-
Gasconade MO-Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln
MO-Madison MO-Marion MO-Moniteau MO-Monroe MO-Montgomery MO-
Osage MO-Pike MO-Ralls MO-Reynolds MO-Saint Charles MO-
Saint Francois MO-Saint Louis City MO-Saint Louis MO-Shelby
MO-Warren MO-Washington MO.
Freeze Watch from Thursday evening through Friday morning for
Sainte Genevieve MO.
Winter Weather Advisory until 10 AM CDT Thursday for Knox MO-
Lewis MO-Shelby MO.
Winter Weather Advisory until 10 AM CDT Thursday for Marion MO.
IL...Freeze Warning from 1 AM to 10 AM CDT Thursday for Adams IL-
Brown IL-Calhoun IL-Greene IL-Jersey IL-Macoupin IL-Madison
IL-Monroe IL-Montgomery IL-Pike IL-Saint Clair IL.
Freeze Watch from Thursday evening through Friday morning for
Bond IL-Clinton IL-Fayette IL-Marion IL-Randolph IL-
Winter Weather Advisory until 10 AM CDT Thursday for Adams IL-
Area Forecast Discussion
National Weather Service Marquette MI
857 PM EDT Wed Oct 30 2019
.SHORT TERM...(This evening through Thursday)
Issued at 319 PM EDT WED OCT 30 2019
Confluent flow at jet level noted in RAP analysis and WV satellite
from the eastern Dakotas and into the Upper Midwest. As would be
expected under this confluent flow, MSAS analysis shows surface high
pressure ridge extending ENE from the Rockies to the Upper Great
Lakes. However, visible satellite shows the cirrus shield building
in from the SW over the U.P. today in advance of a wave quickly
ejecting out of the Rockies and across the Plains states today. This
wave will spin up a surface cyclone tonight along the SW-NE oriented
baroclinic zone stretching from the Southern Plains to Quebec.
However with the parent long wave trough very positively tilted,
this will be a progressive system and not be allowed to amplify
enough to reach Upper Michigan with substantial precip.
Previous NAM runs brought accumulating snowfall to the eastern ~1/3
of the CWA where no other major model did, but the 12z came in line
with the other guidance in showing just the easternmost CWA (ISQ and
ERY and points east) being grazed with very light snow tomorrow
morning through afternoon. Regardless of what the NAM does or does
not show, the basic idea of a progressive wave in a positively
tilted long wave seems to argue for the less amplified solution that
does not bring a surprise snow to any part the U.P., so feel
comfortable keeping POPs and QPF very low. The result for this
forecast is about half an inch of snow for ERY, ISQ, and MNM, and
nada for points west of there from synoptic scale snow. For lows
overnight tonight and highs tomorrow, stuck pretty close to the
median of the distribution (and definitely did not bite on the MAV
guidance that had a low of 8 at Watersmeet!). That ends up being
mostly 20s tonight (maybe some upper teens interior west) and mid to
upper 30s tomorrow.
Now the interesting part. In addition to synoptically-forced precip,
many of the CAMS today develop lake-effect bands/showers in NNW flow
starting around sunrise tomorrow and continuing through the day.
Moisture is progged to be very shallow with saturation only up to 4-
5 kft at best, so found it hard to believe any robust LES will
develop even with 17-18 C delta T`s. Used the NNW LES primary edit
area, filled it in with the HREF/SREF/CONSShort and such but then
lowered them back down to 40 or less POP to account for the dry air
aloft/shallowness of precip. For QPF did pretty much the same -
initially used CAMS to highlight an area then backed down
significantly. End result is again about a half inch of snow at most
in eastern Marquette and western Alger County. But where it gets
interesting is just how shallow the saturation is. It`s possible
that some of this falls as freezing drizzle rather than as snow
showers. Again, QPF amounts are very low and roads are still warm so
not expecting any impacts, but wouldn`t be surprised if some
windshields and other elevated surfaces get glazed tomorrow morning
in Marquette and Alger Counties. For the rest of the Keweenaw and
west, went with only flurries and sprinkles instead of snow
showers/drizzle because of the shorter fetch length in an already
extremely marginal setup. Regardless of any precip, there will
plenty of lake-effect clouds around for almost all of the CWA, so it
will be appropriately gloomy for Halloween.
.LONG TERM...(Thursday night through Wednesday)
Issued at 245 PM EDT WED OCT 30 2019
Upper air pattern will consist of a 500 mb closed low over the lower
Great Lakes 00z Fri with more troughing in the Canadian and northern
Rockies and northern plains. This last trough will dig southeast
into the upper Great Lakes 00z Sat and this trough moves slowly
across the area on Sat. Deeper moisture and 850-500 mb q-vector
convergence moves in on Fri with the dynamics moving out Fri night
into Sat, but the deep moisture remains. Did not make too many
changes to the going forecast.
In the extended, the GFS and ECMWF show a broad 500 mb trough over
the ern half of the U.S. 12z Sun. This broad trough remains over the
area into Wed. Looks active for this forecast period along with
below normal temperatures. Nothing real big, just lots of little
lake effect episodes.
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 817 PM EDT WED OCT 30 2019
Lake-effect clouds continue at CMX with cigs MVFR the last few hours.
Elsewhere, VFR conditions prevail early this evening. Expect MVFR cigs
to develop at all sites late tonight or early Thursday morning as
winds turn northerly and lake-effect clouds push in. Expecting it
to be too dry for -SHSN at IWD and CMX (except for perhaps
passing flurries). Could be on-and-off lake- effect -SHSN at SAW
after about 12z, but even there it might end up being little more
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 319 PM EDT WED OCT 30 2019
N to NW winds 15-20 kts expected tonight and Thursday across the
lake, with a brief increase to 25 kts possible east Thursday
afternoon as a low pressure area tracks through the Lower Great
Lakes. Winds become SW for Friday but stay at or below 20 kts. They
then veer to NW Fri night as another trough approaches from the NW
in Canada. As that trough passes over the lake, winds increase to 25-
30 kts Saturday. Winds become W and then SW behind the trough Sunday
and relax below 20 kts Sunday into Monday. Next chance of 25+ kt
winds after that is not until Tuesday afternoon.