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Office: DVN

FXUS63 KDVN 190837
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
337 AM CDT Fri Oct 19 2018

.SYNOPSIS...
Issued at 242 AM CDT Fri Oct 19 2018

Early this morning the local area was in an area of weak ridging
upstream of a shortwave trough with its axis from northern
Minnesota into Colorado. Scattered showers were observed ahead of
this system from eastern Nebraska into northeast Minnesota. A
secondary area of precipitation was observed from Oklahoma into
eastern Kansas associated with a wing of moisture transport and
warm air advection. Cloud cover, 10 mph winds, and warm air
advection overnight have allowed temperatures to stay mild
overnight, with readings in the 40s and low 50s at 08Z.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 242 AM CDT Fri Oct 19 2018

The elongated shortwave trough out to the west will move through
the area today. This will bring scattered to widely scattered
showers to much of the forecast area this morning and early
afternoon. As the shortwave moves through, the most amplified area
will move across southern Minnesota and northern Iowa into
Wisconsin and northern Illinois. This area is also associated with
the left entrance region of the upper level jet streak so lift
should be sufficient for widespread showers. The moisture however
is limited and will be very narrow ahead of the shortwave. For
instance, models are showing the deep layer moisture will push
across the area in a 3 hour time-span. While moisture has been
advecting in overnight, the DVN 19.00Z sounding was quite dry, PW
value of 0.31 inches, so when the showers do come through they'll
have quite a bit of dry air to move through. This should limit any
precipitation to light amounts, generally a tenth of an inch or
less. Focused the highest rain chances across the northern part of
the forecast area, where the best dynamics will be, but will
include rain chances throughout the forecast area. Cloud cover
will persist for a few hours after the rain exits, which could
impact todays temperatures. Warm air advection will bring 850mb
temperatures ranging from 9C to 13C, but with clouds persisting
into the afternoon, don't have much confidence in how much the
surface will warm and mix to take advantage of the warmer
temperatures aloft. Ultimately, kept highs a bit cooler where
clouds are expected to linger longer, but will need to keep a
close eye on how the situation evolves and if there will be a need
to update highs at some point. Winds will also be a bit stronger
today, as winds shortly above the surface will be blowing at
20-35kts. Forecast soundings would suggest mixing to about 875mb
so should get some periods of gusty conditions.

The shortwave pushes east fairly quickly, with dry conditions,
clearing skies, cooler air, and winds shifting to the west-
northwest by Friday evening. Don't expect winds to drop off
though, keeping the boundary layer mixed, so despite the cold air
moving into the region, (850mb temps 0-2C) only dropped lows
Saturday morning into the upper 30s and 40s.



.LONG TERM...(Saturday through Thursday)
ISSUED AT 242 AM CDT Fri Oct 19 2018

Very strong winds expected Saturday followed by mainly below normal
temperatures.

Saturday
Assessment...high confidence on very strong winds. Low to medium
confidence on precip chances.

A potent upper level disturbance will move through the area on
Saturday. While there are some minor differences on the track of the
system, very strong winds will develop.

Once the inversion breaks Saturday morning, winds will increase
significantly with the strongest winds from late morning through mid-
afternoon. Sustained winds around 25 mph should easily be achieved
with gusts of 40-45 mph.

Dry air may limit the overall areal coverage of showers that occur
with the passage of the upper level system. However, sprinkles if
not isolated to scattered rain showers should be seen across the
northeast half of the area Saturday morning followed by dry
conditions and clearing skies in the afternoon.

Saturday night
Assessment...high confidence

Clear and cold conditions will be seen across the area Saturday
night with low temperatures in the 20s.

Sunday and Sunday night
Assessment...high confidence

Quiet and dry conditions will be seen with temperatures averaging
below normal.

Monday on...

Monday through Wednesday
Assessment...high confidence

Dry conditions will continue through the first half of the week. A
dry frontal passage will occur Monday afternoon/evening that will be
marked with only an increase in clouds.

Wednesday night and Thursday
Assessment...low confidence on precipitation chances

Wednesday night return flow develops across the area as high
pressure moves into the Ohio Valley. The global models have a storm
system forecast to move across the deep south which should intercept
most of the return moisture moving north.

The global models disagree on when precipitation moves back into the
area. This disagreement appears to be centered around the strength
of the high in the eastern Great Lakes/Ohio Valley and the amount of
dry air present.

The GFS keeps the entire area dry Wednesday night/Thursday with not
much in the way of precipitation in western Iowa. The CMC global
keeps the area dry but does develop precipitation across western
Iowa. The ECMWF on the other hand brings light precipitation into
the the area Wednesday night/Thursday with the help of an upper
level disturbance.

As a result of these differences, the model consensus has slight
chance to chance pops Wednesday night and Thursday morning.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
ISSUED AT 1253 AM CDT Fri Oct 19 2018

The first portion of this 24 hour period will be quiet with VFR
conditions and winds below 10kts. A cold front will move towards
the area and pass through the terminals Friday evening. This front
will bring more active weather to the area today. Cloud cover will
increase, and is expected to drop to MVFR around 14-15Z. Rain showers
will accompany these lowered ceilings, with the most widely
scattered showers across the northern parts of the area, impacting
KCID and KDBQ. Going south, the showers should have lesser
coverage so have VCSH, but will watch as the activity moves in to
see if coverage indicates a need to make SH prevailing weather at
both KMLI & KBRL. Winds will also increase this afternoon at
15-20kts with gusts in some areas to 25-30kts. This is a quick
moving system, with rain moving out and ceilings improving this
afternoon. Then winds switch around to the west-northwest by
20.06Z.


&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...Brooks
SHORT TERM...Brooks
LONG TERM...08
AVIATION...Brooks



Office: LOT FXUS63 KLOT 190807 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 307 AM CDT Fri Oct 19 2018 .SHORT TERM... 306 AM CDT Today through Saturday night... Main short term forecast concerns are chances of showers today and again Saturday with a pair of cold fronts, in addition with windy conditions with falling temps Saturday. Parts of northwest and north central Indiana will likely see lake effect precip later Saturday/Saturday night. Low pressure was analyzed north of the Great Lakes over Ontario early this morning, with a cold front trailing southwest across northern and central High Plains. This cold front will move east toward the region today, in association with a mid-level short wave trough emerging from the Plains. 00Z RAOBs from ILX and DVN last evening depicted a deep layer of fairly dry air across the local area, though upstream soundings from TOP/SGF did indicate mid-level moisture which was streaming northeastward ahead of the approaching front. Forecast soundings do depict saturating mid- levels this morning/mid-day, as isentropic upglide and large scale forcing increase ahead of the approaching mid-level wave. This will likely support development of rain showers across the region today, though with amounts of less then a tenth of an inch expected. Isentropic progs from the 300-315 K levels then depict fairly strong downglide and drying developing by evening, suggesting a quick end to precip from west to east. Modestly tight pressure gradient will support breezy southwest winds during the day with gusts around 25 mph ahead of the front, with temps generally in the mid-50s. A stronger short wave is progged to dig south from Manitoba tonight, amplifying an upper trough across the eastern CONUS, and bringing a surge of colder air behind a secondary cold front which will push across the cwa Saturday morning. Strong mid-level height falls, strong PDVA and strong low level convergence should support a period of showers along/ahead of the front Saturday morning/mid-day, before strong drying and subsidence sets in behind the front during the afternoon, ending precip and eroding cloud cover. Strong northwest winds gusting to 40 mph at times will likely result in falling temps through the afternoon, after morning highs in the 40s north and low-mid 50s far south. Surface high pressure then builds quickly south through the Missouri Valley Saturday night, with dry and colder air spreading across the Midwest. Winds should eventually decouple enough on the eastern periphery of the surface ridge, which along with mainly clear skies should produce a hard freeze (mid-upper 20s) over the majority of the forecast area by sunrise Sunday morning. The exception may be in the core of the Chicago urban heat island, and over in northwest Indiana near Lake Michigan. Cold air flowing over the still relatively mild lake waters will set up the likelihood of some lake effect into Saturday night, with respectable delta-Ts of 20C and inversion heights around 10 kft. Lower levels downwind of the lake should remain warm enough to support rain, with the northwest fetch favoring mainly northeast Porter county and areas to the east. Ratzer && .LONG TERM... 306 AM CDT Sunday through Thursday... The upper pattern remains highly amplified through the extended period, with long wave troughing across eastern North America or just off shore, into the middle of next week. Medium range guidance in in pretty good agreement through about Tuesday, before developing some spread in the days 5-7 period. Saturdays strong digging short wave trough is moving off the mid- Atlantic coast by Sunday morning, with a broad area of surface high pressure spreading through the Ohio Valley in its wake. Low level winds turn west-southwesterly as the northern periphery of the surface ridge works east of the area, with resulting modest warm advection allowing temps to rebound to near/around 50 degrees by afternoon after a chilly morning start. Forecast soundings indicate dry profiles, with plentiful sunshine expected, and light southwest low level winds continue Sunday night helping keep mins at or above freezing overnight. Medium-range guidance is in good agreement in depiction of a short wave digging southeast from the Canadian prairie provinces on Monday, and propagating across the Great Lakes by evening. Associated surface low pressure passes well to the northeast of the area, though a trailing cold front pushes into northern IL during the afternoon, and completes its transit of the local forecast area through the evening. A narrow ribbon of low level moisture spreads into the area ahead of the front, though forecast soundings indicate this is mainly limited to the boundary layer and maintain considerable dry air aloft supporting a dry cold fropa. Surface high pressure then builds in across the upper Midwest and western Great Lakes region Tuesday and Tuesday night. Highs on Monday should warm well into the mid-upper 50s in the warm sector ahead of the cold front, and potentially to the 60 degree mark (near normal!) in spots especially across the south/southeast parts of the cwa where the front is not expected to arrive until after sunset. Tuesday doesn't look too much cooler despite the frontal passage, with the bulk of the colder air only glancing the area. Tuesday and Wednesday both look to continue the dry trend, with surface high pressure in the area and highs in the low-mid 50s. As mentioned above, medium-range guidance shows a little more spread by the end of the period. ECMWF notably is a little quicker to move the sprawling surface high off to the east Wednesday night into Thursday, and tries to bring some warm advection precip into the Mississippi Valley late Wednesday night and Thursday in association with a short wave which damps quickly into the upper ridge. These differences are of little impact however, with other sensible weather elements otherwise pretty similar between the guidance at this distance. Ratzer && .AVIATION... For the 06Z TAFs... 1225 am...Forecast concerns include gusty southwest winds later today...a period of scattered showers early in the afternoon then mvfr cigs mid afternoon through early evening. Clouds will slowly thicken and lower through the morning hours as an upper wave approaches. This wave is expected to produce some showers during the late morning across northwest IL and then through the early afternoon across the rest of the area. There is still some uncertainty regarding how widespread these showers will become so maintained vicinity mention for now but its possible that prevailing showers or light rain may be needed with later forecasts. As this area of precip shifts east by mid afternoon... models are still showing the potential for high mvfr cigs which last into the early evening when a cold front moves across the area...clearing out the clouds. Southwest winds generally under 10kts through sunrise will increase later this morning with gusts in the mid 20kt range expected into early this evening. Winds will shift west/northwest with the cold front early this evening with speeds 10-15kts still expected Friday night. cms && .MARINE... 218 PM CDT A strong system will move across Lake Michigan on Saturday. Gusty SW winds on Friday will be replaced with strong NW winds on Saturday, with the highest likelihood for gales across the Indiana nearshore waters midday Saturday into early Saturday evening. KMD && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...LMZ743-LMZ744-LMZ745...7 AM Friday to 10 AM Saturday. Gale Watch...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM Saturday to 10 PM Saturday. Small Craft Advisory...LMZ740-LMZ741-LMZ742...7 AM Friday to 10 PM Friday. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO FXUS63 KLOT 190830 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 330 AM CDT Fri Oct 19 2018 .SHORT TERM... 306 AM CDT Today through Saturday night... Main short term forecast concerns are chances of showers today and again Saturday with a pair of cold fronts, in addition with windy conditions with falling temps Saturday. Parts of northwest and north central Indiana will likely see lake effect precip later Saturday/Saturday night. Low pressure was analyzed north of the Great Lakes over Ontario early this morning, with a cold front trailing southwest across northern and central High Plains. This cold front will move east toward the region today, in association with a mid-level short wave trough emerging from the Plains. 00Z RAOBs from ILX and DVN last evening depicted a deep layer of fairly dry air across the local area, though upstream soundings from TOP/SGF did indicate mid-level moisture which was streaming northeastward ahead of the approaching front. Forecast soundings do depict saturating mid- levels this morning/mid-day, as isentropic upglide and large scale forcing increase ahead of the approaching mid-level wave. This will likely support development of rain showers across the region today, though with amounts of less then a tenth of an inch expected. Isentropic progs from the 300-315 K levels then depict fairly strong downglide and drying developing by evening, suggesting a quick end to precip from west to east. Modestly tight pressure gradient will support breezy southwest winds during the day with gusts around 25 mph ahead of the front, with temps generally in the mid-50s. A stronger short wave is progged to dig south from Manitoba tonight, amplifying an upper trough across the eastern CONUS, and bringing a surge of colder air behind a secondary cold front which will push across the cwa Saturday morning. Strong mid-level height falls, strong PDVA and strong low level convergence should support a period of showers along/ahead of the front Saturday morning/mid-day, before strong drying and subsidence sets in behind the front during the afternoon, ending precip and eroding cloud cover. Strong northwest winds gusting to 40 mph at times will likely result in falling temps through the afternoon, after morning highs in the 40s north and low-mid 50s far south. Surface high pressure then builds quickly south through the Missouri Valley Saturday night, with dry and colder air spreading across the Midwest. Winds should eventually decouple enough on the eastern periphery of the surface ridge, which along with mainly clear skies should produce a hard freeze (mid-upper 20s) over the majority of the forecast area by sunrise Sunday morning. The exception may be in the core of the Chicago urban heat island, and over in northwest Indiana near Lake Michigan. Cold air flowing over the still relatively mild lake waters will set up the likelihood of some lake effect into Saturday night, with respectable delta-Ts of 20C and inversion heights around 10 kft. Lower levels downwind of the lake should remain warm enough to support rain, with the northwest fetch favoring mainly northeast Porter county and areas to the east. Ratzer && .LONG TERM... 306 AM CDT Sunday through Thursday... The upper pattern remains highly amplified through the extended period, with long wave troughing across eastern North America or just off shore, into the middle of next week. Medium range guidance in in pretty good agreement through about Tuesday, before developing some spread in the days 5-7 period. Saturdays strong digging short wave trough is moving off the mid- Atlantic coast by Sunday morning, with a broad area of surface high pressure spreading through the Ohio Valley in its wake. Low level winds turn west-southwesterly as the northern periphery of the surface ridge works east of the area, with resulting modest warm advection allowing temps to rebound to near/around 50 degrees by afternoon after a chilly morning start. Forecast soundings indicate dry profiles, with plentiful sunshine expected, and light southwest low level winds continue Sunday night helping keep mins at or above freezing overnight. Medium-range guidance is in good agreement in depiction of a short wave digging southeast from the Canadian prairie provinces on Monday, and propagating across the Great Lakes by evening. Associated surface low pressure passes well to the northeast of the area, though a trailing cold front pushes into northern IL during the afternoon, and completes its transit of the local forecast area through the evening. A narrow ribbon of low level moisture spreads into the area ahead of the front, though forecast soundings indicate this is mainly limited to the boundary layer and maintain considerable dry air aloft supporting a dry cold fropa. Surface high pressure then builds in across the upper Midwest and western Great Lakes region Tuesday and Tuesday night. Highs on Monday should warm well into the mid-upper 50s in the warm sector ahead of the cold front, and potentially to the 60 degree mark (near normal!) in spots especially across the south/southeast parts of the cwa where the front is not expected to arrive until after sunset. Tuesday doesn't look too much cooler despite the frontal passage, with the bulk of the colder air only glancing the area. Tuesday and Wednesday both look to continue the dry trend, with surface high pressure in the area and highs in the low-mid 50s. As mentioned above, medium-range guidance shows a little more spread by the end of the period. ECMWF notably is a little quicker to move the sprawling surface high off to the east Wednesday night into Thursday, and tries to bring some warm advection precip into the Mississippi Valley late Wednesday night and Thursday in association with a short wave which damps quickly into the upper ridge. These differences are of little impact however, with other sensible weather elements otherwise pretty similar between the guidance at this distance. Ratzer && .AVIATION... For the 06Z TAFs... 1225 am...Forecast concerns include gusty southwest winds later today...a period of scattered showers early in the afternoon then mvfr cigs mid afternoon through early evening. Clouds will slowly thicken and lower through the morning hours as an upper wave approaches. This wave is expected to produce some showers during the late morning across northwest IL and then through the early afternoon across the rest of the area. There is still some uncertainty regarding how widespread these showers will become so maintained vicinity mention for now but its possible that prevailing showers or light rain may be needed with later forecasts. As this area of precip shifts east by mid afternoon... models are still showing the potential for high mvfr cigs which last into the early evening when a cold front moves across the area...clearing out the clouds. Southwest winds generally under 10kts through sunrise will increase later this morning with gusts in the mid 20kt range expected into early this evening. Winds will shift west/northwest with the cold front early this evening with speeds 10-15kts still expected Friday night. cms && .MARINE... 330 am...A strong gradient will develop across the area today as high pressure moves southeast and a cold front approaches from the northwest. Southwest winds will steadily increase after sunrise this morning with gusts to 30kts expected into early this evening. Wind directions will slowly turn more westerly by sunset and then the cold front will shift winds northwest this evening. Speeds will diminish into the 15-25kt range overnight with winds then turning back westerly by Saturday morning. Another stronger cold front will move across the area Saturday morning shifting winds northwest by midday Saturday. A tight gradient combined with much colder air spreading across the region will allow northwest gales 35-40kt to develop. These strong winds will begin to diminish by late afternoon with speeds slowly relaxing under 30kts Saturday evening. High pressure will move from the northern Plains Saturday to the Ohio Valley Sunday which will allow winds to turn back southwesterly on Sunday. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...LMZ743-LMZ744-LMZ745...7 AM Friday to 10 AM Saturday. Gale Watch...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM Saturday to 10 PM Saturday. Small Craft Advisory...LMZ740-LMZ741-LMZ742...7 AM Friday to 10 PM Friday. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
Office: ILX FXUS63 KILX 191007 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 507 AM CDT Fri Oct 19 2018 .SHORT TERM...(Today and tonight) ISSUED AT 304 AM CDT Fri Oct 19 2018 07z surface map indicated high pressure ridge had shifted southeast into the Ohio Valley. Light return flow on the back side of the high, along with increasing high clouds kept temperatures several degrees milder than yesterday, upper 30s south of I-70, to mid 40s in west central Illinois. Aloft, water vapor imagery showed a shortwave trough over the northern Plains and central Rockies. Ahead of the trough, low to mid level flow has veered southwest, increasing warm/moist advection into the Midwest. As WAA continues today and a surface front associated with the upper level disturbance to our northwest approaches, scattered light rain showers are expected. Forecast soundings are initially quite dry, so sprinkles or virga may be more common this morning for areas west of I-55. Forcing and moisture are maximized over the eastern CWA this afternoon, and this is where high chance and likely pops are confined. Most totals even in these areas should remain under 0.10" by time showers diminish late afternoon/early evening. Ahead of the front, gradient tightens for southwest winds to gust 20-25 mph this afternoon. Even with mostly overcast skies, highs should reach the mid to upper 50s. Dry conditions are expected overnight, with mild lows in the 40s. .LONG TERM...(Saturday through Thursday) ISSUED AT 304 AM CDT Fri Oct 19 2018 A stronger cold front associated with a potent shortwave tracking south across the western Great Lakes, will shift south across the area midday Saturday. Behind the front a tight gradient will produce 30-40 mph gusts, and falling afternoon temperatures. By mid to late afternoon, with temperatures falling through the 40s, wind chills will be in the 30s. Forcing ahead of the shortwave will produce scattered showers over northern Illinois and Indiana, which could brush the far NE CWA, particularly areas east of Bloomington to near Danville, around midday. Behind the front, strong 1030+ mb Canadian high pressure will slide down the Missouri Valley for Saturday night and Sunday. This will bring another seasonably cold airmass to the region. Lows in the upper 20s are forecast by Sunday morning, probably necessitating freeze headlines for our southeast 6 counties, where the growing season continues. Dry and seasonable weather is expected for most of next week. Warm advection behind the departing surface ridge could boost highs near normal for Monday, but a dry cool front will return readings a few degrees below normal through mid-week. && .AVIATION...(For the 12Z TAFS through 12Z Saturday morning) Issued at 507 AM CDT Fri Oct 19 2018 High clouds currently over the area will lower and thicken this morning, as moisture increases ahead of a disturbance moving in from the west. Isolated to scattered light showers will develop as the system moves through, from late morning into this afternoon. Ceilings are expected to lower to MVFR for this afternoon and evening, before drier air works in behind the front, later this evening. Southwest winds will be gusty up to 20-23 kts in a tightening pressure gradient ahead of the boundary. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...25 LONG TERM...25 AVIATION...25