Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/30/22
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
928 PM CDT Tue Mar 29 2022
.UPDATE...
Issued at 928 PM CDT Tue Mar 29 2022
Aside from re-trending the hourly weather elements, the main
changes to the forecast this evening were to shave PoPs through
the overnight for the southeastern third of the forecast area and
to ease wind gusts a smidge. While 00z RAOBs indicate regions of
impressively steep lapse rates are floating around aloft, mid-
evening VAPOR AMDAR soundings suggest there`s still quite a bit of
dry air in several layers (surface to 3500 feet and above 750 mb)
which should continue to limit precip chances in the immediate
term. This should change later tonight, especially for our
northwestern locales as large scale forcing for ascent increases
as an upstream 100+ jet streaks pushes across the Mississippi
River. While we`ll look for a continued gradual weakening of the
convective complex arcing into northwest Missouri, the
aforementioned steepened mid-level lapse rates will facilitate
MUCAPE values pushing 250-500 J/kg in spots, more than sufficient
given the magnitude of ascent for lightning. Have inched thunder
chances up a little north and west of I-55 as a result.
No changes to the Wind Advisory headline which goes into effect at
9 AM tomorrow south of the Kankakee River for the potential for
wind gusts to 45 mph which still looks good. Still some questions
regarding how deeply we`ll manage to mix as low-level moisture
streams northward, but incoming guidance indicates that, at least
on a sporadic basis, we`ll mix stronger momentum to the surface as
pressure falls increase through the late-morning hours.
Finally, still keeping an eye on a strong-severe potential through
mid-late afternoon as a strongly forced line of low-topped
convection develops eastward. Big question mark continues to be
the magnitude of surface-based instability (as it usually is with
this early-season events). The presence of a sub-990 mb (and
deepening) low, with 60+ kts of flow just off the deck does,
however, suggest any more organized activity will have the
potential to produce pockets of damaging winds, possibly as far
north as I-80.
Carlaw
&&
.SHORT TERM...
Issued at 222 PM CDT Tue Mar 29 2022
Through Thursday...
The primary forecast concerns with the approaching storm system
include:
- Scattered showers late this evening and overnight expanding in
coverage for the majority of Wednesday
- The potential for thunderstorms Wednesday afternoon, primarily
along and south of I-80, which could feature heavy downpours and
damaging winds
- Widespread gusty winds this afternoon through Thursday morning.
Wednesday afternoon, winds could gust to over 45 mph in areas
southeast of I-55
- The potential for snow showers Thursday morning and afternoon
which could possibly impact the Thursday morning commute
Cloudy skies hang overhead this afternoon ahead of big, approaching
storm system that will drive the forecast over the next few days.
This system is currently centered over the central Plains with its
warm front draped across the Missouri Valley inching into far
southern Illinois. A few pockets of showers are forming along this
warm front and trekking northeastward as they ride along the lee
side of the storm`s associated low level trough. However, the low
levels are far too dry north of the warm front to allow any of
this rain to reach the surface for the time being. It won`t be
until this evening that we start to see moisture advection
sufficient enough to inhibit evaporation and sublimation.
Scattered showers are then expected across most of the area
overnight. As the storm`s center and surface warm front approach
from the west, a good deal of model guidance is suggesting that
the far west and northwest CWA could tap into enough elevated
instability to result in some convective showers and possibly a
thunderstorm or two overnight.
Once the surface warm front passes over and we enter the storm`s
warm sector, that`s when widespread showers will push through the
area. This looks to occur sometime in the mid-morning to early
afternoon with the rain building in from the southwest. This timing
will also allow the whole area to warm into the 60`s with 70`s
probable across parts of the far southeastern CWA. Embedded
thunderstorms appear likely through portions of the afternoon and
evening. While there`s a chance we could see storms develop anywhere
across the CWA, probabilities are higher near and south of I-80
where there is a notably better CAPE profile. Storms in the far
south CWA also have the highest potential of being strong to severe
and featuring damaging wind gusts, torrential downpours, and
possibly some small hail. The widespread rainfall also poses a
threat for rises in river levels and ponding on the roadways.
Continued rainfall and localized ponding will likely result in a
slowed Wednesday evening commute.
The surface cold front is anticipated to pass over the area
overnight pushing the rainfall off to our east. Strong cold air
advection begins to take place immediately following frontal passage
causing temperatures to plummet into the middle and upper 30`s by
Thursday morning and keeping them in the lower 40`s for Thursday`s
high. As the storm propagates to our northeast, precipitation
wrapping around to the backside of the storm`s center will likely
fall on the area Thursday morning in the form of scattered snow
showers. This snow could potentially last as late as Thursday
afternoon and result in light, localized accumulations on cooler
and elevated surfaces. Travel maybe slowed once again Thursday
morning as some may encounter snow during the commute.
Aside from the long-lived precipitation event, strong winds are also
anticipated with this storm system. The surface pressure gradient
will tighten steadily through the remainder of the afternoon and
evening as the Low pushes into the Midwest. Winds will subside
slightly overnight before ramping up again through tomorrow morning.
While the mixed layer across most of the area shouldn`t be overly
deep, strong low level winds will make up for that. 850mb winds by
tomorrow afternoon could reach as high 50-60 kts. The strongest
winds are expected between late tomorrow morning and early tomorrow
evening. Areas southeast of I-55 will feel the brunt of the gusty
winds with deeper mixing expected as a result of stronger WAA. Winds
in these parts could gust upwards of 45+ mph through the afternoon.
The majority of the CWA will see peak gusts between 25 and 35 mph.
A wind advisory has been issued for counties south of I-80 from
9AM through 9PM tomorrow. A tight surface pressure gradient on
the backside of the storm will keep conditions breezy through most
of Thursday before winds die down through the late afternoon and
evening.
Doom/Yack
&&
.LONG TERM...
Issued at 233 PM CDT Tue Mar 29 2022
Thursday night through Tuesday...
Things will be drying out Thursday evening, though rain and possibly
some rain/snow mix will continue to be possible across eastern
parts of northwest Indiana during the evening. Surface high
pressure will arrive from the west Friday morning and cross the
area through the day. This will be accompanied by shortwave upper
ridging bringing warm advection aloft. Highs should warm into the
mid or even upper 40s but winds will be light enough that a modest
lake breeze should develop along the Lake Michigan shore keeping
highs in the lower 40s there.
A fast moving shortwave upper trough will cross the area Saturday
afternoon/evening bringing chances for rain with it. Southerly
winds ahead of the system will allow for further warming into the
50s, but once again, winds will likely be weak enough to allow for
lake breeze development along the Lake Michigan shore. Precip
exits during the evening with another surface high crossing the
area Sunday. The upper flow pattern stays pretty zonal with this
system so temps should actually be a bit warmer on Sunday, though
yet another lake breeze is expected keeping lakeshore areas
cooler. Next week is potentially looking active, starting with a
another weak system passing Sunday evening. Medium range guidance
differs with the evolution of longer wave troughing over western
North America into Tuesday through midweek.
MDB
&&
.AVIATION...
For the 00Z TAFs...
The primary aviation concerns through the next 30 hours are as
follows:
* Spotty showers at all terminals from midnight to daybreak with
a chance for thunder at RFD
* South to southwesterly LLWS from about 03-12Z tonight
* Increasingly gusty south winds at ORD/MDW/DPA/GYY with gusts at
or above 30kt and possibly near 40kt, particularly between
16-21Z
* Strongly-forced narrow band of gusty convection with little to
no lightning sometime between 18-22Z
* Lowering cigs from VFR to MVFR and eventually IFR, especially in
the last 12 hours of the TAF period.
Regional surface analyses depict a deepening surface low pressure
system entering southern Nebraska with an associated warm front
sprawled eastward from southern Iowa to central Kentucky. North
of the warm front and into the lower Great Lakes, increasing
isentropic ascent is contributing to lowering cloud bases and
occasional radar echoes. However, a stout surface dry layer
roughly 5000 ft deep as sampled by recent AMDAR-equipped aircraft
will prevent any precipitation from reaching the ground and keep
cigs VFR through the first half of the overnight period. After
midnight, forecast guidance is insistent that the dry layer
should moisten sufficiently for raindrops to finally reach the
ground and cigs to build downward into MVFR. Given the spotty
coverage expected of the showers, opted to convert the inherited
prevailing SHRA to TEMPOs targeted from about 06-10Z. A higher
coverage of showers with a few embedded thunderstorms and MVFR
cigs appears more likely toward RFD, particularly between 09-12Z.
In addition to shower potential overnight, a stout 50kt low-level
jet will lead to LLWS at all terminals from roughly 03-12Z.
Surface winds are expected to remain out of the southeast
overnight with occasional gusts of 20-25kt.
Shower coverage should decrease after daybreak except at RFD,
giving way to a dry morning. As the aforementioned surface low
pressure system approaches from the west and even modest mixing
commences after daybreak, increasingly gusty winds from the south
appear likely with gusts at or above 30kt at ORD/MDW/DPA/GYY,
particularly between 16-21Z. Note that winds may end up even
stronger, perhaps as strong as 40kt, as indicated by recent
iterations of the HRRR/RAP. Should the stronger wind gusts verify,
cigs would likely end up higher than advertised. For now, will
step upward in explicitly mentioned winds and gusts from the 18Z
package and reassess with the 03/06Z packages, and maintain
mention of MVFR to IFR cigs.
Forecast guidance remains in strong agreement that convection will
develop in the Southern Plains tonight and track northeastward
toward the great Lakes tomorrow morning. While instability will be
weak and likely limit lightning potential, exceptionally strong
forcing associated with the approaching low pressure system will
likely maintain a narrow band of convection through northeastern
Illinois and northwestern Indiana during the afternoon hours. In
collaboration with CWSU ZAU, opted to maintain a mention of -TSRA in
spite of expected little to no lightning given convective-related
impacts, convert the inherited PROB30 groups for TSRA into 3-hour
TEMPOs, and move up the timing modestly from the 18Z package. Note
that any true convective element would likely last far shorter than
3 hours, so further refinement in time is likely in later TAF
packages. In addition, the strong low-level wind fields may
encourage a brief pop of winds with the line from the southwest as
high as 40kt (if not already occurring ahead of the line).
Behind the line of convection, on-and-off showers will likely
prevail as well as high-end IFR/low-end MVFR cigs. Winds will
remain gusty out of the south, but not as strong as earlier in
the TAF period. At the end of the TAF period, a wind shift to
westerly is expected.
Borchardt
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory...ILZ023-ILZ032-ILZ033-ILZ039...9 AM Wednesday to
9 PM Wednesday.
IN...Wind Advisory...INZ010-INZ011-INZ019...9 AM Wednesday to 9 PM
Wednesday.
LM...Small Craft Advisory...IL nearshore waters until 7 PM Wednesday.
Small Craft Advisory...IN nearshore waters until 4 PM Thursday.
&&
$$
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