Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/15/23
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
943 PM CST Tue Feb 14 2023
.UPDATE...
Issued at 931 PM CST Tue Feb 14 2023
Conditions remain mixed in the low levels this evening, more so
than normally would be expected after dark. The low level jet has
maximized over northeast Illinois, and thus occasional wind gusts
to 45 mph, and a few sporadic gusts in the lower 50 mph range,
including at Chicago O`Hare recently with a 1-minute ob at 48 kt
(55 mph). These gusts have also been maximized in the urban areas
that are a bit warmer.
We have correspondingly bumped up the start of the Wind Advisory
for areas south of I-80 but including Cook/DuPage this evening,
even though widespread wind gusts of 45-50 mph have been somewhat
limited away from the metro area. This seemed prudent given the
band of showers over west central IL will encounter this higher
low level jet maximum and may be able to overperform what they`ve
been doing upstream.
There will likely be a lull in winds after this band of showers
moves through overnight. A lightning strike cannot be ruled out,
but given the main instability axis skirts the area to the
northwest, this would be the exception. Latest AMDAR soundings do
have a bit of a warm nose at 3000 ft, but there is still 50+ kt of
winds below that, so we will have to watch the 11pm - 2am window
for some sporadic higher gusts from these showers.
KMD
&&
.SHORT TERM...
Issued at 1258 PM CST Tue Feb 14 2023
Through Wednesday night...
CONUS satellite imagery augmented by a recent hand surface and RAP
analyses depict a maturing surface cyclone over the Southern Plains
within the left exit region of an intensifying 150 kt 250mb jet
streak across the Lower Mississippi River Valley. Arcs of showers
continue to expand near and ahead of the developing surface low with
a broad (and intensifying) WAA regime. The first showers are now
crossing northern Illinois, though the dry low-level airmass
(characterized by surface T/Td spreads of 15-20 degrees) has thus
far chewed up most raindrops. Continued top-down moistening via
evaporation should eventually allow for raindrops to start dotting
the ground this afternoon. The next band of rain is much broader and
encompasses much of Iowa and Missouri, and is on track to reach our
area around or just after sunset. Accordingly, we are anticipating a
2-4 hour period of showers this evening before tapering takes place
from west to east by 10 PM. As the surface low matures and lifts
northeastward over western Iowa this evening, the low-level pressure
gradient will also tighten allowing for south to southeasterly winds
to gradually intensify with gusts of 30-35 mph becoming common by
sunset.
Tonight, the surface low is expected to reach peak intensity (~984
mb or so) while entering southern Minnesota as a dry slot noses into
the Lower Great Lakes and an impressive 60-70kt 850-700mb LLJ slides
overhead. Cooling mid-level temperatures around the periphery of the
low and mid-level drying within the northeastward-spreading dry slot
will steepen mid-level lapse rates and maintain the integrity of a
pool of 150-250 J/kg of MUCAPE spreading northeastward from Missouri
into northern Illinois. At the same time, a narrow plume of surface
dew points ranging from 45-50 degrees currently in southwestern
Missouri will spread northeastward, causing low-level lapse rates to
improve modestly. Taken together, a band of low-topped convection
originating near the MO/KS/IA borders this evening may survive and
sweep across the area overnight, particularly between 04Z/10PM and
7Z/1 AM. With strong low-level wind field in place (re: LLJ) and
steepening low-level lapse rates (re: low-level moisture advection),
any taller convective shower may efficiently transport wind gusts of
45-50 mph toward the ground. Such a threat appears highest northwest
of Interstate 55 in closer proximity to the cold core of the low and
hence better MUCAPE. After touching base with SPC, we felt the
probability of severe-caliber gusts was too low to warrant a formal
mention in a severe weather outlook, though be aware a "pop" of
winds may accompany any shower overnight.
Toward daybreak, surface winds and gusts are expected to increase
markedly as mixing heights build into the base of the departing low-
level wind field and surface pressures rise some 8-12mb/6 hours.
BUFKIT overviews depict peak momentum transfer of 45-50kt at the top
of the forecast mixing channel, which should support surface wind
gusts of 45-50 mph across much or northern Illinois and northwestern
Indiana. For this reason, we opted to expand the inherited Wind
Advisory to the Wisconsin border with the expectation for the
strongest winds to occur primarily between 6-10 AM CST (we padded
the timing of the official product by 2-3 hours on each side). While
winds will gradually decrease through the afternoon hours, it will
feel much colder than the past few days as temperatures slowly fall
through the 40s and eventually 30s by evening.
Borchardt
&&
.LONG TERM...
Issued at 314 PM CST Tue Feb 14 2023
Thursday through Tuesday...
The main weather highlights during the period are:
* Increasing threat for a significant band of accumulating snow
across parts of far northern IL Thursday. Have issued a Winter
Storm Watch for Winnebago, Boone and Ogle counties, where the
greatest threat of 6"+ snow amounts and the most significant
impacts resides.
* Travel impacts also likely south of the watch area, potentially
as far southeast as the I-55 corridor on Thursday as a result
of accumulating ice and snow in a wintry mix.
* Turning sharply colder Friday, but then warming up again into
next weekend.
There continues to be some model differences with the exact track
our next storm system will take on Thursday. While this does
continue to add uncertainty to the finner scale details of the
forecast, a general model/ensemble consensus does point at a
system track that would favor potentially 6"+ snow amounts across
far northern parts of IL (especially near the WI state line), and
a wintry mix south of this heavy snow band across the remainder
of northern IL. While a winter weather advisory will likely be
needed for much of northern IL for Thursday, we have opted to
issue a winter storm watch for Winnebago, Boone and Ogle counties
in far northern IL for Thursday.
A southwest to northeastward oriented baroclinic zone will sag
southward into far northwestern IL and adjacent areas of southern
WI and eastern IA on Wednesday following the departure of the
potent storm system tracking across the Upper Midwest tonight.
This baroclinic zone will be a major driver in the expected band
of heavy snow likely to fall across northern sections of the area
Thursday. Mid-level deformation will strengthen along the storm
systems northwestern periphery as it tracks across central IL into
IN into Thursday, and this will induce what looks to be a rather
impressive southwest to northeast oriented band of 850-700 mb
frontogenesis somewhere right across eastern IA into far northern
IL and southern WI during the day. What potentially makes this
even more interesting is the fact that the frontogenetic response
for upward ascent is likely to occur beneath the favorable
entrance region of a healthy upper level jet over the Upper Great
Lakes. Steepening mid-level lapse rates, and low static stability
will also be favorable for heavy snowfall rates (1"+ per hour)
within this band of snow. As mentioned previously, questions still
remain with the exact placement of the heaviest band of snow.
However, given that our far northwestern counties will be in
close proximity to the main threat area, we felt it prudent to
include them in the winter storm watch.
Areas south of the winter storm watch will not be out of the woods
for travel impacts on Thursday. Northerly surface winds are
expected to drag a subfreezing near surface airmass southward
across much of northern IL through the morning, and this adds
concern for freezing rain and sleet, especially through the
morning as a warm layer aloft will initially be in place across
much of northeastern IL. It also appears that moisture in the DGZ
will be lacking with southward extent over northern IL during the
morning, so freezing drizzle/rain are probable in ares that see
subfreezing temperatures develop (most likely along and northwest
of I-55). Farther south and east temperatures should remain above
freezing through the morning, so any precipitation that falls in
my far southeastern areas should be liquid. While this will not be
a major icing event, minor ice and sleet accumulations are likely
to result in some travel impacts for the Thursday commute,
perhaps as far southeast as around the I-55 corridor. We should
then see a gradual transition over to snow across most areas
through the afternoon on Thursday as better moisture in the DGZ
works eastward with the approach of the main mid-level
disturbance. The precipitation will then end (for most) into
Thursday evening. The only exception to this is that some lake
effect snow showers are likely to persist over parts of Porter
county IN into Friday morning.
Colder air will briefly make a return on Friday as the
aforementioned baroclinic zone shifts southeastward across the
area, making way for a colder air mass to spill in as high
pressure builds across the region. This will be short lived,
however, as southerly to southwesterly flow develops Friday night
into Saturday on the backside of the surface high. This will set
up a quick warm-up and dry period of weather for the weekend.
However, colder and more active weather may make a return the
area into the middle of next week.
KJB
&&
.AVIATION...
For the 00Z TAFs...
Forecast concerns for the terminals...
*Gusty 30 to 40 kt winds through Wednesday afternoon
*Rain showers persisting through early Wednesday morning with
pockets of heavier showers after midnight
*Developing MVFR ceilings this evening lingering through Wednesday
afternoon
A strong 986 mb surface low resides over northern Iowa this
evening which is generating breezy southeasterly winds at the
terminals. While gusts have eased a bit late this afternoon, gusts
are expected to increase into the 30 to 35 kt range this evening
as a stout low-level jet moves overhead. Further intensification
of the winds is expected after 06z this evening in the wake of a
cold front as cold advection allows for better mixing and gusts
to reach into the 35 to 40 kt range. Wind directions will also
become west-southwesterly late this evening behind the cold
front. The gusty winds will persist through Wednesday afternoon
before gusts ease heading into Wednesday evening.
Additionally, a broad area of light to moderate rain continues to
lift northward across Illinois ahead of the aforementioned cold
front. These showers will continue to move through the area this
evening with periods of showers through the night before showers
come to an end early Wednesday morning. While the main area of
rain looks to only cause minor visibility reductions, a more
robust area of convective showers is being observed over western
Missouri and is expected to move into northern Illinois around 05z
this evening. Forecast soundings continue to show that
instability would be increasing as these showers approach which
should allow for a brief period of heavier rainfall, reduced
visibility, and possibly a rumble or two of thunder. Given the
marginal instability have decided to forgo a formal thunder
mention in the TAFs, but did maintain a TEMPO for the heavier rain
and low visibility at RFD, ORD, MDW, and DPA. At this time GYY
looks to remain just south of these convective showers so I have
forgone the lower visibility mention.
Finally, MVFR ceilings are being observed under these areas of
showers and are expected to move over the terminals within the
next couple of hours. While MVFR ceilings are expected to linger
through Wednesday afternoon, there is a chance that some
scattering out of the ceilings may occur Wednesday morning.
Confidence is rather low on this occurring as soundings show
clouds remaining in the 2000 to 3000 ft layer through the rest of
the forecast period, but I did start trending ceilings up towards
the end of the period to account for this potential.
Yack
&&
.MARINE...Issued at 1258 PM CST Tue Feb 14 2023
As a surface low pressure system currently in southern Kansas
matures and lifts into the Upper Mississippi River Valley
tonight, south to southeasterly winds will increase with gusts of
25-30 kt and a few gale force gusts to 35 kt becoming common
overnight. Winds will shift toward the southwest and increase
markedly toward daybreak Wednesday with gales to 40 kt prevailing
through late morning. Southwesterly to westerly winds will then
fade during the afternoon.
Borchardt
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-
ILZ012 until noon Wednesday.
Winter Storm Watch...ILZ003-ILZ004-ILZ005-ILZ008...3 AM Thursday
to 9 PM Thursday.
Wind Advisory...ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-
ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108 until noon
Wednesday.
IN...Wind Advisory...INZ001-INZ002-INZ010-INZ011-INZ019 until noon
Wednesday.
LM...Gale Warning...nearshore waters until noon Wednesday.
&&
$$
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Area Forecast Discussion
National Weather Service Phoenix AZ
523 PM MST Tue Feb 14 2023
.UPDATE...Updated 00z Aviation Discussion...
&&
.SYNOPSIS...
A weather disturbance is bringing very windy conditions ahead of
a cold front today, which will sweep through the region this
evening. The winds are generating pockets of blowing dust. This
system is also bringing precipitation to the central Arizona lower
deserts and light snow accumulations for the higher terrain east
of Phoenix. Well below normal temperatures are anticipated
Wednesday and Thursday morning followed by a gradual warming
trend. More unsettled weather will be possible early next week.
&&
.DISCUSSION...
High wind, dust, rain, thunderstorms, snow, and colder temperatures
are all anticipated through the next 24 hours as a strong trough
digs down through the region. A glance at the map on weather.gov
will quickly prove this trough is expected be impactful. Several
watches, warnings, and advisories have been issued, with nearly
all of Arizona and Southern California covered by at least one
product.
High winds are expected to be the greatest impact through tonight.
Winds have already picked up across the region early this
afternoon, with some locations having already reached advisory-
level wind gusts (40+ mph), including Northwest Pinal County and
parts of Southeast California. A very strong jet streak (150 kts
sampled around 350mb from the 12Z Medford, OR sounding) is helping
drive a deep trough rapidly down the western CONUS. Water vapor
satellite and objective analysis still have the trough near
southern Nevada. A surface cold front recently went through Las
Vegas, NV and resulted in wind gusts up to 60 mph. As the trough
axis and cold front gets closer, the gradient winds will only
increase across the area. So, surface wind speeds are still
expected to increase through the afternoon and likely peak late
this afternoon through this evening. Widespread 30-40 mph wind
gusts are likely, with ~50% chance for 40+ mph peak gusts. The
will be a chance for 50-60+ mph wind gusts as well, with HREF
probabilities favoring high terrain spots east of Phoenix and in
Southwest Imperial County CA. Wind Advisories and High Wind
Warnings are in effect and run through the late evening.
With the strong winds, blowing dust will be a threat through this
afternoon and evening. A considerable dust channel has been
observed on the satellite dust channel and webcams in northern
Imperial County this afternoon. A Dust Advisory has been issued to
cover this. A Blowing Dust Advisory is also in place across the
dust prone Pinal County through this evening. Although dust has
not been observed as of 2PM MST, dust could still become an issue
as gusts increase.
Light low-topped showers developed earlier this morning in the
foothills north of Phoenix and continue to develop further south,
now spread across most of the Phoenix area. Aircraft soundings
still show a dry stable layer between 700-600mb which is limiting
the intensity of the showers. Observed rain rates are mostly
0.10"/hr or less. However, once the colder air arrives later this
afternoon and evening, that helps destabilize the environment
more, shower shower intensity will likely increase. NBM is
maintaining a 10-20% chance for thunderstorms in South-Central AZ
this evening. CAPE overall will be limited, with HREF spread
mostly between 0-100 J/kg and a few pockets above 100 J/kg. The
best forcing will likely come with the strong cold front as it
sweeps through the region. The cold front is progged to move
through the CWA mainly between 5 PM - 12 AM MST today (7-10 MST
through Phoenix). As previously mentioned, gradient winds will be
strongest along and just ahead of the trough. With low-level winds
increasing up to 50-60 mph there will be a chance for
shower/storm driven wind gusts up to these magnitudes. A few hi-
res models even suggest some linear convection segments. Small
hail and graupel will possible with any convectively driven
shower this evening, which could briefly accumulate at lower
elevations.
The aircraft soundings out of Phoenix and the melting layer
algorithm from KIWA radar suggest snow levels are currently around
5-6 kft. Dendrite production is not great right now over South-
Central AZ due to the aforementioned dry layer existing in the
dendritic growth zone. So, any snowfall early this afternoon is
likely limited in rate and accumulation efficiency. This will
change as well this evening as the colder air arrives. The most
significant accumulations are expected to remain above 5000 feet,
though light accumulations are possible as low as 2500 feet,
north and east of Phoenix. For the Valley, snow showers will be
limited to the foothills, generally above 2500-3000 feet in
elevation. Rain amounts will vary but on average, one to two
tenths of an inch is likely. All things considered, hazardous
weather conditions are expected across much of the area today and
tonight, and motorists are urged to exercise caution.
In the wake of this system, clear skies are anticipated
Wednesday with much drier conditions as dew point temperatures
crash down to around 10F or lower by mid-day Wednesday. However,
latest model guidance continues to indicate a trailing vort max,
which will act to elongate the trough into Arizona. Consequently,
breezy conditions will continue down the Lower Colorado River
Valley and the cold will linger with well below normal
temperatures prevailing. High temperatures will struggle to even
reach the mid 50s around Phoenix, and 60 degrees across SW Arizona
and SE California Wednesday. The bigger concern though will be
temperatures Wednesday night and Thursday. Latest NBM indicates
the potential for a widespread late-season freeze event. Many
lower desert locations and valleys across Arizona may observe the
coldest readings so far this winter and Hard Freeze Warnings are
possible, particularly across Pinal County where lows may reach
the upper 20s.
Steady height rises will translate into a warming trend and a
return to near normal temperatures through Saturday. Thereafter,
forecast uncertainty increases, mainly in response to a meandering
closed low in the eastern Pacific. Low pressure systems like this
one are notoriously difficult for the models to resolve and
forecast, and this is reflected in the NBM PoPs, which show an
extended period of 20 percent 12-hour PoPs stretching from
Saturday night through next Tuesday. Model clusters also point to
high uncertainty with regard to precipitation potential, though
temperatures are generally expected to remain at or below normal.
&&
.AVIATION...Updated at 0020Z.
South-Central AZ including KPHX, KIWA, KSDL, KDVT:
The main aviation weather concern through the early to mid-evening
hours will be the potential for a significant uptick in winds. A
cold front is expected to move through the terminals through
04-05z, delivering a convective line of showers with very strong
wind gusts near to potentially exceeding 40 kts. After the
convective line moves through, winds will significantly decrease
with speeds 10-15 kts along with some higher gusts through
Wednesday. CIGS through midnight will fluctuate between 4-6 kft
before lifting overnight with mostly clear skies expected by
Wednesday morning. Wind direction through early evening will
generally be from the south-southwest to southwest and then shift
from the west to west-northwest after the cold front passes
through and remain from this general direction through the rest of
the period.
Southeast California/Southwest Arizona including KIPL and KBLH:
Strong winds along with areas of blowing dust significantly
reducing visibilities will be the main aviation through this
evening. Strong wind gusts between 35-45 kts can be expected
through this evening along with MVFR visibilities, particularly
across BLH, due to blowing dust. A line of showers currently
located near Parker with continue to move southeast through the
next couple hours, delivering VCSH across KBLH. Winds are
expected to significantly diminish during the overnight hours and
through Wednesday, although gusts over 20 kts will continue at
times. Gusts approaching near 30 kts will be possible at KBLH
Wednesday afternoon. Wind directions through this evening will be
from the west to southwest and then switch from the west and
eventually from the northwest during the overnight hours and
through the day on Wednesday.
&&
.FIRE WEATHER...
Very windy conditions are expected today and tonight ahead of a
cold front that will sweep through central this evening. Wind
gusts will generally reach 35-45 mph, but there will spots in the
higher terrain potentially reaching 60-80 mph. This system will
bring another chance of precipitation for the central Arizona
lower deserts this evening and light snow accumulations for the
higher terrain east of Phoenix later tonight. Much cooler and
drier conditions are expected Wednesday. Winds will also subside
Wednesday, though general breeziness will persist. A warming trend
is then expected through the weekend. A low pressure system will
meander in the eastern Pacific early this weekend, however there
is some uncertainty with regard to if and when impacts and
precipitation will next affect the Desert Southwest.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Wind Advisory until 11 PM MST this evening for AZZ530>551-553-
554-559.
Blowing Dust Advisory until 9 PM MST this evening for AZZ551-
553>555-559.
High Wind Warning until 2 AM MST Wednesday for AZZ552-558-561.
Wind Advisory until 2 AM MST Wednesday for AZZ555>557-560-562-
563.
Winter Weather Advisory until 2 AM MST Wednesday for AZZ557-558-
563.
CA...Wind Advisory until 10 PM PST this evening for CAZ560-561-564-
565-568>570.
High Wind Warning until 10 PM PST this evening for CAZ562.
High Wind Warning until 7 PM PST this evening for CAZ563-566-567.
Wind Advisory from 7 PM to 10 PM PST this evening for CAZ563-566-
567.
&&
$$
DISCUSSION...Benedict
AVIATION...Lojero
FIRE WEATHER...Hirsch