Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/05/23
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
530 PM CST Sat Feb 4 2023
.SHORT TERM...
Issued at 155 PM CST Sat Feb 4 2023
Through Sunday night...
Breezy and mild south-southwesterly winds continue to push
temperatures up into the 30s across the area, with even a few low
40s noted over far southern sections of the area. These relatively
mild and breezy conditions will continue into tonight as our area
remains in advance of an approaching weak cold frontal boundary
shifting across the Upper Midwest. A low-level jet will ramp up
overhead this evening as at least some degree of decoupling
occurs. This will result in flow around 2,000 ft AGL topping out
around 50 kt for a period this evening. While these stronger winds
aloft will not reach the surface, this higher wind field off the
surface may continue to support at least some occasional
gustiness up to around 30 mph through the evening. Temperatures
in this regime should hold fairly steady in the low to mid 30s
tonight.
A weak clipper system will shift into the western Great Lakes
Sunday morning. This will push a trailing cold frontal boundary
southeastward across our area during the day. Lower-level cloud
cover looks likely to develop ahead of this front early Saturday
morning as low-level moisture increases. While a brief period of
light rain or drizzle cannot be ruled out with these lower clouds
Sunday morning across far northeastern IL/Northwestern IN, rather
shallow moisture depths suggest this probability to be quiet low.
We have therefore left the forecast dry at this time. Otherwise,
west-northwesterly winds in the wake of the front in the
afternoon, along with continued cloud cover into the afternoon
should hold temperatures generally in the mid 30s north, and the
lower 40s south.
Surface high will build eastward across the area Sunday night.
Clearing skies and light winds under this high may support fog
development overnight into early Monday morning as temperatures
drop into the upper teens and low 20s. Accordingly, a patchy fog
mention has been added to the forecast late Sunday night, mainly
for areas along and west of the Fox Valley.
KJB
&&
.LONG TERM...
Issued at 155 PM CST Sat Feb 4 2023
Monday through Saturday...
The primary weather messages in the upcoming long term period are:
* Potential for lingering fog/freezing fog Monday morning.
* Blustery/windy conditions developing Monday afternoon into
Tuesday. Brief window for light showers and drizzle Monday
night.
* Potential for widespread, soaking rainfall Wednesday night
through Thursday, although still a reasonably large envelope
of uncertainty.
Outside of any left over shallow fog, Monday looks to start off on
a quiet note, but southeasterly breezes will gradually increase
through the afternoon as the surface pressure gradient tightens in
advance of our next disturbance. A pair of fairly sharp vort
lobes embedded within a fast-moving shortwave trough will then
transit the region Monday night into Tuesday morning. Impressive
mass response is readily evident in model kinematic fields and
forecast soundings, with a nearly 70 kt low-level jet core
advertised just above 850 mb by the NAM. Much of this wind will be
out of reach as the lower troposphere saturates with a further
decoupling boundary layer through the evening, but steady 3 to 6
mb/6 hour pressure falls will likely keep occasional 30-35 mph
gusts going during the overnight. Deep saturation up through about
8 kft with broad warm advection and under the left exit of a very
strong upper jet looks like a good setup for fairly widespread
light precipitation (showers and drizzle). Seems like a higher
PoP/low QPF sort of scenario which the NBM tends to struggle with.
Noting universally high probabilities of measurable precipitation
across the ensemble suite, and have boosted PoPs commensurately
Monday night. Could be some lingering spits into Tuesday morning
across NW Indiana.
Modest cold advective regime sweeps into the area during this
period, supporting continue blustery conditions with westerly
winds likely to gust towards 30-35 mph through Tuesday as the
boundary layer destabilizes.
Attention turns to a cutoff low likely to press across the central
and southern Plains into Wednesday. Variability within the
guidance suite seems to be associated with the degree of
interaction with an rapidly-digging and amplified northern stream
wave. Starting to get some better clustering going on within
ensemble systems now, although there`s still a reasonably large
spread in surface low tracks. Generally looks like a slightly more
amplified/slower solution is more favored at this point, and one
towards which the GFS has slowly been trending.
The more amplified solutions show a buckling of the upper jet into
Wednesday night and intense upper divergence within a moistening
airmass (deterministic ECMWF now showing in excess of 1 inch PWATs).
If these solutions pan out, a widespread soaking (and locally
fairly heavy) rain would be in the cards. NBM-delivered likely
PoPs Wednesday night are currently in line at this range. A lagging
northern stream wave may then deliver continued chances for
precip in the region, although there`s obviously a good amount of
spread at this range. Thermal profiles by the end of the week/into
Saturday would likely be supportive of snow, but not currently
seeing anything too concerning in the extended progs.
Carlaw
&&
.AVIATION...
For the 00Z TAFs...
Aviation Forecast Concerns:
* Period of LLWS conditions overnight with west-southwest winds
around 50 kts in the 1500-2000 ft AGL layer.
* Potential for at least sporadic wind gusts into the 25 kt range.
* Cold front passes Sunday morning, with somewhat gradual shift to
more westerly wind during the day and eventually northwest
later in the day/evening.
* Potential MVFR ceilings Sunday/Sunday evening.
Late afternoon surface analysis depicts broad area of low pressure
to the north of the region, and a tighter pressure gradient with
breezy south-southwest winds across the local area. Gradient has
been a bit weaker over far northern IL, which along with cold
ground and lingering snow cover has limited mixing and wind gust
magnitude somewhat. Low level jet of 50-55 kts will develop early
this evening however, which will likely increase surface winds a
bit and also set up a period of LLWS conditions. Some sporadic
surface gusts in the 25+ kt range are possible, though confidence
is low in these being prevailing conditions with shallow mixing as
noted in recent AMDAR aircraft descent soundings into KMDW.
As low pressure moves east-southeast across the northern Great
Lakes into Sunday morning, a trailing cold front will push east
across the terminals. Winds will shift initially more west-
southwest behind the front, then gradually continue to veer to
northwest by Sunday evening. While breezy, gusts look to remain
less than 20-25 kts for the most part behind the front. Model
guidance does indicate the potential for MVFR ceiling development
immediately along and behind the front, which may linger into
Sunday evening. Low levels are fairly dry at this time, so
confidence is somewhat low on timing of the development of MVFR
cigs, though enough support in guidance to include in TAFs at this
time.
Ratzer
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...nearshore waters until 9 AM Sunday.
&&
$$
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Area Forecast Discussion
National Weather Service Salt Lake City UT
400 PM MST Sat Feb 4 2023
.SYNOPSIS...Valley inversions will gradually diminish Sunday
across the northern valleys. A winter storm will impact much of
the state Sunday into Monday.
&&
.SHORT TERM (Through 00Z Tuesday)...The end of the valley
inversions is near, which is good news for residents of the
northern valleys. Inversions south of roughly Ogden have weakened
a bit with overnight cloud cover, well correlated with MDCRS
soundings over the last 12 hours or so. Unfortunately while that
correlated to warmer temperatures for some locations, it did not
result in better air quality as most monitored valleys remain in
the red (unhealthy for all groups) category. Utah DEQ AQ forecast
improvement in most basins Sunday to at least the orange
(unhealthy for sensitive groups) category.
Afternoon satellite and upper air analysis indicates shortwave
ridging over the eastern Great Basin. A relatively deep shortwave
trough is currently approaching the Pacific Coast with a well
defined jet max and associated area of upper diffluence shifting
east across central/southern California.
Expect southwest flow to increase ahead of this trough tonight
into Sunday morning. Suspect this will aid in ventilating the Salt
Lake Valley and potentially portions of the northern Wasatch
Front. North of Ogden, expect inversions to be particularly
difficult to dislodge due to a combination of cold temperatures
and snowpack.
As the previously mentioned upper level diffluence shifts into
Utah early Sunday afternoon, a frontogenic band of precipitation
is expected to develop. Slight variations in position continue
across the guidance envelope, with a significant portion of the
guidance initializing the strongest portion of the band from
roughly Evanston to Cedar City during the afternoon.
Precipitation type will be a low confidence portion of this
forecast. It was largely depend on how persistent inversions
are...and how well valleys ventilate. Currently expect areas
north of Ogden and the Cache Valley to remain largely snow with
the band with the remainder of the Wasatch Front seeing a
rain/snow mix until around 00-03Z Monday. Current expectation is
this will be at the end of the period of moderate to heavy
precipitation as the forcing for the band shift east of the
area...limiting accumulations Ogden and south.
What could go wrong? Well, a combination of higher precipitation
intensity and stronger/faster cold air advection could shift
portions of the Wasatch Front to snow earlier. This would bring
accumulations closer to 1 to 3 inches with this portion of the
system to any areas that remain snow. Something for future shifts
to monitor.
Snow will continue, heavy at times, across the mountains into
Sunday evening before transitioning to a more showery mode. As the
midpoint of the shortwave trough approaches, another cold front
will cross the area, shifting flow to northwest to north and
bringing much colder temperatures to the area Monday morning.
This portion of the storm will be easy precipitation-type wise,
with any precipitation Sunday night into Monday evening to remain
snow.
The best window for snow accumulation along the Wasatch Front will
be Monday morning into early Monday afternoon...which may coincide
with the Monday morning rush hour. Given variations of onset time
across the model guidance, held off on messaging this portion of
the system and will coordinate with relevant partners Sunday.
For now, issued winter weather advisories for all the mountains
and the Wasatch Back. Highest totals are expected for the Wasatch
Range which will do well with both portions of the winter storm.
Will need to monitor the Cache Valley and Wasatch Front north of
Ogden in particular for heavier than expected snow Sunday
afternoon into Sunday evening.
.LONG TERM (After 00Z Tuesday)...Long term period will be a
quieter period overall with a couple of shortwaves impacting the
area. The first shortwave will be exiting the area late
Monday/early Tuesday morning, while the other shortwave is one
that arrives Wednesday and exits the area by late Wednesday
evening. Main impacts for the first system will be the potential
for some lingering snow showers across the northern and central
mountains late Monday night.
There will be a short break on Tuesday where weak ridging moves
into the area before the second shortwave arrives. There is a lot
of uncertainty regarding the strength and location of this system
and exactly how much snow falls. GFS and EC deterministic have the
storm just clipping northern Utah and southwest Wyoming. Looking
at ensemble guidance, the majority of EPS members have the storm a
little stronger and digging further south and west compared to
the GEFS members. If a scenario like the EPS occurs then there is
chance that light accumulations across northern UT valleys could
be possible. A scenario like the GEFS is showing would mean snow
showers would likely be limited to mountainous areas. Regardless
of which scenario takes place, an increase in cloud cover is
likely.
After this system exits the area, cloud cover will disperse and
inversions will be possible for Friday through Sunday.
Temperatures are expected be near or slightly below normal for
most locations. There will be slight warmup in temperatures
beginning on Friday and going through Sunday, however these
temperatures will be slight above normal at best. Looking past the
long term, the CPC 8 to 14 day outlook has above average
precipitation for the entire CWA and in conjunction with this
prediction there looks to be some evidence of a deep trough moving
onshore that could impact the area, however it is too early to
determine the details of the this potential
&&
.AVIATION...KSLC...Northwest winds expected to switch southerly
by late evening, with HZ anticipated to continue reducing VIS
overnight. High base clouds gradually increase ahead of
approaching system, with some isolated RA/SN mix possible by mid
morning. By afternoon, more widespread precipitation expected
along with CIGS lowering and continued reduced VIS. Winds also
expected to shift back northwesterly. Expect likely changeover to
predominately snow before precip tapers off, but low confidence in
timing.
.REST OF UTAH AND SOUTHWEST WYOMING...Northern terminals in
sheltered valleys expected to continue to deal with HZ related VIS
reductions, and potential FZFG overnight (primarily at LGU).
Otherwise, an approaching system will yield an increase in high
base clouds overnight. By morning, northern terminals will see
precip chances increase, with more widespread activity through the
afternoon and into the evening. Precipitation chances will also
increase at southern terminals through the afternoon. Some
precipitation expected to linger into the overnight hours.
Accordingly, reduced CIGS/VIS can be expected during times of
precipitation. MVFR conditions most likely, though IFR can`t be
ruled out during heavier precip.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory from noon Sunday to 5 PM MST Monday for
UTZ108-110>112.
Winter Weather Advisory from 2 PM Sunday to 5 PM MST Monday for
UTZ113-117.
Winter Weather Advisory from 4 PM Sunday to 5 AM MST Monday for
UTZ125.
WY...None.
&&
$$
Kruse/Cecava/Warthen
For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity