Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/07/25
Area Forecast Discussion
National Weather Service Cheyenne WY
859 PM MST Mon Jan 6 2025
.KEY MESSAGES...
- Winter Weather Advisories in effect for light snow with 2-4
inches possible for the I-25 and I-80 corridor including
Cheyenne today through Tuesday. Locally higher amounts
possible.
- Active long term pattern continues through the week with
multiple chances for light snow, mainly in the mountains.
&&
.UPDATE...
Issued at 852 PM MST Mon Jan 6 2025
No major changes made to the forecast as of 04Z this evening as
the forecast remains on track. Mild adjustments made for the
cloud coverage across the region with slight tweaks to PoPs
around Cheyenne. The biggest change was adding the mention of
freezing fog to regions along the I-80 corridor from the I-80
Summit east through Cheyenne County. Freezing fog should be
patchy in nature and likely come to an end as the sun begins to
rise. Most short range guidance shows fog coming to an end by
14Z.
&&
.SHORT TERM /THROUGH TUESDAY/...
Issued at 213 PM MST Mon Jan 6 2025
Latest upper air analysis depicts the trough axis, currently
centered across the Ohio Valley, has continued to travel east as the
closed low become absorbed into the main flow, with the next deep
Pacific trough digging into the Intermountain West. Throughout the
morning hours, an upper level disturbance embedded within the main
flow pushed southeast around 09z this morning, allowing snow to
develop in the morning hours, combined with winds being much lower
than otherwise anticipated across Laramie county. Due to the minimal
downsloping to help limit the snowfall from the periods of calm
winds reported at the ASOS, snow persisted throughout the morning
and afternoon hours.
Attention in the short term forecast focuses on the next trough that
is expected to come within range in the afternoon hours with active
weather expected to persist as snow continues through late Tuesday.
Forecast soundings continue to suggest light to moderate snow with
this next system as low to midlevel moisture is well within the
dendritic growth zone. This becomes much more evident in the lower
counties across the CWA, with the moisture profile centered between
-10c and -20C through early tomorrow afternoon. Should begin to see
snow chances decrease late tomorrow afternoon once dry air becomes
entrained in the midlevels. PWAT anomalies support this model
solution, having PWATs around -1.5 sigma below climatology digging
southward across northern Wyoming beginning around 12z Tuesday and
into northern Colorado by 00z Wednesday. Therefore, will likely see
precipitation beginning to clear from north to south, as the upper
level trough begins to split into a closed low across southern
Arizona. Some concerns persist across the northern counties in the
Nebraska Panhandle with forecast soundings having a deep saturated
layer, with the lowest levels within 0c to -10c up to 1km before
dropping to -10c to -20c above 1km. In the event the midlevels
become entrained with drier air a bit sooner than anticipated, could
see freezing drizzle and freezing fog develop as have been observed
a few days prior. Although, snow forecast seems the most reasonable
solution for the Nebraska Panhandle with the inversion aiding in
continued snow developing with dendrites falling though the layer
and increasing growth from the supercooled liquid in the lower
levels. Other areas to monitor will be the Laramie Valley, where
favorable northwesterly flow will aid in increased upslope flow.
Went ahead and continued trending PoPs upwards for the Laramie
Valley through this evening before northeasterly flow takes hold and
switches from upslope to downslope for that area. In addition, also
bumped up QPF with the latest HiRes model guidance keeping totals
upward to three inches for the city of Cheyenne to match Winter
Weather Advisories in effect through tomorrow morning. Lastly, will
need to monitor the Summit as well, with the latest HRRR indicating
locally higher amounts possible.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Issued at 213 PM MST Mon Jan 6 2025
The long term forecast remains on track with multiple fast moving
systems expected to impact the CWA through the end of the week. The
active pattern can be attributed to somewhat of a blocking high
sitting in the Pacific off the coast of California. This strong
ridge over the Pacific will extend as far north as southeast Alaska.
This will cause any system that impacts the CWA to drop out of
Canada from the north/northwest. Being from Canada these systems
will bring colder temperatures and some precipitation chances. The
first system will arrive Wednesday night, dragging a cold front
along with it. Colder temperatures can be expected for Thursday as
700 mb temperatures behind the front drop to about -12C. This will
lead to chilly temperatures with highs struggling to get to freezing
on Thursday. Given that this system is from Canada, moisture values
are rather unimpressive. Orographic lift will provide the mountains
with a few inches of snow Wednesday night into Thursday, however,
the lower elevations will likely not see any accumulation with this
shortwave. Following quickly behind this system, another will arrive
Friday night, bringing the potential for high winds and greater snow
chances. With the onset of this system, in house guidance is pinging
pretty high probabilities for high winds in the usual southeast
Wyoming wind prones. This would be a gradient driven event with both
elevated values for MSLP gradients as well as CAG-CPR 700 mb height
gradients. As a result, winds aloft will respond, maxing out around
50 to 55 kts with good subsidence, so these winds could make it down
to the surface. Timing of high winds will be late Friday night into
Saturday morning. Precipitation will move into the CWA on Saturday.
Precipitation looks a bit more widespread with this system, with
snow chances likely outside of the high terrain. Will have to keep
an eye on snow amounts as precipitation is expected Saturday and
will linger into the day Sunday.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 437 PM MST Mon Jan 6 2025
An upper level disturbance is expected to move through the area
this evening and overnight. This will bring another round of
light to moderate snowfall to the region. Some of the snowfall
may be heavy at times especially near the higher terrain (at or
above 7kft) of the Laramie Range. Most locations will
experience MVFR/IFR conditions with the higher terrain above
7000ft most likely seeing LIFR conditions. The snow should
taper to flurries by mid morning Tuesday with ceilings generally
climbing above 2kft.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 8 AM MST Tuesday for WYZ116>118.
NE...None.
&&
$$
UPDATE...AM
SHORT TERM...MRD
LONG TERM...SF
AVIATION...REC
Area Forecast Discussion
National Weather Service Dodge City KS
519 PM CST Mon Jan 6 2025
.KEY MESSAGES...
- Unseasonably cold temperatures today for much of the area with
fresh snowpack and light northerly winds.
- Light snow is likely along and west of US-83 daytime Tuesday,
but snow totals will be minimal.
- Another chance of snow exists Thursday into early Friday,
however uncertainty remains.
&&
.DISCUSSION...
Issued at 200 PM CST Mon Jan 6 2025
Midday water vapor satellite imagery and RAP upper air analysis
reveal broad, longwave troughing envelops the entirety of the
CONUS, with a couple vorticity maxima emanating through the
flow; one near the Appalachians and another over the Pacific
Northwest/far western CONUS. At the surface, high pressure has
built into the central plains in the wake of the weekend storm,
supporting widespread clear skies across southwest KS. Despite
plenty of solar insolation, fresh snowpack and light northerly
winds will keep most locations below freezing, with the only
exception being far western KS near the CO border where little
snowpack exists. Tonight will be quiet, with light winds but
increasing clouds over the western zones leading to Tuesday
morning lows ranging from near zero northeast to the mid-teens
southwest.
Early Tuesday, short range ensembles agree the western vorticity
max will have dug southward to near Los Angeles by 12Z. As this
happens, low-level upslope flow and moisture return in eastern
CO and western KS will provide enough support for light snow to
develop mainly along and west of US-83 and continue through much
of the day. Snow totals look to be fairly minimal, with HREF
probability of 1" of snow or greater reaching into the 50-70%
range only in pockets of Hamilton and Stanton County, so 0.5-1"
of snow appears to be a good bet.
Daytime Wednesday, medium range ensembles suggest downsloping
winds will return to southwest KS as surface high pressure
slides southeast into the ArkLaTex region. This along with
partly cloudy skies should foster a noticeable jump in
temperatures with afternoon highs reaching into the low to upper
30s. On Thursday, ensembles are implying yet another chance for
light snow will materialize across our area as a pair of
vorticity maxima merge over northern Mexico and begin to eject
onto the High Plains. However, disagreement remains between the
two main global model ensembles, with the ECMWF EPS mean showing
around 0.5-1.0" of snow while the GEFS mean has virtually
nothing. Given the wave`s positive tilt and the strongest
forcing being displaced well to our south, the GEFS solution
seems to be the most realistic at the moment, but trends will be
monitored. Over the weekend through the end of the period,
ensembles agree broad, longwave troughing will remain in place
over the CONUS, signaling below normal temperatures will
continue for the foreseeable future.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 519 PM CST Mon Jan 6 2025
A few hours into the period, cloud cover will move into the forecast
area from the west. Around 14Z, lower cloud cover will develop
resulting in lowered flight categories excluding HYS. With the lower
ceilings, GCK and LBL has a slight chance (10-20%) for light snow,
but only minor visibility impacts are expected.
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Springer
AVIATION...KBJ
Area Forecast Discussion
National Weather Service Gray ME
1045 PM EST Mon Jan 6 2025
.SYNOPSIS...
Temperatures will continue to run below normal through most of
this week with mostly dry and breezy conditions as the storm
track will be south of New England. There could be a slight
warming trend toward the end of the week.
&&
.NEAR TERM /THROUGH TUESDAY/...
1045 PM Update... Area webcams and AWOS observations indicate
that light snow is falling across the mountains and towards the
Canadian Border and therefore increased PoPs to account for this
activity. Otherwise, just made some minor adjustments to
temperatures and winds.
In addition, the last several runs of the HRRR as well as NAM
are showing a growing potential for a period of strong
northwesterly wind gusts tomorrow afternoon/evening with locally
higher gusts possible within downslope areas. As a result,
blended some of this guidance into the forecast which brings
gusts to near wind advisory criteria in some locations.
Previously...
605 PM Update... Minor changes to reflect latest observational
trends. Other than loading in the latest sfc observations and
tweaking winds and sky cover, the inherited fcst remains on
track.
Previously...
Coastal low continues to pass well to our S this evening, only
producing some mid to highs clouds across the CWA. The system
which will have a bigger impact on us later tonight into
Wednesday will be the the double closed 500 MB lows over E Canad
and their Fujiwara spin, as the W low shifts SE out of srn
Quebec this evening and across N New England overnight. This
will bring another round of clouds to the area and the chance of
SHSN in the mtns, but the bigger effect will happen late
tonight and Tuesday as we see upslope snows develop and winds
increase again toward daybreak. Lows range from around 5 above
in the N to 10-15 in the S.
&&
.SHORT TERM /TUESDAY NIGHT/...
Gusty NW flow picks everywhere a few hours after sunrise with
gusts 25-30 mph common during the day Tuesday. Well see a fair
amount of clouds early as the the flow remains unblocked right
behind this system, but becomes more blocked later in the day. A
few flurries are possible just downwind of the mtns, in the
foothills as well. In the mtns there will be a period of time,
probably midday to afternoon, as the flow becomes blocked, that
the upslope SHSN will really surge, and several inches of snow
will be possible in the favored upslope areas, and some of the
notches as well. But most of the will be above 2500 ft. Still
could see an inch or two spots in the valley areas, especially
through the Whites Tuesday into Tuesday night. Highs on Tuesday
range from 15-20 in the mtns to the mid 20s in the S, while lows
Tue night will generally be in the +5 to +15 range.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
04Z Tuesday Long Term Update.. There continues to be significant
uncertainty in regards to a potential storm system this upcoming
weekend with the GFS and its ensemble members the furthest north
while the the ECMWF misses New England by a wide margin to the
south and east. As a result, did not veer from the latest NBM
given this forecast uncertainty. It will otherwise remain cool
and breezy through much of the period.
Previously...
Overview: Broad cyclonic flow remains overhead through midweek,
allowing breezy conditions, cool temperatures, and upslope snow
showers in the mountains to continue. A change in pattern does
not seem likely until the first half of the weekend.
Details: Continued to increase precip chances in the western ME
mountains and northern NH through mid to late week. The NBM is
having a difficult time addressing this setup, and opted to instead
use blended deterministic models which have been fairly consistent
picking up on upslope snow for the NW slopes. With enough moisture
in the low to mid levels, a consistent NW flow, and tight pressure
gradient, the setup is there for light snow much of the week here.
Will likely see gradual light accumulations...generally 1 to 4
inches in northern NH and far western ME...more at windward faces and
spine of the Whites.
Otherwise, a tight pressure gradient keeps winds gusty through the
week, particularly during the afternoon hours where mixing deepens.
This means some gusts to 30 mph Wed and Thurs afternoon for parts of
southern NH and foothills, with up to 25 mph elsewhere. Amid the
cool airmass, this may lead to wind chills remaining in the single
digits, above and below zero, into midweek.
Extended deterministic and ensemble guidance has been hinting at the
next storm system to impact the east coast moving in during the
Sat/Sun timeframe. There has been a wide spread of solutions as low
pres forms over the southern Plains and tracks towards the east
coast. Thus far, confidence in a final solution is very low as
little consistency exists run to run and suite to suite. Spread of
the low`s center can vary some 300 miles or more, and this has major
implications for the forecast. Current assessment based on ensemble
trend is the low taking a flatter course into the Atlantic off the
Mid-Atlantic coast while some outliers cruise further north towards
the Gulf of Maine. With a rather strong low developing over TX,
there is more uncertainty how this maintains strength as it tracks
east. Worth to track, but overall trend is supporting a shift of
pattern (mainly ridding the region of broad cyclonic flow) late this
week into the weekend.
&&
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
Short Term...Mainly VFR expected through Tue night,except at
KHIE which will likely see periods of MVFR cigs beginning
tonight through Tuesday, and perhaps some brief IFR in SHSN,
especially on Tue afternoon. NW winds pick up again on Tuesday
with morning with gusts to around 25 kts at times.
Long Term...VFR with NW gusts up to 20 kts for much of the mid
week. HIE will likely see chances for light SN through the week,
tapering Friday. Can`t rule out some SHSN making their way out
of the western ME mountains and northern NH, but these time
frames may be short and restricted more towards the foothills,
rarely further to the coast than AUG/LEW/IZG/CON.
&&
.MARINE...
Short Term...Weak low pressure crosses the waters tonight with
strong NW flow behind it starting late tonight and continue into
Tuesday night. Gales are expected on the open waters Tuesday and
at least into Tuesday evening, with some to gusts approaching 40
kt. SCA conditions are expected in the bays. Light freezing
spray continues into Tuesday night.
Long Term...Within broad cyclonic flow, northwest winds and
gusts remain in SCA criteria through mid week. There will be the
chance for occasional gusts to Gale as well, primarily over the
outer coastal waters Wed/Thurs.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Gale Warning from 7 AM Tuesday to 8 AM EST Wednesday for
ANZ150-152-154.
Small Craft Advisory from 7 AM Tuesday to 8 AM EST Wednesday
for ANZ151-153.
&&
$$
NEAR TERM...Tubbs
SHORT TERM...Cempa
LONG TERM...Cornwell
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
846 PM CST Mon Jan 6 2025
.KEY MESSAGES...
- Lake effect snow--briefly heavy--shifting into Porter County
will lead to snow-coated roadways and slick travel this
evening.
- Patchy freezing drizzle on the periphery of the snow band may
lead to some slick spots on untreated surfaces across parts of
Newton, Jasper, Benton, and Iroquois counties.
- Chance (30-50%) for some accumulating snow Friday.
&&
.UPDATE...
Issued at 847 PM CST Mon Jan 6 2025
Primary lake effect band has shifted into northwest Indiana
early this evening, and continues to gradually work its way
eastward. Hourly rates are likely around an inch (plus) per
hour in the heart of the band, although given the eastward
progression, the residence time of these higher rates has
generally been limited to about 60-90 minutes or less. Did boost
snowfall amounts a few hours ago, although may not quite have
been enough. That said, the main part of the band is shifting
entirely into Porter County at this time, and will continue with
targeted GNOWs and some harder messaging here with things
expected to wind down through about 1 AM or so. Latest radar
imagery shows things becoming a bit more cellular, and hires
guidance depicts a gradual shearing apart of the band through
the late evening. Brushed up PoP/weather trends through the
night.
Received a few reports of light freezing drizzle across our
southern locales, and while our radar continues to overshoot
this shallow precipitation, not seeing indications of
significant visibility reductions with it which suggests this
may not be heavy/persistent enough to cause significant travel
impacts. Will continue to indicate some chances for freezing
drizzle around the periphery of the lake effect band through the
night, but things should be on the downtrend overnight.
Carlaw
&&
.DISCUSSION...
Issued at 345 PM CST Mon Jan 6 2025
Through Tuesday Night:
Lake effect precipitation continues this afternoon across the
Chicago metro and points downstream. The coldest temperatures
within the parent stratus deck have been sampled by aircraft to
be around -10C just beneath a strong temperature inversion
between about 4000 and 6000 ft AGL. This is right on the cusp
of what is usually needed for efficient heterogeneous ice
nucleation to occur and support snowflakes being the
dominant/sole hydrometeor type falling out of a cloud deck,
though through much of today, this has proven to just not be
cold enough for snow to be our only precipitation type. Instead,
we`ve had to deal with a mixture of poor quality snow and
freezing drizzle, which is quite unusual for a lake effect
event.
Stronger mesoscale forcing along a convergence axis over Lake
Michigan has fostered the development of a dominant
precipitation band within the broader area of precipitation
spilling inland. Precipitation within the heart of this band has
been all snow, likely due to the stronger forcing fostering
slightly deeper cloud depths, slightly colder in-cloud
temperatures, and a greater degree of turbulence to support the
activation of ice nuclei. This band remains flanked by a mixture
of freezing drizzle and less efficient snowfall on both sides,
and the expectation is for this to continue to be the case into
tonight as this dominant band slides eastward into northwest
Indiana.
The overall degree of impacts from the main snow band and
surrounding freezing drizzle remains somewhat of a question mark
going into tonight. Regarding the snow... impacts (and snowfall
accumulation amounts) would be maximized if the band were to
stall over the same areas. However, the latest radar mosaic
trends don`t look particularly promising for a dominant snow
band sitting over the same locations and producing significant
snowfall amounts, and the last couple of HRRR runs have also
backed off from the `bullseye` 3+" amounts that it was
outputting earlier in Lake and Porter counties in northwest
Indiana. With low-level thermal profiles likely remaining too
warm for the stratus deck to intersect the dendritic growth
zone, snowflake quality will also likely remain poor through
tonight, which may also deter snowfall totals from exceeding 3"
even if the band were to stall out somewhat.
Regarding the freezing drizzle... road impacts from this have
appeared to be quite minimal over the past several hours as air
and pavement temperatures have warmed closer to the freezing
mark. Thermodynamic profiles will not change much tonight from
what they have been today, so there is reason to believe that
drizzle will continue in some capacity into tonight, but how
expansive or persistent it will be remains uncertain.
Temperatures will likely start to fall a bit after sunset,
which may increase the odds that the drizzle starts freezing on
pavement more effectively once again, but this is under the
assumption that it will still be drizzling to begin with.
There`s no straightforward way to handle winter headlines in
borderline/high uncertainty setups like these, but with very
little in the way of roadway impacts occurring the past several
hours and low confidence in notable roadway impacts occurring
tonight, felt that the best course of action at this time was
to cancel the going Winter Weather Advisory for portions of the
Chicago metro and instead put out a Special Weather Statement
for locations where slippery travel from freezing drizzle and/or
snow will remain a possibility late this afternoon into
tonight. The evening shift will have to monitor observational
trends closely and may ultimately need to hoist a short-fused
Winter Weather Advisory if confidence in more notable roadway
impacts occurring increases, but confidence in an advisory
being needed for tonight was too low to warrant having one in
effect right now.
Any lingering lake effect precipitation in northwest Indiana
should end by mid-morning tomorrow as the fetch over Lake
Michigan becomes increasingly northwesterly. High temperatures
tomorrow look to top out in the 20s across our forecast area.
Ogorek
Wednesday through Monday:
A mid-level impulse over the high latitudes of central Canada is
expected to dive southward across the western Great Lakes on
Wednesday. While rather poor lower-level moisture should largely
curtail the threat of any meaningful snow across much of the
area, veering low-level flow over southern Lake Michigan is
likely to setup the focus for another period of lake effect snow
Wednesday into Wednesday night. The northwesterly fetch over the
lake looks to favor the primary focus across northwestern IN and
points eastward on Wednesday. However, while confidence is very
low, we cannot rule out the possibility for some of this activity
to try to work back westward towards the IL shore late Wednesday
night into early Thursday before it dissipates.
A surface ridge axis will pass across the area on Thursday, likely
resulting in dry but continued cold conditions through the day.
Thereafter, the next mid-level wave is expected to shift over the
area Friday into Friday night as a secondary wave ejects
northeastward from the southwestern CONUS. Forecast guidance
continues to suggest these two waves will undergo phasing at some
point late Friday into Friday night across the central CONUS, but
differ on exactly when and where. The degree and timing of this
phasing will ultimately influence the overall evolution of the
system as it passes across our area late Friday. The current
forecast favors a 30-50% chance for light snow for much of the
area, with the highest chances currently along and southeast of
I-55. This does not appear to be a big snow maker for our area,
but some accumulating snow is certainly possible through Friday
night.
Temperatures through the period will remain seasonably cold, with
highs mainly in the mid to upper 20s and lows in the single
digits to the teens.
KJB
&&
.AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 541 PM CST Mon Jan 6 2025
Forecast concerns for the terminals...
- Band of lake effect snow to impact northwest IN this evening
and overnight resulting in some accumulation
- MVFR ceilings to improve late this evening and overnight with
VFR conditions expected for Tuesday
A narrow band of lake effect snow has started to intensify as it
pivots into northwest IN this evening. The lake effect snow is
expected to result in sharp visibility reductions (around 1 SM)
and snow accumulations generally in the 1-3 inch range as it
traverses over GYY and nears VPZ towards midnight. While the
band should gradually weaken as it moves east, guidance
continues to show that at least some snow showers will persist
across portions of northwest IN through the night (mainly east
of GYY after midnight). Additionally, there also remains the
potential for some freezing drizzle to occur on either side of
the main lake effect band but cloud ice appears to be more
abundant in IN think that main precipitation type should be
snow.
Elsewhere, expect the ongoing MVFR ceilings to gradually clear
out this evening as drier air filters in from WI. However, some
lingering lake effect clouds may result in periods of SCT to BKN
MVFR ceilings through the night especially at GYY and possibly
MDW. Otherwise, expect VFR conditions to prevail through the day
on Tuesday with light northwest winds around 5-10 kts.
Yack
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 9 AM CST Tuesday for the IL
nearshore waters.
Small Craft Advisory until 3 PM CST Tuesday for the IN
nearshore waters.
&&
$$
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