TZUTC: 0000
MSGID: 168296.weather@1:2320/105 2dc48663
PID: Synchronet 3.21a-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0
TID: SBBSecho 3.28-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0
BBSID: CAPCITY2
CHRS: ASCII 1
FORMAT: flowed
FOUS11 KWBC 060751
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
251 AM EST Tue Jan 6 2026

Valid 12Z Tue Jan 06 2026 - 12Z Fri Jan 09 2026


...Great Lakes & Northeast...
Days 1-2...

Amplifying shortwave will move steadily eastward from the Great
Lakes tonight, passing off the New England coast Wednesday morning.
While the flow in which this impulse will be embedded is generally
zonal, some modest amplification is progged by the consensus, with
the subsequent height falls overlapping modest LFQ diffluence from
a jet streak to the south to enhance deep layer lift, especially in
the Northeast. This will likely result in two waves of surface low
pressure: one moving from MI into Ontario, with secondary
development occurring off the coast of Maine. The speed at which
this second low develops, as well as its latitude, will have a
strong influence on how much cold air can lock in across New
England within the in-situ wedge. While the trends in the guidance
continue to be a slightly farther south and stronger offshore low,
which will enable more cold air to lock in, mixed precip is still
likely to be the dominant p-type outside of the higher terrain and
across northern New England. This system should remain progressive
as well, limiting total impacts and amounts.

For areas that receive mostly snow (the Adirondacks and northern
New England) WPC probabilities for 4+ inches of accumulations are
modest at 10-30%, but locally reach as high as 50% in NH and ME. South
of there, a mix including freezing rain is likely, which could
produce more than 0.1" of ice (30-50% chance) highest in the
Greens, Berkshires, and Worcester Hills.


...Olympics, Cascades, and Northern/Central Rockies...
Days 1-3...

A powerful storm system over southern AK will work in tandem with
an unusually strong subtropical ridge north of HI to create a
robust 160kt 250mb jet streak in the northeast Pacific. This
will transport potent IVT eastward within pinched but generally
zonal flow, reflected by GEFS probabilities that exceed 80% for 250
kg/m/s, but are less than 25% for 500 kg/m/s. This increasing
moisture, while not exceptional, will be wrung out efficiently by
PVA within shortwaves traversing the flow, the LFQ of a slowly
sinking but strengthening Pacific jet streak, and persistent, at
times continuous, upslope flow, especially in the Olympics and
Cascades. Snow levels will fall to as low as 2,000ft, although the
heavier and more impactful snow will be observed above 3,000ft.
The heaviest snowfall arrives D1, and following a brief break in
the heavier snowfall rates early Wednesday morning, another
disturbance arrives later in the day with more snow in the Cascades
and Olympics. This time, with a colder air-mass aloft, snow levels
dip to as low as 1,000ft Wednesday afternoon and continuing into
Thursday. Although snow levels remain generally at or above 1,000
ft, steepening lapse rates aloft with continued ascent could result
in locally lower snowfall, reflected by the NBM 10th percentile
snow level falling to around 600 ft. While this should still
prevent significant accumulations in the lowlands, some of the
foothills west of the Cascades could see light snowfall on D2 as
well.

With snow nearly continuously falling in these ranges through
Thursday, WPC's 72-hour snowfall probabilities are quite impressive
with high chances (>70%) for snowfall totals >24" above 3,000ft in
the Cascades and Olympics, including passes such as Snoqualmie and
Stevens. At the higher elevations, 4-6 feet of snow is possible.
This snowfall, despite elevated SLRs as the column cools, will
result in dangerous travel across most Cascade Passes, with the
WSSI-P indicating a moderate threat (50-70%) of major impacts
through the Cascades. Motorists should prepare for dangerous travel
and potential pass closures this week.

Farther east into the Northern Rockies and then pivoting down to
the Central Rockies, spokes of energy within the generally zonal
flow will provide sufficient ascent to wring out moisture that
spills across the Cascades. Although snowfall farther east should
be somewhat less impressive than points west, WPC probabilities for
12+ inches during the next 3 days are high (>90%) in the higher
terrain from the Blue Mountains of OR through most of the Northern
Rockies, and down through the Tetons, Wind Rivers, and parts of the
Wasatch. Locally, 2-4 feet is possible in the highest peaks of
these ranges, and pass-level travel will also be significantly
impacted this week.


...Four Corners States...
Day 3...

Shortwave digging southeast from the Pacific Northwest will amplify
rapidly as it approaches the Central Rockies, potentially closing
off over the CO/NM High Plains Thursday night. There continues to
be a lot of spread in the mid-level evolution leading to lower than
typical confidence by D3, however, the cluster analysis (from 00Z/5
which is the most recent available) suggests there is potential for
continued deepening due to more pronounced upstream ridging leading
to a deeper trough (supported by more than 60% of the members,
although many of these are from the CMCE which may be somewhat
under-dispersive at this time). However, the trends in the
incoming 00z suite suggest the trough continues to be deeper, which
may result in a more substantial winter weather event.

As the guidance has trended steadily slower and faster with this
feature, suggesting more impressive deep layer ascent, the
resulting downstream jet streak has also intensified and arced
more impressively poleward. As this jet arcs northward, the
overlap of LFQ diffluence with height falls will likely lead to lee
side cyclogenesis Thursday evening, within a column that, while
will feature generally normal to below normal PWs, will saturate in
response to increasing low- level easterly flow around the
strengthening surface low. With steep lapse rates aloft helping to
cool the column, and flow becoming increasingly favorable to
upslope into the terrain, at least light snow is becoming likely
for much of the terrain and into the High Plains of CO/NM,
including the I-25 metro which has experienced a relative dearth of
snowfall so far this season. While adjustments in the forecast are
likely, current WPC snow probabilities indicate a high risk (>70%
chance) for 4+ inches of snow across much of the CO Rockies,
including the Front Range, and portions of the Wasatch, and down to
the White Mountains of AZ. The lower elevations of I-25 and into
the High Plains have a 10-30% chance of 4+ inches, although locally
higher amounts are possible across the Palmer Divide and Raton
Mesa.


Weiss


$$

= = =
To unsubscribe from WX-STORM and you already have a login, go to
https://lists.illinois.edu and use the "Unsubscribe" link.  Otherwise email
Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.28-Linux
 * Origin: Capitol City Online (1:2320/105)
SEEN-BY: 1/19 100 16/0 19/10 37 104/119 105/81 106/201 114/10 120/302
SEEN-BY: 123/130 128/187 129/14 142/104 153/757 7715 154/10 30 50
SEEN-BY: 154/110 700 201/0 203/0 218/700 840 220/10 20 30 90 221/1
SEEN-BY: 221/6 360 226/18 30 44 50 227/114 229/110 134 206 275 300
SEEN-BY: 229/307 317 400 426 428 470 664 700 705 240/5832 266/512
SEEN-BY: 280/5003 291/111 301/1 320/119 219 319 2119 322/757 762 326/101
SEEN-BY: 335/364 341/66 342/200 396/45 423/81 460/58 633/280 712/848
SEEN-BY: 902/26 2320/0 105 304 3634/12 5020/400 5075/35
PATH: 2320/105 154/10 221/6 1 320/219 229/426