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January 28-29, 2022 Miller abcdefu Storm Threat


WxUSAF
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23 minutes ago, yoda said:

Anyone know the last time PRE and winter weather were discussed in the same sentence?  Interesting mention by LWX in their AFD about it

@csnavywx @WxUSAF

Pete from WPC had a nice thread last night on twitter that EJ posted. Said the banding he thinks could happen could be very similar to the Jan 6/7 event where places like Frederick and west picked up 6+ because of it. 

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13 minutes ago, WxUSAF said:

It’s different but I’ve heard people mention it on Twitter. Nice that they also think there’s upside potential similar to what Pete Mullinax and HM have said. That and the ULL are what I’m watching. 

ah ninja'd

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Just now, mappy said:

Pete from WPC had a nice thread last night that EJ posted. Said the banding he thinks could happen could be very similar to the Jan 6/7 event where places like Frederick and west picked up 6+ because of it. 

Thank you for that... I will try and find it so I can read up on it

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51 minutes ago, yoda said:

LWX has a great and awesomesauce disco this afternoon... hats off to them.  Well written as well

 

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...

...SLIGHT TO ENHANCED WINTER STORM THREAT AS MAJOR STORM LURKS 
OFFSHORE...

Overview...
The evolving large scale weather/jet stream pattern across the 
U.S. as well as latest model guidance continue to suggest the 
potential of a major, rapidly deepening area of low pressure 
moving northward off the East Coast Friday into Saturday. 
Although the brunt of the storm looks to be headed for New 
England, the Mid-Atlantic region will be on the western 
periphery of the rather large system resulting in an increasing 
likelihood of accumulating snow. Uncertainty remains in the all
important details, and users are encouraged to focus on the
broader "low-end" and "high-end" potential snowfall amounts at
this time range, with the caveat that the situation is still
evolving, the storm has yet to form, and continued variability
is likely in the "expected" snowfall amounts as finer scale
details come into clearer focus over the next couple of days.

For the latest forecast details, please visit:
www.weather.gov/lwx/winter.

Technical summary...
A mid-level jet max and weak isentropic lift well ahead of the
large scale trough will impinge on the Allegheny Front beginning
as early as shortly after sundown Thursday. At least scattered
snow shower activity is anticipated as a result Thursday night
over favored upslope areas, with a couple of inches possible
mainly along western facing ridges through daybreak Friday.

This axis of lift will slip slowly southward and eastward during
the day Friday while the upper trough sharpens across the TN/OH
Valley. The trough will have 3 embedded shortwaves within it: a
shortwave pivoting from SE MO to E KY, a southern stream
vorticity ribbon arcing back through the ArkLaMiss to TX, and a
trailing northern stream shortwave diving into the upper Great 
Lakes. It appears the trailing vorticity ribbon will become
ingested in the main shortwave trough, phasing sufficiently to
result in strong surface cyclogenesis in a PVA regime ahead of
the trough as it interacts with a baroclinic zone near the
Bahamas. Meanwhile, the trailing northern stream shortwave
likely also becomes infused into the large trough, aided in part
by very transient/weak blocking from the Arctic high retreating
off through the Canadian Maritimes. As all of these pieces
conjoin, rapidly deepening surface low pressure will track
northward off the Eastern Seaboard. The question is exactly how
far offshore the low tracks. A consensus of the latest
model/ensemble data as well as the background UA pattern suggest
a low track from about 150 miles east of the Outer Banks of NC
to just outside (SE of) the 40 N/70 W benchmark off the New
England coast.

With the lack of a more substantial downstream block over the 
North Atlantic, the low is more likely to track far enough
offshore and deepen far enough to the east and north that the
heaviest band of snow would setup toward the NJ/New England
coast, with the northwestern edge setting up over southern MD
and the Eastern Shore. The infamous gradient between lighter and
heavier snowfall may end up near the I-95 corridor, and thus
bears a very close watch.

Otherwise, most of the accumulating snowfall for the majority of
the area will come from the upper trough axis itself. Snow may
mix with rain at the onset for lower elevations east of I-81 and
south of I-70 Friday afternoon due to boundary layer
temperatures progged into the mid to upper 30s. Upslope 
enhancement over the higher terrain will likely result in 
locally higher amounts over the Alleghenies. One thing to note, 
despite an overall relatively lighter expected snowfall across 
the majority of the area, the overall pattern somewhat resembles
that of a PRE (Predecessor Rain Event), where moisture from an 
intense, distant (offshore) low interacts with a mid- level 
frontal zone. This may result in a band of enhanced snowfall as 
hinted at in some runs of higher resolution guidance, but 
certainty on its magnitude and placement is low at this time.

Of greater certainty is increasing winds and plunging
temperatures as the low lifts out toward the Northeast heading
into Saturday. Dangerously cold wind chills are likely by
Saturday evening, and blowing snow is possible as winds
increase. Snow may linger in the I-95 corridor through Saturday
morning depending on the evolution of the offshore low, but dry
conditions should return areawide east of the Allegheny Front 
by nightfall.

The  “problem” is there are like 6 moving parts to this.  No forecast can be derived from that.  The first snow was an already organized low pressure moving northeast from Atlanta.  Virtually no moving parts and easy to forecast with  usually confirmed outcome 

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