Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
333 PM EST Sun Jan 16 2022

Valid 00Z Mon Jan 17 2022 - 00Z Wed Jan 19 2022

...A deep low pressure system will continue to spread heavy snow northward
across the upper Ohio Valley through the lower Great Lakes and the higher
elevations of New England through Monday...

...Snow will change over to a period of sleet/freezing rain before
changing over to rain across interior Mid-Atlantic and the lower
elevations of New England...

...Some heavy downpours, thunderstorms, and high winds can be expected to
impact the coastal sections of the Mid-Atlantic up through New England
into Monday...

A low pressure system continues to expand and intensify as it moves across
the southeastern U.S. and begins to turn toward the northeast up the
Eastern Seaboard. Arctic air already in place across the central and
eastern U.S. will work in concert with this dynamic system to deliver a
wide swath of more than a foot of heavy snow northward across the upper
Ohio Valley through the lower Great Lakes, as the storm center is forecast
to track up the interior section of the East Coast through Monday. Closer
to the track of the storm center, snow that initially falls is expected to
change over to a period of sleet and/or freezing rain before changing over
to plain rain across interior Mid-Atlantic and up through the lower
elevations of New England. Along the spine of the Appalachians, snow is
forecast to change over to a period of sleet and/or freezing rain as the
storm center approaches. The mixed precipitation should then change back
to snow following the passage of the storm center. Heavy wet snow is
expected across the higher elevations of New England through much of
Monday. Near the immediate coast, some heavy downpours, possibly
thunderstorms, together with high winds can be expected to precede the
storm center as it tracks up the Mid-Atlantic through New England into
Monday.

The center of the deep low pressure system is forecast to move into
southeastern Canada Monday night. This will change the precipitation to
all snow followed by gradual tapering off of the snow Monday night. Much
improved weather is expected to arrive on Tuesday for the Northeast but
the size of the departing system will keep winds blustery.

Meanwhile, a cold front across southern Canada will dip toward the
northern Plains. An Alberta clipper is forecast to form on the front on
Monday and then move toward the Great Lakes on Tuesday. Lingering snow
across the Great Lakes will pick up in intensity on Tuesday as the clipper
approaches. Farther west, accumulating snow is also forecast across
northern Minnesota and northeastern North Dakota. Arctic air behind the
cold front will then surge into the northern Plains on Tuesday. Upslope
snow is forecast to develop and intensify over the northern High Plains
into the northern Rockies on Tuesday as an arctic high pressure system
slides down from western Canada.

Weak onshore flow combined with upper-level energy will develop light rain
and higher elevation snow over parts of the Pacific Northwest Monday
evening into Tuesday. Moreover, lingering upper-level energy slowly
approaching California from the Pacific is forecast to produce scattered
areas of rain Monday evening into Tuesday for southern California.
Meanwhile, a new low pressure system is forecast to form over the southern
Plains on Tuesday. No rainfall is expected with this system. In fact,
dry conditions with a warming trend is forecast for southern Plains on
Tuesday.

Kong


Graphics are available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
158 PM EST Sun Jan 16 2022

Valid 12Z Wed Jan 19 2022 - 12Z Sun Jan 23 2022

...Cooled South to East Coast Snow/Ice Threat with frontal/coastal
low genesis late week...

...Pattern Overview...

A series of impulses will carve out and reinforce a broad mean
trough over the central and eastern states during the extended
period while the upper ridge amplifies offshore the West Coast.
The leading shortwave will track over the Great Lakes region into
the Northeast by Thursday with one behind it digging into the
South Friday and then pulling offshore the Mid-Atlantic/Southeast
region Saturday. This pattern will be conducive for precipitation
to spread across the higher terrain of the Northern and Central
Rockies through Friday and precipitation to span from
Texas/western Gulf Coast, Deep South, Southeast to the
Mid-Atlantic and push eastward beyond the weekend into next early
next week.


...Guidance/Predictability Assessment and Weather
Highlights/Hazards...

Previously, it was noted that there is significant forecast spread
and run to run uncertainty with this latter feature and associated
mid-winter weather focus with frontal wave/coastal low genesis.
The 06Z/12Z guidance continues to have notable spread on the
placement/track of the secondary shortwave feature. In turn, the
QPF placement varies significantly as well, especially across the
Gulf states, Southeast and Southern Appalachia. To combat these
differences, a general blend of the GFS/GEFS mean/CMC/ECWMF/EC
ensemble means were used through all time periods. This provide a
middle ground approach and helped maintain continuity from the
previous forecast cycle.

There is good agreement with an organized low pressure system set
to dig into the north-central U.S. and subsequently track moving
eastward along the U.S./Canadian border through Thursday. This
should bring some snow to the Great Lakes then northern New
England, with locally higher totals expected near typical lake
enhancement areas as cold high pressure sweeps down across the
central and eastern U.S. in the wake of the low in a pattern with
above normal predictability for these features. As the Arctic
blast reaches the southern tier states a wavy cold front will
encounter Gulf moisture to fuel an emerging area of precipitation
up from the South/Southeast. This pattern will be favorable for an
enhanced swath of overrunning snow/ice on the northern periphery
of activity later in the week. This wave may develop into a robust
coastal low/winter storm that tracks up the East Coast.
Meanwhile, The West could see some light precipitation through the
period, particularly over the Pacific Northwest and into the
Northern Rockies as weakening systems cross the region, with
mainly dry conditions elsewhere.

Campbell/Schichtel


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml

Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
253 AM EST Sun Jan 16 2022

Valid 00Z Mon Jan 17 2022 - 00Z Mon Jan 24 2022

A favored composite of reasonably well clustered models and
ensembles indicates that a series of highly energetic Pacific
storms over the next week should hold within a storm track to the
north of the islands, mainly over the mid-latitudes. The weather
over Hawaii should remain generally benign in a surface pattern
mainly favoring land and sea breezes for much of the upcoming week
with limited shower potential. However, a series of fronts
stalling just to the north of the state today, into midweek and
again heading into next weekend do offer an added chance for
showers into the northern islands.

Schichtel

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1046 AM EST Sun Jan 16 2022

Day 1
Valid 16Z Sun Jan 16 2022 - 12Z Mon Jan 17 2022

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

National RADAR mosaic depicts strengthening deep low across the
Deep South shifting through GA with a strong cold front and
associated thunderstorms trailing through central to southern
Florida, particularly near the instability source of the southeast
Gulf of Mexico. Cells have been progressive and sandy ground
conditions are well capable to handle this rainfall threat across
FL through the remainder of the morning.

...Carolinas...
Over the next few hours, further strengthening of the deep low
will accelerate low level wind flow and start to further enhance
tapping the western Atlantic moisture stream. Strong
southeasterly flow in advance of the cold/occluded front will be a
strong atmospheric river with IVT values of 1000 to 1250 kg/m/s
given 1.25"-1.4" of Total Pwats (1.5-2 stand deviations above
normal) and very strong, nearly orthogonal deep layer flow of
50+kts at the boundary layer to 80-90kts in 85-7H layer. This is
generally 3-5 standard anomalies of moisture flux into the system.
The key to excessive rainfall will be strength of thunderstorms.
Along the Carolina Coast, higher theta-e air and deeper marginally
unstable air will exist due to proximity of the Gulf Stream with
250-400 J/kg of MUCAPE to support vertical development as
thunderstorms. Hi-Res CAMs suggest 1-1.5"/hr rates are capable
for a few shallower thunderstorms along coastal SC/NC with streaks
of 2-3" rainfall totals in a 3 to 6 hour period. HREF
probabilities suggest very high potential (90%+) of greater than
1" in 3hrs but only 5-15% of 3"/3hrs. Higher sandy soils and
recent dry conditions suggest these rates/totals are not likely to
exceed FFG values but isolated (less than 5% prob.) of urban, high
run-off particularly near the coast where coastal flooding is
likely given full moon cycle on the tides, strong orthogonal
onshore surface flow, limiting out-wash/backing up lower portions
of riverine systems, but excessive rainfall rates are not likely
high enough to support a Marginal Risk at this time.

Mid-Atlantic to Southwest New England...
As the storm further strengthens lifting north, the overall
steering flow remains very strong and help to progress the
pre-frontal atmospheric river moisture flux northward quickly into
the Mid-Atlantic. However, proximity to the higher
theta-e/unstable air source near the Gulf Stream increases and
reduces capability for stronger thunderstorms. Still, flux values
will continue to increase with strengthening winds and moisture
anomalies further increase due to atypical northward translation
of 1.0-1.25" Total PWat values, between 00-06z, the focus will be
toward NJ and the NY Bight with 800-1000 kg/m/s values in the IVT
nearly 4-6 standard anomaly above normal. This will support
increased rainfall totals of 1-2" from the Mid-Atlantic to
Southwest New England by 12z. Urban flooding is possible with
these totals, but not likely be excessive in nature, though worth
mentioning for areas that are typically prone to flooding during
high-tide or strong onshore flow/surge situations...so adding
rainfall to the mix only increases risk of coastal flooding, yet a
Marginal Risk is not warranted given coverage and rain-rates.

Gallina


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
200 PM EST Sun Jan 16 2022

Day 2
Valid 12Z Mon Jan 17 2022 - 12Z Tue Jan 18 2022

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

...Southern New England and Down-east Maine...
At the start of the day 2 period, the deep surface low will be in
central PA with occluded/cold front crossing through southern
NY/Long Island into southwest New England. The deep sub-tropical
moisture plume/Atmospheric River will continuing directed across
Southeast New England with 1-1.2" Total PWats advecting on
60-100kts of boundary layer to 7H flow, supporting IVT values near
1000 kg/m/s. This is highly anomalous flux but with very limited
instability, heavy rain will be directed across the upglide into
the area. Isolated convective elements may exist supporting
enhanced localized rain rates but will generally be below hourly
FFG values, and therefore not warrant a Marginal Risk at this
time. However, additional rainfall totals of 1-2, perhaps 2.5"
in southwest facing orography that remains above freezing across
southeast MA, southeast NH and Downeast Maine before shifting
east, directing into Maritime Canada after 21z.


Gallina


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
201 PM EST Sun Jan 16 2022

Day 3
Valid 12Z Tue Jan 18 2022 - 12Z Wed Jan 19 2022

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Gallina



Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
300 PM EST Sun Jan 16 2022

Valid 00Z Mon Jan 17 2022 - 00Z Thu Jan 20 2022

...Mid Atlantic through the Interior Northeast...
Days 1-2...
As a northern stream shortwave continues to amplify to its
northwest, the deep low over the Southeast will begin to
accelerate to the north -- tracking through the interior Mid
Atlantic, before lifting across Upstate New York and northern New
England on Monday. Overall, not many changes to the previous
forecast, with the track still favoring snow changing to rain,
with only minor snow accumulations along the I-95 corridor from
Baltimore to Boston this evening. Well to the north and west,
heavy snow is still expected. Coupled upper jet forcing,
overlapping low-to-mid level frontogenesis will help support
impressive snowfall rates, with the latest HREF guidance
indicating rates in excess of 2 inch/hr within the comma-head as
it lifts across eastern Ohio, western Pennsylvania, western and
central New York overnight into Monday. Farther east, highly
anomalous southeasterly low level inflow ahead of the low will
support heavy amounts from the Berkshires and southern Greens to
the White Mountains, where thermal profiles are expected to
support mostly snow.

As the system lifts into Canada, strong northwesterly flow in the
wake of the system will support lake effect snow showers in the
lee of the eastern Great Lakes late Monday into Tuesday --
bolstering snow accumulations across portions of central and
western New York, and western Pennsylvania into the central
Appalachians.

Across eastern Ohio, western Pennsylvania, and western New York,
WPC probabilities indicate that accumulations of 8-12 inches or
likely through late Tuesday. This includes the Pittsburgh,
Cleveland, Buffalo and Rochester metros. Locally heavier amounts
possible, especially in the lee of Lake Erie. Similar totals are
expected for the higher elevations of the Catskills, Adirondacks,
Berkshires, southern Greens, and the Whites.


...Upper Midwest to the Northern Rockies...
Days 2-3...
A clipper system is forecast to dive southeast from western Canada
Monday night and then move east along the Canada-U.S. border from
North Dakota to Minnesota on Tuesday, before continuing east
across the northern Great Lakes Tuesday night into Wednesday.
This is expected to produce a stripe of light to moderate snows
across northern Minnesota and the U.P. of Michigan. A period of
southeasterly flow ahead of the system is expected to bolster
amounts along Minnesota's North Shore on Tuesday. Similarly,
locally heavier amounts are expected across the Keweenaw Peninsula.

Well to the west, the system's trailing cold front is forecast to
drop south across the northern Rockies -- supporting locally heavy
accumulations across the northerstern Montana and northern Idaho
ranges.

Pereira


~~~ Key Messages for Winter Storm Affecting the Eastern U.S.
January 16-17 ~~~

-- Heavy snow rates greater than 1â€/hr are possible along and
just west of the Appalachians today and Monday. Significant
impacts to travel are likely.

-- Ice accumulation will expand northward through the interior
Mid-Atlantic states this evening, creating hazardous travel
conditions.

-- Heavy snow is expected along the Appalachians into the interior
Northeast. Significant snow totals are likely across much of West
Virginia northward through western Pennsylvania/New York, and the
higher elevations of New England. This could result in dangerous
travel and scattered power outages.

-- Along the Atlantic coastline, strong winds and coastal flooding
are likely. Some locations may reach moderate flood levels, with
inundation affecting some coastal roads and structures.

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
158 PM EST Sun Jan 16 2022

Valid 12Z Wed Jan 19 2022 - 12Z Sun Jan 23 2022

...Cooled South to East Coast Snow/Ice Threat with frontal/coastal
low genesis late week...

...Pattern Overview...

A series of impulses will carve out and reinforce a broad mean
trough over the central and eastern states during the extended
period while the upper ridge amplifies offshore the West Coast.
The leading shortwave will track over the Great Lakes region into
the Northeast by Thursday with one behind it digging into the
South Friday and then pulling offshore the Mid-Atlantic/Southeast
region Saturday. This pattern will be conducive for precipitation
to spread across the higher terrain of the Northern and Central
Rockies through Friday and precipitation to span from
Texas/western Gulf Coast, Deep South, Southeast to the
Mid-Atlantic and push eastward beyond the weekend into next early
next week.


...Guidance/Predictability Assessment and Weather
Highlights/Hazards...

Previously, it was noted that there is significant forecast spread
and run to run uncertainty with this latter feature and associated
mid-winter weather focus with frontal wave/coastal low genesis.
The 06Z/12Z guidance continues to have notable spread on the
placement/track of the secondary shortwave feature. In turn, the
QPF placement varies significantly as well, especially across the
Gulf states, Southeast and Southern Appalachia. To combat these
differences, a general blend of the GFS/GEFS mean/CMC/ECWMF/EC
ensemble means were used through all time periods. This provide a
middle ground approach and helped maintain continuity from the
previous forecast cycle.

There is good agreement with an organized low pressure system set
to dig into the north-central U.S. and subsequently track moving
eastward along the U.S./Canadian border through Thursday. This
should bring some snow to the Great Lakes then northern New
England, with locally higher totals expected near typical lake
enhancement areas as cold high pressure sweeps down across the
central and eastern U.S. in the wake of the low in a pattern with
above normal predictability for these features. As the Arctic
blast reaches the southern tier states a wavy cold front will
encounter Gulf moisture to fuel an emerging area of precipitation
up from the South/Southeast. This pattern will be favorable for an
enhanced swath of overrunning snow/ice on the northern periphery
of activity later in the week. This wave may develop into a robust
coastal low/winter storm that tracks up the East Coast.
Meanwhile, The West could see some light precipitation through the
period, particularly over the Pacific Northwest and into the
Northern Rockies as weakening systems cross the region, with
mainly dry conditions elsewhere.

Campbell/Schichtel


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml