Dec. 9-10, 1997 Western Storm
Emerges from the Rockies, Hits the Midwest...
After producing the heaviest snowfall of the season
in parts of the west, the powerful trough that moved into
the west coast on the 7th initiated lee-side
cyclogenesis on the 9th. This system organized
and strengthened over the OK Panhandle during the
afternoon of the 9th and brought moderate snow to MO
and IL by evening. This was a well behaved
system which showed some interesting mesoscale features.
Maximum snowfall (here's
a 12z Dec. 10th snowcover map) fell just to
the left of the 850
mb low track. During the night, the
Quad-Cities, IL radar showed distinctive E-W
heavy snow bands which can be related to
mesoscale insatabilites including CSI. The RUC2 model
(newest version of the RUC with hourly output!) was used
to diagnose the existence of negative
values of equivalent potential vorticity (EPV).
Negative EPV can indicate an environment favorable for
CSI. Note that the negative EPV values did not quite
reach into the region where the banded precipitation (and
heaviest snow) was observed (load the loops below for
additional detail). It is possible that the snow bands
were caused by Weak Symmetric Stability (WSS) as
discussed by Glass
and Moore.
Loop
of Midwest Surface Observations (00Z-06Z 10 Dec.)
Loop
of Quad-Cities radar (0005Z-0424Z 10 Dec.) Worth the
download time!
Loop
of RUC2 EPV and 850-700 mb RH (hourly 00Z-03Z).
Central
IL 00Z Dec. 10 upper-air sounding. (Note the
deep saturated layer and relatively weak southwesterly
unidirectional shear in the mid-levels. The stronger
winds aloft, over 100 KT at 300 mb, were just south of
this location at this time.)
Dec. 10-11, 1997 Then on
through the Great Lakes to the East!
Same winter storm as above. Surface low pressure
was centered between IN and OH on the morning of the
10th. The storm then moved SLOWLY eastward, north of the
Ohio river valley, and into northwest PA by evening.
Heavy snow fell over MI, OH, PA, and NY. Snow was falling
at 2 to 4 inches per hour in western NY during the
afternoon! Here's a separate page with some selected
graphics from this event including observed
snow cover at 18Z and at 00Z 11 December. Here are a few products
issued by local National Weather Service offices.
Dec. 10, 1997 The Rockies Pick
Up More Snow and Blowing Snow
Strong northerly winds in advance of a strong and
building high
pressure ridge over the Pacific Northwest, and
residual
mid level moisture over the Rockies, combined
to produce heavy snow squalls and mountain white-outs
over Colorado and Wyoming.
National Weather Service products
from CO and WY. Also view selected
US graphics for 10 Dec.
Dec. 14, 1997 Sunday Snowstorm
in the South.
Parts of south-central MS awoke to a few inches of
snow on Sunday morning, a very rare event. What's even
more incredible is that is kept snowing for much of the
day with over 7 inches of heavy wet snow reported around
the Jackson, MS area! The band of heavy snow formed to
the north of a rapidly intensifying, and unusually cold, upper
level closed low. Low level mositure was wrapped
westward and lifted into the system from the
east. The air in the mid levels was cold enough for snow,
and as the closed low passed south of MS during the
morning, the near surface layer was cooled to freezing by
the falling precipitation. The 12Z
Jackson, MS sounding showed the surface
temperature and dewpoint were right at the freezing
mark...and stayed there through the entire event. The 12Z
RUC2 6-hour
forecast for precipitation type indicated snow
across all of south central MS and into central AL...with
strong 700-500 mb upward motion over the same region.
Parts of west central AL picked up as much as 4 inches of
snow during the day. Here's a satellite
snapshot showing the area of snow on the day after!
Loop
of Jackson, MS radar (12-16Z 14 Dec. 9-frame loop).
Selected
Products from National Weather Service offices.
CIMSS-UW
Satellite Review
A
map of observed snowfall totals.
Dec. 14, 1997 Moderate Snowfall
over Northern CA Mountains
Strong trough moved into central CA
coast with snow levels dropping to about 3000 feet in the
mountains of northern California, about 4000 feet in the
Sierra. Snow amounts were generally in the 4-8 inch range
with higher amounts in the upper elevations.
Dec. 15-16, 1997 Pacific Northwest
and Idaho Hit with Heavy Wet Snow.
Warm air advection and a very moist tropical
Pacific plume moved over the Cascades of Washington and
Oregon on the 15th with heavy snow falling through the
night. Cold air was trapped in the inland higher
elevation areas of central Washington and eastern Oregon
where several inches of wet snow was reported. The
moisture moved eastward into the northern Bitteroot
Mountains of Idaho on the 16th with heavy snow falling
from about 3000 feet up. Here are a number of products
issued by local National Weather Service offices.
16-Dec.,
1997 12Z GOES-9 IR Satellite Image of the eastern Pacific
and western U.S.
Here's
a 16-Dec., 1997 12Z Sounding from Spokane, WA (OTX)
Dec. 20, 1997 Snow in New Mexico,
Ice in the Texas Panhandle
A broad upper
low moved eastward along the northern border
of Mexico/southern border of AZ on the morning of the
20th. This system sped up and ejected northeast over west
TX later in the day. Strong upslope flow developed over
the mountains of NM where significant snow accumulations
occurred during the day. Farther east...over the TX
Panhandle...a small amount of above freezing air was
pulled into the mid level circulation which turned
falling precipitation into liquid in the low to mid
levels. This rain then fell into a very shallow layer of
below freezing air at the surface bringing significant
black ice and glaze to areas around Lubbock and Amarillo.
A late afternoon radar composite shows an area of moderate
to heavy freezing rain mixed with sleet moving
northward into the TX Panhandle. Lubbock reported over
0.50 inch of freezing rain during the day. The Eta model precipitation
type forecast was very accurate for this event
(note: red region indicates freezing rain). The
12Z 20-Dec. Amarillo sounding appeared to
favor wet snow. However, note the isothermal, near
freezing, layer between 850-700 mb. This layer probably
warmed above freezing when easterly winds brought in
warmer air from the east. Here are a couple of products
issued by local National Weather Service offices.
Dec. 21-23, 1997 Freezing Rain from
Kansas to Pennsylvania and a Burst of Heavy Snow in New
England
Same system as above. Weakening upper low and
associated surface system moved from KS to IN spreading a
swath of generally light freezing rain from the Central
Plains to the southern Great Lakes. Strong warm air
advection moved into western NY and over PA late in the
day on the 22nd. Surface temperatures ranged from just
below freezing, in parts of PA, down to the lower 20's in
parts of NY. Secondary low pressure formed in advance of
the approaching upper trough and strengthened off the Mid
Atlantic coast early on the 23rd. This secondary storm
brought a quick, but significant, influx of Atlantic
moisture into parts of interior and northeastern MA and
southeast NH. Some locally
astounding snowfall totals occurred in these
areas during the morning.
Chatham,
MA 12Z Sounding (note deep saturated isothermal layer and
SE flow)
Have a Look at the 850,
700,
and 500
mb Charts as Initialized on the Eta Model for 12Z Dec.
23rd.
Here is a 7-frame
Loop of the RUC Surface Pressure and Frontogenesis.
(Note the strong frontogenesis just east of the axis of
heaviest snow. Also, here's a look at the 12Z
Surface Temperatures over New England.)
A
1415 UTC IR Satellite Image shows the cold
cloud tops over the area getting the heaviest snow.
Dec. 22-25, 1997 Another Major
Storm Cranks up over the Southwest
A seemingly endless parade of vigorous upper level
troughs keeps coming from the eastern Pacific! Yet
another strong and cold 500 mb system barrelled into the
northern Baja/Gulf of California and closed off over
southwest AZ early on the 22nd. A beautiful swirl of a
comma head developed from this system over much of NM,
the White Mountains, and Mogollon Rim of AZ. Under this
swirl, heavy snow fell throughout the day and into the
night of the 22nd. Several feet of snow likely piled up
in the highest elevations. We're not done with this
system yet...
Short
Loop of 500 mb Pattern (22 Dec. 00Z -23 Dec. 00Z)
Long
Loop (7 frames ~ 1 MB of data) of GOES-9 Visible
"Swirl in the Southwest"
A
Few Products from Local National Weather Service Offices
And
Yet Another System is Right Upstream! (Eta forecast
4-panel)
Heavy rain and thunderstorms
developed over the Southern Plains before dawn on the
23rd. These storms appeared to disrupt the flow of
mositure into the mid and upper level cyclone over NM.
The heaviest snow continued to fall across NM
northeastward across parts of the TX Panhandle and into
southwest KS but there was little organization or
structure to the snow bands. There was also a lack of
arctic air with this system in the lower levels. However,
moderate to occasionally heavy snow did fall over much of
western KS from early on the 23rd through the 24th giving
some locations over a foot of snow. The main upper and
surface systems moved from OK to IL on the 24th leaving
light to moderate snowfall across the upper midwest (Dec.
25 12Z observed snow cover map). The winter
storm picked up speed and quickly departed the U.S. via
New England by late on the 25th. Before departing, the
system brought a glaze of freezing rain to much of
upstate and eastern NY with a mix of sleet, freezing
rain, and snow falling across VT,
NH, and ME.
Dec. 25-26, 1997 New Mexico, Texas,
and Oklahoma Get Some Snow
Positively tilted long wave trough was parked over
the Southwest US with weak impulses being ejected out
across TX and OK. This system didn't bring heavy amounts
of snow, but the rather anomalous southern
position of the polar jet brought areas
of snow and sleet to parts of southern OK and
north TX on the 26th.
Winter
Storm Warning from ABQ on the 25th.
Advisories
from TX/OK NWS Offices on the 26th.
Sounding
from Dallas/Ft. Worth at 12Z on the 26th.
Dec. 27, 1997 Fast Moving Storm
Brings Snow to the East Coast
A quick moving system intensified off the Carolinas
and zipped up the eastern seaboard on the 27th. The fast
movement of the storm, and the lack of very cold air at
the surface, made for mediocre snow amounts from the
mountains of North Carolina northward through WV, VA, MD,
DE, NJ, PA, and NY. Snow became heavier over southeast
New England as the storm strengthened further and moved
into the North Atlantic.
Some
Snowfall Amounts in the Mid Atlantic Region
Winter
Storm Warning from NWS Boston
Snowfall
Amounts from Southern New England
Dec. 29-30, 1997 Major Winter Storm
Moves Up the Eastern Seaboard
An energetic shortwave pressure trough being
propelled along by 140 KT northwesterly flow aloft passed
over the central US on Sunday Dec. 28 (500
mb graphic / 300
mb graphic). Light snow fell from eastern OK
through parts of the Mississippi valley as this system
progressed eastward. Higher snowfall totals would have
occurred were it not for the limited amount of moisture
available to the storm. The disturbance gained additional
strength from the very fast southern stream along the
Gulf Coast, and induced strong surface cyclogenesis over
the Southeast on the 29th. Atlantic and Gulf Moisture
were then brought into the circulation and precipitation
increased dramatically over the Eastern US. Some medium
range forecast models indicated the chance of this major
cyclone over the eastern US several days in advance (ECMWF
from Dec. 27).
Loop
of RUCS Pressure / Near Freezing Temps and Composite
Radar (08-23 UTC Dec. 29th).
Loop
of RUCS Pressure / Near Freezing Temps and Composite
Radar (00-14 UTC Dec. 30th).
Loop
of Eastern US Surface Weather (12Z Dec. 29th through 12Z
Dec. 30th).
Loop
of Eastern US 500 mb Level (00Z Dec. 29th - 12Z Dec.
30th)
Some
Snowfall Amounts
Jan. 3-4, 1998 Freezing Rain
Spreads from the Plains to the Northeast
A strong arctic outbreak brought a layer of shallow
cold air south across the Canadian border into portions
of the central Plains. By late on the 3rd the cold
air had moved over all of KS and much of NW
OK. In the days prior to the cold air outbreak abundant
Gulf moisture moved northward over the plains and
midwest. The cold front encountered the deeper moisture
over the plains as an upper level distubance moved into
the area from the southwest. The result was heavy
freezing rain and thunderstorms during the night of the
3rd from northern
OK northeastward into MO, KS, NE, IA, WI, MN,
and MI. Widespread freezing rain became quite heavy over
portions of MN
and WI during the evening of the 4th.
News
Article About MN Ice Storm
Jan. 3-5, 1998 Heavy Snow from the
Cascades and Sierra East to the Rockies
Another western trough brought moderate to heavy
snowfall across the mountains of the west. Many areas
were affected from WA
to AZ. The first trough moved into the
intermountain region on the 5th and brought moderate to
heavy snow to UT and CO. The Pacific Northwest was
affected by an onslught of cold unstable Pacific air
being rammed into the Cascades which brought almost
continuous heavy snow to the mounatins through the 5th.
NWS
WA Weather Summary for Jan. 5
Jan. 5-9, 1998 Devastating Ice Storm
of Historic Proportions Hits Northern New England
Incredible flow of mositure and warm air moved from
the Gulf Coast and Southeast U.S. northward over below
freezing air from northeast NY eastward into central ME.
This event will not soon be forgotten for its duration
and precipitation amounts. I'm sure we'll see plenty of
case studies on this one. Below are a few links about
this disaster. This ice storm also affected parts of
eastern Canada with the province of Quebec experiencing
their costliest natural disaster in history!
News
Article from AP
News
Article about the Disaster in Canada
Some
Icy Pictures from Maine
Public
Information Statement from Burlington, VT
850 mb Maps: Heights and Temps (12Z
1/8, 00Z
1/9), Moisture Transport (12Z
1/8, 00Z
1/9)
700 mb Maps: Relative Humidity (12Z
1/8, 00Z
1/9)
500 mb Maps: Heights and Vort. (12Z
1/8, 00Z
1/9), Height Falls (12Z
1/8, 00Z
1/9)
300 mb Maps: Heights, Isotachs, Div. (12Z
1/8, 00Z
1/9)
Eastern U.S. Observed Surface
Weather on Jan. 8th for: 03Z,
06Z,
09Z,
12Z,
15Z,
18Z,
21Z
Jan. 7-9, 1998 Heavy Snow from OK to
WI
Strong upper trough moved slowly
from west TX across the Red River and then redeveloped
and moved northward through the Midwest. This system was
the western counterpart to the Northeastern ice storm
(see maps above). Moderate snow in the the colder air
brought generally 3 to 8 inches of snow from northeast OK
to WI with the heaviest amounts (6-8 inches) falling
during the afternoon of the 8th from northern IL into
southeast WI.
Jan. 10-13 , 1998 Cold and Snow in
the Pacific Northwest
A series of storms rolled into Washington and
Oregon from the Pacific. Much of the region was very cold
from an arctic airmass that had seeped into much of
Washington, the Columbia River Gorge, and most of
interior and northern Oregon. Very heavy snow occurred in
parts of the Columbia Gorge, and of course in the
Cascades. At the western terminus of the Columbia Gorge,
and across the northern Willamette valley, precipitation
fell as heavy freezing rain on the 12th. Strong easterly
winds roared through the Gorge and continued to supply
cold low level air to parts of northwest Oregon, around
Portland.
Winter
Storm Warnings
Pacific
NW Surface Map 03Z 11 Jan.
Pacific
NW Surface Map 01Z 13 Jan.
More
Winter Storm Products for 12-13 Jan.
Heavy snow continued across much of
the Cascades and into Northern ID through the week.
Jan. 15 , 1998 Heavy Snow across
Intermountain West
Strong trough and intense west-northwest flow aloft
moved from Pacific Northwest rapidly into UT and then CO.
Winter
Storm Warnings and Advisories
Jan. 15, 1998 East Coast System
Brings Freezing Rain to Mid Atlantic States, Snow to the
Northeast
This was an interesting (i.e. difficult forecast)
East Coast event with a variety of winter weather.
Freezing rain extended from northwest NC into southern
New England on the 15th. Moderate snow (from a northern
stream short wave) moved over northern NY and northern
New England.
12Z,
15 Jan. Roanoke/Blacksburg Sounding (Freezing
Rain!)
Jan.
15th Late Evening Radar Summary (03Z Jan.
16th)
Surface
Plot and RUCS SLP and Temp (03Z Jan. 16th)
Summaries,
Warnings, Statements
Eta Inital 500 mb Plot for 12Z
Jan. 15th and 00Z
Jan. 16th
The snow forecast for parts of southern
New England was a bit on the high side.
However, parts of VT and NH picked up 8-10 inches from
the northern stream short wave as is combined with the
moisture brought northward by the coastal system.
Jan. 18, 1998 Deep Snow in the
Sierra
Vigorous Pacific system brought heavy snow to the
Sierra Nevada. Strong jet stream moved rapidly inland and
across Nevada into the intermountain west on the 19th.
Snow
Totals around CA/NV
Jan. 22-24, 1998 A Mess in New
England
Snow, sleet, and freezing rain
plagued New York and New England. Precipitation remained
primarily snow in VT where 8 to 10 inches accumulated. Up
to 1/2 inch of glaze coated trees and power lines in
central MA while more freezing rain and sleet affected
eastern ME through the 24th.
Jan. 26-28, 1998 Surprise Southern
and Central Appalachian Snowstorm
Vigorous upper circulation spawned surface
cyclogenesis along the southeast coast. This system was
expected to be too warm to produce winter precipitation.
However, low levels of the atmosphere over the
Appalachian mountains cooled sufficiently to support wet
snow. And snow it did! AVL ended up with a foot, and
there were reports of up to 3 feet along the spine of the
Appalachian chain from NC/TN northward into WV and VA!
This storm would make an excellent case study (there were
no winter storm watches out prior to SN+ beginning).
Note: Eta precipitation type output indicated freezing
rain for southwest NC, while point forecast soundings
looked more like snow. Mesoeta forecasts 18 hours prior
to onset of precipitation indicated over 1 inch per hour
snowfall over a small area of southwest NC around AVL
between 09Z and 12Z on 1/27, and turned out to be right
on. Warmer temperatures in mid levels skewed thickness
rules toward mixed rain/snow or sleet, but these
precipitation types were not observed in significant
amounts...it was mostly heavy wet snow.
CNN/AP
Article on the Storm
Loop
of 500 mb from Jan. 26 through Jan. 28
Greensboro, NC Upper Air Soundings for 00Z
Jan. 27th and 12Z
Jan. 27th.
Visible
Satellite Image of Snow On the Appalachians
Feb. 1-5, 1998 Powerful Storms
Affect West and East
An intense storm developed over the Gulf of Mexico
on the 1st moving over FL on the 2nd and bringing
widespread severe weather. This system then moved slowly
northward along the southeast U.S. coast and battered the
Mid Atlantic region with high winds and coastal flooding
on the 4th and 5th. The huge circualtion around the area
of low prtessure brought abundant Atlantic moisture
westward into cold air west of the Appalachians. Very
heavy snow was reported as far west as IN! The highest
accumulations occurred over the Cumberland Plateau and
over the OH valley. This was the strongest storm of the
winter to date along the east coast.
News
Article about the Storm in KY
Loop
of Surface Pressure and Freezing Line
Visible
Satellite Image of the Snowcover in the Ohio Valley
Meanwhile, the west coast continued to be slammed
by intense Pacific cyclones bearing tropical moisture.
Major flooding and mudslides occurred across northern and
central CA. In the Sierra, the snow continued to pile up,
mostly at elevations above 6000.
CNN
Web Page Article
Feb. 6-8, 1998 Heavy Snow in the
Sierra Nevada, Again!
Another in a plethora of power-packed Pacific
systems gave northern California
quite a blow. The storm dropped over 2 feet of snow in
the Sierra, generally above 6000 feet.
Storm
Totals from NWS Reno, NV
Feb. 23-24, 1998 Northeastern
Storm Drops Heavy Snow
New York and Vermont were hit
hard by a slow moving cyclone with a large circulation.
Over a foot of snow across from parts of NY's southern
tier to the Champlain valley and the Green Mountains of
VT.
Feb. 23-25, 1998 Intense
Pacific Storm brings more snow to the Sierra, then the
Rockies.
Feb. 25-27, 1998 Western Storm
moves into the Northern Plains and Produces Blizzard
Conditions.
Note: Sorry about limited
information on these latest storm systems. Other projects
are attracting my attention. I will, however, at least
try to keep the dates logged on the significant events.
As time permits, I may also add more information.
