Winter Storm and Heavy Snow in Pennsylvania, March 20 to 21, 2018

Name: Winter Storm and Heavy Snow in Pennsylvania, March 20 to 21, 2018
Start: 2018-03-20T10:00
End: 2018-03-21T19:00
Location: Pennsylvania

March 20 to 21, 2018 · NWS PBZ · 11 events in 11 counties and zones

Southern stream low brought a period of mixed precipitation across the higher elevations, which eventually changed to snow cross much of the upper Ohio Valley as an upper trough pivoted overhead and coastal low development enhanced cold advection across the region. While ice amounts generally were a a tenth of an inch or less, snow amounts of 6-8 inches, with some isolated higher amounts…

Where it happened

Every event with a place to put it; 10 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 11

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS PBZ wrote it up.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Pittsburgh, PA wrote its last area forecast discussion before the first event at Mar 20, 8:27 AM EST, 1 hour 33 minutes earlier.

Area forecast discussion, Mar 20, 8:27 AM EST, 1 hour 33 minutes before

Area Forecast Discussion
National Weather Service Pittsburgh PA
927 AM EDT Tue Mar 20 2018

.SYNOPSIS...
A wintry mix of precipitation is expected today with low
pressure. The mix should change to snow tonight before gradually
tapering off Wednesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Added a Winter Weather Advisory for the Laurel Highlands through
early afternoon. Temperatures on the ridge tops are near
freezing, and should fall some as evaporative cooling occurs
when precip begins. Enough warm air aloft exists for precip to
fall as rain, and freeze on surfaces. Previous discussion below.

A wintry mix of precip should overspread the region mainly S of
I 80 today as low pressure tracks across the TN and OH Valley
regions. Warm advection ahead of the low should result in mainly
rain or a rain snow mix S of I 70 outside of the higher
terrain. Rain and snow is expected N of I 70, along with a
brief, slight chance for freezing rain. Little if any
accumulation of ice or snow is expected with marginal
temperatures and the high March sun angle, though the colder
Laurel Highlands could see an inch or two of snow. Some model
progs appear to be too high with high QPF/snowfall due to
overdone strong omega bullseyes in warm advection.

The higher terrain of WV and MD should see snow and freezing
rain transition to mainly snow today. Will maintain the Winter
Storm Warning for the expected snow and ice accumulations, with
temperatures more favorable for accumulation with cold E upslope
flow.

Precip should decrease in coverage this afternoon as the best
upper support and lift exits.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
A second low is progged to dig across the OH/TN Valleys tonight
and part of Wednesday. Cold advection in the wake of the initial
Tuesday low should result in all snow across the region.
Maintained the Winter Weather Advisory and the Winter Storm
Warning with accumulation expected as temperatures drop below
freezing at night. Expecting generally 2-4 inches total for
areas S of I 80, with amounts from 6-12 inches in the higher
terrain where the Winter Storm Warning is in effect.

The snow should taper off from N-S Wednesday as lift/upper
support shifts off the E Coast with a developing coastal low.
Dry weather returns with shortwave ridging Wednesday night and
Thursday. Below average temperatures are expected to continue.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Surface ridging should maintain dry weather until a srn stream
low returns rain and snow chances S of I 80 Sat thru early Sun
night. Limited POPs to chance with a significant model shift swd
with the low in recent solutions. An Ern CONUS ridge should
return dry weather later Sun and part of Mon before a Midwest
trough returns low precip chances late Mon.

&&

.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
Conditions will continue to deteriorate as precipitation
spreads north and low levels. KMGW should remain all rain
however, ports to the north will see a wintry mix eventually
changing over to all snow and IFR restrictions by early
afternoon. Improvement to low MVFR late afternoon through the
evening until snow coverage increases again as a second sfc low
approaches the region.

OUTLOOK...
Restrictions, albeit with gradual improvement, are likely into
Thursday morning.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...Winter Storm Warning until 8 PM EDT Wednesday for MDZ001.
OH...Winter Weather Advisory from 8 PM this evening to 8 PM EDT
     Wednesday for OHZ039>041-048>050-057>059-068-069.
PA...Winter Weather Advisory from 8 PM this evening to 8 PM EDT
     Wednesday for PAZ013-014-020>023-029-031-073>075.
     Winter Weather Advisory until 1 PM EDT this afternoon for
     PAZ074-076.
     Winter Storm Warning from 8 PM this evening to 8 PM EDT
     Wednesday for PAZ076.
WV...Winter Weather Advisory from 8 PM this evening to 8 PM EDT
     Wednesday for WVZ001>004-012-021-509.
     Winter Storm Warning until 8 PM EDT Wednesday for WVZ512>514.
     Winter Storm Warning from 8 PM this evening to 8 PM EDT
     Wednesday for WVZ510-511.

&&

Hazardous weather outlook, Mar 20, 3:53 AM EST, 6 hours 7 minutes before

Hazardous Weather Outlook...UPDATED
National Weather Service Pittsburgh PA
453 AM EDT Tue Mar 20 2018

MDZ001-WVZ512>514-210900-
Garrett-Eastern Preston-Western Tucker-Eastern Tucker-
453 AM EDT Tue Mar 20 2018

...WINTER STORM WARNING IN EFFECT UNTIL 8 PM EDT WEDNESDAY...

This Hazardous Weather Outlook is for western Maryland and northern
West Virginia.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Storm Warning.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Storm Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.

WVZ510-511-210900-
Ridges of Eastern Monongalia and Northwestern Preston-Preston-
453 AM EDT Tue Mar 20 2018

...WINTER STORM WARNING IN EFFECT FROM 8 PM THIS EVENING TO 8 PM EDT
WEDNESDAY...

This Hazardous Weather Outlook is for northern West Virginia.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Storm Warning.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Storm Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.

OHZ039>041-048>050-057>059-068-069-PAZ013-014-020>023-029-031-073-
075-WVZ001>004-012-021-509-210900-
Tuscarawas-Carroll-Columbiana-Coshocton-Harrison-Jefferson-Muskingum-
Guernsey-Belmont-Noble-Monroe-Lawrence-Butler-Beaver-Allegheny-
Armstrong-Indiana-Washington-Greene-Westmoreland-Fayette-Hancock-
Brooke-Ohio-Marshall-Wetzel-Marion-Monongalia-
453 AM EDT Tue Mar 20 2018

...WINTER WEATHER ADVISORY IN EFFECT FROM 8 PM THIS EVENING TO 8 PM
EDT WEDNESDAY...

This Hazardous Weather Outlook is for east central Ohio, southwest
Pennsylvania, west central Pennsylvania, western Pennsylvania,
northern West Virginia and northern panhandle of West Virginia.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Weather Advisory.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Weather Advisory.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.

PAZ007>009-015-016-210900-
Mercer-Venango-Forest-Clarion-Jefferson-
453 AM EDT Tue Mar 20 2018

This Hazardous Weather Outlook is for northwest Pennsylvania and
west central Pennsylvania.

.DAY ONE...Today and Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.

PAZ074-210900-
Westmoreland Ridges-
453 AM EDT Tue Mar 20 2018

...WINTER WEATHER ADVISORY IN EFFECT UNTIL 1 PM EDT THIS AFTERNOON...
...WINTER WEATHER ADVISORY IN EFFECT FROM 8 PM THIS EVENING TO 8 PM
EDT WEDNESDAY...

This Hazardous Weather Outlook is for southwest Pennsylvania.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Weather Advisory.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Weather Advisory.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.

PAZ076-210900-
Fayette Ridges-
453 AM EDT Tue Mar 20 2018

...WINTER WEATHER ADVISORY IN EFFECT UNTIL 1 PM EDT THIS AFTERNOON...
...WINTER STORM WARNING IN EFFECT FROM 8 PM THIS EVENING TO 8 PM EDT
WEDNESDAY...

This Hazardous Weather Outlook is for southwest Pennsylvania.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Weather Advisory.
   Winter Storm Warning.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Storm Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
 conditions according to Standard Operating Procedures.

In the hours before

Local storm report, Mar 20, 7:04 AM EST, 2 hours 56 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
804 AM EDT TUE MAR 20 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0802 AM     FREEZING RAIN    GRANTSVILLE             39.70N  79.16W
03/20/2018  E0.00 INCH       GARRETT            MD   COUNTY OFFICIAL

&&

EVENT NUMBER PBZ1802347

JD

Local storm report, Mar 20, 8:01 AM EST, 1 hour 59 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
901 AM EDT TUE MAR 20 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0858 AM     FREEZING RAIN    TERRA ALTA              39.44N  79.54W
03/20/2018  E0.00 INCH       PRESTON            WV   COUNTY OFFICIAL

&&

EVENT NUMBER PBZ1802348

JD

Local storm report, Mar 20, 8:51 AM EST, 1 hour 9 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
951 AM EDT TUE MAR 20 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0948 AM     FREEZING RAIN    1 W FLAT ROCK           39.77N  79.50W
03/20/2018  E0.00 INCH       FAYETTE            PA   TRAINED SPOTTER

            -FZ CHANGING OVER TO WET SNOW AT 0930 L.

&&

EVENT NUMBER PBZ1802349

JD

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

5 winter weather, 4 heavy snow, 2 winter storm. Local standard time, as filed.

Winter Storm, Fayette Ridges

When: March 20, 10:00 AM EST to March 21, 7:00 PM EST
Where: Fayette Ridges forecast zone
Reported by: Trained Spotter
Coordinates: 39.920, -79.647 (the zone’s center; the record gives no point)

Winter Storm, Westmoreland Ridges

When: March 20, 10:00 AM EST to March 21, 7:00 PM EST
Where: Westmoreland Ridges forecast zone
Reported by: Trained Spotter
Coordinates: 40.311, -79.467 (the zone’s center; the record gives no point)

Heavy Snow, Allegheny

When: March 20, 1:00 PM EST to March 21, 7:00 PM EST
Where: Allegheny forecast zone
Reported by: Trained Spotter
Coordinates: 40.469, -79.981 (the zone’s center; the record gives no point)

Winter Weather, Butler

When: March 20, 1:00 PM EST to March 21, 3:30 PM EST
Where: Butler forecast zone
Reported by: COOP Observer
Coordinates: 40.912, -79.913 (the zone’s center; the record gives no point)

Heavy Snow, Westmoreland

When: March 20, 1:00 PM EST to March 21, 7:00 PM EST
Where: Westmoreland forecast zone
Reported by: Trained Spotter
Coordinates: 40.311, -79.467 (the zone’s center; the record gives no point)

Winter Weather, Armstrong

When: March 20, 1:00 PM EST to March 21, 7:00 PM EST
Where: Armstrong forecast zone
Reported by: COOP Observer
Coordinates: 40.812, -79.464 (the zone’s center; the record gives no point)

Heavy Snow, Indiana

When: March 20, 1:00 PM EST to March 21, 7:00 PM EST
Where: Indiana forecast zone
Reported by: Trained Spotter

Winter Weather, Fayette

When: March 20, 1:00 PM EST to March 21, 7:00 PM EST
Where: Fayette forecast zone
Reported by: COOP Observer
Coordinates: 39.920, -79.647 (the zone’s center; the record gives no point)

Winter Weather, Beaver

When: March 20, 6:00 PM EST to March 21, 3:30 PM EST
Where: Beaver forecast zone
Reported by: COOP Observer
Coordinates: 40.682, -80.349 (the zone’s center; the record gives no point)

Winter Weather, Lawrence

When: March 20, 6:00 PM EST to March 21, 3:30 PM EST
Where: Lawrence forecast zone
Reported by: COOP Observer
Coordinates: 40.991, -80.334 (the zone’s center; the record gives no point)

Heavy Snow, Mercer

When: March 21, 3:00 AM EST to 11:00 AM EST
Where: Mercer forecast zone
Reported by: Emergency Manager
Coordinates: 41.302, -80.258 (the zone’s center; the record gives no point)

What these are

Winter Storm: A storm that brought snow, sleet or freezing rain at warning levels, usually over several hours or days.
Heavy Snow: Snowfall reaching the local warning threshold without the other hazards of a winter storm.
Winter Weather: Snow, sleet or freezing rain below warning levels that still caused disruption, damage or casualties.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Pennsylvania in 2018 Every state in 2018 This day in weather history Warnings in Pennsylvania, March 2018

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 747835, 747863, 747803, 747819, 747838, 747871, 747873, 747891, 747824, 747890, 747887.