Severe Thunderstorm Warning 1, NWS Pittsburgh, PA

Area Forecast Discussion
National Weather Service Pittsburgh PA
409 PM EST Tue Jan 8 2019

.SYNOPSIS...
Showers and a few thunderstorms will accompany a cold front
this evening. Much colder air will follow, and rounds of
northwest flow snow showers are forecast for Wednesday and
Thursday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Next round of showers/scattered thunderstorms is incoming ahead of a
Great Lakes mid-level trough and a cold front moving across
Ohio. Likely PoPs are in place for this activity. Low level
lapse rates have been able to steepen thanks to clearing across
the CWA, and there is sufficient speed shear to support
thunderstorms. However, with low dewpoints, overall CAPE is
weak, and is best north of Pittsburgh. This is where the best
chance of strong to marginally severe wind gusts lies. Cannot
rule out some small hail with what little CAPE there is
extending into the hail growth zone.

Wind gusts will continue to be monitored as well.  Expect mixing and
strong pressure rises behind the front to produce 35-45 MPH gusts
across much of the area. The going wind advisory in the ridges will
stand as is for now, as this remains the main area where stronger
wind gusts are expected for a period behind the front/convection.

The cold front sweeps across during the evening, which will unlock
the door to colder air.  The changeover from rain to snow will occur
overnight from northwest to southeast, and be pretty much complete
by 12Z.  Accumulation should be a bit slow to commence given the
warm temperatures today, but should be in progress towards sunrise
especially north of I-80 and along the ridges.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
This period will be dominated by mid-level troughing and cold NW
flow in the low levels, with 850 mb temperatures dropping into
the -14C to -17C range. Rounds of snow showers are forecast. Accumulating
snow will be most prevalent Wednesday and Wednesday night,
during which time steep low-level lapse rates and good moisture
in the dendritic growth zone will be present. As expected in
this pattern, the higher accumulations will be seen in the I-80
corridor, due to lake enhancement, and along the southeast
ridges, due to upslope effects.

Given the length of favorable upslope conditions in the ridges,
headlines have been issued. Eastern Tucker County has been
placed in a Winter Storm Warning as that area is expected to
meet criteria (at least 8 inches in 24 hours). A Winter Weather
Advisory surrounds this location with several inches of
accumulation forecast. Additional headlines, particularly to
areas near/north of I-80, can't be ruled out.

By Thursday, inversion heights start to lower, and moisture
becomes less favorable. Snow showers will taper off through the
afternoon as the trough departs and high pressure approaches.
Temperatures will of course end up below normal.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Dry and cold weather will be in place Friday.

Uncertainty continues regarding the weekend system. We continued
to rely on Superblend for now. While some snow accumulation is
possible Saturday into Sunday, it still appears that the bulk of
the system, and the snow, will track to the south. The system
certainly will be monitored in the coming days.

High pressure, dry weather, and seasonable temperatures are
expected early next week.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
General VFR forecast until the frontal passage later this
evening, though periods of MVFR possible mainly along and north
of I-70. Scattered showers will continue through the early just
south of Lake Erie, with occasional lightning strikes.
Additionally, SW winds will increase this afternoon, with gusts
between 20 to 30kts possible.

More widespread shower development will occur late this
afternoon with the approach of the sfc cold front and a more
pronounced disturbance aloft. Enough instability and shear will
create potential for lightning develop for sites north of I-70,
but confidence low on terminal impact. Highlighted KFKL for VCTS
as it will have the best potential. The front will also feature
a notable pressure drop plus strong winds aloft, creating the
potential for a brief period of wind gusts between 30 to 40kts.

MVFR conditions expected behind the frontal passage, with rain
showers changing to snow while becoming more isolated and
scattered in nature. Note that more significant vis/cig
restrictions will be possible in more robust snow shower bands,
especially for locations southeast of Lake Erie.

.Outlook...
Restrictions will generally persist under cool NW flow that will
produce periods of lake enhanced snow showers over the next few
days.  Some improvements possible by the end of the week.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...Winter Weather Advisory from 4 AM Wednesday to noon EST
     Thursday for MDZ001.
     Wind Advisory until 1 AM EST Wednesday for MDZ001.
OH...None.
PA...None.
WV...Winter Weather Advisory from 4 AM Wednesday to noon EST
     Thursday for WVZ511>513.
     Wind Advisory until 1 AM EST Wednesday for WVZ512>514.
     Winter Storm Warning from 4 AM Wednesday to noon EST Thursday
     for WVZ514.

&&

Hazardous Weather Outlook
National Weather Service Pittsburgh PA
756 AM EST Tue Jan 8 2019

OHZ039>041-048>050-057>059-068-069-PAZ016-020>023-029-031-073-075-
WVZ001>004-012-021-509-091300-
Tuscarawas-Carroll-Columbiana-Coshocton-Harrison-Jefferson-Muskingum-
Guernsey-Belmont-Noble-Monroe-Beaver-Allegheny-Armstrong-Indiana-
Washington-Greene-Westmoreland-Fayette-Hancock-Brooke-Ohio-Marshall-
Wetzel-Marion-Monongalia-
756 AM EST Tue Jan 8 2019

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.

Scattered showers this afternoon could produce strong wind gusts
between 30 to 35 mph, which could cause damage to tree limbs and blow
around loose outdoor items.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

MDZ001-WVZ512>514-091300-
Garrett-Eastern Preston-Western Tucker-Eastern Tucker-
756 AM EST Tue Jan 8 2019

...WINTER STORM WATCH IN EFFECT FROM LATE TONIGHT THROUGH THURSDAY
AFTERNOON...

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 Watch.

.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 Watch.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

PAZ074-076-WVZ510-511-091300-
Westmoreland Ridges-Fayette Ridges-
Ridges of Eastern Monongalia and Northwestern Preston-Preston-
756 AM EST Tue Jan 8 2019

This Hazardous Weather Outlook is for southwest Pennsylvania and
northern West Virginia.

.DAY ONE...Today and Tonight.

Rain showers will change to snow showers tonight. Accumulations are
expected. An advisory may be needed.

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

Snow showers will continue into Thursday. Additional accumulations
are expected. An advisory may be needed.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

PAZ007>009-013>015-091300-
Mercer-Venango-Forest-Lawrence-Butler-Clarion-
756 AM EST Tue Jan 8 2019

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

.DAY ONE...Today and Tonight.

A few thunderstorms will develop late this morning into the
afternoon that could approach severe limits and produce strong to
damaging winds. In addition, wind gusts between 30 to 40mph will be
possible with a cold frontal passage tonight that could cause tree
limb damage.

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

Snow showers starting early Wednesday morning will continue into
Thursday. Additional accumulations are expected. An advisory may be
needed.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

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Special Weather Statement
National Weather Service Pittsburgh PA
420 PM EST TUE JAN 8 2019

PAZ009-015-016-082215-
Jefferson-Forest-Clarion-
420 PM EST TUE JAN 8 2019

...A STRONG THUNDERSTORM CAPABLE OF PRODUCING HAIL AND GUSTY WIND
WILL AFFECT THE AREA...

At 419 PM EST, a strong thunderstorm was located near Knox, moving
northeast at 30 mph.

Wind gusts up to 55 mph and hail up to the size of nickels are
possible with this storm.

Locations impacted include...
Clarion...                        Brookville...
Knox...                           Rimersburg...
Brockway...                       Sligo...
Strattanville...                  Limestone...
Shippenville...                   Corsica...
Callensburg...                    Sigel...

This includes  Interstate 80 in Pennsylvania between mile markers 51
and 81.

LAT...LON 4125 7874 4104 7951 4121 7961 4143 7907
      4141 7909 4134 7909 4135 7908 4136 7904
      4135 7902 4137 7897 4145 7898 4145 7900
      4147 7896 4144 7896 4144 7897 4142 7897
      4136 7896 4126 7874
TIME...MOT...LOC 2119Z 246DEG 28KT 4116 7948

07

Special Weather Statement
National Weather Service Pittsburgh PA
428 PM EST TUE JAN 8 2019

PAZ007>009-014-015-082215-
Forest-Butler-Clarion-Venango-Mercer-
428 PM EST TUE JAN 8 2019

...A LINE OF STRONG THUNDERSTORMS CAPABLE OF PRODUCING HAIL AND GUSTY
WIND WILL AFFECT THE AREA...

At 427 PM EST, radar indicated strong thunderstorms were located
along a line extending from 10 miles northwest of Sugarcreek to near
New Wilmington. Movement was east at 50 mph.

Wind gusts up to 55 mph and hail up to the size of nickels are
possible with these storms.

Locations impacted include...
Hermitage...                      Sharon...
Oil City...                       Grove City...
Franklin...                       Sharpsville...
Greenville...                     Sugarcreek...
Farrell...                        New Wilmington...
Tionesta...                       Mercer...

This includes the following highways...
  Interstate 79 in Pennsylvania between mile markers 114 and 138.
  Interstate 80 in Pennsylvania between mile markers 0 and 37.

LAT...LON 4124 7954 4112 8026 4113 8052 4149 8052
      4149 8001 4159 7985 4162 7983 4163 7930
TIME...MOT...LOC 2127Z 248DEG 43KT 4149 8006 4114 8026

07