Snow & Ice Threats:

Winter Storm Watches are issued at longer ranges when confidence is lower in meeting the warning criteria. Warnings and advisories are issued when confidence is high that widespread accumulations will meet these criteria.

Winter Storm Warning (Heavy Snow) threshold map

(5 or 6 inches depending on location)

When the threat is predominantly snow or a mix of snow and sleet.

Ice Storm Warning threshold map

(0.25 inch or 0.50 inch depending on location)

When the threat is predominantly Freezing Rain (Ice)

Winter Weather Advisory threshold map

(2 or 3 inches depending on location)

When the threat is predominantly snow or a mix of snow and sleet.

Freezing Rain Advisory threshold map

When the threat is predominantly Freezing Rain (Ice) = Trace 

These counties have a special designation so that we can word statements to better specify the threats posed by lake effect snow: rapid changes in snow intensity/visibility, and the potential for narrowly focused high snow accumulations.  

Lake effect Snow Counties (map)

Sustained or frequent gusts to 35 mph or greater and considerable falling and/or blowing snow. These conditions must last for at least 3 hrs. Usually associated with snow accumulations of 6+" in Central PA.

Blizzard Warning threshold map

Extreme Heat Warning:

  Heat Index values will attain or exceed 105°F.

Extreme Heat Watch:

  Possibility that Extreme Heat Warning Criteria may be met at longer ranges (12 to 48 hours out).

Extreme Heat Warning threshold map

Heat Advisory:

  Heat Index will be equal to or greater than 100°F, but less than 105°F.

Heat Advisory threshold map

Extreme Cold Warning 

  Values of -20 F or colder along and south of I-80, and -25 F or colder for areas north of I-80

Extreme Cold Warning threshold map

Cold Weather Advisory

  Values of -10 F or colder along and south of I-80, and -15 F or colder for areas north of I-80

Cold Weather Advisory threshold map

High Wind Warning 

  Sustained winds 40 mph or greater, for better than 1 hour - and/or wind gusts 58 mph or greater, for any duration.

High Wind Watch

  Possibility that High Wind Warning Criteria may be met at longer ranges (24 to 48 hrs out).

High Wind Warning/Watch Map

Wind Advisory

  Sustained winds 31 to 39 mph, for better than 1 hour - and/or wind gusts 46 to 57 mph for any duration.

Wind Advisory Map

Dates we issue frost/freeze products

We will issue Frost Advisories and Freeze Warnings between the dates on first map below and the actual first freeze of that autumn (second map below). Caveat: During abnormally warm early spring seasons, we may begin to issue frost and freeze products earlier than specified on the map on the left. 

As you might expect, the growing season is much shorter in the Northern Mountains than in the Lower Susquehanna Valley.

Frost Advisory

  A widespread frost, which typically occur with mainly clear skies and light winds, and low temperatures near or slightly above freezing (33°F to 36°F).

Freeze Warning 

  Low temperatures across the whole county/zone at or below 32°F.

Freeze Watch 

  Possibility that Freeze Warning Criteria may be met at longer ranges (24 to 48 hrs out).

The BEGINNING of the "growing season" is set by the average date of the last freeze in Spring, and normally happens during very late April to mid May in Central PA.

See a map of the Median Date of the Last Freeze in Spring

The END of the "growing season" occurs when most of the county/NWS zone has had it's first freeze in the autumn (1/2 or more of the zone has reached 32°F or below) which usually occurs in October in Central PA. This map for context of when the first freeze usually occurs.

Median Date of the First Autumn Freeze

Dense Fog Advisory

  Widespread areas of fog reducing the visibility to 1/4 mile or less.

Dense Fog Advisory threshold map

We rely heavily and constantly consult with regional fire managers from the PA DCNR and Allegheny National Forest while making fire weather warning decisions. 

• Winds must be sustained at 20 mph (17 knots) for two hours or more, and
• Minimum Relative Humidity (which usually occur in the afternoon) must be 30 percent or less, and
• 10-hour Fuel Moistures must be 10 percent or less (and expected to remain there for two or more days).

Fire Weather Watch

  All three of the above criteria are expected to develop simultaneously within 12-24 hours.

Red Flag Warning

  All three of the above criteria are being met currently, or are imminent.

  When conditions are expected to be near Red Flag Warning criteria, the office may issue a Special Weather Statement under the header "PHLSPSCTP (WWUS81 KCTP) explaining the conditions.