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Strong Storm System Brings Heavy Mountain Snow to the Sierra Nevada and Critical Fire Weather Conditions to the Plains

A Pacific storm system will continue to bring low elevation rain and mountain snow to much of the West through Wednesday, with heavy mountain snow expected in the higher elevations of the Sierra Nevada. This system will also bring strong winds to the Intermountain West, Rockies, and Plains, which will create Critical fire weather conditions for the High Plains. Read More >

Overview

A line of strong thunderstorms developed in parts of the Midwest during the day on Friday, and moved rapidly east through Pennsylvania. These thunderstorms produced high winds across much of the state with storm damage reported from Warren to Lancaster Counties. What produced these thunderstorms and why were they so severe?

Warm and very humid air set up residence across the state Friday, with temperatures reaching into the upper 80s and low 90s. This combined with Dewpoint Temperatures approaching 70 degrees resulted in a very unstable atmosphere. Warm and dry air aloft prevented us from seeing the popcorn thunderstorms that most of have been dealing with this spring. Instead, a cold front in the Midwest would provide the focus for thunderstorms. Tapping into the dry air aloft and a strong Low Level Jet helped these thunderstorms develop very strong downdrafts and a Rear Inflow Jet. These combined to rapidly accelerate the line of thunderstorms and resulting widespread wind damage.

Top wind speed reported at local airports:

University Park

32 MPH
Blair Co Airport 46 MPH
Bradford 44 MPH
Capitol City Airport 37 MPH
Clearfield 47 MPH
Williamsport 47 MPH
Johnstown 52 MPH
Middletown Airport 33 MPH
Thomasville 38 MPH
Selinsgrove 41 MPH
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EACH BLUE DOT REPRESENTS A WIND DAMAGE REPORT
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MAXIMUM TEMPERATURES OVER PENNSYLVANIA FOR JUNE 8TH, 2007 TWO DAY PRECIPITATION TOTALS FROM NWS COOP REPORTING STATIONS ENDING 7:00 AM JUNE 10TH, 2007
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UPPER AIR SOUNDING FROM PITTSBURGH 8:00 AM FRIDAY MORNING UPPER AIR SOUNDING FROM PITTSBURGH 2:00 PM FRIDAY AFTERNOON
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