WINTER WEATHER Freezing rain –Dangerous –Costly –Potentially deadly –Special “subset” of overrunning Shallow layer of sub-freezing air along the ground
WINTER WEATHER
WINTER WEATHER … ice ice baby Ice zone …… 850 mb T’s …. -> * -1 to mb THK -> * 540 – 552dm * Depends on nature of cold air north of warm front
WINTER WEATHER Precipitation type –Depends on the thermal profile!
WINTER WEATHER FZRAFZRA PLPL SNSN RNRN
ICE PELLET SOUNDING
WINTER WEATHER FREEZING RAIN SOUNDING
WINTER WEATHER Sounding type?
WINTER WEATHER Sounding type?
WINTER WEATHER Sounding type?
“COLD AIR DAMMING” H CREST OF APPALACHIAN MOUNTAINS COLD HIGH PRESSURE SYSTEM … air circulates clockwise around the high
COLD AIR DAMMING COLD AIR DRIVEN SOUTH WARM AIR ASCENDING COLD AIR
PRECIPITATION AROUND CYCLONE: WINTER DURING COLD AIR DAMMING More places receive icy precipitation due to COLD AIR DAMMING
Special Case: Valleys of the West
FREEZING RAIN EVENTS CLIMATOLOGY
PRECIPITATION AROUND CYCLONE: WINTER DURING COLD AIR DAMMING More places receive icy precipitation due to COLD AIR DAMMING
WINTER WEATHER ICE PELLET SOUNDING
WINTER WEATHER FREEZING RAIN SOUNDING
“COLD AIR DAMMING” H COLD AIR FLOWING ALONG THE GROUND IMPACTS APPALACHIAN MOUNTAINS. The air GETS DEFLECTED SOUTHWARD ALONG EASTERN SLOPES OF MTNS. COLD AIR DAMMING CAN CAUSE SUB-FREEZING AIR TO PUSH FARTHER SOUTH ALONG THE GROUND …. CREATING a DANGEROUS RECEIPE FOR ICING (FREEZING RAIN AND SLEET) CREST OF APPALACHIAN MOUNTAINS COLD AIR DAMMING WOULD NOT EXIST WITHOUT THE MOUNTAINS COLD HIGH PRESSURE SYSTEM … air circulates clockwise around the high COLD AIR DAMMING IMPACTS AREAS ALONG EAST SLOPES OF APPALACHIANS FROM THE CAROLINAS TO NEW ENGLAND … INCLUDING EASTERN PENNSYLVANIA!!!
PRECIPITATION AROUND CYCLONE: WINTER DURING COLD AIR DAMMING - Comparing this slide to previous slide AND note how much more expansive the region of sleet and freezing rain is in the ‘overunning zone ! - Also note how the shape of the Warm front takes on a very curvy character! This is how cold air damming affects the type of precipitation that occurs in a winter storm ! More places receive icy precipitation due to COLD AIR DAMMING