Heavy snow impacted Italy and the Balkans with record...

Heavy snow impacted Italy and the Balkans with record snows on both sides of the Adriatic. 100.8” of snow fell in 18 hours. Pescocostanzo, Italy – 21 miles away – picked up 94.5”. The WMO will confirm whether the snowfall did indeed surpass the current 24 hour snowfall record (75.8” at Silver Lake, Colorado set in 1921).

Capracotta record snowfall setup

• Due to the terrain near Capracotta, this village is most susceptible to weather coming from the northeast. As noted in the upper air and surface pressure, wind, temperature, and precipitable water (PWAT) patterns attached, this event provided a near-perfect setup for heavy snow. The center of the low pressure system formed to the southwest of the area; resulting in strong northeast winds over the town. These winds channeled high PWAT air over Capracotta and temperatures continued to drop during the event.

Italy : the terrain and station location

Zoomed In Terrain Near Capracotta terrain favors upslope and funneled winds from northeast

The Pattern from the CFSRV2 Climate forecast system re-analysis version 2

• 500 hPa heights and anomalies – Deep cut-off low develops over Italy south of affected

region • Surface

– Secondary cyclone develops south of the region – Surge high PWAT air from south and east of region

• 850 hPa – Temperatures fell -4 to -6C – Strong northeasterly winds

• Jet – Strong 250 hPa jet about the close cyclone

500mb Pattern

Localized 500mb Pattern

Surface Pattern

Precipitable Water (PWAT)

250mb Winds

850mb Temps

850 U Winds

850mb V Winds

250mb U Winds

250mb V Winds

The impacts

• Pictures from the web and new outlets – Deep snow

– Channels for roads between snow banks

– Buried cars

– Snow covered ski slopes til June?

Source: meteoweb.eu

Source: meteoweb.eu

Source: meteoweb.eu

Source: meteoweb.eu

Source: meteoweb.eu

Source: meteoweb.eu

Source: ABC7 WJLA

Video – enter slide show mode and click play to view or visit https://www.youtube.com/watch?v=GjsUgauEzVs

Source: Telemolise

Video – enter slide show mode and click play to view or visit https://www.youtube.com/watch?v=9it3Sge13y0

GEFS forecasts

• Indications of potential heavy precipitation – 24 hours 25 to 75 mm – Localized in Italy and Balkans

• Pattern well predicted – 500 hPa – Winds – Cold for snow

GEFS Probability 25 mm QPF 24 hour period 6-Forecast cycles

GEFS Probability 25 mm QPF 24 hour period

GEFS mean QPF and each member 75mm or more QPF

500 hPa and anomaly forecasts 18Z 5 March

V-wind forecasts

U-wind forecasts valid 18Z 5 March

850 hPa temeperatures

GEFS forecasts

• Indicated the pattern and potential • QPF was in the general areas of heavy snowfall

– Regional area of Italy – Regional area of Balkans

• Strong 850 hPa winds well predicted – Case model QPF knew where lift was – Regional scale models likely would have focused the

QPF and refined forecasts of heavy snowfall which is beyond the skill of a global forecast system.

Snowfall map

Source: snow-forecast.com

7-day snowfall may from March 5th to March 11th, 2015

NASA imagery from 10 March 2015, showing the snowfall impact from the event.

Source: meteoweb.eu

Summary

• Record snow event for city – Possible but unlikely world record snowfall for 18

hours.

• Cut-off low for late season snow – Had several signals in the standardized anomaly

fields – Strong forcing implies some predictability