MASA ["May-sah"] E-mail list/Webpage/Newsletter/BBS
Promoting severe weather Identification, Evaluation, & Reporting.
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WX-Talk, WX-Chase, Skywarn www.execpc.com/~svoros
Although the Storm Prediction Center
(SPC) has a moderate Risk for severe
weather in the deep south, and has
issued a Public Severe Weather Outlook,
the plains and some portions of the
midwest are experiencing their first
taste of Old Man winter, thus its time
for some of us to refresh our memories:
=20
FALL/WINTER WEATHER TERMS
Advisory Terminology
The following advisories will be used to ALERT the public of
situations that may cause some inconvenience or difficulty to
travelers or people who must be outdoors.
BLOWING/DRIFTING SNOW ADVISORY=20
Used when wind-driven snow intermittently reduces visibility
to 1/4 mile or less. Travel may be hampered. Strong winds
create blowing snow by picking up old or new snow.
FREEZING RAIN or FREEZING DRIZZLE ADVISORY
Generally used only during times when the intensity of freezing
rain or drizzle is light and ice accumulations are less than 1/4
inch.
LAKE SNOW ADVISORY
Issued when lake-effect snow squalls are expected to accumulate
to 3 to 6 inches in 12 hours over the southern Great Lakes region
and up to 8 inches in 12 hours over the northern Great Lakes
region.
SHORT TERM FORECAST (NOWCAST)
A short-term forecast designed to give specific, detailed
forecast information for the next 1 to 6 hours on a county basis.
Non-severe, advisory, and warning information is contained in
these forecasts which are routinely issued several times
per day, and more often in some events.
SLEET ADVISORY
Issued for expected sleet accumulations of less than =AB inch.
SNOW ADVISORY
Used when a snowfall generally exceeds 2 inches but is not
expected to accumulate 6 inches or more in a 12 hour period. May
be used for 1 or 2 inch snowfalls if occurring at the beginning
of the snow season or after a prolonged period between snow
events. Some mountain locations have snow advisories issued for
4 to 7 inch accumulations in 12 hours.
SEVERE WEATHER STATEMENT
Issued when the forecaster wants to follow up a blizzard warning
with important information on the progress of the blizzard.
SPECIAL WEATHER STATEMENT
Issued when the forecaster wants to pass information on to the
public about widespread, developing or approaching weather that
is not expected to be severe, but nonetheless is significant.
WINTER WEATHER ADVISORY
Used when a mixture of precipitation is expected such as snow,
sleet and freezing rain or freezing drizzle.
****** Warning Terminology
The following terms WARN the public of more serious winter
weather situations that may cause impossible traveling conditions
and could pose a threat to life and property.
BLIZZARD WARNING/ GROUND BLIZZARD WARNING
Issued for winter storms with sustained winds or frequent gusts
to 35 miles per hour or greater and considerable falling snow
(Blizzard Warning) and/or blowing snow reducing visibility to
less than 1/4 mile. If there is only blowing /drifting snow
occurring, then it is called a Ground Blizzard Warning. These
conditions are expected to last at least 3 hours.
HEAVY SNOW WARNING
Issued for snowfalls of 6 inches or more in 12 hours or less; or
8 inches or more in 24 hours or less (lesser amounts early or
late in the season). Light winds (less than 10 mph) generally
accompany these situations, with the primary hazard being heavy
snow. Some mountainous regions have thresholds of 8 inches or
more in 12 hours, or 10 or more inches in 24 hours. Some areas of
the country have lower threshold values, such as 4 inches or more
in 12 hours, or 6 inches in 24 hours, such as in southern Ohio,
Kentucky, etc.
ICE STORM WARNING
Issued when damaging ice accumulations are expected during
freezing rain situations; walking and driving becoming extremely
dangerous. Ice accumulations are usually 1/4 inch or greater.
LAKE SNOW WARNING
Issued when accumulations of lake-effect snow squalls is expected
to be 6 inches or more in 12 hours, or 8 inches in 24 hours in
the southern Great Lakes region; and 8 inches in 12 hours or 10
inches in 24 hours over the northern Great Lakes region.
SEVERE WEATHER STATEMENT
Issued when the forecaster wants to follow up a blizzard warning
with important information on the progress of the blizzard.
SHORT TERM FORECAST (NOWCAST)
A short-term forecast designed to give specific, detailed
forecast information for the next 1 to 6 hours on a county basis.
Non-severe, advisory, and warning information is contained in
these forecasts which are routinely issued several times per day,
and more often during busy weather periods.
SLEET WARNING=20
Issued when accumulations of sleet covering the ground to a depth
of =AB inch or more are expected. This is a relatively rare event.
SPECIAL WEATHER STATEMENT
Issued when the forecaster wants to pass information to the
public about widespread, developing or approaching weather that
is not expected to be severe, but nonetheless is significant.
WINTER STORM WATCH=20
Issued when conditions are favorable for the development of
hazardous weather elements such as heavy snow and/or blizzard
conditions, or significant accumulations of freezing rain or
sleet. These conditions may occur singly, or in combination with
others. Watches are usually issued 24 to 48 hours in advance of
the event(s).
WINTER STORM WARNING=20
Issued when hazardous winter weather conditions are imminent or
very likely, including any occurrence or combination of heavy
snow, wind- driven snow, sleet and/or freezing rain/drizzle.
Winter Storm Warnings are usually issued for up to a 12 hour
duration, but can be extended out to 24 hours. The term
"near-blizzard" may be incorporated into the "winter storm
warning" for serious situations which fall just short of official
blizzard conditions.
***** Non-preciptation Weather Terms
The following advisory terms are used to ALERT the public of
weather situations that are not necessarily associated with
precipitation, but need to be highlighted. The warning terms are
used to WARN the public of non-precipitation events that could be
a threat to life and/or property.
FROST ADVISORY
Issued in growing season to indicate formation of widespread
frost. Overnight lows in the 30s will usually result in
widespread frost, especially in the lower to middle 30s with
light winds.
WIND ADVISORY (also LAKE WIND ADVSRY)
Issued when sustained winds of 30 mph or greater are expected to
last for 1 hour or more, or for gusts of 45 to 57 mph for any
duration. Lake Wind Advisories are issued for area lakes in
some of the Northern Plains states when sustained winds of 30 mph
or more are expected.
WIND CHILL ADVISORY
Issued for wind chills of 35 below zero (F.) or colder for a
sustained period of time. Winds are expected to be at least 10
mph. Threshold values will be "warmer" in more southern
latitudes.
HIGH WIND WARNING
Sustained winds of 40 mph or greater are expected to last for 1
hour or longer. Also issued if winds of 58 mph or more are
anticipated for any duration. Some mountain locations have
threshold values of 50 mph sustained for 1 hour or more, and any
duration gust to 70 mph or more.
FREEZE WARNING
Used during the growing season when temperatures at/near the
ground are expected to drop well below freezing (32 Degrees F.)
over a widespread area for a significant amount of time,
regardless of whether frost forms or not.
WIND CHILL WARNING
Issued when wind chill values are expected to reach 50 below zero
or lower (upper Midwest, Northern Plains, some mountain areas)
along with wind speeds below 10 mph. Other locations in the
eastern or southern parts of the U.S. have a warning threshold of
35 below zero, or perhaps even "warmer."
END OF FEED FROM THE MILWAUKEE AREA SKYWARN ASSOCIATION, INC. =20