{"id":1588,"date":"2022-07-10T11:17:51","date_gmt":"2024-07-10T11:16:51","guid":{"rendered":"http:\/\/ialert.com\/blog\/?p=1588"},"modified":"2026-04-28T01:55:43","modified_gmt":"2026-04-28T01:55:43","slug":"glossary-of-weather-terms-beginning-with-l","status":"publish","type":"post","link":"https:\/\/ialert.com\/blog\/weather-articles\/weather-glossary\/glossary-of-weather-terms-beginning-with-l\/","title":{"rendered":"Glossary of Weather Terms – Beginning with “L”"},"content":{"rendered":"

Wondering what is lake effect snow<\/strong>, when the NWS issues a lake effect snow warning<\/strong>, or what La Nina does to winter weather<\/strong>? Trying to understand lightning safety tips<\/strong> or how a low pressure system<\/strong> drives storms?<\/p>\n

Jump to weather terms beginning with the letter:<\/h3>\n

A<\/a> | B<\/a> | C<\/a> | D<\/a> | E<\/a> | F<\/a> | G<\/a> | H<\/a> | I<\/a> | J<\/a> | K<\/a> | L<\/a> | M<\/a> | N<\/a> | O<\/a> | P<\/a> | Q<\/a> | R<\/a> | S<\/a> | T<\/a> | U<\/a> | V<\/a> | W<\/a> | X<\/a> | Y<\/a> | Z<\/a><\/p>\n

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Weather Terms Beginning with “L”<\/strong><\/h3>\n

La Nina<\/strong><\/h4>\n

La Nina is the cooling phase of the ENSO climate cycle in the tropical Pacific that typically produces cooler, snowier winters in the northern US and drier, warmer conditions in the Southwest and Southeast, and enhances Atlantic hurricane activity. La Nina winters often deliver significant snow to the Upper Midwest, Great Lakes, and northern Plains. See the full La Nina definition under “E” (ENSO) for a complete explanation of the El Nino\/La Nina cycle and its global impacts.<\/p>\n

Lake Effect Snow<\/strong><\/h4>\n

Lake effect snow is heavy, localized snowfall produced when cold Arctic air flows over the relatively warm open waters of the Great Lakes (or other large inland bodies of water). The cold air picks up heat and moisture from the lake surface and produces convective snow bands that can deliver 2-5 inches per hour and 12-40 inches of snow in a single event. Lake effect snow is most intense downwind of the Great Lakes, Buffalo, NY is the most famous example, and occurs primarily from November through January before lake surfaces freeze. The bands are so isolated and intense that one side of a highway can have 2 inches of snow while the other has 2 feet.<\/p>\n

Lake Effect Snow Warning<\/strong><\/h4>\n

A Lake Effect Snow Warning is issued by the NWS when lake effect snow is expected to produce snowfall rates of 2 or more inches per hour or total accumulations of 8 or more inches (thresholds vary by NWS office). Residents in lake effect snow zones should keep emergency supplies in vehicles, allow extra travel time, and be prepared for rapidly deteriorating visibility. A Lake Effect Snow Advisory is issued for less intense events (4-7 inches). Lake Effect Snow Watches are issued 12-48 hours ahead when heavy lake effect snow is possible.<\/p>\n\n\n\n\n\n\n\n\n\n\n
Feature<\/th>\nLake Effect Snow Warning<\/th>\nWinter Storm Warning<\/th>\nBlizzard Warning<\/th>\n<\/tr>\n<\/thead>\n
Snow source<\/td>\nCold air over warm Great Lake waters<\/td>\nLarge-scale synoptic storm<\/td>\nLarge storm or existing snow with strong winds<\/td>\n<\/tr>\n
Area affected<\/td>\nNarrow band (10-30 miles wide)<\/td>\nLarge regional area<\/td>\nLarge regional area<\/td>\n<\/tr>\n
Typical accumulation<\/td>\n8-24+ inches in the band<\/td>\n6-12+ inches<\/td>\nVariable (can be less snow but high wind)<\/td>\n<\/tr>\n
Snowfall rate<\/td>\n2-5 in\/hour possible<\/td>\n1-2 in\/hour typical<\/td>\nVariable; drifting more important<\/td>\n<\/tr>\n
Visibility<\/td>\nNear zero in the band<\/td>\nReduced<\/td>\nUnder 1\/4 mile for 3+ hours<\/td>\n<\/tr>\n
Duration<\/td>\n12-72 hours<\/td>\n12-48 hours<\/td>\n3+ hours of blizzard conditions<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Land Breeze<\/strong><\/h4>\n

A land breeze is a local wind that blows from land toward the sea at night, when the land cools faster than the adjacent water surface. The cooler, denser air over land flows toward the warmer, lower-pressure air over the water. Land breezes are typically light (5-10 mph) and occur in coastal areas, the nighttime counterpart of the sea breeze, which blows from sea to land during the day due to daytime differential heating. Land and sea breezes can influence local thunderstorm development along coastlines.<\/p>\n

Lapse Rate<\/strong><\/h4>\n

The lapse rate is the rate at which air temperature decreases with increasing altitude. The standard atmospheric lapse rate is approximately 3.5 degrees F per 1,000 feet (6.5 degrees C per km). The dry adiabatic lapse rate (DALR) is 5.5 degrees F per 1,000 feet for unsaturated rising air; the saturated adiabatic lapse rate (SALR) is 2.5-3 degrees F per 1,000 feet for rising saturated (cloudy) air due to the release of latent heat. When the environmental lapse rate exceeds the DALR, the atmosphere is absolutely unstable and thunderstorm development can be explosive. Meteorologists analyze lapse rates from radiosonde data to forecast convective potential.<\/p>\n

Latent Heat<\/strong><\/h4>\n

Latent heat is the energy absorbed or released during a phase change, from solid to liquid to gas or vice versa, without a change in temperature. When water evaporates, it absorbs latent heat, cooling the surface. When water vapor condenses into cloud droplets, it releases latent heat into the surrounding air, warming it and fueling cloud and storm development. Latent heat release is the primary energy source for tropical cyclones, lake effect snow, and convective storms. The high latent heat of water is why hurricanes can be so powerful and why wet conditions feel colder than dry conditions at the same temperature.<\/p>\n

Lee Side (Leeward)<\/strong><\/h4>\n

The lee side is the downwind side of a mountain range or obstacle, sheltered from the prevailing wind. The lee side typically experiences dry, warm conditions due to orographic effects, as air rises over the windward side and drops its moisture through precipitation, it descends on the lee side and warms adiabatically (the chinook effect). Rain shadows develop on the lee side of mountain ranges. The eastern slopes of the Cascades, the dry Great Basin, and the eastern side of the Rockies are all in the lee of their respective mountain ranges. Severe thunderstorms often develop along lee troughs across the Plains.<\/p>\n

Lightning<\/strong><\/h4>\n

Lightning is an electrical discharge between oppositely charged regions within a thunderstorm (cloud-to-cloud or intracloud lightning) or between the thunderstorm and the ground (cloud-to-ground lightning). Cloud-to-ground lightning is the most dangerous to people and property. The return stroke, the visible lightning bolt we see, travels upward from ground to cloud at roughly one-third the speed of light. Lightning temperatures can reach 50,000 degrees F, five times hotter than the sun’s surface. Thunder is produced by the rapid expansion of superheated air along the lightning channel. The “30\/30 rule”: if thunder occurs within 30 seconds of a lightning flash, seek shelter immediately; wait 30 minutes after the last thunder before going back outside. Read more: Lightning Safety<\/a> and Lightning Myths<\/a>.<\/p>\n

Lightning and Thunderstorm Safety<\/strong><\/h4>\n

The NWS does not issue separate “Lightning Warnings”, lightning hazard is implied in any Severe Thunderstorm Warning or Tornado Warning. The NWS does issue Special Weather Statements for approaching thunderstorms with frequent lightning. Lightning kills an average of 20-40 people in the US annually. Most deaths occur in open fields, under trees, and on or near water. The safest location during a thunderstorm is a substantial building or a hard-topped metal vehicle. Avoid tall isolated trees, open fields, hilltops, and bodies of water during any thunderstorm activity.<\/p>\n

Local Storm Report (LSR)<\/strong><\/h4>\n

A Local Storm Report is an NWS product issued to record observed severe weather events including tornadoes, hail, damaging winds, and flooding. LSRs are generated from reports submitted by storm spotters, emergency managers, law enforcement, the public, and automated sensors. They appear as icons on weather.gov maps and are used to verify warnings, document storm damage, and improve future forecasts. Trained Skywarn storm spotters are the primary source of reliable ground truth for NWS warning operations, and submitting accurate LSRs is one of the most valuable contributions a spotter makes.<\/p>\n

Low Pressure System (Cyclone)<\/strong><\/h4>\n

A low pressure system is an area of the atmosphere where atmospheric pressure is lower than the surrounding environment. Air flows counterclockwise (in the Northern Hemisphere) into the low center and rises, producing clouds, precipitation, and storm activity. The strength of a low is measured by its central pressure, deep lows (under 970 mb) produce the most severe weather. When a low’s central pressure drops more than 24 mb in 24 hours, a process called “explosive cyclogenesis” or “bombing out”, hurricane-force winds can develop in non-tropical storms. Low pressure systems are steered by the jet stream and are responsible for most of the significant weather in the continental US.<\/p>\n

Lifted Index (LI)<\/strong><\/h4>\n

The Lifted Index is a measure of atmospheric instability calculated by comparing the temperature of a hypothetically lifted air parcel to the actual air temperature at 500 mb (approximately 18,000 feet). Positive LI values indicate stable conditions. Values of 0 to -2 indicate marginally unstable conditions (thunderstorms possible). Values of -3 to -5 indicate moderate instability (severe thunderstorms possible). Values below -6 indicate extreme instability where violent tornadoes are possible if other ingredients are present. The Lifted Index is used alongside CAPE to assess daily severe weather potential across the country.<\/p>\n

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Frequently Asked Questions, “L” Weather Terms<\/strong><\/h3>\n

What is lake effect snow and where does it occur?<\/h4>\n

Lake effect snow forms when cold Arctic air flows over the warm open waters of the Great Lakes, picking up heat and moisture that then rises and produces intense snow bands downwind. The Great Lakes stay open until late December or January, making October through January the primary lake effect snow season. The heaviest impacts occur in narrow bands, typically 10-30 miles wide, downwind of the lakes. Buffalo, New York (downwind of Lake Erie and Lake Ontario) is the most famous lake effect snow city, but communities downwind of all five Great Lakes are affected. Individual events can dump 12-40 inches of snow in 24-48 hours.<\/p>\n

When does the NWS issue a Lake Effect Snow Warning?<\/h4>\n

A Lake Effect Snow Warning is issued when lake effect snow is expected to produce snowfall rates of 2 or more inches per hour or total accumulations of 8 or more inches (thresholds vary slightly by NWS office). A Lake Effect Snow Advisory is issued for lighter events of 4-7 inches. Residents in lake effect snow zones should keep emergency supplies in vehicles, allow significantly extra travel time, and be aware that conditions can change from clear to near-zero visibility in minutes as you enter the snow band. The bands are highly localized, one side of a road may be clear while the other is in a white-out.<\/p>\n

What is lightning and how dangerous is it?<\/h4>\n

Lightning is a massive electrical discharge produced by charge separation in thunderstorms. The return stroke, the visible bolt, heats the air to 50,000 degrees F (five times hotter than the sun’s surface) in a fraction of a second. The rapid expansion of that superheated air creates the shockwave we hear as thunder. Lightning kills an average of 20-40 people in the US annually and injures hundreds more. The safest locations during a thunderstorm are a substantial building or a hard-topped vehicle. Avoid trees, open fields, hilltops, and bodies of water. The 30-30 rule: if thunder arrives within 30 seconds of a lightning flash, seek shelter and wait 30 minutes after the last clap of thunder before going back outside.<\/p>\n

What is a low pressure system?<\/h4>\n

A low pressure system is an area where atmospheric pressure is lower than its surroundings. Air flows counterclockwise into the center of a low (in the Northern Hemisphere) and rises, cooling and producing clouds and precipitation. Low pressure systems are responsible for most of the significant weather events in the US, from nor’easters and Plains blizzards to tornado-producing supercell outbreaks. The lower the central pressure, the stronger the storm. When a low’s central pressure drops more than 24 millibars in 24 hours, a process called explosive cyclogenesis or “bombing out”, hurricane-force winds can develop even without tropical origins.<\/p>\n

What is the lapse rate in meteorology?<\/h4>\n

The lapse rate is the rate at which temperature decreases with increasing altitude. The standard atmosphere lapse rate is about 3.5 degrees F per 1,000 feet. When the actual lapse rate in a layer of air exceeds the dry adiabatic lapse rate (5.5 degrees F per 1,000 feet), that layer is absolutely unstable and any rising air parcel will accelerate upward, producing explosive thunderstorm development. Meteorologists analyze lapse rates from weather balloon data to determine whether the atmosphere is stable, conditionally unstable, or absolutely unstable, which is one of the most important factors in forecasting severe weather.<\/p>\n

What is latent heat and why is it important in weather?<\/h4>\n

Latent heat is the energy absorbed or released during phase changes of water, evaporation, condensation, freezing, and melting. When water vapor condenses into cloud droplets, it releases latent heat into the surrounding air, warming it and causing it to continue rising. This is the primary fuel source for thunderstorms, hurricanes, and lake effect snow. Tropical cyclones are essentially heat engines driven by latent heat released as warm ocean moisture condenses into the eyewall’s thunderstorms. The higher the sea surface temperature, the more latent heat is available, and the more intense a hurricane can potentially become.<\/p>\n

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