Great Salt Lake effect
Encyclopedia
The Great Salt Lake effect is a small but detectable influence on the local climate
and weather around the Great Salt Lake
in Utah
, United States
. In particular, snowstorms are a common occurrence over the region and have major socio-economic impacts due to their significant precipitation amounts. The Great Salt lake never freezes and can warm rapidly which allows lake-effect precipitation
to occur from September through May. Lake-enhanced snowstorms are often attributed to creating what is locally known as "The Greatest Snow on Earth."
blows across a relatively warm lake
. This is common after a cold front
passage, where the winds are predominantly northwesterly and the air is much colder than the lake. When the land-lake breeze blows towards the lake, there is a convergence zone
that acts to channel the cold air over the center of the lake and further enhance precipitation. The salinity
of the Great Salt Lake prevents freezing but reduces the saturation vapor pressure and latent heat flux into the overlying air. As a result, minimal amounts of moisture and latent heat
are added to the air moving over the lake. The Great Salt Lake primarily provides a lifting mechanism and acts as an atmospheric destabilizer, which encourages convection
. This is in contrast to the Great Lakes
, where the lakes contribute significant amounts of moisture
and latent heat. The high relief of the Wasatch mountains further capitalizes on lake enhancement and can receive multiple feet of snow from lake-effect alone.
radar
system. An accurate forecast involves identifying the crucial requirements for lake-effect precipitation. The basic requirements are a conditionally unstable environment, significant moisture and a lifting mechanism. Many different variables go into these requirements. Through extensive analyses and field experiments the understanding of lake-effect snowstorms has improved drastically in recent years. Many general rules of thumb have been developed in order to predict the occurrence, location and severity of lake-effect snow.
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
and weather around the Great Salt Lake
Great Salt Lake
The Great Salt Lake, located in the northern part of the U.S. state of Utah, is the largest salt water lake in the western hemisphere, the fourth-largest terminal lake in the world. In an average year the lake covers an area of around , but the lake's size fluctuates substantially due to its...
in Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. In particular, snowstorms are a common occurrence over the region and have major socio-economic impacts due to their significant precipitation amounts. The Great Salt lake never freezes and can warm rapidly which allows lake-effect precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
to occur from September through May. Lake-enhanced snowstorms are often attributed to creating what is locally known as "The Greatest Snow on Earth."
Lake enhancement
Lake-effect snow around the Great Salt Lake is generated in a similar fashion to elsewhere in the world. For the Great Salt Lake, lake enhanced precipitation occurs when a strong, cold, northwesterly windWind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...
blows across a relatively warm lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
. This is common after a cold front
Cold front
A cold front is defined as the leading edge of a cooler mass of air, replacing a warmer mass of air.-Development of cold front:The cooler and denser air wedges under the less-dense warmer air, lifting it...
passage, where the winds are predominantly northwesterly and the air is much colder than the lake. When the land-lake breeze blows towards the lake, there is a convergence zone
Convergence zone
Convergence zone usually refers to a region in the atmosphere where two prevailing flows meet and interact, usually resulting in distinctive weather conditions....
that acts to channel the cold air over the center of the lake and further enhance precipitation. The salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
of the Great Salt Lake prevents freezing but reduces the saturation vapor pressure and latent heat flux into the overlying air. As a result, minimal amounts of moisture and latent heat
Latent heat
Latent heat is the heat released or absorbed by a chemical substance or a thermodynamic system during a process that occurs without a change in temperature. A typical example is a change of state of matter, meaning a phase transition such as the melting of ice or the boiling of water. The term was...
are added to the air moving over the lake. The Great Salt Lake primarily provides a lifting mechanism and acts as an atmospheric destabilizer, which encourages convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
. This is in contrast to the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
, where the lakes contribute significant amounts of moisture
Moisture
Humidity is the amount of moisture the air can hold before it rains. Moisture refers to the presence of a liquid, especially water, often in trace amounts...
and latent heat. The high relief of the Wasatch mountains further capitalizes on lake enhancement and can receive multiple feet of snow from lake-effect alone.
Forecasting lake-effect snow
Accurate prediction of snowstorms developing in the lee of the great Salt Lake is one of the major forecast challenges facing northern Utah. Forecasting skill has drastically improved in recent years due to a better observational network including the NEXRADNEXRAD
NEXRAD or Nexrad is a network of 159 high-resolution Doppler weather radars operated by the National Weather Service, an agency of the National Oceanic and Atmospheric Administration within the United States Department of Commerce...
radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
system. An accurate forecast involves identifying the crucial requirements for lake-effect precipitation. The basic requirements are a conditionally unstable environment, significant moisture and a lifting mechanism. Many different variables go into these requirements. Through extensive analyses and field experiments the understanding of lake-effect snowstorms has improved drastically in recent years. Many general rules of thumb have been developed in order to predict the occurrence, location and severity of lake-effect snow.
Rules of thumb
- A strong Northwesterly flow maximizes precipitation for the Salt Lake Valley.
- A minimal temperature difference of 29 °F (16 °C) {fact} between the surface and the 700 mbar (70 kPa) height is needed, but not necessarily sufficient in itself to cause lake-effect snow.
- An inversion or stable layer below 700 mbar (70 kPa) has never yielded lake-effect snow.
- Lake-effect snow can occur in concert with synoptic scale storm systems.
- A large lake-land temperature difference favors over-lake convergence.
- Lake-effect is typically initiated during the night when land-breeze convergence is favored and convection occurs predominantly over the lake.
- During the daytime lake-effect precipitation dissipates when solar heating creates scattered widespread convection over the land.
- The 700 mbar winds typically determine the geographic position of the precipitation
- Limited amounts of directional and vertical wind shear tend to produce heavier precipitation events.
- The Great Salt Lake contributes minimal amounts of moisture so that upstream moisture is a crucial variable.