The Great Salt Lake effect is a small but detectable influence on the local

climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...

and weather around the Great Salt Lake in

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

. In particular,

snowstorms A winter storm is an event in which wind coincides with varieties of precipitation that only occur at freezing temperatures, such as snow, mixed snow and rain, or freezing rain. In temperate continental climates, these storms are not necessar ...

are a common occurrence over the region and have major

socio-economic Socioeconomics (also known as social economics) is the social science that studies how economic activity affects and is shaped by social processes. In general it analyzes how modern societies progress, stagnate, or regress because of their local ...

impacts due to their significant precipitation amounts. The Great Salt lake almost never freezes and can warm rapidly, which allows lake enhanced 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. However, the Great Salt Lake primarily provides a lifting mechanism and acts as an atmospheric destabilizer, which encourages

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the conve ...

. This is in contrast to the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lak ...

, where the lakes contribute significant amounts of

moisture Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some commercial products. Moisture also refers to the amount of water vapo ...

and latent heat. Great Salt Lake enhanced precipitation occurs when a strong, cold, northwesterly

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ho ...

blows across a relatively warm

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...

. This is common after a

cold front A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough of low pressure. It often forms behind an extratropical cyclone (to the west in the Northern ...

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 A convergence zone in meteorology is a region in the atmosphere where two prevailing flows meet and interact, usually resulting in distinctive weather conditions. This causes a mass accumulation that eventually leads to a vertical movement a ...

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 Vapor pressure (or vapour pressure in English-speaking countries other than the US; see spelling differences) or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phase ...

and

latent heat flux Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process — usually a first-order phase transition. Latent heat can be underst ...

into the overlying air. As a result, minimal amounts of moisture and

latent heat Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process — usually a first-order phase transition. Latent heat can be underst ...

are added to the air moving over the lake. The high relief of the Wasatch mountains further capitalizes on lake enhancement and can receive multiple feet of snow from lake-effect alone.

Climatology

The number of events varies considerably from year to year, according to the synoptic set-up. The average is 4 to 5 well-defined events annually and the same number of marginal events. Slightly more than half of the well-defined events persist for 13 to 24 hours. In a 2000 study, researchers found that the larger number of cases were between October and February, with outlier cases in September and April or May. However a review of many more cases in 2012 found that the peaks of activity was really in the fall (mid-October to mid-December) and spring (early April) and that there was a minimum between those maximum. That same study found on average 13 events per year, well or not so well defined combined. Most well-defined events leave accumulations of or more, and in some cases more than , along a well-defined corridor.

Forecasting lake-effect snow

Forecasting skill has drastically improved in recent years due to a better observational network including the

NEXRAD NEXRAD or Nexrad (Next-Generation Radar) is a network of 160 high-resolution S-band Doppler weather radars operated by the National Weather Service (NWS), an agency of the National Oceanic and Atmospheric Administration (NOAA) within the United S ...

weather radar Weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly pulse- ...

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, which results in a minute-by-minute event. 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 set of rules has been developed by local forecasters to predict the development of lake enhanced snow: *A strong Northwesterly flow maximizes precipitation for the Salt Lake Valley. *A minimal temperature difference of 29 °F (16 °C) between the surface and the height is needed, but not necessarily sufficient in itself to cause lake-effect snow. *An inversion or stable layer below 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.

References

{{Reflist, 33em Climate of the Rocky Mountains Natural history of Utah Snow or ice weather phenomena Great Salt Lake Features of the Uinta Mountains Wasatch Range

Lake enhancement

Climatology

Forecasting lake-effect snow

Rules of thumb

See also

References