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The Great Plains Dryline Type 1 - Diurnally-Forced Dryline Type 2 - Dynamically-Forced Dryline Type 1 - Diurnally Forced Dryline Air on upwind (upslope) side of dry line is represented by a deep mixed layer Air west of the dryline has broken the inversion and so upper level dry and warm air from the EML has mixed down The inversion breaks on its western extremity first because the inversion is closest to the surface there As the daytime surface mixed layer deepens to the inversion throughout the day, the inversion break (dryline position) works its way eastward West of the dryline, mixing of the deep EML with the shallow moist layer produces : Gusty westerly surface winds Very low humidities Warm temperatures Type 1 - Diurnally Forced Dryline (Cont'd.) Air east (downslope) of the dryline is relatively moist and cool, although there tends to be only a small virtual temperature contrast across the dryline Shallow moist boundary layer Source of moisture includes Evapotranspiration Advection from east (Gulf) Moist boundary layer reaches depth of the inversion at the point of the dryline Type 1 - Daily Evolution Late morning and afternoon: Boundary layer grows below nocturnal inversion dryline eats its way eastward Evening: Nocturnal inversion forms Moisture trapped under inversion Early morning Plants become active and transpire raising moisture under inversion Slope flow commences enhancing inversion Type 2 - Dynamically Forced Dryline Response to mountain wave drag on the tropospheric jet stream Integrates mesoscale downslope flow surges of momentum and dry air into a coherant streamwise front Results in meso-beta and meso-gamma scale gravity wave-induced bulges of dry air, momentum and nonconserved isentropic potential vorticity Severe convection focused in meso-gamma scale gravity wave-induced bulge locations