SNOWSTORMS CAUSE MAJOR SOCIETAL IMPACTS SUCH AS PUBLIC SAFETY TRANSPORTATION AND COMMERCE ESPECIALLY IN THE HIGHLY POPULATED EAST COAST REGION OF THE UNITED STATES (US). MULTISCALE SNOW BANDS WITHIN THE NORTHWEST QUADRANT OF WINTER STORMS ARE THE PRIMARY FOCAL POINTS FOR THE MOST INTENSE SNOWFALL BUT ARE POORLY UNDERSTOOD AND THEREFORE DIFFICULT TO FORECAST. THE INVESTIGATION OF MICROPHYSICS AND PRECIPITATION FOR ATLANTIC COAST-THREATENING SNOWSTORMS (IMPACTS) COMPRISES A SET OF AIRCRAFT AND PAYLOADS IDEALLY-SUITED TO THE STUDY OF EASTERN US SNOWSTORMS. USING DATA FROM A "SATELLITE-SIMULATING" ER-2 AIRCRAFT AND IN-SITU MEASUREMENTS FROM A CLOUDPENETRATING P-3 AIRCRAFT IMPACTS WILL PROVIDE IMPORTANT OBSERVATIONS AND RESEARCH FOR UNDERSTANDING THE MECHANISMS OF SNOW BAND FORMATION AND EVOLUTION WITHIN WINTER STORMS WILL PROVIDE OBSERVATIONS THAT WILL ENABLE FUTURE IMPROVEMENTS TO THE MEASUREMENT OF SNOWFALL FROM SPACE AND WILL PROVIDE IMPORTANT DATA FOR THE VALIDATION AND IMPROVEMENT OF NUMERICAL MODELS. THE IMPACTS SCIENCE OBJECTIVES ARE TO: (1) CHARACTERIZE THE SPATIAL AND TEMPORAL SCALES AND STRUCTURES OF SNOWBANDS IN NORTHEAST US WINTER STORMS; (2) UNDERSTAND THE DYNAMICAL THERMODYNAMICAL AND MICROPHYSICAL PROCESSES THAT PRODUCE THE OBSERVED STRUCTURES; (3) APPLY THIS UNDERSTANDING OF THE STRUCTURES AND UNDERLYING PROCESSES TO IMPROVE REMOTE SENSING AND MODELING OF SNOWFALL. IMPACTS INSTRUMENT SUITE INCLUDES MULTIPLE FREQUENCY RADAR (W KA KU AND X BANDS) PASSIVE MICROWAVE (10-183 GHZ) AND LIDAR ON THE ER-2 AND IN-SITU CLOUD MICROPHYSICS ATMOSPHERIC STATE PARAMETERS AND DROPSONDE ON THE P-3. AIRCRAFT DATA WILL BE COMBINED WITH GROUND-BASED RAWINSONDES AND OPERATIONAL RADARS RESEARCH RADARS SATELLITE DATA AND MODEL-DERIVED ANALYSES AND SIMULATIONS TO ACHIEVE THE MISSION SCIENCE OBJECTIVES. IMPACTS ADDRESSES THE NASA EARTH SCIENCE ENTERPRISE SCIENCE GOAL TO STUDY EARTH TO ADVANCE SCIENTIFIC UNDERSTANDING AND MEET SOCIETAL NEEDS AND THE NASA WEATHER FOCUS AREA'S RESEARCH OBJECTIVE TO "ENABLE IMPROVED PREDICTIVE CAPABILITY FOR WEATHER AND EXTREME WEATHER EVENTS." IMPACTS IS ALSO RELEVANT TO THE NATIONAL ACADEMIES RECOMMENDATION FOR A DESIGNATED PROGRAM FOCUSED ON CLOUDS CONVECTION AND PRECIPITATION. PROJECT START IS JANUARY 1 2019 WITH A DURATION OF FIVE YEARS. THE REGION OF FOCUS IS THE US NORTHEAST INCLUDING THE IMMEDIATE OFFSHORE AREA AND A SECONDARY REGION IN THE MIDWEST DEPENDING ON WHERE SNOWSTORMS ARE OCCURRING. MEASUREMENTS WILL BE COLLECTED DURING THREE 6-WEEKS DEPLOYMENTS EACH FROM MID-JANUARY THROUGH FEBRUARY 2020-2022 IN ORDER TO BEST MATCH THE CLIMATOLOGY OF SNOWSTORMS IN THE US NORTHEAST AND MIDWEST.