RECENT STUDIES OF EXTRATROPICAL STORM SYSTEMS ASSOCIATED WITH WATER VAPOR INTRUSIONS (WVIS; ALSO REFERRED TO AS ATMOSPHERIC RIVERS) INDICATE UP TO THAT HALF OF THESE EVENTS COINCIDE WITH EXTREME PRECIPITATION (IN THE TOP 2% ACCUMULATION). IN THE HIGH-LATITUDE REGIONS WINTERTIME WVIS ARE COUPLED TO EXTREME PRECIPITATION MORE THAN HALF OF THE TIME. ADDITIONALLY REGIONAL ANALYSES OF WVIS INDICATE THAT SNOW AND MIXED-PHASE PRECIPITATION CONTAINS ON AVERAGE FOUR TIMES THE AMOUNT OF POTENTIAL ACCUMULATION WHEN COINCIDENT WITH WVIS AS COMPARED TO STORM SYSTEMS WITHOUT WVIS. THIS PROPOSAL AIMS TO CAPITALIZE ON THE ABUNDANT OBSERVATIONS AND PRODUCTS FROM THE GLOBAL PRECIPITATION MEASUREMENT (GPM) MISSION AT HIGH-LATITUDES TO STUDY A MODE OF PRECIPITATION THAT HAS SIGNIFICANT IMPLICATIONS FOR LOCAL POPULATIONS AND CLIMATE. MORE THAN FIVE SEASONS OF WINTER DATA FROM THE GMI WILL BE LEVERAGED TO ADDRESS THE FOLLOWING QUESTIONS: 1. DO EXTREME SNOW AND MIXED-PHASE EVENTS ASSOCIATED WITH WVIS CONTRIBUTE DISPROPORTIONATELY TO THE WATER CYCLE IN HIGH-LATITUDE REGIONS? 2. HOW WELL DO GPM OBSERVATIONS CHARACTERIZE THE STRUCTURE AND INTENSITY OF SNOW ASSOCIATED WITH THESE WVI-ENHANCED EXTREME EVENTS? COMPARISONS BETWEEN GPM MICROWAVE IMAGER (GMI) PRODUCTS AND HIGH-LATITUDE GROUND-BASED MEASUREMENTS DEMONSTRATE THAT GMI PROVIDES SKILL FOR QUANTIFYING HIGH-IMPACT SNOWFALL EVENTS. THIS STUDY WILL UTILIZE THE GLOBAL GMI OBSERVATIONS AT HIGH-LATITUDE TO QUANTIFY HIGH-IMPACT WVI-INFLUENCED WINTERTIME PRECIPITATION EVENTS BETWEEN MARCH 2014 AND PRESENT. GMI BRIGHTNESS TEMPERATURE SIGNATURES AND SNOW RATE PRODUCTS WILL BE USED TO CHARACTERIZE THE FREQUENCY INTENSITY AND SPATIAL STRUCTURE OF THE WVI-ENHANCED SNOW AND MIXED-PHASE PRECIPITATION. THE PROPOSED WORK WILL ADDITIONALLY CAPITALIZE ON THE ABUNDANCE OF HIGH-LATITUDE OBSERVATION FROM GMI TO EXAMINE THE TEMPORAL EVOLUTION OF THESE EXTREME EVENTS. FURTHER THIS WORK WILL LEVERAGE EXISTING GROUND-BASED INSITU AND REMOTE SENSING INSTRUMENT OBSERVATIONS LOCATED AT A HIGH-LATITUDE SITE TO EVALUATE GMI SNOW ESTIMATES IN SELECT CASES OF PRECIPITATION ASSOCIATED WITH WVIS. THESE COMPARISONS WILL PROVIDE GUIDANCE CONCERNING GPM HIGH-LATITUDE PRECIPITATION DETECTION CHARACTERISTICS AND ASSESS THE ESTIMATES OF THE FRACTION OF SNOW ACCUMULATION ASSOCIATED WITH WVIS DERIVED FROM GMI OBSERVATIONS USING GROUND-BASED MEASUREMENTS. THE PROPOSED WORK ADDRESSES SEVERAL GPM MISSION SCIENCE OBJECTIVES AND ALIGNS WITH THE PRIORITIES OUTLINED IN 2.3 METHODOLOGY DEVELOPMENT FOR IMPROVED APPLICATION OF SATELLITE DATA PRODUCTS. THE PROPOSED WORK WILL COMPOSITE THE OBSERVATIONS FROM THE GPM CORE OBSERVATORY TO SPATIALLY AND TEMPORALLY CHARACTERIZE SNOW ASSOCIATED WITH HIGH-LATITUDE WVIS AT THE GLOBAL SCALE THEREBY IMPROVING ON PAST STUDIES USING REANALYSIS. BY EXAMINING SNOW AND MIXED- PHASE PRECIPITATION COINCIDENT WITH WVIS THIS WORK WILL CHARACTERIZE SIGNIFICANT WEATHER EVENTS AND IMPROVE PREDICTIONS OF HIGH-IMPACT HAZARDS SUCH AS FLOODING. THIS WORK WILL HELP TO ADVANCE HYDROLOGICAL MODELS AND PARAMETERIZATIONS THROUGH EVALUATION OF THE INSTANTANEOUS SNOW RATES RETRIEVED FROM THE GMI AUGMENTED WITH MEASUREMENTS FROM THE FIELD SITE. IT IS IMPORTANT TO CHARACTERIZE THESE EXTREME EVENTS AS THEY CAN HAVE LARGE SOCIETAL ECONOMIC AND HYDROLOGICAL IMPACTS.