Quantitative Precipitation Forecast
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
000 FOUS11 KWBC 011953 QPFHSD PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 352 PM EDT WED APR 01 2015 VALID 00Z THU APR 02 2015 - 00Z SUN APR 05 2015 DAYS 1 TO 2... ...CENTRAL ROCKIES/HIGH PLAINS... A SHORTWAVE TROUGH IS FORECAST TO MOVE OUT OF THE NORTHERN PLAINS AND INTO THE GREAT LAKES ON THURSDAY/DAY 1...WITH ITS ASSOCIATED COLD FRONT DROPPING SOUTH INTO THE SOUTHERN PLAINS AND SOUTHERN COLORADO. MEANWHILE...AN OTHER TROUGH IS FORECAST TO MOVE EASTWARD FROM THE GREAT BASIN STATES. THE COMBINATION OF A BUILDING ANTICYCLONE TO THE NORTH BEHIND THE FRONT AND THE APPROACHING SHORTWAVE SHOULD ALLOW POST-FRONTAL UPSLOPE FLOW TO DEVELOP AS A SURFACE LOW REFORMS IN SOUTHEASTERN COLORADO AND THEN MOVES EAST NORTHEASTWARD. MODERATE TO HEAVY SNOW IS EXPECTED TO DEVELOP IN THE EXIT REGION OF AN AMPLIFYING UPPER JET AT THE BASE OF THE APPROACHING TROUGH ACROSS CENTRAL AND NORTHERN COLORADO INTO THE PLAINS OF EASTERN COLORADO. SIX TO 12 INCH SNOWS ARE POSSIBLE ALONG THE FOOTHILLS OF THE COLORADO ROCKIES WITH A LOW PROBABILITY OF LOCALLY GREATER THAN A FOOT OF SNOW. THE AMPLITUDE OF THIS SYSTEM APPEARS TO BE SLIGHTLY WEAKER AND FARTHER NORTH THAN IN PREVIOUS FORECASTS POSSIBLY RESULTING IN SLIGHTLY LOWER SNOWFALL ACCUMULATIONS THAN INDICATED YESTERDAY. A MULTI MODEL BLEND WAS USED TO GENERATE THE INITIAL DETAILS OF THE FORECAST WHILE EARLY MORNING MODEL SOLUTIONS WERE USED TO FINE TUNE THE DETAILS. DAYS 2 TO 3... ...UPPER OHIO VALLEY/LOWER GREAT LAKES/NORTHEAST... THE AFOREMENTIONED TROUGH OVER THE GREAT BASIN CONTINUES TO MOVE EASTWARD AND APPROACHES THE EAST COAST ON FRIDAY INTO EARLY SATURDAY. LOW PRESSURE MOVES FROM THE SOUTHERN PLAINS NORTHEASTWARD ACROSS THE LOWER OHIO VALLEY ACROSS THE MIDDLE ATLANTIC STATES BEFORE MOVING JUST EAST OF NEW ENGLAND BY EARLY SATURDAY. THERE IS STILL QUITE A VARIATION BETWEEN MODELS IN THIS DEVELOPING SYSTEM WITH THE INTENSITY OF THIS SYSTEM RANGING FROM RELATIVELY MODEST TO SIGNIFICANT. AS A RESULT...AS COLD AIR MOVES IN WITH THE DEVELOPING SYSTEM...RAIN CHANGING TO SNOW APPEARS TO BE QUITE POSSIBLE FROM THE UPPER OHIO VALLEY/LOWER GREAT LAKES WITH MOSTLY LIGHT AMOUNTS TO INCREASINGLY HEAVIER ACCUMULATIONS FROM NORTHWESTERN PENNSYLVANIA ACROSS WESTERN AND NORTHERN NEW YORK AND NORTHERN NEW ENGLAND. WHILE THE 12Z NAM REMAINS SLIGHTLY FARTHER EAST THAN SOME OF THE OTHER MODELS...THE 12Z GFS REMAINS NOT QUITE AS ROBUST AS THE 00Z AND 12Z ECMWF/12Z UKMET. USED A COMBINATION OF THESE MODELS AND THEIR RESPECTIVE MEANS...INCLUDING THE 9Z SREFMEAN TO COME UP WITH A COMPROMISE FORECAST WITH A MODERATE TO HIGH PROBABILITY OF 4 TO 8 INCHES OF SNOW FROM NORTHWESTERN PENNSYLVANIA NORTHEASTWARD ACROSS WESTERN AND NORTHERN NEW YORK INTO NORTHERN NEW ENGLAND. THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT. KOCIN $$

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.