Quantitative Precipitation Forecast
Issued by NWS

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000 FOUS11 KWBC 230912 QPFHSD PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 511 AM EDT SUN APR 23 2017 VALID 12Z SUN APR 23 2017 - 12Z WED APR 26 2017 ...PACIFIC NORTHWEST/NORTHERN AND CENTRAL ROCKIES... SHOWERS ARE FORECAST BECOME MORE NUMEROUS ACROSS THE REGION BY EARLY SUN AS A SHORTWAVE RIDGE GIVES WAY TO A SERIES OF PROGRESSIVE SHORTWAVE TROUGHS THAT ARE EXPECTED TO CARVE OUT A BROAD UPPER TROUGH THAT WILL EXTEND ACROSS THE WESTERN U.S. EXPECT SNOW SHOWERS TO DEVELOP ALONG THE NORTHERN TO CENTRAL CASCADES AND PORTIONS OF THE NORTHERN ROCKIES FROM CENTRAL ID TO NORTHWESTERN WY ON SUN. BUT WITH SNOW LEVELS EXPECTED TO BE FAIRLY HIGH...WIDESPREAD HEAVY ACCUMULATIONS ARE NOT EXPECTED THROUGH EARLY MON. SHOWERS ARE EXPECTED TO CONTINUE ACROSS PACIFIC NORTHWEST AND NORTHERN ROCKIES INTO EARLY TUE WHILE EXTENDING SOUTH INTO THE CENTRAL ROCKIES WITH THE ARRIVAL OF A SECOND...MORE ROBUST SHORTWAVE. AMPLE MOISTURE AND LOWER SNOW LEVELS ARE EXPECTED TO RAISE THE POTENTIAL FOR HEAVIER SNOW ACCUMULATIONS ACROSS PORTIONS OF THE CASCADES AND NORTHERN ROCKIES. A MID LEVEL WAVE DEVELOPING OVER WY MON NIGHT IS EXPECTED TO HELP ACCENTUATE THE LOW LEVEL INFLOW/UPSLOPE FLOW INTO THE SOUTHWESTERN MT...NORTHWESTERN AND CENTRAL WY RANGES...RAISING THE THREAT FOR LOCALLY HIGH ELEVATION SNOWS THERE AS WELL TUE NIGHT INTO WED. ON TUE MODELS SHOW THE TROUGH BEGINNING TO AMPLIFY AND SHIFT EAST INTO THE PLAINS...WITH SHOWERS DIMINISHING FROM NORTH TO SOUTH ACROSS MUCH OF WY INTO CO BY EARLY WED. FURTHER NORTHWEST...SNOW SHOWERS ARE EXPECTED TO CONTINUE ACROSS THE MOUNTAINS AS A SERIES OF SHORTWAVES EMBEDDED WITHING BROADLY DIFFLUENT ALOFT CONTINUE TO INFLUENCE THE REGION. THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT. ...NORTHERN NORTH DAKOTA/MINNESOTA... THE COLD FRONT CURRENTLY SAGGING SOUTH ACROSS THE UPPER MIDWEST AND NORTHERN PLAINS IS EXPECTED TO LINGER ACROSS THE REGION INTO EARLY MON...BEFORE LIFTING BACK TO THE NORTH AHEAD OF A DEVELOPING LOW ASSOCIATED WITH ONE OF THE PREVIOUSLY NOTED SHORTWAVES MOVING ACROSS THE WEST. SOME LIGHT SNOW ACCUMULATIONS ARE POSSIBLE ACROSS FAR NORTHERN MN BEFORE PRECIPITATION LIKELY CHANGES OVER TO RAIN ON MON. SOME LIGHT SNOW ACCUMULATIONS ARE ALSO POSSIBLE ON THE BACKSIDE OF THE SYSTEM OVER NORTHERN ND...BUT OVERALL THE GREATEST THREAT FOR ANY SIGNIFICANT ACCUMULATIONS IS EXPECTED TO CENTER TO THE NORTH ACROSS SOUTHERN MANITOBA AND WESTERN ONTARIO. THIS SYSTEM IS EXPECTED TO WEAKEN AS IT LIFTS INTO WESTERN ONTARIO ON TUE. HOWEVER...LOW PRESSURE AND HEAVIER PRECIPITATION IS EXPECTED TO DEVELOP AND LIFT NORTHEAST ALONG THE BOUNDARY AS THE NEXT OF THE WESTERN U.S. SHORTWAVES MOVES OUT INTO THE CENTRAL U.S. STRONG SURFACE HIGH PRESSURE SUPPORTED BY CONFLUENT FLOW ALOFT IS FORECAST TO CENTER OVER CENTRAL CANADA WED MORNING. STRONG NORTHEASTERLY WINDS BETWEEN THE HIGH AND THE LOW LIFTING UP FROM THE SOUTH WILL DRAW MUCH COLDER AIR FROM CANADA DOWN ACROSS THE UPPER MIDWEST. THIS WILL SET THE STAGE FOR A MIXED PRECIPITATION EVENT ALONG THE WESTERN SHORES OF LAKE SUPERIOR WED MORNING. WHILE ACCUMULATING SNOWS ARE POSSIBLE ACROSS NORTHWEST MN...SEVERAL OF THE 00 UTC MODELS RUNS SHOW A PERIOD OF FREEZING RAIN WITH SIGNIFICANT ICE ACCUMULATIONS FURTHER TO THE EAST ACROSS NORTHWESTERN WI INTO THE WESTERN U.P. OF MI. PEREIRA $$

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