Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 190755
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
354 AM EDT SAT APR 19 2014

VALID 12Z SAT APR 19 2014 - 12Z TUE APR 22 2014

...PACIFIC NORTHWEST...

A SHORT WAVE TROUGH CROSSING THROUGH THE PAC NW ON SAT INDUCES A
700 MB JET MAX NEAR 50 KT AND 700-500 MB VERTICAL MOTION MAXIMA OF
5-10 MICROBARS/SEC.  THIS COMBINES WITH MOISTURE FLUXES ON
SOUTHWEST FLOW AND WARM ADVECTION AND STEEP LASE RATES OF 7-7.5
DEGREES C/KM TO PRODUCE A PERIOD OF SNOW CENTERED JUST AFTER 00Z
SUN.  DRYING ALOFT AFTER 06Z IN THE 700-500 MB LAYER AS THE UPPER
RIDGE APPROACHES RESULTS IN A DECREASE IN SNOW COVERAGE/INTENSITY.
THE 12-00Z ECMWF/GFS QPF/TEMP PROFILES WERE GIVEN GREATER
WEIGHTING IN THE FORECAST.


...NERN MN...

A SHORT WAVE TROUGH WITH A DYNAMIC UPPER JET STREAK WILL TRACK
ALONG THE NRN TIER OF THE COUNTRY FRI NIGHT INTO SAT...BRINGING A
ROUND OF MIXED FROZEN PRECIP ACROSS NERN MN.
MORNING TEMPS HAVE DROPPED BELOW FREEZING IN THE ARROWHEAD OF MN
WHILE A BAND OF PRECIPITATION APPROACHES FROM THE WEST.  A SHIELD
OF WARM ADVECTION/ISENTROPIC LIFT PRECIP CROSSES NORTHEAST
MN...ALLOWING THE BANDED PRECIP TO CONTINUE SAT MORNING.  LIGHT
RAIN SI EXPECTED TO FALL INTO THE COLD AIR MASS UNTIL THE THREAT
ENDS WITH THE COMBINATION OF SFC TEMPS RISING ABV FREEZING AND
WARM ADVECTION ENDING.  SO FAR ANY SNOW HAS BEEN MINIMAL WITH A
BRIEF PERIOD POSSIBLE BEFORE WARMING CREATES THE TRANSITION TO
MIXED PRECIP TYPES.  THE EVENT SHOULD BE OVER LATE SAT AFTERNOON
WITH THE THREAT MOVING DOWNSTREAM INTO ONTARIO.  THE 12-00Z
ECMWF/GFS QPF/TEMP PROFILES WERE GIVEN GREATER WEIGHTING IN THE
FORECAST.

THE PROBABILITY FOR SIGNIFICANT ICING IS LESS THAN 10 PERCENT ON
DAYS 2 AND 3.

PETERSEN

$$





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