Quantitative Precipitation Forecast
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FOUS11 KWBC 132026
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
426 PM EDT SUN APR 13 2014

VALID 00Z MON APR 14 2014 - 00Z THU APR 17 2014

..CO-NM ROCKY MOUNTAINS/HIGH PLAINS/NORTHERN PLAINS/UPPER MS
VALLEY...

DAY 1...
CONTINUED UPSLOPE FLOW INTO THE SANGRE DE CRISTO RANGE TONIGHT IN
CONJUNCTION WITH PERSISTENT 700-500 MB LAYER RH OF 90-99 PERCENT
PLUS 700-500 MB VERTICAL MOTIONS PERSISTING OVERNIGHT LEAD TO THE
PRIMARY THREAT OF HEAVY SNOWS IN THIS AREA.  AMOUNTS TAPER FURTHER
NORTH IN CO AS ASCENDING MOTION TAPERS SOONER TONIGHT.
TEMPERATURES OVER THE HIGH PLAINS START ABV FREEZING AND COOL
AFTER THE FRONTAL PASSAGE.  LIMITED DURATION OF ASCENT IN THE POST
FRONTAL ENVIRONMENT
LEADS TO LIGHT ACCUMULATION IN LOWER ELEVATIONS FROM SOUTHEAST CO
TO SOUTHWEST KS AND THE OK PANHANDLE TO THE TX BORDER. THE MODELS
CONTINUE TO HAVE LOW LEVEL TEMPERATURE DIFFERENCES AS TO THE RATE
OF COLLING WHILE ASCENDING MOTION IS STILL OCCURRING.
FOR LIQUID EQUIVALENT AMOUNTS...THE MODELS SHOWED GOOD AGREEMENT
WITH THE UPSLOPE FLOW-FORCED PORTIONS BUT DIFFERED OVER THE HIGH
PLAINS...WITH THE NAM HALF AN INCH HIGHER THAN THE CONSENSUS
AMOUNTS OVER SOUTHWEST KS.

DAY 3...
ANOTHER ROUND OF SNOW IS EXPECTED TO REACH PORTIONS OF THE
NORTHERN ROCKIES BY TUESDAY NIGHT...
WITH THE JET PROPAGATING SOUTH FROM MT ACROSS WY INTO CO
SUPPORTING UPPER DIVERGENCE MAXIMA AND PERIODS OF SNOW IN THE
IMPACTED RANGES.  A LOW LEVEL FRONTAL BNDRY DRIFTS SOUTH ACROSS MT
AND THE DAKOTAS WITH A WAVE OF LOW PRESSURE DEVELOPING ALONG WITH
THE POSSIBILITY OF A 700 MB LOW CLOSING OFF AS THE WAVE APPROACHES
THE UPPER MS VALLEY.  LOW-MID LEVEL FRONTOGENESIS SUPPORTS SNOW
DEVELOPING IN THE COLD SECTOR AND INCREASING AS THE LOW DEEPENS
ACROSS CENTRAL MN TO WI...AND HIGHER PRECIPITABLE WATER VALUES GET
ADVECTED INTO REGION..NEAR 0.0 INCHES BY 00Z THU.
THE MODELS HAVE TYPICAL TIMING/INTENSITY DIFFERENCES WITH THE 700
MB WAVE AND SUBSEQUENTLY THE SFC WAVE...LEADING TO DIFFERENCES ON
THE AXIS/ORIENTATION/AMOUNTS OF SNOW.


THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

...GREAT LAKES/NEW YORK/NORTHERN NEW ENGLAND DAYS 1-3...

RECENT RADAR IMAGES AND SURFACE OBSERVATIONS SHOW AN AREA OF SNOW
ON THE NORTHWEST EDGE OF PRECIP ACROSS NORTHERN NE TO NORTHWEST
IA...DRIFTING NORTHEAST.  THIS AREA DRIFTS NORTHEAST OVERNIGHT
INTO MON AS THE MID LEVEL DEFORMATION AND UPPER LEVEL COUPLED JET
MOVES ACROSS WI INTO THE UP OF MI.  THE SFC WAVE CROSSES LOWER MI
INTO ONTARIO MONDAY.
A SECOND WAVE FORMS ON THE TRAILING FRONT BY TUE MORNING AND
CROSSES NY INTO QUEBEC.  A SIMILAR SITUATION CONTINUES...WITH THE
WARM PRE-FRONTAL AIR MASS COOLING AND THE CHANCE FOR SUFFICIENT
COOLING WHILE ASCENT IS STILL OCCURRING FOR RAIN TO CHANGE TO SNOW
FOR SEVERAL HOURS BEFORE THE ASCENT QUITS AS THE WAVE PROGRESSES
STEADILY ALONG THE FRONT.
LIKEWISE...THE FRONT MOVES ACROSS NORTHERN NEW ENGLAND TUE NIGHT
AND FINALLY OFFSHORE WED...BRINGING THE CHANCES FOR POST-FRONTAL
SNOW TO A CLOSE.
IN THE ABSENCE OF A WELL DEFINED LOW LEVEL CIRCULATION TO DRIVE
SUSTAINED ASCENT IN THE COLD AIR...LOW TO MODERATE RISKS FOR
SIGNIFICANT SNOW ARE SHOWN EACH DAY.  THE MODELS DIFFER ON THE
TIMING OF THE FRONT AS WELL AS THE WAVES PROPAGATING ALONG THE
FRONT.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.


PETERSEN



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