Quantitative Precipitation Forecast
Issued by NWS

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730
FOUS11 KWBC 260752
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
352 AM EDT SUN MAR 26 2017

VALID 12Z SUN MAR 26 2017 - 12Z WED MAR 29 2017

DAYS 1 THROUGH 3...

...WESTERN U.S....

EPISODES ON MODERATE TO LOCALLY HEAVY MOUNTAIN SNOWS ARE EXPECTED
IN THE PACIFIC NORTHWEST SUNDAY...UT RANGES MON...AND THE RANGES
OF CO AND ADJACENT NM/WY ON TUE.

ON DAY 1...SUNDAY... A SLOWLY APPROACHING 700 MB TROUGH AND FRONT
AND ASSOCIATED SURFACE COLD FRONT SHOULD OCCUR. AS A
RESULT...MOIST FLOW INTO THE TERRAIN SHOULD BRING PERIODS OF
MODERATE TO HEAVY SNOW TO THE WINDWARD TERRAIN OF THE WA/OR
CASCADES AND SIERRA NEVADA RANGE. A LOWER AMPLITUDE WAVE OUT AHEAD
OF THE MAIN TROUGH/FRONT PROGRESSES ACROSS OR INTO ID TO BRING
LIGHT TO MODERATE AMOUNTS INTO THE BLUE MNTNS AND BOISE/SALMON
RIVER MNTNS.

ON DAY 2...MONDAY...THE 700 MB WAVE PROGRESSES OUT OF CA ACROSS NV
AND UT...WITH MULTIPLE MODELS SHOWING A CLOSED LOW AND SHARPENING
FRONT IN UT AND AZ.  A BAND OF SNOW DEVELOPS WITHIN THE
DEFORMATION ZONE IN THE PROXIMITY OF THE FRONT...WHICH OCCURS
ACROSS  CENTRAL AND NORTHERN UT AND ADJACENT SOUTHWEST WY AND
NORTHERN AZ.

QUASI-ZONAL FLOW SETTING UP OVER THE NORTHWEST BEHIND THE
AMPLIFYING UPPER TROUGH SHOULD ALLOW SNOW TO REDEVELOP MONDAY
NIGHT...CONTINUING
INTO TUE IN THE RANGES OF NORTHERN WA ON TUE AS THE ECMWF SHOWS A
300 MB JET MAXIMA WITH EMBEDDED DIVERGENCE MAXIMA CROSSING
NORTHERN WA INTO THE ID PANHANDLE.

ON DAY 3...TUESDAY...THE 700 MB LOW DRIFTS EAST FROM NORTHERN
AZ/SOUTHERN UT ACROSS SOUTHERN CO/NORTHERN NM IN THE
NAM/ECMWF/CANADIAN/GFS. THE MODELS SUGGEST IT COULD REACH THE HIGH
PLAINS OF CO/NM..SO SNOW COULD EVENTUALLY CHANGE TO RAIN WITH
FALLING HEIGHT/TEMPERATURES WITH THE FRONTAL PASSAGE.  THE HEAVIER
SNOW IS TARGETED FOR THE RANGES OF CO AND NORTHERN
NM...PARTICULARLY THE SAN JUAN MNTNS AND FRONT RANGE OF CO/NM.

THE PROBABILITY OF RECEIVING A QUARTER INCH OF FREEZING RAIN IS
LESS THAN 10 PERCENT ACROSS THE WESTERN US.


...INTERIOR NEW YORK AND NEW ENGLAND...

FREEZING RAIN IS EXPECTED FOR PORTIONS OF INTERIOR NEW YORK AND
NEW ENGLAND   AS ISENTROPIC LIFT OCCURS WITHIN THE 850-700 MB WARM
ADVECTION ZONE WHILE A SURFACE RIDGE OF HIGH PRESSURE REINFORCES
THE COLD AIR AT THE SURFACE.
THE SURFACE WARM FRONT DOES LIFT NORTH WITH TIME...MOVING THE RISK
AREA FURTHER NORTH ON MON AND TUE.

PROBABILISTIC GUIDANCE SUGGESTS THE GREATEST POTENTIAL FOR
ACCUMULATING FREEZING RAIN WILL BE OVER THE ADIRONDACKS AND
CATSKILLS OF NEW YORK...THEN EAST INTO THE GREEN AND WHITE
MOUNTAINS AND RANGES OF WESTERN MAINE.
THE AMOUNT OF LIQUID EQUIVALENT PRECIPITATION OCCURRING WITHIN THE
LOW LEVEL DRY AIR PROVIDED BY THE ARCTIC HIGH ACROSS SOUTHEASTERN
CANADA WILL DETERMINE THE EXACT DISTRIBUTION OF PRECIPITATION
TYPES AND AMOUNTS DURING THIS EVENT.

SNOW WILL ALSO BE POSSIBLE WITH THIS SYSTEM...BUT SIGNIFICANT
ACCUMULATIONS SHOULD BE MOSTLY CONFINED TO THE NORTHERN HALF OF
MAINE. THE MODELS DIFFER
ON TUE AS TO WHETHER A SECONDARY WAVE DEVELOPS ALONG THE COLD
FRONT TO PRODUCE AN ADDITIONAL SURGE OF SNOW OR A WAVE DOES NOT
DEVELOP...KEEPING AMOUNTS LOWER. THE ECMWF AND ENSEMBLE MEAN SHOW
THE 700-500 MB WAVE LOWER IN AMPLITUDE AND WEAKER/FURTHER OFFSHORE
LOW PRESSURE DEVELOPMENT...AND THUS LESS SNOW IN MAINE.  THE
GFS/NAM SHOW A HIGHER AMPLITUDE TROUGH AND CLOSER IN LOW
DEVELOPMENT...THUS POTENTIAL FOR SEVERAL INCHES IN NORTHERN MAINE.


PETERSEN


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