Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 172119
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
418 PM EST TUE JAN 17 2017

VALID 00Z WED JAN 18 2017 - 00Z SAT JAN 21 2017

INTERIOR OF WASHINGTON/OREGON/IDAHO...

HIGH PROBABILITIES OF 0.25 INCHES OF ICE ARE DEPICTED BY A
COMPOSITE OF ALL DETERMINISTIC AND ENSEMBLE GUIDANCE FOR THE
PORTLAND AREA EASTWARD THROUGH THE COLUMBIA RIVER GORGE THEN ALONG
A BROAD STRIP OF THE BASIN AND FOOTHILLS THROUGH
TODAY/TONIGHT/WEDNESDAY BEFORE WANING. WHILE THE PROBABILITIES OF
0.25 INCHES OF ICE ARE HIGH...THEY WOULD LIKELY BE EVEN HIGHER AND
SUPPORT HIGH PROBABILITIES OF HIGHER THRESHOLDS OF 0.5/0.75/1.0
INCHES IF THE MEMBERSHIP CONSISTED OF HIGHER RESOLVING GUIDANCE.
BEST ESTIMATES OF ICE STORM TOTALS ARE FOR BROAD AREAS OF 0.25 TO
0.5 INCHES WITH LOCALIZED TOTALS POSSIBLY EXCEEDING 1 INCH IN
PARTS OF THE COLUMBIA RIVER GORGE.

REFER TO LOCAL WFO WATCHES/WARNINGS FOR MORE SPECIFIC
INFORMATION/UPDATES/POTENTIAL IMPACTS FROM THE ICE.

REST OF THE PACIFIC NORTHWEST/CALIFORNIA/INTERMOUNTAIN WEST...

AREAS OF SNOWFALL WILL BLOSSOM ND THROUGH THE DAY ON WEDNESDAY
ACROSS THE HIGHER ELEVATIONS OF THE WEST BEGINNING WEDNESDAY AS
SNOW LEVELS DROP WITH THE ARRIVAL OF THE NEXT MAJOR UPPER TROUGH.
UNTIL THEN...THERE IS GENERAL MODEL AGREEMENT FOR SNOW ACROSS THE
NORTHERN CASCADES OF WASHINGTON...WITH THE SREF ARW MEMBERS
GENERALLY LESS SUPPORTIVE COMPARED TO THE SREF NMMB MEMBERS AS
WELL AS THE GEFS/ECMWF ENSEMBLE MEMBERS. FOR WEDNESDAY AND
WEDNESDAY NIGHT...THE HIGHEST PROBABILITIES OF SNOW AFFECT THE
SISKIYOUS/SIERRAS/BLUE MOUNTAINS/SAWTOOTH/BITTERROOTS...WITH
GENERALLY CLOSE CLUSTERING OF ALL ENSEMBLE MEMBERS. FOR THURSDAY
AND THURSDAY NIGHT.  IN THE PERIOD FROM THURSDAY INTO
FRIDAY...LOWERING HEIGHTS/FALLING TEMPERATURES SHOULD ONCE AGAIN
LEAD TO SNOW AT OR ABOVE 5000 FT IN THE MOUNTAINS OF SOUTHERN CA
WITH HIGHEST SNOWFALL AMOUNTS AT HIGHER ELEVTIONS.

NORTHEAST/NEW ENGLAND...

A RISK OF FREEZING RAIN WILL PERSIST INTO THE EVENING AND
OVERNIGHT HOURS ACROSS PARTS OF NEW ENGLAND AND NORTHEAST FROM
PARTS OF THE ADIRONDACKS/CATSKILLS.  THE RISK OF FREEZING PCPN
WILL BE TAPERING OFF...THOUGH...AS WARMER AIR MAKES ITS WAY
NORTHWARD AND FORCES A CHANGE IN PTYPE TO RAIN.  HIGHR RESOLVING
SREF/ECMWF ENSEMBLE MEMBERS STILL MORE SUPPORTIVE OF ICE COMPARED
TO THE COARSER RESOLVING GEFS MEMBERS.

REGARDING SNOW...LOW PROBABILITIES OF 8 INCHES EXTEND ACROSS
PORTIONS OF NH INTO PARTS OF ME. AS WAS THE CASE IN THE 17/12Z
FORECAST...THE VARIOUS ENSEMBLE SYSTEMS TODAY REMAIEND FAIRLY
DISPERSIVE...SUGGESTING LOW CONFIDENCE IN THE 8 INCH TOTALS.
SIMILARLY...THE ENSEMBLE SYSTEMS ARE MORE SUPPORTIVE OF 4 INCH
PROBABILITIES...WITH THE SREF/GEFS MEMBERS A LITTLE FARTHER NORTH
WITH THEIR CENTROID OF HIGHEST CHANCES COMPARED TO THE ECMWF
ENSEMBLE MEMBERS WHICH ARE A LITTLE FARTHER SOUTH.

OVERALL HOWEVER...THE SPREAD IN MINIMAL AND HELPS TO ACCOUNT FOR
THE RANGE OF POSSIBILITIES WITH THE TRACK AND SPEED OF THE LOW
TRANSFERRING TO THE COAST.

BANN

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