Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 222117
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
416 PM EST SUN FEB 22 2015

VALID 00Z MON FEB 23 2015 - 00Z THU FEB 26 2015


...INTERMOUNTAIN WEST/ROCKY MOUNTAINS INTO CENTRAL/SRN PLAINS AND
LOWER MS VALLEY TO THE SOUTHERN APPALACHIANS...

FOR DAYS 1 AND 2...LATE SUN TO LATE TUE...MODELS SHOW A
WELL-DEFINED UPPER LEVEL SHORTWAVE TROUGH DROPPING SOUTH THROUGH
NORTHERN CA SUN EVENING WITH AN UPPER CENTER FORECAST TO CLOSE OFF
ALONG THE CA-NV BORDER BY EARLY MON.  THIS SYSTEM IS EXPECTED TO
CONTINUE TO SINK FURTHER TO THE SOUTH AND THEN EAST...ROTATING
INTO THE FOUR CORNERS REGION BY EARLY TUE.  INCREASING DIVERGENCE
ALONG THE LEFT-EXIT REGION OF A STRENGTHENING JET SOUTH OF THE LOW
AND LOW-MID LEVEL FRONTOGENESIS ARE EXPECTED TO INTERACT WITH
MOIST SOUTHWESTERLY LOW LEVEL INFLOW AHEAD OF THE LOW...RAISING
THE THREAT FOR HEAVY SNOWS...PARTICULARLY ACROSS PORTIONS OF
NORTHERN AZ INTO SOUTHERN UT AND WESTERN CO...WHERE A
SLIGHT-MODERATE RISK FOR AN ADDITIONAL FOOT OR MORE IS INDICATED
ON DAY 1.  BY DAY 2...THE THREAT FOR HEAVY SNOW IS EXPECTED TO
DECREASE AS THE UPPER LOW BEGINS TO SHEAR OUT TO THE EAST AND THE
LOW LEVEL MOISTURE DECREASES.

DOWNSTREAM...MODEST ISENTROPIC LIFT WELL TO THE NORTH OF THE
ARCTIC FRONT WILL SUPPORT GENERALLY LIGHT FREEZING RAIN FROM THE
TEXAS HILL COUNTRY INTO EAST TEXAS...SPREADING THROUGH THE LOWER
MISSISSIPPI VALLEY TO THE SOUTHERN APPALACHIANS AS IT INTERACTS
WITH A PAIR OF LOW AMPLITUDE SHORTWAVES.

WPC FAVORED A BLEND OF THE NCEP GUIDANCE WITH THE ECMWF FOR DAY
1...DISCOUNTING BOTH THE NAM AND GFS THEREAFTER AS THE NAM/GFS
MOVED TO THE PROGRESSIVE SIDE OF THE GUIDANCE WITH THE LOW AS IT
MOVED OUT OF THE SOUTHWEST...WHILE THE NAM BECAME AN AMPLIFIED
OUTLIER AS WELL.

...GREAT LAKES...

OVERALL MODEL GUIDANCE INDICATES A PROGRESSIVE UPPER TROUGH
CROSSING THE GREAT LAKES REGION ON TUE. MOSTLY LIGHT WARM
ADVECTION SNOWFALL AHEAD OF AN APPROACHING COLD FRONT IS
ANTICIPATED WITH THE BEST CHANCES FOR 4 INCHES OCCURRING OVER NWRN
LOWER MICHIGAN WITH SOME OROGRAPHIC ENHANCEMENT AND POSSIBLE POST
FRONTAL LAKE EFFECT.

...NORTHERN ROCKIES/NORTHERN PLAINS/MO VALLEY...

A LOW-AMPLITUDE SHORTWAVE DROPPING SOUTH INTO THE NORTHERN
ROCKIES/PLAINS ON WED IS EXPECTED TO GENERATE MAINLY LIGHT SNOWS
ACROSS THE NORTHERN ROCKIES.  MEANWHILE...A STRIPE OF LIGHT
AMOUNTS IS EXPECTED TO DEVELOP FURTHER TO THE EAST ACROSS THE
NORTHERN PLAINS INTO THE MID MO VALLEY.  WPC FAVORED A BLEND OF
THE UKMET/ECMWF.

...NEW ENGLAND...

SHORTWAVE TROUGH MOVING ACROSS THE GREAT LAKES IS EXPECTED TO LIFT
ACROSS THE NORTHEAST.  STRONG SOUTHERLY INFLOW AHEAD OF AN
ASSOCIATED SURFACE WAVE DEVELOPING OVER THE GULF OF MAINE ON WED
IS EXPECTED TO PRODUCE A BRIEF PERIOD OF SNOW ACROSS EASTERN MAINE
BEFORE SHIFTING TO THE EAST.

PEREIRA



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