Quantitative Precipitation Forecast
Issued by NWS

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
000
FOUS11 KWBC 210815
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
414 AM EDT SAT MAR 21 2015

VALID 12Z SAT MAR 21 2015 - 12Z TUE MAR 24 2015


...NORTHERN PLAINS INTO UPPER MIDWEST/MS VALLEY SUN-EARLY MON...

A SHORT WAVE TROUGH WILL PROCEED THROUGH THE NRN ROCKIES AND BEGIN
TO REACH THE NRN PLAINS AND UPPER MIDWEST BY SUN.
TWO POSSIBLE ZONES OF SNOW WILL BE POSSIBLE. INITIALLY THE LIGHT
SNOW WILL OCCUR ACROSS EXTREME NERN MT INTO ND ON LATE SAT
NIGHT/SUN AS A BAND OF 850-700 MB CONVERGENCE CROSSES THE REGION.
HOWEVER WITH THE DEVELOPMENT OF STRONG WARM ADVECTION AND A STRIPE
OF LOW-MID LEVEL FRONTOGENESIS... A NARROW ZONE OF SNOWFALL IS
EXPECTED FROM SERN MN/NERN IA INTO SRN WI AND ADJACENT NRN IL SUN
TO EARLY MON.

THE NAM/GFS/ECMWF SHOW A TIGHT GRADIENT IN PRECIP AMOUNTS TYPICAL
OF A NARROW BAND OF FRONTOGENETIC FORCING...SO MINOR CHANGES IN
THE AXIS OF THE FRONT WILL RESULT IN SIGNIFICANT CHANGES IN
SNOWFALL ACCUMULATIONS.  BOUNDARY LAYER TEMPS RISE ABOVE FREEZING
SOUTH OF THE FRONT...CUTTING DOWN ON ACCUMULATIONS AS YOU GO SOUTH
IN IA/IL.

...RANGES OF THE PACIFIC NORTHWEST TO NORTHERN ROCKIES SUN
NIGHT-MON NIGHT...

ON SUN NIGHT-MON...PAC MOISTURE TRANSPORT DEVELOPS AS AN UPPER
TROUGH APPROACHES FROM THE WEST AND A COUPLED UPPER JET
DEVELOPS...ENHANCING UPPER DIVERGENCE COMING ONSHORE SUN NIGHT
FROM THE EAST PACIFIC INTO SOUTHERN OR AND NORTHERN CA. THE UPPER
JET MAXIMA PERSISTING ACROSS NORTHERN CA MON LEAVES FAVORABLE
DIFLUENT FLOW AND UPPER DIVERGENCE MAXIMA ACROSS THE NORTHWEST
INTO THE NORTHERN ROCKIES MONDAY. BECAUSE OF THE
PERSISTENCE...LONG DURATION OF SNOW SHOWER ACTIVITY SHOULD RESULT
IN SEVERAL INCHES ACROSS THE UPSLOPE AREAS FROM THE OR CASCADES
INTO THE RANGES OF SOUTHERN TO CENTRAL ID AND NORTHWEST WY/WESTERN
MT.

HEAVY SNOWFALL ACROSS THE WRN TERRAIN AND WPC FOLLOWED A
MULTI-MODEL AND 21Z SHORT RANGE ENSEMBLE MEAN BLEND FOR THE HEAVY
SNOW PROBABILITIES.

...NORTHERN NEW YORK/NEW ENGLAND SAT...

A NORTHERN STREAM SHORT WAVE AND COLD FRONT WILL CROSS THE LOWER
LAKES AND NORTHERN NEW YORK/NEW ENGLAND SAT. THIS SYSTEM WILL LACK
THE MOISTURE AVAILABILITY BUT ASCENT AIDED BY PRE-FRONTAL
CONVERGENCE SHOULD RESULT IN LIGHT TO MDT ACCUMULATIONS FROM
UPSTATE NY THROUGH NRN VT/NH INTO MAINE THROUGH SUN MORNING.
HIGHER AMOUNTS OCCUR WHERE THERE IS ENHANCED UPSLOPE FLOW...SUCH
AS THE TUG HILL PLATEAU OF NY.  THE STEADILY CHANGING WIND
DIRECTIONS AND MAXIMA IN LOW LEVEL CONVERGENCE IN THE BOUNDARY
LAYER WORKS AGAINST BANDS SETTING UP FOR AN EXTENDED PERIOD IN ANY
ONE LOCATION.
THE MODELS/ENSEMBLES ARE IN GOOD AGREEMENT ON THE FRONTAL
PROGRESSION SO A MULTI-MODEL/ENSEMBLE CONSENSUS APPROACH WAS TAKEN
IN THE FORECAST.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT DAYS
1-3.

PETERSEN


$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.