Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 280855
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
354 AM EST TUE FEB 28 2017

VALID 12Z TUE FEB 28 2017 - 12Z FRI MAR 03 2017

...WEST...

SNOWFALL WILL BE ON A DECREASING TREND TODAY ACROSS THE HIGHER
TERRAIN OF AZ/NM/CO AS THE TROUGH AXIS BEGINS TO SHIFT OFF TO THE
EAST. ADDITIONAL SNOWFALL AMOUNTS WILL GENERALLY STAY BELOW
6"...WITH ISOLATED HIGHER AMOUNTS ALONG THE HIGHEST TERRAIN OF THE
MOGOLLON RIM AND THE SAN JUAN MOUNTAINS.

PERIOD OF SNOW WILL CONTINUE OVER THE NEXT SEVERAL DAYS OVER THE
HIGHER TERRAIN OF THE NORTHWEST AS MULTIPLE SHORTWAVES MOVE
ACROSS. GENERALLY LOOKING AT 10-20" THROUGH 12Z FRIDAY ACROSS THE
HIGHER TERRAIN OF NORTHERN ID AND WESTERN MT. HEAVIER AMOUNTS ARE
LIKELY ACROSS THE WA CASCADES...WITH SNOWFALL BEING ENHANCED BY
THE APPROACH OF A FRONT AND AN ENHANCED PLUME OF MOISTURE.
SNOWFALL THROUGH 12Z FRIDAY WILL BE AS HIGH AS 2-4 FEET ACROSS THE
HIGHER TERRAIN OF THE NORTHERN CASCADES.

...UPPER MS VALLEY/UPPER GREAT LAKES...

LONGWAVE TROUGHING MOVING INTO THE CENTRAL PORTION OF THE COUNTRY
WILL BRING A FEW CHANCES FOR SNOW ACROSS THE GREAT LAKES REGION.
OVERALL A PRETTY COMPLEX EVOLUTION WITH MULTIPLE SHORTWAVES AND
SURFACE LOW REFLECTIONS EMBEDDED WITHIN THE BROAD TROUGHING.
LIKELY TO HAVE A SWATH OF MAINLY LIGHT SNOW TODAY ACROSS PORTIONS
OF NORTHEAST MN INTO FAR NORTHERN WI AND THE UP OF MI. THE GFS HAS
BACKED OFF FROM ITS MORE SIGNIFICANT SNOWFALL THAT IT WAS SHOWING
YESTERDAY...AND THUS NOW THERE IS A MULTI MODEL AGREEMENT FOR A
GENERAL 2-5".

ONE AREA OF LOW PRESSURE IS FORECAST TO MOVE FROM EASTERN NE
ACROSS THE GREAT LAKES INTO TONIGHT. HOWEVER THERE IS A GROWING
MODEL AGREEMENT THAT TRAILING SHORTWAVE ENERGY WILL HELP FORM A
TRAILING AREA OF LOW PRESSURE THAT WILL TRACK ALONG THE BAROCLINIC
ZONE...INTENSIFYING EAST OF MI WEDNESDAY. COLDER AIR SHOULD BE
ABLE TO WRAP INTO THIS SECOND AREA OF LOW PRESSURE...ALLOWING FOR
A SHIELD OF ACCUMULATING SNOWFALL IN THE DEVELOPING COMMA HEAD.
STILL QUITE A BIT OF UNCERTAINTY ON THE EXACT EVOLUTION OF THIS
SYSTEM AND THUS WITH SNOWFALL AMOUNTS AS WELL. THE 0Z RUNS OF THE
ECMWF/GFS/UKMET ALL TRENDED FURTHER NORTHWEST AND SIGNIFICANTLY
HEAVIER WITH THE SNOWFALL AXIS FROM SOUTHERN WI INTO
CENTRAL/NORTHERN MI. NOT READY TO COMPLETELY BUY INTO THIS OUTCOME
JUST YET...AS THE SETUP IS VERY SENSITIVE AND IT WOULD NOT BE
SURPRISING IF MODELS END UP TRENDING BACK TO A LESS WOUND UP
SYSTEM AND LOWER SNOWFALL AMOUNTS. WITH THAT SAID...CAN NOT IGNORE
RECENT TRENDS...AND THUS WILL GO AHEAD AND BUMP UP OUR SNOWFALL
FORECAST...JUST NOT AS EXTREME AS SOME OF THE RECENT DETERMINISTIC
RUNS. OUR FORECAST ENDS UP PRETTY CLOSE TO THE 0Z GEFS
MEAN...WHICH SEEMED LIKE A GOOD MIDDLE GROUND SOLUTION BETWEEN THE
OLDER LESS IMPRESSIVE DETERMINISTIC RUNS AND THE NEWER HEAVIER
RUNS. WITH ALL ENSEMBLE SUITES SEEMING TO HAVE A DECENT HANDLE ON
THE RANGE OF POSSIBLE SOLUTIONS FOR THIS SYSTEM...THINK THE WPC
SNOWFALL PROBABILITIES ARE PROBABLY PRETTY ACCURATE FOR THIS
EVENT. ACROSS FAR SOUTHEAST WI INTO CENTRAL/NORTHERN MI THE 25TH
PERCENTILE SNOWFALL IS CURRENTLY DEPICTED AS 1-2"...WITH THE 75TH
PERCENTILE 5-8". THE HIGHEST PROBABILITIES OF SIGNIFICANT SNOWFALL
ARE ACROSS NORTHEAST MI...WITH A 40-60% CHANCE OF 6"+ AND A 10-30%
CHANCE OF 8"+.

CHENARD







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