Quantitative Precipitation Forecast
Issued by NWS

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838
FOUS11 KWBC 232010
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
409 PM EDT MON OCT 23 2017

VALID 00Z TUE OCT 24 2017 - 00Z FRI OCT 27 2017


DAYS 1-3...

...UPPER MIDWEST...

AS A SOUTHERN STREAM SHORTWAVE LIFTING NORTH THROUGH THE OH VALLEY
PHASES WITH A NORTHERN STREAM TROUGH AMPLIFYING OVER MIDWEST...A
POWERFUL FALL STORM SYSTEM IS FORECAST TO LIFT NORTH ACROSS LOWER
MICHIGAN MON NIGHT.  SURFACE LOW PRESSURE CURRENTLY CENTERED OVER
THE OH VALLEY WILL CONTINUE TO DEEPEN AS IT LIFTS FURTHER
NORTH...WITH MOST OF THE GUIDANCE SHOWING A 980-985 MB LOW MOVING
INTO THE EASTERN U.P. EARLY TUE.  BY TUE
AFTERNOON-EVENING...MODELS SHOW ENOUGH COLD AIR ON THE BACKSIDE OF
THE SYSTEM FOR RAIN CHANGING TO SNOW ACROSS PORTIONS OF THE
WESTERN U.P. INTO FAR NORTHERN WISCONSIN.  GUIDANCE IS IN
GENERALLY GOOD AGREEMENT THAT WARM BOUNDARY LAYER CONDITIONS WILL
HAMPER THE POTENTIAL FOR SIGNIFICANT ACCUMULATIONS OUTSIDE OF THE
HIGHER TERRAIN OF THE EASTERN U.P.  MOST OF THE 12 UTC MODELS
SHOWED SUPPORT FOR AT LEAST A COUPLE OF INCHES OF SNOW ACROSS THE
HURON MOUNTAINS...WITH SOME OF THE GUIDANCE SHOWING HEAVIER
TOTALS...AS SUGGESTED BY WPC PROBABILITIES...WHICH INDICATE A
SLIGHT RISK FOR ACCUMULATIONS OF 8-INCHES OR MORE BY THE END OF
THE DAY 1 PERIOD (ENDING 00 UTC WED).

THE AFOREMENTIONED SYSTEM IS FORECAST TO GRADUALLY WEAKEN AND LIFT
NORTH...USHERED OUT BY AN UPSTREAM SHORTWAVE FORECAST TO MOVE
PROGRESSIVELY FROM WESTERN CANADA EARLY WED INTO THE NORTHERN
PLAINS AND UPPER MIDWEST THU MORNING.  GUIDANCE SHOWS THE
POTENTIAL FOR A STRIPE OF SIGNIFICANT SNOWS NORTH OF THE LOW
CENTER...WITH THE HEAVIEST AMOUNTS MOST LIKELY TO FALL ACROSS
SOUTHERN CANADA.  HOWEVER...SIGNIFICANT MODEL SPREAD AND POOR
MODEL RUN-TO-RUN CONTINUITY WITH THIS SYSTEM IS LIMITING
CONFIDENCE IN ANY PARTICULAR SOLUTION.  THE WPC PREFERENCE WAS FOR
A LOW TRACK A LITTLE FURTHER SOUTH THAN THE NAM...WITH SOME
HEAVIER SNOW ACCUMULATIONS THAN THE NAM ACROSS NORTHERN
MINNESOTA...SIMILAR TO THE GFS AND THE 00 UTC ECMWF.

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

PEREIRA

$$





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