Quantitative Precipitation Forecast
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FOUS11 KWBC 292055
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
454 PM EDT FRI APR 29 2016

VALID 00Z SAT APR 30 2016 - 00Z TUE MAY 3 2016

DAYS 1-3...

***CENTRAL ROCKIES AND EXTENDING INTO NEBRASKA***

A LATE SEASON SNOW STORM IS FORECAST TO AFFECT THE CENTRAL ROCKIES
AND EXTENDING INTO THE WESTERN HALF OF NEBRASKA AND SOUTHWEST
SOUTH DAKOTA THROUGH THE WEEKEND.  A WELL-DEVELOPED UPPER-LEVEL,
NEGATIVELY TILTED TROUGH AND SHORTWAVE ENERGY OVER COLORADO ON
FRIDAY AFTERNOON IS FORECAST TO SLOWLY MOVE NORTHEASTWARD OVER THE
CENTRAL PLAINS BY SATURDAY AFTERNOON, AFTER WHICH POINT WEAKENING
OCCURS AND THE FEATURE BECOMES MORE SHEARED OUT.  INCREASING LOW
LEVEL EASTERLY WINDS TOWARDS THE COLORADO FRONT RANGE WILL RESULT
IN COOLING UPSLOPE FLOW AND TRANSITIONING TO A DYNAMIC COOLING
SITUATION WITH THE DEFORMATION ZONE.

THE GUIDANCE REMAINS IN GOOD AGREEMENT ON THE PROSPECTS OF HEAVY
SNOW ACROSS MUCH OF THE COLORADO ROCKIES AND THE ADJACENT
FOOTHILLS, BUT FARTHER AWAY FROM THE TERRAIN THE FORECAST IS A
LITTLE MORE CHALLENGING WITH THE MODEL GUIDANCE VARYING SOME WITH
RESPECT TO PRECIPITATION TYPE.  THERE HAS BEEN A WESTWARD TREND
WITH THE QPF OVER THE PAST 24 HOURS OF MODEL RUNS, THUS LEADING TO
SOME HEAVIER AMOUNTS OVER NEBRASKA AND THE BLACK HILLS OF SOUTH
DAKOTA.  TEMPERATURE PROFILES HERE ARE THE UNCERTAIN PART OF THE
FORECAST, AND A DIFFERENCE OF JUST A FEW DEGREES COULD RESULT IN
NOTEWORTHY DIFFERENCES IN THE OBSERVED SNOWFALL TOTALS.  IN
SITUATIONS LIKE THIS, THE ACCUMULATIONS WILL BE DEPENDENT ON THE
SNOWFALL RATES, WITH BETTER DYNAMIC COOLING IN AREAS OF HEAVIER
PRECIPITATION AND OVERCOMING WARMER ANTECEDENT GROUND
TEMPERATURES.  LOW SNOW-TO-LIQUID RATIOS ARE EXPECTED WITH THIS
EVENT OVER THE PLAINS.

ON SUNDAY, ANOTHER AREA OF ACCUMULATING SNOW IS EXPECTED ACROSS
SOUTHERN COLORADO INTO NORTHERN NEW MEXICO WITH THE NEXT JET
STREAK AND MID-LEVEL SHORTWAVE DIGGING ACROSS THE DESERT
SOUTHWEST, WHICH IS FORECAST TO REACH THE FOUR-CORNERS REGION BY
SUNDAY NIGHT.  THE SAN JUANS AND SANGRE DE CRISTO RANGES WILL
LIKELY GET THE HEAVIEST SNOW FROM THIS SECOND SYSTEM.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

HAMRICK/KOCIN

$$





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