Quantitative Precipitation Forecast
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14
000
FOUS11 KWBC 202030
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
330 PM EST TUE FEB 20 2018

VALID 00Z WED FEB 21 2018 - 00Z SAT FEB 24 2018


DAYS 1-3...

...PLAINS AND MISSISSIPPI VALLEY INTO GREAT LAKES, OHIO VALLEY,
AND NORTHEAST...

ANOMALOUS GULF MOISTURE FEEDING NORTH WILL FUEL PRECIPITATION FROM
THE SOUTHERN PLAINS TO THE MISSISSIPPI AND OHIO VALLEYS OVER THE
NEXT COUPLE OF DAYS.  ON THE NORTHWEST PORTION OF THE
PRECIPITATION AREA, AN INVADING ARCTIC AIRMASS WILL PRODUCE
FREEZING RAIN AND SLEET WITH BANDS OF SNOW POSSIBLE.

TONIGHT INTO WEDNESDAY, THE GREATEST CHANCE FOR WINTRY
PRECIPITATION WILL BE FROM EASTERN OK ACROSS MO/IL/NORTHWEST
IN/MI.  THE SURFACE COLD FRONT MOVES EAST FROM THE MID MS VALLEY
AND OH VALLEY AS HIGH PRESSURE DRIFTS EAST FROM THE NORTHERN
PLAINS TO THE UPPER MS VALLEY.  THIS ALLOWS THE BANK OF COLD AIR
IN OK/KS/IA/WI TO MOVE SLOWLY EAST INTO THE AFOREMENTIONED THREAT
AREAS AND CHANGE RAIN TO MIXED SLEET AND FREEZING RAIN.
INDIVIDUAL MODEL RUNS HAVE POTENTIAL FOR HALF AN INCH LIQUID
EQUIVALENT FALLING AS FREEZING RAIN.  THE LATEST WPC PROBABILITIES
ARE SHOWING A DAY 1 MODERATE RISK OF ICE ACCUMULATIONS EXCEEDING
0.25-INCHES FROM EAST CENTRAL MISSOURI INTO CENTRAL ILLINOIS. NONE
OF THE INDIVIDUAL MODEL RUNS HAVE POTENTIAL FOR FOUR OR MORE
INCHES OF SNOW.

ON WEDNESDAY NIGHT INTO THU, A SECOND SURGE OF MID LEVEL
WARM/MOIST ADVECTION AND BANDS OF CONVERGENCE OCCUR FROM THE
SOUTHERN AND CENTRAL PLAINS AND MOVE NORTHEAST TOWARDS MO.
POTENTIAL IS THERE FOR ADDITIONAL SLEET/FREEZING RAIN
ACCUMULATIONS CENTERED IN EASTERN KS AND ADJACENT NORTHEAST OK AND
NORTHWEST MO. MUCH OF THE UNCERTAINTY STEMS FROM MULTIPLE PRECIP
TYPES AND NOT A LONG DURATION OF ANY ONE TYPE...SO LIGHT AMOUNTS
OF EACH TYPE OF FROZEN PRECIP ARE EXPECTED.

THE WAVY FRONT IS FORECAST TO MOVE EAST ACROSS NEW YORK AND NEW
ENGLAND. IN THE BAND OF MID LEVEL FRONTOGENESIS...COLD SECTOR
ASCENT OCCURS FROM THE NORTHERN OH VALLEY ACROSS AREA NEAR THE
NY/PA BORDER AS COLD AIR DRAINS INTO THE REGION FROM THE GREAT
LAKES.  THE RAIN GRADUALLY CHANGES TO A MIXTURE OF PRECIP
TYPES..STARTING AS FREEZING RAIN AND SLEET AND POSSIBLY SNOW AT
THE NORTHERN EDGE OF THE PRECIP SHIELD. THE MODELS DIFFER AS TO
HOW FAR INTO THE COLD AIR MASS TO SHOW PRECIPITATION.

ON THU NIGHT-FRI, CONFLUENT MID LEVEL FLOW AND WARM ADVECTION
STREAM FROM THE MID MS VALLEY TO THE GREAT LAKES...CREATING
POTENTIAL FOR LIGHT ICING WHERE SFC TEMPS REMAIN BELOW FREEZING IN
THESE AREAS. THE NAM/ECMWF/CANADIAN GLOBAL SHOW A 700 MB WAVE
CROSSING THE NORTHERN PLAINS THAT PRODUCES MID LEVEL WARM/MOIST
ADVECTION INTO THE UPPER MS VALLEY AND ADJACENT UPPER
LAKES...RESULTING IN POTENTIAL FOR SEVERAL INCHES OF SNOW.

...PACIFIC NORTHWEST TO NORTHERN ROCKIES/GREAT BASIN/SOUTHWEST...

TONIGHT THROUGH WED NIGHT...A 700 MB TROUGH CROSSES OR INLAND INTO
AND ACROSS THE NORTHERN ROCKIES.  LOW LEVEL CONVERGENCE ALONG AND
NEAR THE TROUGH PRODUCES LIFT THAT RESULTS IN SNOW IN WESTERN OR.
WED NIGHT INTO THU...THE WAVE DRIFTS SOUTHEAST INTO CA/NV BRINGING
THE SNOW FURTHER SOUTH INTO THE RANGES OF NORTHERN CA/NV AND
DOWNSTREAM INTO UT AND ID...WHERE BANDS OF 700 MB CONVERGENCE
DEVELOP DOWNSTREAM FROM THE TROUGH AXIS. SEVERAL INCHES OF SNOW
ARE EXPECTED IN TERRAIN OF THESE AREAS. THE HIGHEST AMOUNTS ARE
FORECAST IN THE SAN JUAN MOUNTAINS OF SOUTHWEST CO...WHERE THE NAM
SHOWS POTENTIAL FOR UP TO A FOOT OF SNOW.

ON THU NIGHT-FRI...THE 700 MB CIRCULATION DRIFTS OUT OF NV INTO UT
PRODUCING SNOW AS THE CIRCULATION APPROACHES.  SOUTHWEST FLOW
DOWNSTREAM FROM THE TROUGH PRODUCES ENHANCED LIFT AND A SURGE OF
MOISTURE INTO THE RANGES OF SOUTHERN UT AND NORTHERN AZ INTO
WESTERN CO...WHERE SEVERAL INCHES ARE POSSIBLE WHERE THE FLOW
TURNS UPSLOPE IN WINDWARD TERRAIN.

THE PROBABILITY OF SIGNIFICANT ICING (0.25 INCHES) IS LESS THAN 10
PERCENT DAY 3.

PETERSEN


$$





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