THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


EXTENDED FORECAST DISCUSSION




EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1155 AM EDT WED MAR 22 2017

VALID 12Z SAT MAR 25 2017 - 12Z WED MAR 29 2017

...OVERVIEW/GUIDANCE EVALUATION/PREFERENCES...

THE OPERATIONAL MODELS AND GLOBAL ENSEMBLE MEANS ARE IN RELATIVELY
GOOD AGREEMENT AT THE BEGINNING OF THE MEDIUM RANGE PERIOD,
DEPICTING A LARGE SCALE TROUGH ALONG THE WEST COAST, AN UPPER
LEVEL LOW OVER THE CENTRAL PLAINS, AND A RIDGE OVER THE SOUTHEAST
U.S.  THE UPPER LOW IS FORECAST TO LIFT TOWARDS THE NORTHEAST AND
WEAKEN INTO AN OPEN WAVE BEFORE BECOMING ABSORBED INTO THE MEAN
UPPER FLOW OVER NEW ENGLAND AFTER MONDAY.  THE INITIAL TROUGH
ALONG THE WEST COAST IS FORECAST TO REACH THE CENTRAL PLAINS BY
EARLY IN THE WEEK, AND MAY BRIEFLY BECOME A CLOSED LOW WITHIN THE
SOUTHERN STREAM.  THE GREATEST AMOUNT OF UNCERTAINTY COMES BY DAY
6 (TUESDAY MORNING) WITH THE THIRD SYNOPTIC SYSTEM CROSSING THE
WESTERN U.S. WITH THE SPAGHETTI PLOTS SHOWING A VERY WIDE RANGE OF
POSSIBLE SOLUTIONS.

THE FORECAST WAS BASED ON ROUGHLY A THIRD OF PREVIOUS WPC
CONTINUITY THROUGH THE ENTIRE PERIOD.  A NEARLY EQUAL BLEND OF THE
6Z GFS/GEFS MEAN AND 00Z ECWMF/EC MEAN COMPRISED THE REMAINING 2/3
OF THE BLEND FOR THE FIRST HALF OF THE FORECAST PERIOD, AND 1/3
EACH OF THE GEFS MEAN, EC MEAN, AND WPC CONTINUITY FOR THE LAST
HALF OF THE FORECAST PERIOD.  GIVEN THE LARGE SPREAD NOTED DURING
THE DAY 6 AND 7 TIME PERIODS, FORECAST CONFIDENCE IS BELOW
AVERAGE. 


...SENSIBLE WEATHER/HIGHLIGHTS...

SHOWERS AND THUNDERSTORMS ARE LIKELY ON SATURDAY ACROSS THE OHIO
AND TENNESSEE VALLEYS, AND STRATIFORM RAIN ACROSS THE GREAT LAKES
REGION.  BY MONDAY, THE AREA OF PRECIPITATION IS EXPECTED TO REACH
THE EAST COAST.  THE NEXT TROUGH CROSSING THE SOUTHERN PLAINS TO
THE LOWER MISSISSIPPI VALLEY COMBINES WITH MOISTURE RETURN FROM
THE GULF OF MEXICO TO PRODUCE A SECOND ROUND OF CONVECTION ACROSS
THE SOUTHERN AND CENTRAL PLAINS INTO THE DEEP SOUTH LATER SUNDAY
INTO MONDAY.  WIDESPREAD SHOWERS AND MOUNTAIN SNOW ARE EXPECTED TO
ACCOMPANY THE FRONTAL SYSTEM MOVING ONSHORE INTO THE PACIFIC
NORTHWEST AND NORTHERN ROCKIES FOR THE BEGINNING OF THE WORK WEEK.
 THE SOUTHERN STREAM PORTION OF THIS WAVE COMES ACROSS THE
SOUTHWEST TUESDAY AND WILL LIKELY RESULT IN A CLOSED UPPER LOW,
WITH ADDITIONAL AREAS OF VALLEY RAIN AND MOUNTAIN SNOW FROM THE
GREAT BASIN TO THE CENTRAL AND SOUTHERN ROCKIES.

ABOVE NORMAL TEMPERATURES ARE EXPECTED TO PERSIST THIS WEEKEND
INTO EARLY NEXT WEEK ACROSS THE OHIO VALLEY AND EXTENDING
SOUTHWARD TO THE GULF COAST OVER THE WEEKEND AND INTO EARLY NEXT
WEEK.  A TIGHT TEMPERATURE GRADIENT WILL LIKELY BECOME ESTABLISHED
ACROSS THE MID-ATLANTIC REGION AS A BACK DOOR COLD FRONT SWEEPS
SOUTHWARD FROM NEW ENGLAND.  THE PROGRESSION OF TROUGHS ACROSS THE
PACIFIC NORTHWEST AND THEIR ASSOCIATED SHOWERY CONDITIONS KEEPS
TEMPERATURES BELOW NORMAL FOR THESE AREAS.

HAMRICK





Last Updated: 1155 AM EDT WED MAR 22 2017