THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


EXTENDED FORECAST DISCUSSION




EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1211 PM EDT SUN JUN 26 2016

VALID 12Z WED JUN 29 2016 - 12Z SUN JUL 03 2016

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

MODELS REMAINED IN GOOD AGREEMENT WITH THE LARGE SCALE EVOLUTION
OF FLOW OVER THE LOWER 48 LATER THIS WEEK AND INTO NEXT
WEEKEND...KEEPING A RIDGE IN THE WEST AND RELOADING THE TROUGH IN
THE EAST.  THERE ARE STILL SOME DIFFERENCES THAT NEED TO BE
RESOLVED WITH THE EXACT DETAILS OF AN UPPER LOW POTENTIALLY
CLOSING OFF AND TRACKING JUST NORTH OF THE GREAT LAKES REGION NEXT
FRIDAY AND SATURDAY...AND THERE REMAINS VARYING SOLUTIONS WITH THE
TIMING/AMPLITUDE OF IMPULSES OF ENERGY WHILE THEY ROUND THE
WESTERN U.S. RIDGE AND TRACK INTO THE GREAT PLAINS.  HOWEVER...THE
GREATEST SPREAD IN THE GUIDANCE AND UNCERTAINTY IN THE FORECAST IS
WITH THE PROGRESSION OF A DEEP VORTEX IN THE GULF OF ALASKA AND
POSSIBLE HEIGHT FALLS INCHING IN OVER THE NORTHWESTERN U.S. NEXT
WEEKEND.  NEITHER THE DETERMINISTIC GFS OR ECMWF SHOWED GOOD
RUN-TO-RUN CONTINUITY OR MATCHED WELL WITH ITS MEAN...SO THE WPC
FORECAST STAYED CLOSE TO A COMBINATION OF THE PREVIOUS WPC
FORECAST AND THE LATEST ENSEMBLE MEAN GUIDANCE BY NEXT WEEKEND. 


...WEATHER HIGHLIGHTS...

A FRONTAL BOUNDARY SETTLING IN OVER THE SOUTHERN TIER OF THE
NATION AND BACK INTO THE LEE OF THE CENTRAL/NORTHERN ROCKIES WILL
SERVE AS A FOCUS FOR SHOWER AND THUNDERSTORM ACTIVITY TOWARDS THE
MIDDLE OF THE WEEK AND INTO NEXT WEEKEND.  THE GREATEST THREAT FOR
ORGANIZED AREAS OF HEAVY RAIN WILL BE ACROSS THE CENTRAL PLAINS
AND LOWER/MIDDLE MISSISSIPPI VALLEY AS IMPULSES OF ENERGY ROUNDING
THE WESTERN U.S. RIDGE POTENTIALLY INTERACT WITH MOISTURE POOLING
ALONG THE STALLED FRONTAL BOUNDARY.  SHOWERS AND THUNDERSTORMS
WILL ALSO BE POSSIBLE WITH A COLD FRONT DROPPING THROUGH THE UPPER
MIDWEST AND GREAT LAKES LATE NEXT WEEK AS WELL AS OVER THE FOUR
CORNERS STATES....WHERE MOISTURE IS EXPECTED TO INCREASE ACROSS
THE REGION. 

IN TERMS OF TEMPERATURES OVER THE LOWER 48...DAYTIME HIGHS SHOULD
STAY NEAR OR BELOW NORMAL BENEATH THE UPPER TROUGH CARVING OUT
OVER THE EASTERN HALF OF THE NATION.  PERSISTENT RIDGING IN THE
WEST SHOULD KEEP TEMPERATURES ABOVE NORMAL FROM THE WEST COAST TO
THE ROCKIES...WITH THE EXCEPTION OF THE FOUR CORNERS
STATES...WHERE THE INCREASE IN MOISTURE AND PRECIPITATION SHOULD
KEEP DAYTIME HIGHS CLOSER TO NORMAL FOR THIS TIME OF YEAR.


GERHARDT





Last Updated: 1211 PM EDT SUN JUN 26 2016