Prognostic Meteorological Discussion
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FXUS02 KWBC 251556
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1155 AM EDT THU MAY 25 2017

VALID 12Z SUN MAY 28 2017 - 12Z THU JUN 01 2017

PATTERN OVERVIEW AND MODEL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
AN UPPER RIDGE WILL BUILD IN OVER THE WESTERN THIRD OF THE NATION
THIS WEEKEND AND EARLY NEXT WEEK WHILE A DOWNSTREAM UPPER
TROUGH/CLOSED LOW PROGRESSES FROM THE NORTHERN PLAINS/SOUTH
CENTRAL CANADA TO THE GREAT LAKES REGION.  TOWARDS THE MIDDLE OF
NEXT WEEK...RIDGING SHOULD BEGIN TO SUPPRESS OVER THE WEST WHILE A
CUT-OFF LOW DEVELOPS OVER SOUTHERN CALIFORNIA AND HEIGHT FALLS
FROM APPROACHING SYSTEMS IN THE NORTH PACIFIC EDGE INLAND OVER THE
PACIFIC NORTHWEST.

MODELS REMAINED LOCKED-IN TO THE LONG WAVE PATTERN SETTING UP OVER
THE CONUS THIS WEEKEND AND EARLY NEXT WEEK...BUT THEN SOME
FORECAST UNCERTAINTY AND MODEL SPREAD DEVELOP WITH THE CUT-OFF LOW
AND APPROACHING NORTH PACIFIC SYSTEMS IMPACTING THE WESTERN U.S.
BY THE MIDDLE OF NEXT WEEK.  THERE ALSO REMAINS SOME UNCERTAINTY
WITH THE DETAILS OF SHORTWAVE IMPULSES ROTATING WITHIN THE LARGE
UPPER TROUGH/CLOSED LOW CROSSING THE NORTH CENTRAL U.S....WHICH
HAS LED TO SOME INCONSISTENCIES WITH A SURFACE LOW TRACKING OUT OF
THE OHIO VALLEY ON SUNDAY AND POSSIBLE WEAK SURFACE WAVES LIFTING
UP THE NORTHEAST COAST EARLY NEXT WEEK.  THE WPC DAY 3-7 FORECAST
STARTED WITH A BLEND OF THE 06Z GFS/GEFS...00Z ECMWF/ECMWF
ENSEMBLE MEAN...AND CONTINUITY IN ORDER TO SMOOTH OUT SOME OF THE
SMALLER SCALE DETAIL DIFFERENCES OF THE FORECAST.


WEATHER HIGHLIGHTS
~~~~~~~~~~~~~~~~~~
WARM AND DRY CONDITIONS ARE EXPECTED ACROSS MUCH OF THE WESTERN
THIRD OF THE NATION THIS WEEKEND AND INTO EARLY NEXT WEEK.  THE
GREATEST POSITIVE TEMPERATURE ANOMALIES SHOULD BE OVER THE PACIFIC
NORTHWEST WHERE DAYTIME TEMPERATURES COULD SURPASS 90F IN SOME
LOCATIONS...BUT THEN A COOLING TREND SHOULD BEGIN BY THE MIDDLE OF
NEXT WEEK AS HEIGHT FALLS FROM APPROACHING SYSTEMS IN THE NORTH
PACIFIC PRESS INLAND OVER THE NORTHWEST.  MEANWHILE...AN UPPER
TROUGH/CLOSED LOW PROGRESSING THROUGH THE NORTH-CENTRAL U.S. WILL
SPREAD BELOW NORMAL TEMPERATURES FROM THE NORTHERN/CENTRAL PLAINS
THIS WEEKEND TO MUCH OF THE MIDWEST/GREAT LAKES REGION EARLY NEXT
WEEK.

MOISTURE ADVECTING NORTHWARD OUT OF THE GULF OF MEXICO WILL FUEL
POTENTIALLY HEAVY RAIN AND THUNDERSTORMS ALONG/AHEAD OF A FRONTAL
BOUNDARY PRESSING EAST/SOUTHEASTWARD OUT OF THE SOUTHERN PLAINS
INTO THE MID-SOUTH...WITH LESSER AMOUNTS ACROSS THE
NORTHEAST/MID-ATLANTIC STATES.  THE TAIL END OF THE BOUNDARY IS
EXPECTED TO STALL AND INTERACT WITH ENERGY MOVING THROUGH THE
SOUTHWEST, BRINGING ADDITIONAL HEAVY RAINFALL TO PORTIONS OF THE
SOUTHERN PLAINS.

GERHARDT/ROTH

$$





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