Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3
000
FXUS02 KWBC 291557
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1156 AM EDT MON MAY 29 2017

VALID 12Z THU JUN 1 2017 - 12Z MON JUN 5 2017

PATTERN OVERVIEW AND MODEL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

THE OVERALL UPPER LEVEL PATTERN ACROSS NORTH AMERICA DURING THE
MEDIUM RANGE PERIOD WILL LIKELY BE RATHER AMPLIFIED WITH AN OMEGA
BLOCK OVER CANADA AND QUASI-ZONAL FLOW OVER THE CONTINENTAL UNITED
STATES, AND A BROAD RIDGE EXTENDING ACROSS THE PLAINS AND INTO
CENTRAL CANADA.  A COUPLE OF WEAK DISTURBANCES ARE EXPECTED TO
TRACK FROM THE SOUTHWEST TO THE CENTRAL PLAINS WHICH WILL SERVE TO
ENHANCE RAIN AND THUNDERSTORM COVERAGE.  THE MID-LEVEL VORTEX
ACROSS THE GREAT LAKES IS EXPECTED TO RE-ESTABLISH ITSELF BY NEXT
MONDAY, WHICH SHOULD KEEP TEMPERATURES IN CHECK AND PREVENT HEAT
WAVES FROM DEVELOPING ACROSS THE EASTERN U.S. DURING THIS TIME.

IN TERMS OF THE MODELS, THE 6Z GFS SHOWED POOR RUN-TO-RUN
CONTINUITY FROM ITS PREVIOUS RUNS AND DEVIATED FROM THE MODEL
CONSENSUS BY FRIDAY, SO THE 00Z GFS WAS USED FOR THE FIRST HALF OF
THE FORECAST PERIOD.  GIVEN THAT THE ECMWF WAS MORE CONSISTENT AND
CLOSER TO THE ENSEMBLE MEAN GUIDANCE, A SLIGHTLY GREATER
PERCENTAGE OF IT WAS INCORPORATED.  THE 00Z CMC APPEARED MORE
AMPLIFIED WITH THE TROUGH OVER THE PACIFIC NORTHWEST THROUGH
SATURDAY, BUT NOT OUT OF THE REALM OF POSSIBILITY.  BOTH THE
OPERATIONAL GFS AND ECWMF ARE HINTING AT THE DEVELOPMENT OF A
SOUTHERN STREAM CUT-OFF LOW OVER CALIFORNIA BY MONDAY, BUT
CONFIDENCE IN THIS SCENARIO REMAINS RATHER LIMITED AT THIS TIME.
THE EC MEAN INDICATED A STRONGER CENTRAL RIDGE BUILDING INTO
CANADA THAT THE GEFS MEAN.  FOR THE PRESSURES, 500 HPA HEIGHTS,
AND WIND GRIDS WE USED A BLEND THAT WAS MAINLY DETERMINISTIC
THROUGH FRIDAY AND THEN TRANSITIONED TO MORE OF THE EC MEAN AND
GEFS MEAN THROUGH MONDAY.


WEATHER HIGHLIGHTS
~~~~~~~~~~~~~~~~~~

NEAR TO BELOW AVERAGE TEMPERATURES ARE EXPECTED TO CONTINUE INTO
EARLY NEXT WEEK ACROSS MUCH OF THE EASTERN U.S. DUE TO LINGERING
UPPER LEVEL TROUGHING AND THE PASSAGE OF A COLD FRONT ACROSS THE
GULF COAST REGION.  HOWEVER, OVERNIGHT LOWS ACROSS THE GULF COAST
REGION SHOULD BE NEAR TO SLIGHTLY ABOVE NORMAL GIVEN ABUNDANT
CLOUD COVER.  MEANWHILE, WARM CONDITIONS ARE EXPECTED ACROSS MUCH
OF THE INTERMOUNTAIN WEST, WITH AN APPROACHING COLD FRONT BRINGING
SOME SCATTERED SHOWERS AND STORMS TO THE PACIFIC NORTHWEST AND
NORTHERN ROCKIES.

THE HEAVIEST RAINFALL AND THUNDERSTORM ACTIVITY DURING THIS PERIOD
IS LIKELY FROM THE CENTRAL PLAINS TO THE CENTRAL APPALACHIANS WITH
THE DISTURBANCES MOVING EAST FROM THE SOUTHWEST U.S.  LOCALLY
HEAVY RAINS ARE ANTICIPATED IN AREAS THAT HAVE RECEIVED ABOVE
NORMAL RAINFALL THUS FAR THIS SPRING, AND THIS COULD LEAD TO
FLOODING ISSUES FOR SOME AREAS.

HAMRICK/ROTH

$$





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