Prognostic Meteorological Discussion
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000
FXUS02 KWBC 271448
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1048 AM EDT MON JUL 27 2015

VALID 12Z THU JUL 30 2015 - 12Z MON AUG 03 2015

THE PREDOMINATE INFLUENCE ON THE LONGWAVE PATTERN ACROSS THE
UNITED THROUGH THE MEDIUM RANGE PERIOD WILL LIKELY BE A
WESTWARD-BUILDING AND EXPANDING UPPER HIGH ACROSS THE SOUTHWEST
FOR WHICH THE MODELS HAVE STRONG AGREEMENT AND SUPPORT FROM THE
ENSEMBLES.  ACCOMPANYING THE UPPER HIGH IS AN ASSOCIATED UPPER
CYCLONE THAT BECOMES NEARLY STATIONARY OVER HUDSON BAY.  THE
PROXIMITY OF THESE LARGE-SCALE FEATURES TO EACH OTHER FAVORS
PERSISTENCE OF ABOVE NORMAL TEMPERATURES AND BELOW NORMAL RAINFALL
ACROSS THE WEST...OTHER THAN THE DEVELOPING MONSOONAL FLOW OVER
THE SOUTHWEST.  MEANWHILE...NEAR TO OCCASIONALLY BELOW NORMAL
TEMPERATURES ARE ANTICIPATED OVER THE GREAT LAKES/OH
VALLEY...WHILE ABOVE NORMAL RAINFALL IS EXPECTED OVER THE
SOUTHEAST...NEAR THE BASE OF THE LONGWAVE TROUGH AND IN VICINITY
OF DECAYING FRONTAL BOUNDARIES.

ACROSS THE PACIFIC NORTHWEST...FORECAST CONFIDENCE IS A BIT LESS
DUE TO A SHORTER WAVELENGTH PATTERN THAT HAS THE POTENTIAL TO BE
SIGNIFICANTLY INFLUENCED BY THE TYPICALLY MORE UNCERTAIN FLOW
CROSSING THE NORTHERN PACIFIC.  THERE ARE SOME INDICATIONS THOUGH
THAT THE FLOW WILL REMAIN CLOSE TO NEUTRAL OR JUST SLIGHTLY
AMPLIFIED DUE TO THE LARGE-SCALE TROUGH DOWNSTREAM THAT SHOULD
HELP TO WEAKEN OR DECAY APPROACHING SYSTEMS FROM THE PACIFIC.  FOR
THIS REASON...PREFER THE WEAKER MODEL SCENARIOS ACROSS THIS REGION
THAT ARE BEST APPROXIMATED BY THE 00Z NAEFS BCMEAN.  FOR
CONTINUITY PURPOSES HOWEVER...THE BLEND OF THIS SOLUTION PEAKS AT
50 PERCENT WITH THE MORE AMPLIFIED 12Z 07/26 ECMWF WHICH WAS USED
PREVIOUSLY.  THIS APPROACH ALSO ADJUSTS THE CURRENT SOLUTION
TOWARD THE CONSENSUS THUS CREATING MORE FLEXIBILITY FOR ANY FUTURE
ADJUSTMENTS.  REGARDING FORECAST CONFIDENCE...VALUES ARE ABOVE
AVERAGE DAYS 3/4...AVERAGE DAY 5...AND BELOW AVERAGE DAYS 6/7.

JAMES

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