Preliminary Forecasts
Issued by NWS

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FXUS02 KWNH 260652
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
251 AM EDT TUE MAY 26 2015

VALID 12Z FRI MAY 29 2015 - 12Z TUE JUN 02 2015

...OVERVIEW...
THE RIDGE ACROSS THE SOUTHEAST GRADUALLY ERODES ALONG ITS
NORTHWEST FLANKS THIS MEDIUM PERIOD---AS A MID-LEVEL CYCLONE
LOCATED IN THE PACIFIC NORTHWEST --- MIGRATES EASTWARD ACROSS
SOUTHERN CANADA. THE SURFACE CYCLONE GENERATES A COLD FRONT THAT
SPREADS ACROSS THE MISSOURI AND OHIO VALLEYS---AND PROVIDES THE
FOCUS FOR MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS.

WEST OF THE CONTINENTAL DIVIDE --- UPPER-LEVEL RIDGING BEGINS TO
ANCHOR OVER THE DESERT SOUTHWEST --- AND A BROAD TROUGH TAKES
SHAPE IN THE EASTERN PACIFIC WITH MID-LEVEL ENERGY MIGRATING
NORTHWESTWARD INTO THE WEST COAST--- ALONG THE WESTERN PERIPHERY
OF THIS UPPER RIDGE.

...UNCERTAINTY ASSESSMENT/MODEL PREFERENCES...
THE 25/12Z ECENS/NAEFS AND GEFS MEANS DEPICT A TEMPORARY
`RESHUFFLE` OF THE UPPER FLOW PATTERN ACROSS HIGH LATITUDE CANADA
--- RESULTING IN A FLAT-ZONAL WESTERLY FLOW ACROSS SOUTH CENTRAL
CANADA AND SUBSTANTIAL UPPER-LEVEL RIDGING ACROSS THE SUBTROPICS.
THEIR CONSENSUS LEADS TO --- THE CUTOFF LOW CURRENTLY LOCATED IN
SOUTHERN BRITISH COLUMBIA AND NORTHEASTERN WASHINGTON MIGRATING
EASTWARD DURING THE FIRST HALF OF THE PERIOD. AND A SECOND PACIFIC
WAVE TO FOLLOW --- MIGRATING ACROSS THE PACIFIC NORTHWEST IN THE
DAY 6-7 PORTION OF THE MEDIUM RANGE.

...SENSIBLE WEATHER HIGHLIGHTS...
TRIPLE-DIGIT TEMPERATURE READINGS RETURN TO THE DESERT SOUTHWEST.

AXIS OF RAINFALL SHIFTS FROM THE SOUTHERN PLAINS TO NEW ENGLAND
--- FOLLOWING A  FRONTAL PROGRESSION ACROSS THE LOWER 48 AND
ASSOCIATED SURFACE CYCLONE TRACK FROM THE UPPER GREAT LAKES TO THE
ST LAWRENCE VALLEY.

VOJTESAK


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