Prognostic Meteorological Discussion
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FXUS02 KWBC 260530
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
129 AM EDT FRI MAY 26 2017

VALID 12Z MON MAY 29 2017 - 12Z FRI JUN 02 2017

PATTERN OVERVIEW AND MODEL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THE GENERAL FLOW PATTERN BECOMES LESS AMPLIFIED THIS PERIOD AS A
DEEP CYCLONE NEAR THE GREAT LAKES LIFTS NORTHEAST INTO EASTERN
CANADA AND A DEEP LAYERED CYCLONE IN THE NORTHEAST PACIFIC ERODES
TO THE NORTHERN MEMBER OF A REX-LIKE PAIR OUT WEST, WHICH ALLOWS
THE SOUTHWEST TROUGH TO EVOLVE INTO A WESTERN US TROUGH WITH TIME.
 THE GUIDANCE IS IN BETTER THAN AVERAGE/GOOD AGREEMENT THROUGH THE
PERIOD.  FOR THE PRESSURES, 500 HPA HEIGHTS, AND WIND GRIDS, USED
A COMPROMISE OF THE 12Z CANADIAN/12Z UKMET/12Z ECMWF/18Z GFS FOR
MONDAY INTO WEDNESDAY BEFORE BLENDING IN INCREASINGLY AMOUNTS OF
THE 12Z NAEFS AND 12Z ECMWF ENSEMBLE MEAN TO ACCOUNT FOR
UNCERTAINTY LATER ON.  THE TEMPERATURES, DEW POINTS, CLOUDS,
WEATHER, AND PRECIPITATION CHANCES WERE BASED ON AN EVEN MIX OF
ENSEMBLE MEAN AND DETERMINISTIC GUIDANCE.  THE DAYS 4-7 QPF WAS
BASED ON A ROUGH COMPROMISE OF THE 12Z ECMWF/00Z GFS SOLUTIONS.


WEATHER HIGHLIGHTS
~~~~~~~~~~~~~~~~~~
WARM AND DRY CONDITIONS ARE EXPECTED ACROSS MUCH OF THE WESTERN
THIRD OF THE NATION INTO EARLY NEXT WEEK.  THE GREATEST POSITIVE
TEMPERATURE ANOMALIES SHOULD BE OVER THE PACIFIC NORTHWEST WHERE
DAYTIME TEMPERATURES COULD SURPASS 90F IN SOME LOCATIONS.  A
COOLING TREND WILL BE POSSIBLE BY THE MIDDLE, BRINGING THE PROMISE
OF LATE SEASON RAINS TO THE REGION, AS THE MAIN BELT OF THE
WESTERLIES PRESS INLAND OVER THE NORTHWEST AND CARVES OUT
TROUGHING.  MEANWHILE...AN UPPER TROUGH/CLOSED LOW PROGRESSING
THROUGH THE NORTH-CENTRAL U.S. WILL SPREAD BELOW NORMAL
TEMPERATURES 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 EARLY NEXT WEEK, WITH MODEST 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 EARLY TO MID NEXT WEEK WHICH COULD SPREAD QUICKLY
ACROSS THE MID-MISSISSIPPI VALLEY TOWARDS THE NORTHERN
MID-ATLANTIC STATES.

ROTH/GERHARDT

$$




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