Prognostic Meteorological Discussion
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000
FXUS02 KWBC 041601
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1200 PM EDT WED MAY 04 2016

VALID 12Z SAT MAY 07 2016 - 12Z WED MAY 11 2016

GENERAL FLOW PATTERN
~~~~~~~~~~~~~~~~~~~~
A BLOCKY UPPER-LEVEL FLOW PATTERN ACROSS THE COUNTRY COULD EVOLVE
INTO A REX BLOCK BY MID-WEEK NEXT WEEK.  A CUTOFF LOW IN THE
SOUTHWEST IS FORECAST TO BECOME LESS AMPLIFIED AND LIFTS
NORTHEASTWARD INTO THE CENTRAL/NORTHERN PLAINS BY NEXT WEDNESDAY
WHEREAS ANOTHER CUTOFF LOW IN THE NORTHEAST IS EXPECTED TO LIFT
OUT INTO THE CANADIAN MARITIMES.  MODEL ENSEMBLES...ESPECIALLY THE
ECMWF PACKAGE...ARE SUGGESTING THAT THE PATTERN WILL EVOLVE INTO A
REX BLOCK BY NEXT WEDNESDAY AS A POSSIBLE CUTOFF HIGH IN CANADA
BECOMES SITUATED NORTH OF THE DEAMPLIFYING LOW IN THE PLAINS.


MODEL PREFERENCES
~~~~~~~~~~~~~~~~~
THE GUIDANCE IS MUCH MORE AGREEABLE THAN SEEN ON PAST DAYS.  FROM
DAYS 3/SAT TO 5/MON...THE WPC PRESSURE FIELD...500 HPA HEIGHTS AND
WIND GRIDS...ARE DERIVED FROM A BLEND OF THE 00Z ECMWF AND THE 06Z
GFS MIXING IN WITH SOME OF THE RESPECTIVE ENSEMBLE MEANS.  THE GFS
AND GEFS CONTINUE TO LAG BEHIND THE EC PACKAGES BUT HAVE SPED UP
TOWARD THE ECMWF SOLUTION IN THE MOST RECENT RUNS.  BY DAY
7/WED...THE ECMWF AND EC MEANS ARE SUGGESTING THE FORMATION OF A
CUTOFF HIGH/HIGH AMPLITUDE RIDGE IN CENTRAL CANADA.  THE 06Z GEFS
MEAN HAS ALSO TRENDED TOWARD A HIGHER AMPLITUDE RIDGE IN THE SAME
GENERAL AREA.  IT APPEARS THAT THE ECMWF IS LEADING TOWARD A REX
BLOCK SCENARIO BY DAY 7 NEXT WED...AND THUS MUCH OF THE WPC BLEND
HAS BEEN WEIGHED TOWARD THE EC MEANS BY DAY 7.


WEATHER HIGHLIGHTS/THREATS
~~~~~~~~~~~~~~~~~~~~~~~~~~
THE NORTHWEST STAYS QUITE WARM AND DRY AS RIDGING ALOFT ATTEMPTS
TO PERSIST NEARBY THROUGH THE PERIOD.  A DEEP LOW/TROUGH WORKING
NORTHEASTWARD OUT OF THE SOUTHWEST WILL SPREAD A BROAD AREA OF
RAIN AND HIGHER ELEVATION SNOWS THROUGH THE GREAT BASIN INTO THE
ROCKIES...WITH LEAD RAINS DEVELOPING OVER THE CENTRAL US SUNDAY
INTO NEXT WEDNESDAY...INCLUDING THE RAIN-WEARY ARKLATEX. HIGHEST
TOTALS ARE EXPECTED ACROSS PORTIONS OF CO/WY THEN OUT OVER THE
PLAINS. SPC HAS A 15% RISK AREA OF SEVERE STORMS ON SATURDAY AHEAD
OF THE COLD FRONT FROM WEST TEXAS NORTHWARD TO WESTERN KANSAS AND
EASTERN COLORADO. TEMPERATURES WITH THE SYSTEM ARE EXPECTED TO BE
10-15F BELOW AVERAGE UNDER THE UPPER LOW. RIDGING ALOFT AHEAD OF
THIS SYSTEM IS EXPECTED TO SUPPORT LEAD WARMING SPREADING FROM THE
PLAINS SATURDAY INTO THE EAST WITH TIME.  PRECIPITATION ACROSS THE
NORTHEAST WILL BE SLOW TO CLEAR THIS PERIOD DUE TO A PERSISTENT
DEEP CYCLONE NEAR ATLANTIC CANADA WHICH WON`T PULL AWAY FROM THE
REGION UNTIL TUESDAY AND A FRONTAL ZONE MEANDERING ACROSS THE
SOUTHERN MID-ATLANTIC STATES.

THERE APPEARS TO BE SOME CERTAINTY REGARDING THE PRESSURE FIELD IN
THE NORTHERN PLAINS BY DAY 7 AS THE MODELS ARE STILL RESOLVING TO
A STEADIER SOLUTION TO THE EVOLVING REX PATTERN.  THE RAIN COULD
MOVE FARTHER EASTWARD INTO THE MIDWEST AHEAD OF THE LOW IN THE
PLAINS.

KONG/ROTH

$$




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