Preliminary Forecasts
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FXUS02 KWNH 010531
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
130 AM EDT SUN MAY 01 2016

VALID 12Z WED MAY 04 2016 - 12Z SUN MAY 08 2016

GENERAL FLOW PATTERN
~~~~~~~~~~~~~~~~~~~~
THE GUIDANCE ADVERTISES AN OMEGA BLOCK ACROSS THE LOWER 48 THIS
PERIOD, WITH RIDGING IN THE HIGH PLAINS TO MISSISSIPPI VALLEY
SANDWICHED BETWEEN A PAIR OF CLOSED/DEEP CYCLONES ACROSS THE WEST
AND NEAR THE MID-ATLANTIC STATES.


MODEL PREFERENCES
~~~~~~~~~~~~~~~~~
THE DETERMINISTIC GUIDANCE WHICH MOST CLOSELY MATCHED THE 18Z
GEFS/12Z NAEFS/12Z ECMWF ENSEMBLE MEAN SOLUTIONS AND ENSEMBLE LOW
CLUSTERING WERE THE 18Z/00Z GFS.  AS SUCH, THE 500 HPA
HEIGHTS/PRESSURES/WINDS WERE BASED ON A 50/30/20 BLEND OF THE 18Z
GFS/12Z NAEFS MEAN/12Z ECMWF ENSEMBLE MEAN THROUGH THE PERIOD.
OTHER GRIDS SUCH AS TEMPERATURES/RAIN CHANCES/WEATHER/DEW
POINTS/CLOUDS WERE BASED MORE HEAVILY ON THE 12Z NAEFS MEAN AND
12Z ECMWF ENSEMBLE MEAN SOLUTION.  THE DAYS 4-7 RAINFALL FORECAST
WAS BASED ON A COMPROMISE OF THE 18Z GFS/00Z GFS/12Z ECMWF THROUGH
THE PERIOD, THOUGH THE PERCENTAGE OF THE 12Z ECMWF USED FELL OFF
QUITE A BIT DURING THE DAYS 6-7 PERIOD DUE TO ITS UNDESIRABLE
SOLUTIONS IN THE EAST AND NORTHWEST.


WEATHER HIGHLIGHTS/THREATS
~~~~~~~~~~~~~~~~~~~~~~~~~~
THE DEEP CYCLONE HEADING INTO THE WEST WILL SPREAD A BROAD AREA OF
RAIN (SNOW AT THE HIGHEST ELEVATIONS) FROM THE WEST COAST INTO THE
ROCKIES AND THE HIGH PLAINS BY NEXT WEEKEND.  BEST POTENTIAL FOR
HIGHEST TOTALS SHOULD EXTEND OVER FAVORED TERRAIN INLAND FROM THE
CENTRAL WEST COAST EASTWARD INTO THE NORTH-CENTRAL AND CENTRAL
ROCKIES.  NORTHERN AREAS SHOULD SEE TEMPERATURES REMAIN 5-15F
ABOVE NORMAL MOST OF NEXT WEEK WITH THIS WARMTH EXTENDING INTO THE
NORTHERN PLAINS.  CENTRAL AND SOUTHERN LOCATIONS OVER THE WEST
WILL TREND STEADILY COOLER WITH SOME HIGHS MORE THAN 10F BELOW
NORMAL BY NEXT WEEKEND.

RIDGING MOVING FROM THE PLAINS TO THE MISSISSIPPI VALLEY IS
EXPECTED TO LEAD TO WARM ANOMALIES, MAINLY ACROSS THE NORTHERN
PLAINS/UPPER MIDWEST, TO THE TUNE OF 8-12F.  OUT EAST, A TREND
TOWARD A COOL AND UNSETTLED PATTERN IN ANTICIPATED WITH THE
HIGHEST RAINFALL POTENTIAL FROM THE CENTRAL APPALACHIANS AND
MID-ATLANTIC STATES NORTHWARD.  WHILE THE LOW TEMPERATURES ARE
EXPECTED TO BE BELOW NORMAL IN THE SOUTHEAST, HIGH TEMPERATURES
ARE FORECAST TO BE 4-8F BELOW THE AVERAGE FOR EARLY MAY FROM THE
GREAT LAKES INTO THE MID-ATLANTIC STATES MID- TO LATE WEEK.

ROTH
$$




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