Prognostic Meteorological Discussion
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FXUS02 KWBC 221729
PMDEPD

EXTENDED FORECAST DISCUSSION...AMENDED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1228 PM EST WED FEB 22 2017

VALID 12Z SAT FEB 25 2017 - 12Z WED MAR 01 2017

OVERVIEW
~~~~~~~~
A STRONG RIDGE, THE NORTHERN MEMBER OF A REX BLOCK EARLY ON, IS
EXPECTED TO MOVE SOUTHEAST ACROSS THE NORTHEASTERN PACIFIC TOWARDS
THE WEST COAST.  THIS SHOULD ALLOW THE UPPER TROUGH EXTENDED FROM
NUNAVUT INTO THE WEST EARLY TO PROGRESS INTO THE PLAINS BY MID
NEXT WEEK.  MEANWHILE, RIDGING AMPLIFIES NEAR CUBA/THE BAHAMAS/THE
EASTERN FL STRAITS DUE TO THE TROUGH MOVING INTO THE PLAINS.  THE
GUIDANCE SHOWS GOOD AGREEMENT WITH THESE IDEAS, WHICH ARE ALSO
EXPRESSED IN THE ENSEMBLE MEAN SOLUTIONS.


MODEL EVALUATION/PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THE GUIDANCE SHOWS VERY GOOD AGREEMENT TODAY -- WHICH AUGERS WELL
FOR THE FORECAST -- PARTICULARLY FOR SATURDAY AND SUNDAY WHEN THE
00Z UKMET, 00Z CANADIAN, 06Z GFS, AND 00Z ECMWF SHOW GOOD
AGREEMENT.  THEREAFTER, THE UKMET LEAVES THE PACK AS WAS
CONSIDERED LESS USEFUL.  STILL, OTHER THAN STRENGTH ISSUES WITH
THE SYSTEM MOVING THROUGH THE WEST INTO THE PLAINS/MIDWEST, THE
00Z CANADIAN/00Z ECMWF/06Z GFS SHOW VERY GOOD AGREEMENT.  FOR THE
PRESSURES, 500 HPA HEIGHTS, AND WIND GRIDS, USED A 25/25/25/25
SPLIT OF THE 00Z UKMET, 00Z CANADIAN, 06Z GFS, AND 00Z ECMWF INTO
SUNDAY MORNING.  THEREAFTER, DROPPED THE UKMET IN FAVOR FOR THE
00Z NAEFS AND ECMWF ENSEMBLE MEANS, WHICH WE SLOWLY INCREASED
PERCENTAGES FOR IN THE BLEND WHILE STILL KEEPING COMPONENTS OF THE
CANADIAN, ECMWF, AND GFS THROUGH NEXT WEDNESDAY.  THE TEMPERATURE,
DEW POINT, CLOUD, WEATHER, AND PRECIPITATION CHANCE GRIDS WERE
MORE ENSEMBLE MEAN BASED, AS USUAL.  FOR THE DAYS 4-7 QPF, THERE
WERE SUBSTANTIAL DIFFERENCES BETWEEN THE GFS AND ECMWF DESPITE
SIMILAR LOOK MASS FIELDS, AS CONVECTIVE PRECIPITATION APPEARS
LIKELY FOR PORTIONS OF THE MID-SOUTH AND LOWER OHIO VALLEY.  THIS
IS DUE TO DIFFERENCES IN TIMING OF WHEN THE CONVECTION WOULD
DEVELOP AS ANY LONGER LIVED CONVECTIVE SYSTEMS WOULD TEND TO
FOLLOW FORWARD PROPAGATING VECTORS EASTWARD.  SINCE CONVECTIVE
INITIATION TIMING IS UNRESOLVABLE WITH PRECISION FIVE DAYS INTO
THE FUTURE, USED A ROUGH COMPROMISE OF THE 06Z GFS, 12Z GFS (WHICH
IS CLOSE TO A MIDDLE GROUND IN THE OHIO VALLEY), AND 00Z ECMWF.


WEATHER HIGHLIGHTS/THREATS
~~~~~~~~~~~~~~~~~~~~~~~~~~
FOR THE WEST, THE SYSTEM MOVING IN THIS WEEKEND INTO THE FIRST
HALF OF NEXT WEEK WILL SPREAD A BROAD AREA OF RAIN AND HIGHER
ELEVATION/INLAND SNOW ACROSS CA, THE GREAT BASIN, AND SOUTHWEST.
EXPECT HIGHEST TOTALS OVER THE FAVORED HIGHER RELIEF OF
CALIFORNIA.  THE POTENTIAL STILL EXISTS FOR THE SYSTEM TO BRING A
PERIOD OF STRONG WINDS AS IT MAKES LANDFALL IN CA.  THE EASTWARD
PROGRESSION OF THE UPR TROUGH WILL SUPPORT A DRYING TREND MIDWEEK
WITH PRIMARY FOCUS OF LIGHT TO MODERATE PRECIPITATION TO LIKELY TO
SHIFT TO THE NORTHWEST/NORTHERN ROCKIES AT THAT TIME.
PERSISTENTLY BELOW NORMAL TEMPERATURES ARE EXPECTED MOST AREAS
WITH SPOTS SEEING 10-15F COLD ANOMALIES FOR HIGHS ON MULTIPLE
DAYS.  LOW TEMPERATURE ANOMALIES SHOULD BE LESS EXTREME CENTRAL
AND SOUTHERN AREAS DUE TO CLOUDS/PRECIP.

THE EASTERN HALF OF THE LOWER 48 WILL SEE INCREASING
COVERAGE/INTENSITY OF PRECIPITATION EARLY TO MID NEXT WEEK AS AN
AREA OF LOW PRESSURE TRACKS THROUGH THE PLAINS INTO THE GREAT
LAKES AND RETURNING MOISTURE FROM THE GULF OF MEXICO INTERACTS
WITH A LEADING WARM FRONT/TRAILING COLD FRONT.  THE BEST POTENTIAL
FOR HEAVY RAINS EXISTS OVER THE OH AND TN VALLEYS.  THE MOST
MEANINGFUL WINTRY WEATHER SHOULD BE CONFINED TO FAIRLY NORTHERN
LATITUDES.  THE LEADING STORM SYSTEM AFFECTING THE EAST EARLY IN
THE PERIOD WILL LIKELY BRING HEAVIEST RAIN TO THE NORTHEAST.
BELOW NORMAL TEMPERATURES MAY EXTEND INTO THE PLAINS SATURDAY
BEFORE A WARMING TREND THAT COULD BE SLOWED DOWN BY SNOW COVER
ACROSS THE UPPER MIDWEST.  EAST COAST STATES SHOULD SEE ONE MORE
WARM DAY SATURDAY BEFORE NEAR/SLIGHTLY BELOW NORMAL TEMPS MOVE IN
FROM THE PLAINS/MS VLY.  THE SYSTEM LIKELY TO EMERGE FROM THE
PLAINS AND TRACK INTO THE GREAT LAKES NEXT WEEK WILL LIKELY BRING
ANOTHER SURGE OF WARMTH TO CENTRAL AND EASTERN AREAS, THOUGH
EASTERN AREAS SHOW GREATER UNCERTAINTY DUE TO THE DISTANCE OF THE
CYCLONE TRACK AND THE USUAL PERSISTENCE OF COLD AIR DAMMING EAST
OF THE APPALACHIANS.  LOW TEMPERATURES COULD BE 20-30F ABOVE
NORMAL ALLOWING FOR SOME DAILY RECORDS WHILE ANOMALIES FOR DAYTIME
HIGHS LOOK SOMEWHAT LESS EXTREME.

ROTH/RAUSCH
$$





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