Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6
000
FXUS02 KWBC 221412
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
911 AM 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, 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
AND 00Z ECMWF.  SHOULD THE 12Z GFS MASS FIELDS APPEAR USEFUL, IT
COULD BE THROWN INTO THE QPF MIX MIDDAY.


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
$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.