Skip Navigation Links weather.gov 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center

 
 

 

Follow the Weather Prediction Center on Facebook Follow the Weather Prediction Center on Twitter
NCEP Quarterly Newsletter
WPC Home
Analyses and Forecasts
   National High & Low
   WPC Discussions
   Surface Analysis
   Days ½-2½ CONUS
   Days 3-7 CONUS
   Days 4-8 Alaska
   QPF
   PQPF
   Flood Outlook
   Winter Weather
   Storm Summaries
   Heat Index
   Air Quality
   Tropical Products
   Daily Weather Map
   GIS Products
Current Watches/
Warnings

Satellite and Radar Imagery
   Satellite Images
   National Radar
Product Archive
WPC Verification
   QPF
   Medium Range
   Model Diagnostics
   Event Reviews
International Desks
Development and Training
   Development
WPC Overview
   About the WPC
   Staff
   WPC History
   Accomplishments
   Other Sites
   FAQs
Meteorological Calculators
Contact Us
   About Our Site
 
USA.gov is the U.S. Government's official web portal to all federal, state, and local government web resources and services.
 
Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1556Z Sep 18, 2014)
 
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
 
Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1156 AM EDT THU SEP 18 2014

VALID 12Z SUN SEP 21 2014 - 12Z THU SEP 25 2014

...BIG PATTERN CHANGE FOR THE PACIFIC NORTHWEST NEXT WEEK...


...OVERVIEW...

MUCH OF THE NORTHERN HEMISPHERE SHOULD UNDERGO A PATTERN CHANGE
OVER THE NEXT WEEK AS A STRONG PACIFIC JET /170KTS OR SO/ MOVES
EASTWARD ACROSS THE DATELINE. THE AMPLIFIED RIDGE/TROUGH PATTERN
ACROSS THE WEST/EAST AT THE START OF THE MEDIUM RANGE IS FORECAST
TO PUSH EASTWARD... WHICH WILL ESSENTIALLY FLIP THE PATTERN ACROSS
THE CONUS. INITIAL TROUGHING IN THE EAST WILL SUPPORT A SFC COLD
FRONT THAT WILL PUSH OFFSHORE THE EAST COAST BY EARLY NEXT WEEK
AND INTO THE GULF BY TUE/D5 WITH HIGH PRESSURE IN ITS WAKE. A LEAD
COLD FRONT IN THE PACIFIC SHOULD APPROACH WA/OR EARLY IN THE WEEK
BUT DISSIPATE AS STRONGER UPSTREAM MID-LEVEL ENERGY SWINGS THROUGH
BEHIND IT... WHICH SHOULD MAINTAIN ITSELF INTO THE PAC NW BY THE
END OF THE PERIOD.


...GUIDANCE/UNCERTAINTY ASSESSMENT AND PREFERENCES...

THE MODELS/ENSEMBLES HAVE HAD A WORLD OF TROUBLE RESOLVING THE
PATTERN ACROSS THE PACIFIC -- THE FORECASTS FROM TWO DAYS AGO ARE
BASICALLY 180 DEGREES OUT OF PHASE -- BUT HAVE COME INTO MUCH
BETTER AGREEMENT IN THEIR RECENT CYCLE. THE AREAS OF CONTENTION
LIE IN THE NORTHEAST AROUND TUE/D5 WHERE THE 06Z GFS AND MANY
00Z-06Z GEFS MEMBERS LINGER ENERGY IN NEW ENGLAND WHEREAS THE
CONSENSUS IS TO KEEP IT PROGRESSIVE AND MOVE IT OUT OF THE AREA.
WAVELENGTH SPACING DIFFERENCES BETWEEN THE ECMWF AND GFS ENSEMBLES
SEEM TO BE CONTRADICTORY -- THE GEFS ARE QUICKER IN THE WEST BUT
SLOWER IN THE EAST -- BUT THE FLOW IS COMPLICATED BY THE NORTHERN
STREAM IN EASTERN CANADA. PREFER TO STICK WITH CONTINUITY AND THE
LARGER AGREEMENT NEAR THE ECMWF... BUT INCLUDED A VERY MINOR
GFS/GEFS WEIGHTING GIVEN THE POSSIBILITY OF A SLOWER EXIT OF THE
TROUGH MIDWEEK NEXT WEEK.

IN THE WEST... THE GFS AND GEFS MEMBERS ARE LIKELY SHOWING THEIR
TYPICAL BIAS OF BEING TOO QUICK BY WED-THU/D6-7 TO BRING TROUGHING
INTO THE WEST... AS THE TREND IN THE ECMWF ENSEMBLES -- AND EVEN
THE GEFS -- HAS BEEN SLOWER. IN ADDITION... THE EXTRATROPICAL
TRANSITION OF CURRENT TROPICAL STORM FUNG-WONG LATE IN THE PERIOD
EAST OF JAPAN SHOULD ACT TO AMPLIFY/SLOW THE PATTERN AT LEAST
SOMEWHAT ACROSS THE PACIFIC. 00Z ECMWF/ECENS MEAN WERE THE
PREFERENCE FOR MIDWEEK NEXT WEEK IN THE WEST.


...SENSIBLE WEATHER HIGHLIGHTS...

COOLER/WARMER THAN AVERAGE TEMPERATURES WILL FOLLOW THE UPPER
RIDGE/TROUGH PATTERN FROM WEST TO EAST THOUGH THE PAC NW SHOULD
SEE THE LARGEST SWING FROM WARM TO COOL DURING THE PERIOD.
PRECIPITATION SHOULD FOCUS ALONG THE EXITING COLD FRONT IN THE
EAST AND THROUGH FLORIDA AS IT STALLS IN THE GULF. THE REMNANTS OF
ODILE WILL PUSH THROUGH OK AND MERGE WITH THE FRONTAL BOUNDARY...
LIKELY ENHANCING THE PRECIPITATION OVER THE SOUTHERN PLAINS AT
LEAST AT THE START OF THE MEDIUM RANGE. THEREAFTER... AN UPPER LOW
INITIALLY OVER CALIFORNIA WILL SLOWLY MOVE THROUGH ID/WY TOWARD
THE DAKOTAS WHICH SHOULD BE A PROGRESSIVE FOCUS FOR PRECIP THROUGH
THE PERIOD. FINALLY... WITH THE APPROACH OF A BONA FIDE COLD FRONT
INTO WA/OR AND NORTHERN CALIFORNIA... AND PW VALUES PERHAPS RISING
TO +2 TO +3 STANDARD DEVIATIONS... THE WA/OR COASTS SHOULD SEE
THEIR FARE SHARE OF RAIN WED-THU/D6-7.


FRACASSO