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
   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 0640Z Apr 24, 2015)
 
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
240 AM EDT FRI APR 24 2015

VALID 12Z MON APR 27 2015 - 12Z FRI MAY 01 2015

...OVERVIEW...

THE DOMINANT FOCUS OF THE MEDIUM RANGE FCST IN TERMS OF COMBINED
SENSIBLE WEATHER IMPACTS AND UNCERTAINTY WILL BE ON THE EVOLUTION
OF CLOSED LOW ENERGY EJECTING FROM THE SRN HIGH PLAINS AND ONE OR
MORE BUNDLES OF NRN STREAM ENERGY FLOWING INTO AN ERN CONUS MEAN
TROUGH.  IMPORTANT DETAILS ARE OF THE TYPE THAT CAN BE DIFFICULT
TO RESOLVE VERY FAR IN ADVANCE BUT WILL HAVE SIGNIFICANT INFLUENCE
ON SENSIBLE WEATHER.  UPSTREAM THERE IS FAIR AGREEMENT THAT A WRN
CONUS MEAN RIDGE SHOULD GRADUALLY BUILD TOWARD THE PLAINS AS AN
ERN PAC MEAN UPR TROUGH HEADS TOWARD THE WEST COAST... THOUGH
GUIDANCE SHOWS INCREASING DIVERGENCE FOR SHRTWV DETAILS THAT WILL
INFLUENCE TIMING/SWD EXTENT OF NWRN CONUS PCPN.


...GUIDANCE EVALUATION AND PREFERENCES...

FOR CNTRL-ERN CONUS EVOLUTION THERE IS DECENT CLUSTERING INTO DAY
4 TUE.  AFTER THAT TIME THE UNCERTAINTY IN FCST DETAILS INCREASES
FAIRLY RAPIDLY GIVEN THE MODEL/ENSEMBLE SPREAD IN HOW NRN
PLAINS/MS VLY ENERGY MAY INTERACT WITH THE SRN PLAINS FEATURE. 
THE APPROACH OF ONE OR MORE UPSTREAM SHRTWVS FURTHER COMPLICATES
THE FCST MID-LATE PERIOD.  THUS FAR THE GEFS/ECMWF MEANS HAVE BEEN
THE MOST STABLE GUIDANCE SOURCES OVERALL WITH THE TRACK/TIMING OF
ASSOC LOW PRES FROM THE GULF COAST INTO THE WRN ATLC... WITH ONLY
TYPICAL RUN TO RUN VARIATIONS.  AT THE MOMENT LATEST OPERATIONAL
MODELS ARE SIMILAR TO OR A LITTLE SLOWER THAN THESE MEANS AND IN
THE SLOWER PORTION OF THE VERY BROAD ENSEMBLE SPREAD FOR TIMING. 
RECENT 12-HRLY GFS/ECMWF RUNS HAVE OFFERED QUITE VARIED EVOLUTIONS
SFC/ALOFT THUS PROVIDING FURTHER SUPPORT TO MAINTAINING MORE OF AN
ENSEMBLE MEAN EMPHASIS UNTIL THE MODELS STABILIZE.  LATE IN THE
PERIOD CONFIDENCE IS FAIRLY LOW IN THE PAST TWO 00Z GFS RUNS THAT
BRING CNTRL CANADA CLOSED LOW ENERGY INTO THE NORTHEAST AND AS A
RESULT PULL WRN ATLC LOW PRES TOWARD NEW ENGLAND.  THAT SAID...
SUCH AN EVOLUTION ALOFT WOULD STILL FIT WITHIN THE EXPECTED MEAN
PATTERN SO CANNOT FULLY DISCOUNT SUCH A SCENARIO.

SHRTWV DETAIL DIFFS WITHIN THE TROUGH OFF THE NWRN COAST BECOME
APPARENT ALREADY BY DAY 4 TUE.  LATEST GFS RUNS AND ESPECIALLY THE
00Z VERSION ARE NOTICEABLY SLOWER THAN MOST OTHER SOLNS WITH A
LEADING SHRTWV.  THEREAFTER THE 12Z/23 AND 00Z/23 ECMWF RUNS
BECOME PROGRESSIVE EXTREMES WITH TRAILING ENERGY... BRINGING IT
INTO THE DOWNSTREAM MEAN RIDGE MORE AGGRESSIVELY THAN OTHER MODELS
AND THE 12Z/18Z GEFS MEANS AND 12Z ECMWF/CMC MEANS.

A BLEND OF THE 18Z GFS/12Z GEFS MEAN AND 12Z ECMWF/ECMWF MEAN BEST
REPRESENTS EXISTING CONSENSUS FOR THE MON-TUE PORTION OF THE FCST.
 THEN FOR DAYS 5-7 WED-FRI PREFER A 70/30 WEIGHTING OF THE 12Z
ECMWF MEAN/GEFS MEAN.


...SENSIBLE WEATHER HIGHLIGHTS...

COMBINATION OF UPR LOW ENERGY EJECTING FROM THE SRN HIGH PLAINS
AND ASSOC LOW PRES TRACKING ALONG THE GULF COAST INTO THE ATLC
SHOULD GENERATE SOME AREAS OF HVY PCPN FROM PORTIONS OF THE SRN
HALF OF THE ROCKIES OR HIGH PLAINS THROUGH THE SRN TIER STATES. 
SOME AREAS LIKELY TO BE AFFECTED HAVE ALREADY RECEIVED SIGNIFICANT
RNFL TOTALS OVER RECENT WEEKS.  CONSULT SPC OUTLOOKS FOR LATEST
INFO REGARDING SEVERE WEATHER THREATS... CURRENTLY INDICATED OVER
THE SRN PLAINS EARLY IN THE PERIOD.  COVERAGE AND INTENSITY OF
PCPN OVER THE CNTRL-NRN PARTS OF THE EAST IS MUCH MORE UNCERTAIN
AND DEPENDENT ON DIFFICULT TO RESOLVE ASPECTS OF MULTIPLE FEATURES
ALOFT.  MEANWHILE THE PATTERN FARTHER WWD WILL SUPPORT MULTIPLE
EPISODES OF LGT TO PERHAPS LOCALLY MDT PCPN OVER THE PAC NW AND
VICINITY.  THE MOST NOTABLE EXTREMES IN TEMPS WILL BE FROM THE
CNTRL-SRN HIGH PLAINS INTO THE SOUTHEAST WHERE CLOUDS/PCPN SHOULD
HOLD DAYTIME HIGHS TO 5-20F BELOW NORMAL ONE OR MORE DAYS... AND
FROM THE WEST INTO THE NRN PLAINS WHERE SOME LOCATIONS MAY SEE
READINGS UP TO 10-20F ABOVE NORMAL.

RAUSCH