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 1618Z Aug 15, 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
1218 PM EDT FRI AUG 15 2014

VALID 12Z MON AUG 18 2014 - 12Z FRI AUG 22 2014

...OVERVIEW...

A LOW AMPLITUDE/PROGRESSIVE PATTERN OVER THE CONUS AT THE START OF
THE MEDIUM RANGE PERIOD SHOULD HOLD THROUGH THE MIDDLE OF NEXT
WEEK...BEFORE A LONG WAVE TROUGH SETS UP ALONG THE WESTERN U.S.
LATE NEXT WEEK.  THE MAIN FEATURES IMPACTING THE LOWER 48 WILL BE
A SURFACE WAVE TRACKING FROM THE OHIO VALLEY TO NORTHERN
MID-ATLANTIC COAST MONDAY-WEDNESDAY...A SHORT-WAVE THROUGH
DROPPING INTO THE UPPER MIDWEST MONDAY...AN UPPER LOW POTENTIALLY
CLOSING OFF OFF THE CALIFORNIA COAST WEDNESDAY INTO THURSDAY...AND
HEIGHT FALLS DIGGING INTO THE NORTHWESTERN U.S. LATE NEXT WEEK.


...MODEL DIFFERENCES/PREFERENCES... 

AFTER DAYS OF LARGE SPREAD AND UNCERTAINTY...THE MODELS APPEAR TO
HAVE CONVERGED ON A SOLUTION WITH THE SURFACE WAVE TRACKING
THROUGH THE OHIO VALLEY EARLY NEXT WEEK.  THE 00Z UKMET APPEARS TO
BE AN OUTLIER AND TRACKS A DEEPER SURFACE LOW NORTHEASTWARD
THROUGH THE LOWER GREAT LAKES...SO THE WPC FORECAST FAVORED THE
GFS/ECMWF SOLUTION OF TRACKING A FLATTER SYSTEM EASTWARD THROUGH
THE NORTHERN MID-ATLANTIC STATES AND OFF THE COAST.

IN REGARDS TO THE SHORTWAVE EXPECTED TO DROP INTO THE UPPER
MIDWEST AND THEN WEAKEN WHILE LIFTING THROUGH THE UPPER GREAT
LAKES DURING THE MIDDLE OF NEXT WEEK...MODELS WERE IN FAIRLY GOOD
AGREEMENT WITH THIS FEATURE; HOWEVER...THE LATEST RUNS OF THE GFS
ENDED UP ON THE SLOWER/MORE AMPLIFIED SIDE OF MODEL SPREAD BY
TUESDAY.  THE WPC FORECAST WAS WEIGHTED TOWARDS THE 00Z ECMWF
SINCE IT SEEMED TO FIT IN BEST WITH ENSEMBLE MEAN GUIDANCE.

BY THE END OF NEXT WEEK...MODELS ARE STILL SHOWING LARGE AMOUNTS
OF UNCERTAINTY BOTH WITH THE LOW POTENTIALLY CLOSING OFF OFF THE
CALIFORNIA COAST AND WITH HEIGHT FALLS DIGGING INTO THE NORTHWEST.
 WITH EACH PIECE OF DETERMINISTIC GUIDANCE HAVING ITS OWN
RUN-TO-RUN CONTINUITY ISSUES...THE WPC FORECAST WAS BASED OFF A
COMBINATION OF THE FAIRLY AGREEABLE 00Z GEFS/ECMWF ENSEMBLE MEANS.



...SENSIBLE WEATHER HIGHLIGHTS...

WET AND STORMY WEATHER WILL ACCOMPANY THE SURFACE WAVE TRACKING
THROUGH THE OHIO VALLEY/MID-ATLANTIC STATES EARLY NEXT WEEK...WITH
PERIODS OF HEAVY RAINS AND STRONG THUNDERSTORMS POSSIBLE.  SHOWERS
AND THUNDERSTORMS ARE ALSO EXPECTED WITH THE SHORTWAVE DROPPING
INTO THE UPPER MIDWEST/GREAT LAKES AND AT THE LEADING EDGE OF
HEIGHT FALLS DIGGING INTO THE NORTHWEST...WHICH SHOULD IMPACT THE
NORTHERN PLAINS BY LATE NEXT WEEK.  

THE RELATIVELY FLAT AND PROGRESSIVE FLOW OVER THE CONUS SHOULD
LIMIT ANY LARGE TEMPERATURE EXTREMES.  IN GENERAL...TEMPERATURES
WILL BE ABOVE NORMAL SURROUNDING THE CENTRAL ROCKIES/HIGH
PLAINS...BENEATH MODEST RIDGING ALOFT.  ALSO...WITH MEAN TROUGHING
SETTING UP OVER THE WESTERN U.S. LATE NEXT WEEK...DAYTIME HIGHS
SHOULD BE BELOW NORMAL. 


GERHARDT