July 11 NWS Medium Range US Outlook

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
154 PM EDT SUN JUL 11 2010

VALID 12Z WED JUL 14 2010 - 12Z SUN JUL 18 2010

FINAL DAYS 3-7 FRONTS/SEA LEVEL PRESSURES WERE COMPOSED USING A
BLEND OF THE 00-12Z NCEP/00Z ECMWF ENSEMBLE MEANS WITH THE 00Z
ECMWF AND 06Z GFS PARALLEL RUN. NO MAJOR CHANGES WERE MADE IN THE
12Z GFS/NCEP ENSEMBLE MEAN/GFS PARALLEL/UKMET/CANADIAN GLOBAL
FORECASTS...SO A FEW ADJUSTMENTS WERE MADE TO BLEND WITH THE 12Z
FORECASTS REGARDING THE CYCLONE EVOLUTION OVER
MANITOBA/ONTARIO/QUEBEC/ADJACENT NEW ENGLAND.

A PERSISTENT 500 MB TROUGH REMAINS IN PLACE THIS PERIOD ACROSS THE
PACIFIC NORTHWEST/SOUTHWESTERN CANADA. A CLOSED 500 MB LOW ON DAY
THREE /14 JULY IN SOUTH CENTRAL CANADA DRIFTS EAST NORTHEAST TO
THE MANITOBA/ONTARIO BORDER BY 12Z THU 15 JUL...ONTARIO BORDER
WITH HUDSON BAY 12Z FRI 16 JUL...WITH GROWING SPREAD AFTERWARD AS
THE MODELS ARE SPLIT AS TO WHETHER THE LOW SHEARS OR REFORMS WITH
A SECOND CENTER ON SAT/SUN. GIVEN THE PARADE OF LOWS ON THE
SPAGHETTI DIAGRAM WITHOUT MUCH CLUSTERING...THE PREFERENCE BECOMES
THE CONSENSUS SOLUTION...BEST REPRESENTED BY THE ENSEMBLE MEANS.
THE CANADIAN GLOBAL MODEL WAS AN OUTLIER IN THE TREATMENT OF THE
CANADIAN CYCLONE(S) AND WITH THE 00Z CANADIAN MEAN/00Z UKMET
LINING UP BETTER WITH THE NCEP/ECMWF ENSEMBLE MEANS...NO WEIGHTING
WAS GIVEN TO THE 00Z CANADIAN GLOBAL. THE 06Z GFS MOVES A LOW
FASTER ACROSS SOUTHEAST CANADA TOWARDS NEW ENGLAND AND TRAILING
FRONT INTO THE UPPER LAKES. THIS SOLUTION WAS ON THE EDGE OF THE
CLUSTER OF SOLUTIONS...SO THE 06Z GFS PARALLEL WAS USED INSTEAD.

A WARM CORE 500 MB RIDGE WHICH PERSISTS OVER THE SOUTHERN ROCKIES
AND SOUTHERN PLAINS THROUGH THE PERIOD...WITH STANDARDIZED 500 MB
HEIGHT/TEMPERATURE ANOMALIES SHOWING THE HIGHER ANOMALIES ACROSS
THE DESERT SOUTHWEST...WHERE THE GEFS/GFS/ECMWF INDICATE HEIGHTS
NEAR 2 STANDARD DEVIATIONS ABOVE NORMAL. EAST OF THE SOUTHERN
PLAINS PORTION OF THE MID LEVEL RIDGE...THERE IS FORECAST TO BE A
WEAKNESS OVER THE SOUTHEAST US...ALLOWING DIURNAL SHOWERS/STORMS
TO DEVELOP OVER THE MOUNTAINS AND IN IN LEE TROUGH AREAS. A
SECOND CENTER OF HIGH HEIGHTS IS FCST OVER THE SOUTHWEST ATLANTIC.


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