Prognostic Meteorological Discussion
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000
FXUS02 KWBC 271605
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1204 PM EDT WED JUL 27 2016

VALID 12Z SAT JUL 30 2016 - 12Z WED AUG 03 2016

...OVERVIEW AND GUIDANCE EVALUATION/UNCERTAINTY ASSESSMENT...

COMPARED TO YESTERDAY...MODELS HAVE COME INTO MUCH BETTER
AGREEMENT WITH THE GLOBAL PATTERN. AT THE START OF THE
FORECAST...BROAD LONGWAVE TROUGHING WILL BE IN PLACE FROM THE
LOWER MO VALLEY INTO THE MID-ATLANTIC REGION. MULTIPLE EMBEDDED
SHORTWAVES WILL EJECT NORTHEASTWARD WITH PERHAPS A SURFACE WAVE
CROSSING THE OH VALLEY ON SATURDAY. POTENTIALLY CONVECTIVELY
INDUCED...THIS AXIS OF LOW PRESSURE IS DEPICTED STRONGER IN THE
00Z UKMET WHILE BEING DISPLACED TO THE NORTH ACROSS THE
MID-ATLANTIC. ENSEMBLE LOW PLOTS INDICATE THIS STRENGTH/POSITION
ARE OFFSET QUITE A BIT FROM THE STRONGER CLUSTERING. DURING THE
FOLLOWING COUPLE OF DAYS...THIS WEAK UPPER TROUGH WILL CONTINUE
EDGING EASTWARD WITH MULTI-DAY TRENDS SHOWING THE ECMWF SUITE
MOVING TOWARD A MORE PROGRESSIVE SOLUTION. ULTIMATELY THIS HAS
MOVED ITS FORECAST CLOSER TO RECENT GFS RUNS WHICH WERE DEEMED TOO
QUICK YESTERDAY. BY 02/1200Z...THE 06Z GFS GETS AHEAD OF THE 00Z
ECMWF WITH THE LATTER HAVING STRONGER ENSEMBLE SUPPORT BASED ON
500-MB HEIGHT COMPARISONS.

THE LARGER SPREAD IN THE GUIDANCE SEEMS TO BE CONFINED TO THE
WESTERN HALF OF THE NATION IN RESPONSE TO A DIGGING TROUGH INTO
THE PACIFIC NORTHWEST ON SUNDAY MORNING. BY AS EARLY AS DAY
4/SUNDAY...THERE ARE NOTABLE DIFFERENCES IN PLACEMENT WITH THE 00Z
CMC/UKMET FAVORING A SLOWER MORE POSITIVELY TILTED TROUGH AXIS. ON
THE OTHER HAND...AS THE 06Z GFS HAD SPED UP FROM ITS RECENT
RUN...IT HAS NOW JOINED THE MORE PROGRESSIVE 00Z ECMWF/ECMWF
ENSEMBLE MEAN. THIS SEPARATION IN THE SOLUTION CAMPS CONTINUES TO
INCREASE INTO NEXT WEEK WHICH LEADS TO ADDITIONAL DIFFERENCES IN
THE UPSTREAM PATTERN OVER THE NORTHEAST PACIFIC. AS THE INITIAL
UPPER TROUGH STRENGTHENS ACROSS CENTRAL CANADA...ANOTHER SHORTWAVE
OFF THE PACIFIC MOVES INTO THE NORTHWESTERN U.S. BY TUESDAY
MORNING. THIS IS AGREED UPON BY THE 06Z GFS/00Z ECMWF AS WELL AS
THE ENSEMBLE MEANS. ACROSS THE CENTER OF THE COUNTRY...HEIGHTS
FURTHER BUILD NEXT WEEK WITH A 594-DM RIDGE SETTLING OVER THE
SOUTH-CENTRAL U.S. OVERALL...FELT ENOUGH CONFIDENCE TO USE A
COMBINATION OF THE 06Z GFS/00Z ECMWF THROUGH DAY 5/MONDAY WITH A
MINIMAL AMOUNTS OF THEIR RESPECTIVE MEANS ADDED AT THE END OF THIS
TIME SPAN. THEREAFTER...UNCERTAINTY WITH THE EVOLUTION OF FEATURES
ACROSS THE WESTERN/CENTRAL U.S. LED TO MORE OF AN ENSEMBLE BASED
FORECAST WITH SLIGHTLY HIGHER WEIGHTING TOWARD THE 00Z ECMWF
ENSEMBLE MEAN.


...SENSIBLE WEATHER HIGHLIGHTS...

GIVEN THE RELATIVELY LOW-AMPLITUDE FLOW ACROSS THE
NATION...FORECAST TEMPERATURE ANOMALIES ARE NOT TERRIBLY
SIGNIFICANT DURING THE PERIOD. ON DAY 3/SATURDAY...A WEAKENING
UPPER RIDGE ACROSS THE WESTERN U.S. WILL FAVOR ANOTHER HOT DAY
WITH FORECAST HIGHS AROUND 5 TO 10 DEGREES ABOVE NORMAL WHICH
EQUATES TO 105 TO 110 DEGREE READINGS OVER THE SOUTHWESTERN U.S.
VALLEY LOCALES. ELSEWHERE...SLIGHTLY COOLER WEATHER WILL PREVAIL
THIS WEEKEND FROM THE NORTHERN PLAINS TO THE OH VALLEY GIVEN THE
PRECIPITATION THREATS COUPLED WITH THE STATIONARY FRONT BEING
DISPLACED WELL TO THE SOUTH. EVENTUALLY A RETURN TO HOT WEATHER IS
LIKELY ACROSS THE CENTER OF THE COUNTRY GIVEN THE EXPECTATION OF
BUILDING HEIGHTS.

A WET PATTERN IS LIKELY ALONG THE MEANDERING FRONTAL ZONE
STRETCHING FROM THE CENTRAL U.S. EASTWARD INTO THE
MID-ATLANTIC/CAROLINAS. FORECAST CONFIDENCE IS NOT VERY HIGH GIVEN
MUCH OF THE ACTIVITY WILL BE CONVECTIVELY DRIVEN.
OTHERWISE...EXPECT AN UPTICK IN THUNDERSTORM COVERAGE ACROSS THE
FOUR CORNERS...PARTICULARLY AZ AS INCREASING MONSOONAL MOISTURE
WORKS ITS WAY NORTHWARD. THE GFS SOLUTIONS SEEM TO BE A BIT MORE
ROBUST IN THEIR QPF AMOUNTS.


RUBIN-OSTER


$$





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