Preliminary Forecasts
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7
000
FXUS02 KWNH 260638
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 AM EDT FRI AUG 26 2016

VALID 12Z MON AUG 29 2016 - 12Z FRI SEP 02 2016

...OVERVIEW...

THE ULTIMATE STRENGTH AND TRACK OF PSBL TROPICAL DEVELOPMENT THAT
MAY REACH THE GULF OF MEXICO FROM NEAR THE ERN BAHAMAS CONTINUES
TO BE THE GREATEST UNCERTAINTY OF THE FCST.  CONSULT THE NATIONAL
HURRICANE CENTER`S TROPICAL WEATHER OUTLOOK FOR LATEST INFO
REGARDING PSBL DEVELOPMENT.  AS FOR LARGER SCALE EVOLUTION MOST
GUIDANCE DEPICTS AN ADJUSTMENT IN UPR RIDGE EMPHASIS FROM THE MID
ATLC TO THE CNTRL U.S. AS A MEAN TROUGH AMPLIFIES NEAR THE WEST
COAST AND A BROADER/FLATTER MEAN TROUGH SETTLES NEAR THE EAST
COAST.  DIFFS PRIMARILY INVOLVE AMPLITUDE/LONGITUDE OF THE WEST
COAST TROUGH AND MEDIUM TO SMALLER SCALE DETAILS WITHIN THE
EVOLVING ERN TROUGH.


...GUIDANCE/UNCERTAINTY ASSESSMENT...

THE FEATURE THAT MAY TRACK INTO THE GULF OF MEXICO HAS GREATER
THAN AVG FCST UNCERTAINTY DUE TO DIFFS IN STEERING DEPENDING ON
EXACTLY HOW STRONG THE FEATURE BECOMES AND PSBL DEPENDENCE ON
EXACT DETAILS OF HOW THE MID ATLC RIDGE ALOFT GIVES WAY TO THE
RIDGE OVER THE CNTRL U.S..  MODEL AND ENSEMBLE SPREAD REMAINS
QUITE WIDE RANGING FROM WEAK/SUPPRESSED SOLNS ACROSS THE SRN GULF
TO ALONG THE WEST COAST OF THE FLORIDA PENINSULA.  SOME NEW 00Z
SOLNS DIFFER FROM THEIR 12Z RUNS.  ONGOING GUIDANCE SPREAD FAVORS
MAINTAINING CONTINUITY NEAR YDAYS FCST WITH A TRACK OVER THE
E-CNTRL GULF.

ELSEWHERE ASIDE FROM A MODEL/ENSEMBLE MEAN CONSENSUS FCST ON DAY 3
MON... LATEST GEFS/ECMWF MEANS BEST REFLECT THE LARGE SCALE
AGREEMENT FOR THE TROUGHS NEAR THE WEST COAST AND APPROACHING THE
EAST COAST WHILE DOWNPLAYING LOWER CONFIDENCE DETAIL
UNCERTAINTIES.  AT SOME FCST HRS THE 12Z/18Z GEFS MEANS ALIGN THE
WEST COAST TROUGH A LITTLE WWD OF MOST OTHER SOLNS SO THE GEFS
MEAN WAS GIVEN SOMEWHAT LESS WEIGHT THAN THE ECMWF MEAN.  THERE
ARE INDICATIONS FROM SOME GUIDANCE THAT AN EMBEDDED UPR LOW MAY
EXIST WITHIN THE TROUGH AND HAVE AN ORIGIN FROM N-CNTRL CANADA AND
SRN-SERN ALASKA COAST.  THE NEW 00Z GFS/CMC RUNS ARE QUITE SIMILAR
BY DAY 7 FRI AND HAVE A TROUGH AXIS NEAR THE MEANS.


...WEATHER HIGHLIGHTS/THREATS...

CURRENTLY THE ERN HALF OF THE GULF COAST APPEARS TO HAVE THE BEST
POTENTIAL FOR SOME LOCALLY HVY RNFL IN ASSOC WITH THE FEATURE THAT
MAY TRACK INTO THE GULF OF MEXICO FROM NEAR THE ERN BAHAMAS.  COLD
FRONT PUSHING E/SE FROM THE NRN PLAINS THROUGH THE EAST COAST MAY
BE ACCOMPANIED BY SCT CONVECTION.  TRAILING PART OF THIS FRONT
WILL LIKELY BECOME STNRY OVER THE NRN PLAINS AND BE A
CONTRIBUTOR... ALONG WITH SHRTWV ENERGY ALOFT... TO ONE OR MORE
EPISODES OF NRN TIER CONVECTION.  THE UPR TROUGH AMPLIFYING NEAR
THE WEST COAST ALONG WITH WHAT REMAINS OF AN ERN PAC UPR LOW
REACHING THE WRN STATES BY TUE-WED MAY GENERATE SOME RNFL ALONG
THE PAC NW COAST AND PSBLY INLAND.  IMPULSES ALOFT AND ADEQUATE
MSTR COULD ALSO SUPPORT ACTIVITY OVER PORTIONS OF THE ROCKIES.
FOR THE OVERALL 5-DAY PERIOD EXPECT ABOVE NORMAL TEMPS FROM THE
GRTBASIN/NRN ROCKIES THROUGH THE NRN PLAINS AND INTO THE EAST.
THE AMPLIFYING UPR TROUGH NEAR THE WEST COAST WILL TEND TO KEEP
HIGHS BELOW NORMAL OVER THAT REGION.

RAUSCH

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.