THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


EXTENDED FORECAST DISCUSSION




EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1107 AM EDT WED JUL 29 2015

VALID 12Z SAT AUG 01 2015 - 12Z WED AUG 05 2015

...SERN US HEAVY RAINFALL THREAT...

...MODEL/UNCERTAINTY ASSESSMENT...

THE WPC MEDIUM RANGE SURFACE FRONTS/PRESSURES AND 500 MB PROGS
ALONG WITH THE 2.5KM SENSIBLE WEATHER GRIDS HAVE BEEN PRIMARILY
DERIVED FROM REASONABLY WELL CLUSTERED GUIDANCE FROM THE 06 UTC
GFS/GEFS MEAN...00 UTC ECMWF...AND 00 UTC NAEFS/ECMWF ENSEMBLE
MEANS THIS WEEKEND. DETERMINISTIC MODEL FORECAST SPREAD INCREASES
DAYS 5-7 MON-WED...ESPECIALLY UPSTREAM ACROSS THE CHAOTIC NERN
PACIFIC. THIS SEEMS TO THEN FAVOR AN ENSEMBLE BASED SOLUTION AS A
TEMPLATE FOR MANUALLY ADDED DETAIL CONSISTENT WITH STILL
COMPATABLE GEFS/NAEFS/ECMWF ENSEMBLE MEANS. THIS FORECAST STRATEGY
MAINTAINS GOOD WPC CONTINUITY IN A PATTERN WITH OVERALL SLIGHTLY
ABOVE AVERAGE PREDICTABILITY.

...PATTERN OVERVIEW AND SENSIBLE WEATHER HIGHLIGHTS/THREATS...

MID-UPPER LEVEL RIDGING SPREADS OUT FROM THE W-CENTRAL US. EXPECT
CONTINUED MONSOONAL ACTIVTY IN THE MOISTURE PLUMED WRN PERIPHERY
THROUGH THE SWRN US AND INTERMOUNTAIN W/ROCKY STATES. PACIFIC AND
NRN STREAM IMPULSES RUNNING AROUND AND OVERTOP THE RIDGE TEND TO
DIG SEWD DOWNSTREAM UNDERNEATH A CLOSED E-CENTRAL CANADIAN VORTEX
ALOFT AND INTO A SPLIT ERN US TROUGH POSITION. ENERGY ACROSS THE
US NRN/NERN TIER WILL FORCE SEVERAL CONVECTION FOCUSING FRONTAL
SYSTEMS OVER THE REGION. LOWER LATITUDE ENERGIES WILL MEANWHILE
FOCUS WAVY FRONTAL ORGANIZATION AND DEEPER MOISTURE TO FUEL
CONVECTIVE DOWNPOURS AND A POTENTIAL HEAVY RAINFALL THREAT DOWN
ACROSS THE SERN US.

SCHICHTEL





Last Updated: 1107 AM EDT WED JUL 29 2015