424
FXUS02 KWBC 130700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST MON NOV 13 2023
VALID 12Z THU NOV 16 2023 - 12Z MON NOV 20 2023
...PATTERN OVERVIEW AND GUIDANCE EVALUATION/PREDICTABILITY
ASSESSMENT...
IT REMAINS THE CASE THAT THE UPPER PATTERN ACROSS THE LOWER 48
WILL FEATURE A SLOWLY-MOVING UPPER LOW OFF THE COAST OF CALIFORNIA
THAT GRADUALLY WORKS INLAND NEXT WEEKEND, OUTPACED BY NORTHERN
STREAM UPPER RIDGING MOVING INTO SOUTHWESTERN CANADA. IN THE EAST,
A TROUGH IN THE SOUTHEAST WILL MOVE EASTWARD WITH ITS SURFACE
REFLECTION CARRYING A LOW PRESSURE CENTER ACROSS FLORIDA. THIS
SYSTEM MAY MERGE/INTERACT WITH A FRONTAL BOUNDARY MOVING THROUGH
THE GREAT LAKES TO FORM A DEEPER AREA OF LOW PRESSURE NEAR OR JUST
OFFSHORE THE MID-ATLANTIC/NORTHEAST NEXT WEEKEND. MUCH OF THE REST
OF THE MIDDLE OF THE COUNTRY WILL BE DRY WITH MILD TEMPERATURES
FOR MID-NOVEMBER.
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM NOW
MORE BROADLY WELL CLUSTERED MASS FIELD GUIDANCE OF THE LATEST
GFS/ECMWF/UKMET/CANADIAN AND GEFS/ECMWF ENSEMBLE MEANS ALONG WITH
THE NATIONAL BLEND OF MODELS AND WPC CONTINUITY. APPLIED MOST
BLEND WEIGHT TO THE MODELS FOR BETTER DETAIL/TRENDS THURSDAY INTO
SATURDAY, BEFORE APPLYING GREATER FOCUS TO THE ENSEMBLE MEANS AS
FORECAST SPREAD SLOWLY BUT STEADILY INCREASES THROUGH LONGER TIME
FRAMES.
..WEATHER/HAZARDS HIGHLIGHTS
THE RECENT SLOWER AND DRIER TREND IN THE GUIDANCE OVER CALIFORNIA
HAS PROMPTED REMOVAL OF ALL MARGINAL RISK AREAS. THOUGH RAINFALL
IS LIKELY OVER MUCH OF THE SUNSHINE STATE, THE EVOLUTION OF THE
SYSTEM MAY TRANSLATE THE BULK OF THE HEAVIER RAIN EAST OF THE
FLORIDA PENINSULA BY THURSDAY. HOWEVER, KEPT THE WPC EXCESSIVE
RAINFALL OUTLOOK (ERO) MARGINAL RISK AREA OVER ATLANTIC COASTAL
AREAS FOR THE DAY 4/THURSDAY ERO GIVEN EASTERLY FLOW AND A SLOW
RELAXATION OF WELL ABOVE NORMAL PRECIPITABLE WATER OVER THE REGION
UNTIL THE SYSTEM FULLY PASSES.
FOR THE WEST/SOUTHWEST, THE SLOW APPROACH OF THE CLOSED SOUTHERN
STREAM UPPER LOW WILL ONLY GRADUALLY BRING IN BOUTS OF LIGHT TO
MODERATE/TERRAIN ENHANCED RAIN AND MOUNTAIN SNOW THAT EXPAND
EASTWARD IN TIME. THE DELAY IN THE HEIGHT FALLS LIKELY LESSENS THE
STRONGER MOISTURE FLUX INTO THE AREA AS THE SYSTEM FILLS BEFORE
MOVING ASHORE, BUT MOST AREAS WILL SEE AT LEAST MEASURABLE
RAINFALL (ESPECIALLY COASTAL AREAS) OUTSIDE SOME OF THE SHADOWED
DESERTS. AS THE AMPLIFIED UPPER SYSTEM FINALLY CROSSES THE DIVIDE,
RETURN FLOW OUT OF THE GULF OF MEXICO WILL HELP INCREASE MOISTURE
OVER THE PLAINS THEN MISSISSIPPI VALLEY, WITH RAIN EXPANDING IN
COVERAGE LATE WEEKEND INTO EARLY NEXT WEEK. AT THE SAME TIME,
ANOTHER PACIFIC SYSTEM, BUT IN THE NORTHERN STREAM, WILL PROGRESS
INLAND FROM THE NORTHWEST TO THE NORTH-CENTRAL ROCKIES FOR THE
WEEKEND ALONG WITH A QUICK SWATH OF RAIN AND MOUNTAIN SNOW BEFORE
EJECTING INTO THE NORTH-CENTRAL STATES TO LIFT LIMITED MOISTURE
INTO THE REGION.
MEANWHILE, AMPLIFIED NORTHERN STREAM UPPER TROUGH ENERGY SLATED TO
SWEEP FROM THE NORTHERN PLAINS THURSDAY THROUGH THE NORTHEAST THIS
WEEKEND ALONG WITH AN ASSOCIATED AND WAVY FRONTAL SYSTEM. LIMITED
MOISTURE AND PRECIPITATION OVER THE MIDWEST/GREAT LAKES MAY BE
ENHANCED FRIDAY INTO SATURDAY FROM THE MID-ATLANTIC/CAROLINAS UP
THROUGH THE NORTHEAST IN FEED OFF THE ATLANTIC. MODEL QPF VARIES
FROM MODEST TO HEAVY AMOUNTS, ESPECIALLY FOR NEW ENGLAND AS
DEPENDENT ON UNCERTAIN SYSTEM DETAILS AND STRENGTH/INTERACTION
WITH A LEAD COASTAL LOW SET TO LIFT UP THE EAST COAST.
SCHICHTEL
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES ARE AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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