734
FXUS02 KWBC 150701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST WED NOV 15 2023
VALID 12Z SAT NOV 18 2023 - 12Z WED NOV 22 2023
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE VALID SATURDAY-MONDAY WAS
PRIMARILY DERIVED FROM A COMPOSITE BLEND OF REASONABLY WELL
CLUSTERED GUIDANCE FROM THE 18 UTC GFS AND 12 UTC ECMWF/CANADIAN
ALONG WITH THE 01 UTC NATIONAL BLEND OF MODELS (NBM) AND WPC
CONTINUITY. THIS SOLUTION HAS GOOD MULTI-MODEL ENSEMBLE SUPPORT IN
A PATTERN WITH SEEMINGLY ABOVE NORMAL PREDICTABILITY. OPTED TO
SHIFT GUIDANCE PREFERENCE TOWARD THE GEFS/ECMWF/CANADIAN ENSEMBLE
MEANS BY NEXT TUESDAY/WEDNESDAY TO MITIGATE GROWING MODEL RUN TO
RUN CONTINUTY ISSUES AND FORECAST SPREAD. EMPHASIS ON THE
ECMWF/CANADIAN MEANS OFFERS SLIGHTLY MORE AMPLIFIED FLOW THAN THE
GEFS. THIS SEEMS MORE CONISTENT WITH RECENT PATTERN TRENDS. 00 UTC
GUIDANCE OVERALL SEEMS IN LINE.
..WEATHER/HAZARDS HIGHLIGHTS
THE STEADY MARCH OF AN AMPLIFIED UPPER TROUGH AND WAVY FRONTAL
SYSTEM ACROSS THE NORTHEAST WILL FAVOR A SWATH OF MODERATELY HEAVY
PRECIPITATION ACROSS THE REGION INTO SATURDAY. THE INTERACTION OF
THE UPPER TROUGH AND A LEADING COASTAL LOW SET TO LIFT NORTHWARD
OVER THE WESTERN ATLANTIC SHOULD COMBINE TO CREATE A WINDOW WITH
SUBSTANTIALLY INCREASING MOISTURE INFLOW INTO EASTERN NEW ENGLAND.
THIS MAY FOCUS SEVERAL INCHES OF RAIN, WITH BEST LIKELIHOOD IN
DOWNEAST MAINE. HOWEVER, MODEST INSTABILITY AND RAIN RATES IN
COMBINATION WITH THE EXISTING ANTECEDENT CONDITIONS DOES NOT SEEM
TO SUPPORT ISSUANCE OF ANY WPC EXCESSIVE RAINFALL OUTLOOK (ERO)
THREAT AREAS AT THIS TIME. MEANWHILE, COOLING POST-FRONTAL
VERTICAL TEMPERATURE FIELDS ALSO OFFER POTENTIAL IN THIS PATTERN
FOR WRAPBACK SNOWS OVER NORTHERN NEW ENGLAND AND ALSO TO THE LEE
OF THE LOWER GREAT LAKES IN THE WAKE OF SYSTEM PASSAGE.
FOR THE WEST, THE SLOW APPROACH OF THE CLOSED SOUTHERN STREAM
UPPER LOW WILL GRADUALLY BRING LIGHT TO MODERATE TERRAIN ENHANCED
RAIN AND MOUNTAIN SNOW FROM CALIFORNIA TO THE SOUTHWEST/GREAT
BASIN INTO THIS WEEKEND. MANY AREAS WILL SEE AT LEAST MEASURABLE
RAINFALL (ESPECIALLY COASTAL AREAS) OUTSIDE SOME OF THE SHADOWED
DESERTS. NO EXCESSIVE RAINFALL RISK (EROS) AREAS ARE EXPECTED, BUT
THERE MAY BE SOME GUSTY WINDS WITH SYSTEM PASSAGE. AS THE
AMPLIFIED UPPER SYSTEM FINALLY CROSSES THE DIVIDE INTO THE SOUTH,
RETURN FLOW OUT OF THE GULF OF MEXICO WILL INCREASE MOISTURE OVER
THE PLAINS AND MISSISSIPPI VALLEY, WITH RAIN CHANCES EXPANDING IN
COVERAGE LATE WEEKEND INTO EARLY NEXT WEEK. LEAD CYCLOGENESIS MAY
INCREASINGLY OFFER A HEAVY RAINFALL THREAT TO MONITOR FOR MONDAY
AS A DEEPENING MOISTURE INFLOW FOCUS FEEDS ESPECIALLY INTO THE
LOWER MISSISSIPPI VALLEY AND VICINITY. WIDESPREAD MODERATE TO
LOCALLY ENHANCED RAINS ARE LIKELY TO THEN SPREAD DOWNSTREAM
THROUGH THE EAST-CENTRAL U.S. AND THE EAST TUESDAY INTO NEXT
WEDNESDAY WITH SOUTHERN STREAM UPPER TROUGH AND WAVY FRONTAL
SYSTEM PROGRESSION. THE EXTENT OF NORTHWARD EXPANSION OF THE
PRECIPITATION SHIELD OVER TIME WILL BE DEPENDENT ON INFLUX OF
DIGGING NORTHERN STREAM UPPER TROUGH ENERGY THAT IN THIS PATTERN
MAY ALSO BE SUFFICIENT TO SUPPORT COOLED TEMPS AND MODEST SWATH OF
FAR NORTHERN TIER STATES SNOW.
MEANWHILE, AMPLE PACIFIC SYSTEM ENERGY WITHIN NORTHERN STREAM FLOW
WILL DIG SHARPLY SOUTHEASTWARD FROM THE NORTHWEST THROUGH THE
INTERMOUNTAIN WEST AND ROCKIES THIS WEEKEND INTO EARLY NEXT WEEK
TO FOCUS A SWATH OF RAIN (ENHANCED OVER COASTAL AREAS OF THE
PACIFIC NORTHWEST) AND INLAND/TERRAIN ENHANCED MOUNTAIN SNOWS
GIVEN UPPER DYNAMIC SUPPORT. AN AMPLIFIED UPPER RIDGE WILL THEN
BUILD OVER THE WEST COAST EARLY NEXT WEEK TO STABLIZE AND WARM.
HOWEVER, UPSTREAM PACIFIC SYSTEM ENERGIES MAY WORK INTO ENOUGH
INTO THIS RIDGE TO BRING ANOTHER OPPORTUNITY FOR ORGANIZED
PRECIPITATION INTO THE PACIFIC NORTHWEST NEXT TUESDAY/WEDNESDAY.
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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