410
FXUS02 KWBC 151856
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
155 PM EST WED NOV 15 2023
VALID 12Z SAT NOV 18 2023 - 12Z WED NOV 22 2023
..OVERVIEW
THE MEDIUM RANGER PERIOD (SATURDAY NOVEMBER 18 THROUGH WEDNESDAY
NOVEMBER 22) WILL FEATURE A SPLIT FLOW PATTERN WITH EMBEDDED LOW
PRESSURE SYSTEMS IN THE NORTHERN AND SOUTHERN STREAMS. SYSTEMS IN
THE NORTHERN STREAM WILL TRACK EAST ACROSS CENTRAL/SOUTHERN CANADA
AND SYSTEMS IN THE SOUTHERN STREAM WILL TRACK EAST ACROSS THE
SOUTHERN UNITED STATES AND CURVE NORTHEAST ALONG THE EAST COAST.
THIS PATTERN WILL BRING PRECIPITATION CHANCES TO THE NORTHEAST AND
WEST COAST THIS WEEKEND, THE SOUTHERN/CENTRAL PLAINS AND
LOWER/MIDDLE MISSISSIPPI VALLEY EARLY NEXT WEEK, AND TO THE EAST
COAST MID-NEXT WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODEL AGREEMENT ON THE UPPER LEVEL PATTERN HAS INCREASED
DRASTICALLY TODAY AS COMPARED TO YESTERDAY, INCREASING CONFIDENCE
IN THE CURRENT FORECAST. THERE ARE STILL UNCERTAINTIES IN SMALLER
SCALE FEATURES THAT WILL AFFECT THE TIMING AND LOCATION OF SURFACE
FEATURES, ESPECIALLY THE SYSTEM IN THE SOUTHERN U.S. NEXT WEEK AND
ASSOCIATED PRECIPITATION. FOR THE AFTERNOON FORECAST, THE WPC
MODEL BLEND INCLUDES ONLY DETERMINISTIC GUIDANCE FOR DAYS 3 AND 4
(SATURDAY AND SUNDAY), AND INCLUDES DETERMINISTIC GUIDANCE AND
ENSEMBLE MEANS TO SMOOTH OUT MODEL SPREAD FOR DAYS 5-7 (MONDAY
THROUGH WEDNESDAY). THE 12Z GUIDANCE BECAME AVAILABLE AFTER THE
FORECAST WAS MADE, BUT REMAINS IN LINE WITH WPCS CURRENT FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
AN AMPLIFIED TROUGH AND WAVY FRONTAL SYSTEM WILL TRACK ACROSS THE
NORTHEAST THIS WEEKEND WHILE A LOW PRESSURE SYSTEM IN THE ATLANTIC
MOVES NORTH PARALLEL TO THE EAST COAST. AHEAD OF THE WAVY COLD
FRONT, MOISTURE WILL SURGE INTO EASTERN NEW ENGLAND AS THE
ATLANTIC SYSTEM APPROACHES, WHICH WILL POTENTIALLY ALLOW FOR
SEVERAL INCHES OF RAIN TO FALL IN THE REGION, WITH THE BEST
CHANCES IN DOWNEAST MAINE. MODEST INSTABILITY AND RAIN RATES IN
COMBINATION WITH SOILS THAT ARE RELATIVELY DRY COMPARED TO
CLIMATOLOGY/HISTORICAL CONDITIONS WILL LIKELY LIMIT ANY FLOODING
POTENTIAL WITH THIS EVENT. IN ADDITION TO RAINFALL, COLDER AIR
WRAPPING AROUND THE BACKSIDE OF THE SYSTEM WILL ALLOW FOR WINTRY
PRECIPITATION AND SNOW OVER NORTHERN NEW ENGLAND AND DOWNSTREAM OF
THE GREAT LAKES.
ELSEWHERE, HEAVY RAINFALL POTENTIAL WILL REMAIN LOW THROUGH THE
WEEKEND, BUT WILL LIKELY INCREASE ACROSS THE EASTERN U.S. NEXT
WEEK AS A LOW PRESSURE SYSTEM MOVES ACROSS THE REGION. THE LOW
WILL DEVELOP IN THE LEE OF THE ROCKIES OVER THE CENTRAL/SOUTHERN
PLAINS ON SUNDAY AND MOVE EAST TOWARDS THE MISSISSIPPI VALLEY
EARLY NEXT WEEK BEFORE CURVING TOWARDS THE NORTHEAST BY MID-WEEK.
THE TIGHTENING PRESSURE GRADIENT AS THE LOW FORMS WILL LIKELY
PRODUCE A PERIOD OF HIGH WINDS ACROSS THE HIGH PLAINS EARLY NEXT
WEEK. CONSIDERABLE UNCERTAINTY SURROUNDS THIS SYSTEM; HOWEVER,
THERE IS A SIGNAL FOR POTENTIAL HEAVY RAINFALL TUESDAY AND
WEDNESDAY THAT WILL NEED TO BE CLOSELY MONITORED AS WE APPROACH
THE EVENT. AMPLE MOISTURE WILL STREAM INTO THE SOUTHERN AND
EASTERN U.S. AHEAD OF THE SYSTEM, AND IF THE CURRENT FORECAST
HOLDS, URBAN/FLASH FLOODING COULD BE A CONCERN IN THE VICINITY OF
THE CENTRAL/SOUTHERN APPALACHIANS ON TUESDAY AND THE MID-ATLANTIC
AND NORTHEAST ON WEDNESDAY. FLOODING POTENTIAL MAY BE ESPECIALLY
CONCERNING FOR THE METRO AREAS IN THE NORTHEAST, INCLUDING NEW
YORK CITY.
IN THE WEST, UNSETTLED WEATHER IS EXPECTED THROUGH THE WEEKEND AS
A CLOSED SOUTHERN STREAM UPPER LOW MOVES ACROSS THE SOUTHWEST
SATURDAY INTO SUNDAY AND ANOTHER SYSTEM DIGS INTO THE NORTHWEST ON
SUNDAY. LIGHT TO MODERATE TERRAIN ENHANCED RAINFALL AND MOUNTAIN
SNOW IS EXPECTED FROM CALIFORNIA TO THE SOUTHWEST AND GREAT BASIN
WITH MANY AREAS FORECAST TO RECEIVE AT LEAST MEASURABLE RAINFALL
(ESPECIALLY COASTAL AREAS) OUTSIDE OF SOME SHADOWED DESERTS. GUSTY
WINDS WILL ALSO ACCOMPANY THE SOUTHERN SYSTEM. THE NORTHERN SYSTEM
WILL FOCUS A SWATH OF RAIN (ENHANCED OVER THE COASTAL PACIFIC
NORTHWEST) AND INLAND/TERRAIN ENHANCED MOUNTAIN SNOWS ACROSS THE
CASCADES AND NORTHERN ROCKIES. AN AMPLIFIED UPPER RIDGE WILL THEN
BUILD OVER THE WEST COAST EARLY NEXT WEEK, RESULTING IN MORE
STABLE AND DRY WEATHER. HOWEVER, UPSTREAM PACIFIC SYSTEM ENERGIES
MAY WORK INTO THIS RIDGE ENOUGH TO BRING ANOTHER OPPORTUNITY FOR
ORGANIZED PRECIPITATION IN THE PACIFIC NORTHWEST NEXT
TUESDAY/WEDNESDAY.
DOLAN/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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