340
FXUS02 KWBC 070659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST THU MAR 07 2024
VALID 12Z SUN MAR 10 2024 - 12Z THU MAR 14 2024
...STRONG STORM TO BRING RAIN/SNOW AND HIGH WINDS TO THE NORTHEAST
SUNDAY INTO THE NEXT WORK WEEK...
...MULTI-DAY UNSETTLED PERIOD ALONG THE NORTHERN-CENTRAL WEST
COAST CONTINUING INTO EARLY NEXT WEEK...
..OVERVIEW
DEEPENING AND CONSOLIDATING LOW PRESSURE WILL BRING A PERIOD OF
RAIN/SNOW AND HIGH WINDS TO THE NORTHEAST DURING SUNDAY-MONDAY
WHILE A BROAD AREA OF DRY WEATHER PREVAILS BEHIND THIS SYSTEM AS
FAR WEST AS THE CENTRAL-SOUTHERN ROCKIES AND SOUTHWEST. THE
SERIES OF SHORTWAVES AND SURFACE FRONTS BRINGING RAIN AND MOUNTAIN
SNOW TO THE PACIFIC NORTHWEST/NORTHERN CALIFORNIA WILL ALREADY BE
IN PROGRESS AT THE START OF THE PERIOD EARLY SUNDAY AND SHOULD
CONTINUE INTO TUESDAY. THESE SYSTEMS SHOULD EXTEND SNOW INTO THE
NORTHERN ROCKIES. THE FINAL UPPER TROUGH IN THIS SERIES SHOULD
THEN MOVE INLAND AND AMPLIFY BY WEDNESDAY-THURSDAY AS AN UPPER
RIDGE AMPLIFIES/SHARPENS OFF THE WEST COAST. THE TROUGH MAY CLOSE
OFF AN UPPER LOW OVER THE FOUR CORNERS OR SOUTHWEST. THIS FEATURE
WILL PUSH THE WEST COAST MOISTURE INTO THE CENTRAL ROCKIES BY
WEDNESDAY AND ULTIMATELY INTERACT WITH INCREASING LOW LEVEL GULF
OF MEXICO INFLOW TO START GENERATING RAINFALL OVER THE SOUTHERN
PLAINS BY AROUND NEXT THURSDAY. A MEAN RIDGE ALOFT SETTING UP
OVER THE CENTRAL/EAST-CENTRAL U.S. WILL SUPPORT AN EXPANDING AREA
OF ABOVE NORMAL TEMPERATURES TO THE EAST OF THE ROCKIES, WITH THE
GREATEST ANOMALIES LIKELY TO BE OVER THE NORTHERN PLAINS/UPPER
MIDWEST EARLY-MID WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST GUIDANCE CONTINUES TO OFFER STEADY CONVERGENCE FOR THE
SYSTEM AFFECTING THE NORTHEAST EARLY IN THE WEEK. DYNAMICAL
MODELS/ENSEMBLES AND MACHINE LEARNING MODELS ALL AGREE FAIRLY WELL
UPON AN UPPER LOW TRACKING FROM THE GREAT LAKES TO JUST OFF THE
NEW ENGLAND COAST EARLY SUNDAY INTO EARLY MONDAY, WHILE AMONG TWO
INITIAL SURFACE LOWS (NORTHERN OF LAKE ONTARIO AND FAR SOUTHERN
NEW ENGLAND) THE SOUTHERN ONE BECOMES THE DOMINANT SYSTEM AND
REACHES A POSITION NEAR DOWNEAST MAINE BY EARLY MONDAY. OVER
RECENT RUNS THE UKMET HAS BEEN THE MOST RELUCTANT TO TREND TOWARD
CONSENSUS (TENDING TO BE SLOW), AND WHILE THE NEW 00Z RUN HAS
FINALLY ADJUSTED TO CONSENSUS ALOFT ITS SURFACE LOW IS WEST OF THE
MAJORITY AS OF EARLY MONDAY. THIS SYSTEM SHOULD TRACK EASTWARD
THEREAFTER. A MODEL BLEND EMPHASIZING THE GFS/ECMWF PROVIDES A
REASONABLE STARTING POINT FOR THIS SYSTEM.
GUIDANCE CONTINUES TO SHOW TYPICAL VARIABILITY/SPREAD FOR THE
SHORTWAVES COMING INTO THE WEST, AND ESPECIALLY FOR THE ONE THAT
ARRIVES BY EARLY MONDAY AND CONTINUES ACROSS THE LOWER 48
THEREAFTER. SOLUTIONS OFFER A GENERAL SIGNAL FOR GENERAL AREA OF
LOW PRESSURE/FRONTAL SYSTEM REACHING THE CENTRAL U.S. BY TUESDAY,
BUT SURFACE DEPICTIONS INCREASINGLY DIVERGE BY WEDNESDAY-THURSDAY
DUE TO LOW-PREDICTABILITY DIFFERENCES IN DETAILS ALOFT AS THE
ENERGY PASSES THROUGH THE LONGER-TERM MEAN RIDGE. AS THE FINAL
UPPER TROUGH MOVES INTO THE WEST BY WEDNESDAY-THURSDAY, GFS/GEFS
TRENDS OVER THE PAST DAY OR SO HAVE LED TO IMPROVED AGREEMENT
TOWARD AN AMPLIFIED SCENARIO ADVERTISED BY EARLIER ECMWF/CMC RUNS
AND THEIR MEANS. MOST OF THE RECENT RUNS FROM ECMWF-INITIALIZED
MACHINE LEARNING MODELS OFFER REASONABLE SUPPORT FOR THE CURRENT
DYNAMICAL MODEL/ENSEMBLE MEAN CONSENSUS FOR THE LATE-PERIOD
AMPLIFYING UPPER TROUGH.
GUIDANCE COMPARISONS FOR THE 12Z/18Z CYCLE LED TO STARTING THE
UPDATED FORECAST WITH AN OPERATIONAL MODEL COMPOSITE EMPHASIZING
MORE GFS/ECMWF WEIGHT FOR THE FIRST HALF OF THE PERIOD, FOLLOWED
BY A TRANSITION TOWARD 30-40 PERCENT TOTAL 18Z GEFS/12Z ECENS
INCLUSION ALONG WITH THE GFS/ECMWF/CMC BY WEDNESDAY-THURSDAY AS
SOME DETAILS BECOME MORE AMBIGUOUS.
..WEATHER/HAZARDS HIGHLIGHTS
DURING THE DAY 4 EXCESSIVE RAINFALL OUTLOOK PERIOD COVERING
SUNDAY-SUNDAY NIGHT, MOST GUIDANCE SHOWS THE SOUTHERN OF TWO
SEPARATE SURFACE LOW CENTERS AS OF EARLY SUNDAY (OVER SOUTHERN NEW
ENGLAND, VERSUS THE OTHER ONE NORTH OF LAKE ONTARIO) BECOMING THE
MAIN LOW ALONG THE NORTHERN NEW ENGLAND COAST AND REACHING NEAR
DOWNEAST MAINE BY EARLY MONDAY. DURING THE DAY SUNDAY THERE WILL
BE A PERIOD OF STRONG ATLANTIC INFLOW AHEAD OF THE ADVANCING LOW,
WITH RECENT GUIDANCE FAIRLY CONSISTENT IN SHOWING SIGNIFICANT QPF
CENTERED OVER MAINE ON TOP OF WET GROUND FROM SHORTER TERM
RAINFALL. THUS THE DAY 4 ERO MAINTAINS A MARGINAL RISK AREA OVER
THE SOUTHERN HALF OR SO OF MAINE, WITH A MODEST TRIMMING OF THE
NORTHERN AREA TO ACCOUNT FOR AVERAGE GUIDANCE LOCATION OF THE
RAIN-SNOW LINE. WINTER WEATHER OUTLOOK PROBABILITIES CONTINUE TO
SHOW GREATER THAN 50 PERCENT CHANCES FOR AT LEAST 0.25 INCH LIQUID
IN THE FORM OR SNOW OVER PORTIONS OF INTERIOR NEW ENGLAND ON
SUNDAY. SOME LAKE EFFECT/TERRAIN-ENHANCED SNOW SHOULD EXTEND
FARTHER WESTWARD. LIGHTER SNOW MAY CONTINUE OVER NORTHERN NEW
ENGLAND INTO MONDAY. MEANWHILE THIS STORM MAY PRODUCE HIGH WINDS
DURING SUNDAY-MONDAY OVER SOME AREAS FROM THE CENTRAL
APPALACHIANS/MID-ATLANTIC INTO THE NORTHEAST.
THE RAPID SUCCESSION OF FRONTAL SYSTEMS BRINGING MULTIPLE DAYS OF
RAIN AND MOUNTAIN SNOW TO THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA SHOULD ALREADY BE IN PROGRESS AT THE START OF THE
PERIOD EARLY SUNDAY AND WILL LIKELY CONTINUE INTO TUESDAY BEFORE
AN APPROACHING RIDGE SUPPORTS A DRIER TREND. SOME OF THIS
MOISTURE WILL BRING SNOW INTO THE NORTHERN ROCKIES. THE DAYS 4-5
EROS DEPICT A MARGINAL RISK AREA ALONG THE PACIFIC NORTHWEST INTO
NORTHERN CALIFORNIA COAST FOR THIS EVENT. GUIDANCE CONTINUES TO
SHOW SOME MIXED MESSAGES FOR DETAILS OF MAGNITUDE/DISTRIBUTION OF
MOISTURE AND RAINFALL TOTALS, BUT WET GROUND CONDITIONS SHOULD
LOWER THE THRESHOLD FOR LOCALIZED RUNOFF ISSUES WHERE THE
RELATIVELY HIGHER RAINFALL RATES OCCUR. AS THE FINAL UPPER TROUGH
IN THE SERIES AMPLIFIES AND MOVES INLAND, EXPECT THE BEST FOCUS
FOR RAIN AND MOUNTAIN SNOW TO SHIFT INTO THE CENTRAL ROCKIES BY
WEDNESDAY. THEN RAINFALL MAY INCREASE IN COVERAGE AND INTENSITY
OVER THE SOUTHERN PLAINS BY NEXT THURSDAY.
MEAN RIDGING ALOFT OVER THE CENTRAL/EAST-CENTRAL U.S. WILL SUPPORT
AN EXPANDING AREA OF ABOVE NORMAL TEMPERATURES TO THE EAST OF THE
ROCKIES. THE CORE OF WARMEST ANOMALIES SHOULD COVER PARTS OF THE
NORTHERN PLAINS INTO THE UPPER MIDWEST DURING MONDAY-WEDNESDAY,
WITH HIGHS POTENTIALLY AT LEAST 20-25F ABOVE NORMAL. LESSER WARM
ANOMALIES WILL GRADUALLY DISPLACE THE NEAR OR SLIGHTLY BELOW
READINGS OVER THE SOUTH AND EAST AS OF SUNDAY-MONDAY. OVER THE
WEST, THE WET/SNOWY PATTERN OVER NORTHERN-CENTRAL WEST COAST AND
EVENTUALLY INTO THE ROCKIES WILL MAINTAIN MODERATELY BELOW AVERAGE
HIGHS AND NEAR/ABOVE AVERAGE LOWS THROUGH EARLY NEXT WEEK. UPPER
TROUGHING THAT AMPLIFIES INLAND BY WEDNESDAY-THURSDAY SHOULD
SPREAD A BROADER AREA OF COOL DAYTIME HIGHS ACROSS THE WEST WITH
LOWS DECLINING TOWARD NORMAL.
RAUSCH
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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