751
FXUS02 KWBC 040700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST MON MAR 04 2024
VALID 12Z THU MAR 07 2024 - 12Z MON MAR 11 2024
...WET PATTERN FOR PARTS OF THE EASTERN U.S., ESPECIALLY ACROSS
THE SOUTH...
...MULTI-DAY UNSETTLED PERIOD ALONG THE NORTHERN-CENTRAL WEST
COAST STARTING LATE THIS WEEK...
..OVERVIEW
WITH A LEADING WAVE TRACKING OVER THE WESTERN ATLANTIC EARLY IN
THE PERIOD, THE PRIMARY FOCUS OF THE FORECAST WILL BE ON AN UPPER
TROUGH TRACKING ACROSS THE LOWER 48 AND SUPPORTING A VIGOROUS
SURFACE SYSTEM THAT WILL SPREAD A BROAD AREA OF MOISTURE ACROSS
THE EASTERN HALF OF THE COUNTRY FROM LATE THIS WEEK THROUGH THE
WEEKEND, AFTER PRODUCING SOME SNOW/LOW ELEVATION RAIN OVER THE
SOUTHERN HALF OF THE ROCKIES. THE BEST POTENTIAL FOR SNOW WITH
THIS SYSTEM WILL BE OVER NEW ENGLAND BY THE WEEKEND. THERE WILL
BE A BROADENING DRIER TREND WITH TIME BEHIND THIS SYSTEM, WHILE A
MEAN TROUGH ALOFT SETTING UP NEAR THE WEST COAST WILL BRING A
SERIES OF FRONTAL SYSTEMS AND PERSISTENT RAIN/HIGHER ELEVATION
SNOW TO THE NORTHERN-CENTRAL WEST COAST LATE THIS WEEK INTO NEXT
WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE FORECAST CONTINUES TO SHOW RELATIVELY GOOD AGREEMENT IN THE
BIG-PICTURE THEMES AND OPERATIONAL MODELS/ENSEMBLES PLUS 12Z
ECMWF-INITIALIZED MACHINE LEARNING MODELS AS A WHOLE DO NOT SEEM
TO SHOW PRONOUNCED CLUSTERING TOWARD ONE SIDE OR ANOTHER OF THE
SPREAD WHERE DISAGREEMENTS EMERGE. EARLY IN THE PERIOD, THERE WAS
MORE PROMINENT CLUSTERING AWAY FROM THE 12Z UKMET/CMC WHICH
TRACKED LEADING WESTERN ATLANTIC LOW PRESSURE CLOSER TO NEW
ENGLAND THAN OTHER GUIDANCE. 00Z MODEL TRENDS HAVE GENERALLY
SHIFTED FARTHER OFFSHORE. WITHIN THE LARGE SCALE UPPER TROUGH
CROSSING THE LOWER 48, LOWER-PREDICTABILITY EMBEDDED SHORTWAVE
DETAILS CONTINUE TO MAKE IT DIFFICULT TO HAVE MUCH CONFIDENCE IN
ASSOCIATED SURFACE LOW SPECIFICS FROM THE PLAINS INTO THE EAST.
THUS THAT PART OF THE DETERMINISTIC FORECAST WILL LIKELY CONTINUE
TO SHUFFLE AROUND SOME OVER COMING CYCLES. BY SUNDAY-MONDAY THERE
IS A GENERAL SIGNAL IN THE GUIDANCE THAT NORTHERN STREAM ENERGY
COULD TRY TO CONSOLIDATE AN UPPER LOW OVER OR NEAR THE NORTHEAST,
WITH DYNAMICAL AND MACHINE LEARNING MODELS NOT REALLY CLUSTERING
IN A PRONOUNCED FASHION IN TERMS OF LOCATION/TIMING. REGARDLESS
OF THE PLAINS THROUGH EAST EVOLUTION, THERE IS RELATIVELY BETTER
AGREEMENT TOWARD LOW PRESSURE EMPHASIS SHIFTING TO NEAR NEW
ENGLAND OR THE CANADIAN MARITIMES BY NEXT MONDAY. FARTHER WEST, A
LEADING SHORTWAVE SHOULD COME ASHORE INTO THE WEST ON SATURDAY
(WEAKENING AS IT PROGRESSES TOWARD THE CENTRAL U.S. MEAN RIDGE)
AND FOLLOWED BY ANOTHER SHORTWAVE/FRONTAL SYSTEM BY MONDAY. SOME
GUIDANCE STARTS TO TREND OUT OF PHASE OVER THE EASTERN
PACIFIC/WESTERN U.S. TOWARD THE END OF THE PERIOD. FOR THE
UPDATED FORECAST BASED ON 12Z/18Z GUIDANCE, AN OPERATIONAL MODEL
COMPOSITE EMPHASIZING THE GFS/ECMWF MORE THAN THE UKMET/CMC LOOKED
BEST EARLY IN THE PERIOD. THEN A TRANSITION TO A MODEL/ENSEMBLE
MEAN MIX HELPED TO KEEP THE FORECAST FAIRLY STEADY LATER IN THE
PERIOD AS GREATER DETAIL UNCERTAINTIES AROSE.
..WEATHER/HAZARDS HIGHLIGHTS
THE FORECAST CONTINUES TO SHOW AN ACTIVE WEATHER PATTERN OVER
EASTERN HALF OF THE COUNTRY FROM LATE THIS WEEK ONWARD.
PRECIPITATION ALONG THE EAST COAST IN ASSOCIATION WITH A LEADING
WAVE TRACKING OVER THE WESTERN ATLANTIC SHOULD BE CONFINED MOSTLY
TO PARTS OF NEW ENGLAND AND NORTHERN MID-ATLANTIC BY THE START OF
THE PERIOD EARLY THURSDAY. THERE ARE SOME LINGERING SIGNALS FOR
AT LEAST ISOLATED SIGNIFICANT TOTALS BUT THIS IS WITHIN A BROADER
TREND FOR LESS COVERAGE/LOWER AMOUNTS OVERALL. THIS SCENARIO
CONTINUES TO FAVOR NO RISK AREA IN WHAT WILL NOW BE THE DAY
4/THURSDAY EXCESSIVE RAINFALL OUTLOOK. SOME PRECIPITATION MAY BE
IN THE FORM OF SNOW WHERE MOISTURE REACHES FAR ENOUGH NORTH IN
NORTHERN NEW ENGLAND. UPPER TROUGHING THAT EMERGES FROM THE WEST
WILL SUPPORT A FAIRLY VIGOROUS SURFACE SYSTEM TRACKING FROM THE
CENTRAL U.S. INTO THE EAST/NORTHEAST FROM LATE THIS WEEK THROUGH
THE WEEKEND. WITH THE COMBINATION OF GUIDANCE SCATTER FOR DETAILS
AND FAIRLY LOW SOIL MOISTURE PERCENTILES OVER THE REGION, THE DAY
4/THURSDAY-THURSDAY NIGHT ERO MAINTAINS A ONLY A MARGINAL RISK
AREA FROM PARTS OF THE SOUTHERN HALF OF THE PLAINS INTO THE
SOUTH-CENTRAL MISSISSIPPI VALLEY AS CONVECTION DEVELOPS IN
ASSOCIATION WITH LOW PRESSURE AND ATTACHED FRONTS. AS THE PLAINS
SYSTEM TRACKS EAST/NORTHEAST BY FRIDAY-FRIDAY NIGHT AND LIFTS A
LEADING WARM FRONT NORTHWARD (WITH INTERACTING
MOISTURE/INSTABILITY), GUIDANCE IS PERSISTENT WITH ITS HEAVY
RAINFALL SIGNAL OVER PARTS OF THE SOUTH/SOUTHEAST. THEREFORE THE
DAY 5 ERO HAS INTRODUCED A SLIGHT RISK AREA COVERING LOCATIONS
FROM MISSISSIPPI EAST/NORTHEAST INTO THE FAR WESTERN CAROLINAS.
THE NORTHWESTERN PART OF THE SURROUNDING MARGINAL RISK AREA
ACCOUNTS FOR A SIGNAL IN SOME OF THE GUIDANCE FOR A SECONDARY AXIS
OF ENHANCED RAINFALL FROM THE SOUTH-CENTRAL PLAINS NORTHEASTWARD,
NEAR THE SURFACE LOW TRACK. MEANINGFUL RAINFALL COULD EXTEND
FARTHER NORTH/NORTHEAST OF THE CURRENT MARGINAL RISK AREA BUT IN
THE ABSENCE OF INSTABILITY IN THE GUIDANCE THUS FAR.
PRECIPITATION OF VARYING INTENSITY WILL CONTINUE TO OVERSPREAD THE
EAST GOING INTO THE WEEKEND. SOME POCKETS OF SNOW WILL BE
POSSIBLE ON THE NORTHWEST PERIPHERY OF THE MOISTURE SHIELD, FROM
THE CENTRAL HIGH PLAINS INTO THE GREAT LAKES, BUT WITH
PROBABILITIES NOT REACHING MUCH MORE THAN 10 PERCENT FOR 0.25 INCH
LIQUID IN THE FORM OF SNOW. NEW ENGLAND WILL SEE GREATER SNOW
POTENTIAL, WITH SOME AREAS ALREADY SUFFICIENTLY COLD AS THE SYSTEM
REACHES THE GREAT LAKES/MID-ATLANTIC AND THEN THE PATTERN BECOMING
INCREASINGLY FAVORABLE AS LOW PRESSURE EMPHASIS SHIFTS MORE
OFFSHORE BY AROUND LATE SUNDAY-MONDAY. THIS SYSTEM MAY PRODUCE
SOME BRISK WINDS AS WELL.
THE UPPER TROUGH MOVING THROUGH THE WEST LATE THIS WEEK WILL
PRODUCE SNOW AND LOWER ELEVATION RAIN OVER PORTIONS OF THE
SOUTHWEST AND SOUTHERN HALF OF THE ROCKIES. THEN THE MEAN TROUGH
ALOFT SETTING UP NEAR THE WEST COAST WILL BRING A SERIES OF
FRONTAL SYSTEMS AND RAIN/MOUNTAIN SNOW TO THE PACIFIC NORTHWEST
AND NORTHERN CALIFORNIA FROM FRIDAY INTO NEXT WEEK. MOST OF THIS
ACTIVITY SHOULD BE IN THE LIGHT TO MODERATE RANGE FRIDAY-SATURDAY,
WITH POTENTIAL FOR LOCALLY HEAVIER TOTALS BY SUNDAY-MONDAY. SOME
OF THIS MOISTURE SHOULD EVENTUALLY EXTEND INTO THE NORTHERN
ROCKIES.
SYSTEM PROGRESSION ACROSS THE LOWER 48 LATE THIS WEEK INTO THE
WEEKEND WILL BRING AN AREA OF MODERATELY BELOW NORMAL TEMPERATURES
(POCKETS OF HIGHS UP TO 10-15F BELOW AVERAGE) ACROSS THE WEST INTO
THE HIGH PLAINS THURSDAY-SATURDAY, WHILE WARMTH OVER THE EASTERN
HALF OF THE COUNTRY ON THURSDAY WILL GET CONFINED MORE TOWARD THE
EAST COAST BY THE WEEKEND. NEAR TO SLIGHTLY BELOW NORMAL HIGHS
SHOULD PREVAIL OVER THE EAST BY NEXT SUNDAY-MONDAY. ALSO DURING
THAT TIME, THE NORTHERN-CENTRAL PLAINS AND VICINITY WILL TREND
STEADILY WARMER (HIGHS REACHING 10-20F ABOVE NORMAL BY MONDAY)
UNDER THE INFLUENCE OF MEAN RIDGING ALOFT WHILE THE MEAN TROUGH
SETTING UP NEAR THE WEST COAST WILL PROMOTE SLIGHTLY BELOW NORMAL
DAYTIME HIGHS AND GRADUALLY WARMING LOWS.
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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