901
FXUS02 KWBC 030700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST SUN MAR 03 2024
VALID 12Z WED MAR 06 2024 - 12Z SUN MAR 10 2024
...WET PATTERN FOR PARTS OF THE EASTERN U.S., ESPECIALLY ACROSS
THE SOUTH AND PARTS OF THE EAST COAST...
..OVERVIEW
MODELS AND ENSEMBLES ADVERTISE A COUPLE WET SYSTEMS AFFECTING THE
EASTERN HALF OF THE COUNTRY DURING THE PERIOD, WITH ONE CONFINED
NEAR THE EAST COAST MID-LATE WEEK AND THAN A MUCH BROADER ONE
PROGRESSING ACROSS THE CENTRAL-EASTERN U.S. LATE WEEK THROUGH THE
WEEKEND AS UPPER TROUGH ENERGY INITIALLY CROSSING THE WEST
CONTINUES EASTWARD. THIS WESTERN UPPER TROUGH AND ASSOCIATED
SURFACE REFLECTION WILL INITIALLY PRODUCE AREAS OF LIGHT TO
MODERATE PRECIPITATION FROM CALIFORNIA INTO THE ROCKIES MID-LATE
WEEK. A TRAILING UPPER RIDGE WILL PROMOTE A DRIER TREND OVER MOST
OF THE WEST BUT THEN A TRAILING UPPER TROUGH AND ONE OR MORE
SURFACE FRONTS SHOULD BRING PRECIPITATION BACK TO THE PACIFIC
NORTHWEST/NORTHERN CALIFORNIA BY LATE WEEK THROUGH NEXT WEEKEND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE IS STARTING TO TREND A LITTLE CLOSER TOGETHER FOR WHAT
HAS BEEN A VERY DIVERSE FORECAST ALONG THE EAST COAST MID-LATE
WEEK, WHILE DETAIL UNCERTAINTY LOOKS TO PERSIST FOR THE OVERALL
UPPER TROUGH CROSSING THE LOWER 48 AND ASSOCIATED SURFACE
SPECIFICS. SLOWER TRENDS IN THE GFS AND FASTER TRENDS IN THE
ECMWF HAVE LED TO BETTER CLUSTERING FOR THE UPPER TROUGH REACHING
THE WEST COAST AROUND NEXT SATURDAY.
COMPARISONS AMONG 12Z/18Z GUIDANCE FAVORED LEANING AWAY FROM THE
GFS AND TO SOME DEGREE GEFS ALONG THE EAST COAST FOR THE MID-LATE
WEEK SYSTEM, WITH OTHER GUIDANCE INCLUDING THE 12Z
ECMWF-INITIALIZED MACHINE LEARNING MODELS ALL SUGGESTING THAT THE
SURFACE LOW TRACK SHOULD BE SOMEWHAT SOUTH AND/OR OFFSHORE VERSUS
THE GFS. THE NEW 00Z GFS STILL EXTENDS ITS PRECIPITATION SHIELD
FARTHER NORTHWEST THAN MOST OTHER GUIDANCE BUT AT LEAST IT SURFACE
LOW TRACK SEEMS TO BE TRENDING IN THE RIGHT DIRECTION. MEANWHILE
THE 12Z UKMET STRAYED MUCH FLATTER THAN CONSENSUS WITH NORTHERN
STREAM FLOW, ULTIMATELY LEADING TO A MUCH SLOWER THAN CONSENSUS
SOLUTION. THEREFORE THE FIRST HALF OF THE UPDATED FORECAST
EMPHASIZED THE ECMWF/CMC WITH MINORITY INPUT FROM THE 18Z GEFS
MEAN.
BEHIND THAT SYSTEM, THERE CONTINUES TO BE GOOD LARGE SCALE
AGREEMENT FOR THE OVERALL UPPER TROUGH PROGRESSING EASTWARD ACROSS
THE LOWER 48 DURING THE PERIOD, ALONG WITH SUPPORT FOR AN
ORGANIZED SURFACE SYSTEM. HOWEVER A LOT OF THE EMBEDDED SHORTWAVE
DETAILS HAVE LOW PREDICTABILITY SEVERAL DAYS OUT IN TIME, SO
CONFIDENCE IS STILL NOT VERY GOOD IN RESOLVING THE ULTIMATELY
TRACK AND STRENGTH OF ASSOCIATED SURFACE LOW PRESSURE. CURRENTLY
THE MOST AGREEABLE THEME IN THE GUIDANCE IS FOR THE PLAINS LOW
PRESSURE TO TRACK INTO THE OHIO VALLEY/GREAT LAKES BY SATURDAY
WITH POTENTIAL FOR COASTAL DEVELOPMENT BY SUNDAY. A
MODEL/ENSEMBLE MEAN BLEND PROVIDES A GOOD STARTING POINT FOR
DEPICTING THIS SYSTEM IN PRINCIPLE WHILE ACCOUNTING FOR THE LOW
CONFIDENCE IN DETAIL SPECIFICS.
WITH GUIDANCE SIGNIFICANTLY IMPROVING FOR TIMING OF THE UPPER
TROUGH REACHING THE NORTHWEST AROUND SATURDAY, THE PRIMARY
DIFFERENCES NOW ARISE BY SUNDAY WITH THE GFS BEGINNING TO STRAY A
LITTLE FASTER THAN CONSENSUS FOR THE LEADING SHORTWAVE ENERGY.
THERE IS REASONABLE AGREEMENT WITH A SECOND SHORTWAVE BEING POISED
TO APPROACH THE NORTHWEST ON SUNDAY.
..WEATHER/HAZARDS HIGHLIGHTS
THE EASTERN HALF OF THE COUNTRY WILL SEE AN ACTIVE WEATHER PATTERN
DURING THE PERIOD. A DEVELOPING WAVE AFFECTING AREAS NEAR THE
EAST COAST MID-LATE WEEK SHOULD PRODUCE ONE AREA OF ENHANCED
PRECIPITATION, BUT WITH DETAILS CONTINUING TO SHOW LOWER THAN
AVERAGE CONFIDENCE DUE TO HIGH SENSITIVITY TO EXACT SURFACE LOW
TRACK. THE NEW DAY 4/WEDNESDAY-WEDNESDAY NIGHT EXCESSIVE RAINFALL
OUTLOOK PROPOSES SOME ADJUSTMENT TO THE PRIOR DAY 5 MARGINAL RISK
AREA, MAINTAINING A SIGNIFICANT PORTION OF THE ORIGINAL AREA THAT
OVERLAPPED WITH RELATIVELY LOWER FFGS OVER PARTS OF THE CENTRAL
APPALACHIANS/NORTHERN MID-ATLANTIC (BUT WITH MIXED SIGNALS FOR QPF
TOTALS) AND EXPANDING IT TO INCLUDE SOUTHERN NEW ENGLAND WHERE
THERE IS A LITTLE BETTER OF A SIGNAL FOR HEAVIER RAINFALL
POTENTIAL. SOME SIGNIFICANT PRECIPITATION IN THE FORM OF RAIN
AND/OR SNOW MAY CONTINUE NORTHEASTWARD OVER NEW ENGLAND INTO DAY
5/THURSDAY-THURSDAY NIGHT BUT CONFIDENCE IN TOTALS OR
PRECIPITATION TYPE DISTRIBUTION (WITH SOME SNOW POSSIBLE EVEN
CLOSE TO THE NEW ENGLAND COAST IF THE SURFACE TRACK IS FAR ENOUGH
OFFSHORE) IS TOO LOW TO DEPICT ANY RISK AREA FOR THE DAY 5 ERO.
AS UPPER TROUGHING EMERGES FROM THE WEST, A FAIRLY VIGOROUS
SURFACE SYSTEM SHOULD DEVELOP OVER THE CENTRAL U.S. LATE THIS WEEK
AND CONTINUE INTO THE EAST BY NEXT WEEKEND. THE DAY
5/THURSDAY-THURSDAY NIGHT ERO DEPICTS 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. BY FRIDAY THE PAST COUPLE DAYS OF
GUIDANCE HAVE BEEN SIGNALING POTENTIAL FOR HEAVIER RAINFALL OVER
PORTIONS OF THE SOUTHEAST AND THIS WILL CONTINUE TO BE MONITORED.
OTHERWISE, YET TO BE DETERMINED SYSTEM DETAILS WILL DICTATE OTHER
AREAS IN THE EASTERN HALF OF THE COUNTRY THAT MAY SEE SIGNIFICANT
PRECIPITATION FROM THIS SYSTEM. SOME LOCATIONS FROM THE CENTRAL
HIGH PLAINS INTO THE UPPER MIDWEST, GREAT LAKES, AND NEW ENGLAND
COULD SEE SOME SNOW BUT CURRENTLY WITH 24-HOUR PROBABILITIES OF
0.25 INCH LIQUID IN THE FORM OF SNOW STAYING UNDER 30 PERCENT THUS
FAR.
EXPECT A WAVY FRONTAL SYSTEM TO BRING LIGHT TO LOCALLY MODERATE
PRECIPITATION TO CALIFORNIA ON WEDNESDAY WITH SOME RAIN AND HIGHER
ELEVATION SNOW EXTENDING EASTWARD INTO THE ROCKIES MID-LATE WEEK.
MOST OF THE WEST WILL SEE A DRIER TREND AS THIS MOISTURE
PROGRESSES EASTWARD, THOUGH THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA SHOULD SEE A REBOUND IN RAINFALL/MOUNTAIN SNOW LATE
THIS WEEK INTO THE WEEKEND WITH THE APPROACH/ARRIVAL OF AN UPPER
TROUGH AND A COUPLE FRONTAL SYSTEMS.
THE UPPER TROUGH CROSSING THE WEST MID-LATE WEEK WILL PROMOTE
BELOW NORMAL TEMPERATURES ACROSS MOST OF THE REGION, WITH SOME
AREAS OF HIGH TEMPERATURES AS COOL AS 10-15F BELOW AVERAGE ALSO
EXTENDING INTO PARTS OF THE HIGH PLAINS FOR A TIME. NEGATIVE
ANOMALIES FOR MORNING LOWS SHOULD BE CONFINED MORE TO THE
NORTHWEST/GREAT BASIN. BY NEXT WEEKEND CLOUDS AND PRECIPITATION
MAY KEEP HIGHS A LITTLE BELOW NORMAL OVER THE PACIFIC NORTHWEST
NEXT WEEKEND BUT OTHER PORTIONS OF THE WEST SHOULD TREND TOWARD
NORMAL AS UPPER RIDGING BUILDS IN, WHILE TEMPERATURES SHOULD RISE
TO ABOVE NORMAL LEVELS OVER THE NORTHERN PLAINS. THE EASTERN HALF
OF THE COUNTRY SHOULD STAY ON THE WARM SIDE OF NORMAL MID-LATE
WEEK WITH THE MOST ANOMALOUS READINGS OF PLUS 20-30F FOR MORNING
LOWS ON WEDNESDAY FROM PARTS OF THE OHIO/TENNESSEE VALLEY INTO THE
NORTHEAST. THESE VALUES MAY LEAD TO SOME DAILY RECORDS FOR WARM
LOWS IF THEY HOLD FOR THE CALENDAR DAY. EASTWARD PROGRESSION OF
THE LATE WEEK/WEEKEND STORM SYSTEM WILL BRING A COOLING TREND FROM
WEST TO EAST, WITH HIGHS OVER THE EASTERN THIRD OF THE COUNTRY
DECLINING TO NEAR OR SLIGHTLY BELOW NORMAL BY NEXT SUNDAY.
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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