524
FXUS02 KWBC 041859
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 PM EDT THU MAY 04 2023
VALID 12Z SUN MAY 07 2023 - 12Z THU MAY 11 2023
..OVERVIEW
THE FORECAST FLOW PATTERN OVER NORTH AMERICA NEXT WEEK LOOKS TO
FEATURE MEAN RIDGING OVER THE CENTRAL-EASTERN CONUS AND MEAN
TROUGHING OVER THE CENTRAL-WESTERN CONUS. THE AMPLE YET UNCERTAIN
DOWNSTREAM EJECTION OF NUMEROUS UPPER-LEVEL IMPULSES AND
ASSOCIATED WEATHER FOCUSING SURFACE SYSTEMS ARE EXPECTED TO TAP AN
INFLUX OF GULF MOISTURE TO FAVOR BROAD AND WIDESPREAD SHOWER/STORM
CHANCES FROM THE PLAINS TO THE MISSISSIPPI VALLEY/MIDWEST AND
SOUTHEAST/EAST. CONDITIONS WILL REMAIN UNSEASONABLY COOL IN THE
WEST UNDER THE INFLUENCE OF MEAN TROUGHING, WITH A DAILY
PRECIPITATION FOCUS FOR THE NORTHWEST/NORTHERN TIER OF THE REGION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE STILL SHOWS A GENERALLY SIMILAR AND SLOWLY EVOLVING
LARGER SCALE PATTERN THROUGH THE WEEKEND INTO MONDAY DESPITE
TRANSITIONAL BLOCKY FLOW OVER NORTH AMERICA AND ADJOINING WATERS.
FORECAST SPREAD HAS DECREASED A BIT IN THIS PERIOD, BOLSTERING
FORECAST CONFIDENCE TO NEAR AVAERAGE LEVELS OVERALL. EVEN SO,
AMPLE DIFFERENCES AND RUN TO RUN CONSISTENCY ISSUES REMAIN WITH
LOCAL WEATHER FOCUSING SMALLER SCALE SYSTEMS EMBEDDED WITHIN THE
FLOW. A COMPOSITE BLEND OF REASONABLY COMPATIBLE MODEL GUIDANCE
FROM THE 06 UTC GFS AND 00 UTC ECMWF/UKMET/CANADIAN SEEMS TO
PROVIDE A GOOD FORECAST BASIS THAT TENDS TO MITIGATE SMALLER SCALE
VARIANCE CONSISTENT WITH SYSTEM PREDICTABILITY, BUT SYSTEM
CONTINUITY IS LESS THAN STELLAR. THIS SOLUTION THOUGH DOES HAVE
GOOD ENSEMBLE AND NATIONAL BLEND OF MODELS (NBM) SUPPORT. ENSEMBLE
SPAGHETTI AND CLUSTER PLOTS HOWEVER THEN SHOW A MORE RAPID
INCREASE IN FORECAST SPREAD/UNCERTAINLY FOR THE REST OF NEXT WEEK.
ACCORDINGLY, THE WPC MEDIUM RANGE PRODUCT SUITE WAS THEN PRIMARILY
DERIVED FROM A STILL COMPATIBLE 06 UTC GEFS/00 UTC ECMWF ENSEMBLE
MEANS AND THE NBM. THE NEWER 12 UTC GUIDANCE SUITE AND TRENDS HAVE
OVERALL REMAINED IN LINE WITH THIS AFOREMENTIONED FORECAST PLAN.
..WEATHER/HAZARDS HIGHLIGHTS
A STEADY SUPPLY OF GULF MOISTURE OVER THE CENTRAL TO EASTERN
UNITED STATES WILL FAVOR A STORMY AND WET PATTERN NEXT WEEK.
EMBEDDED SHORTWAVE ENERGY ALOFT AS WELL AS GENERAL FRONT
PROGRESSION WILL DICTATE THE CHANCES FOR LOCALLY HEAVIER RAINFALL.
THE EXPERIMENTAL WPC MEDIUM RANGE EXCESSIVE RAINFALL OUTLOOK (ERO)
IS SET TO ISSUE A "MARGINAL RISK" THREAT AREA OVER THE
MIDWEST/SOUTHWESTERN GREAT LAKE STATES, BY MONDAY GIVEN A DECENT
GUIDANCE SIGNAL FOR SUPPORTING SHORTWAVE AND SURFACE FRONTAL WAVE
APPROACH TO FOCUS MOISTURE/INSTABILITY. WHILE NO OTHER EROS HAVE
BEEN INTRODUCED IN THE DAY 4/5 TIMEFRAME, THE ENVIRONMENT WOULD
SUGGEST THERE WILL LIKELY EVENTUALLY BE ADDITIONAL MARGINAL RISK
AREAS, IF NOT HIGHER. MODEL QPF HAS OTHERWISE BEEN RATHER
NEBULOUS, FROM THE SOUTHERN PLAINS AND MISSISSIPPI VALLEY EASTWARD
ACROSS THE EAST-CENTRAL U.S. TO THE MID-ATLANTIC/CAROLINAS. WITH
THE 12 UTC ECMWF TRENDING FAVORABLY COMPARED TO THE PRIOR 00 UTC
RUN, THERE IS NOW A GROWING SIGNAL FOR MORE ORGANIZED
PRECIPITATION WITH STRONG CONVECTION AND TO SHIFT FOCUS BACK FROM
THE ROCKIES INTO THE PLAINS NEXT WEDNESDAY/THURSDAY WITH SLOW
APPROACH OF A MAIN UPPER TROUGH/HEIGHT FALLS OUT FROM THE WEST.
HIGH TEMPERATURES WILL BE RUNNING ABOVE AVERAGE BROADLY FROM THE
PLAINS TO THE SOUTHEAST/MID-ATLANTIC UNDER THE INFLUENCE OF MEAN
RIDGING ALOFT, WITH SOME UNSEASONABLY WARM HIGHS 15+ DEGREES ABOVE
AVERAGE CENTERED ON THE CENTRAL PLAINS/MIDDLE MISSISSIPPI VALLEY.
SEASONABLE TEMPERATURES AND LOW PRECIPITATION CHANCES ARE EXPECTED
ACROSS THE NORTHEAST WITH HIGH PRESSURE IN THE VICINITY THROUGH
THE FORECAST PERIOD. SOME TEMPERATURE FLUCTUATION AS WELL AS
BREEZY WINDS MAY EFFECT NEW ENGLAND DEPENDENT ON THE PROXIMITY OF
AN UPPER-LEVEL CLOSED LOW OVER CANADA AND SUBSEQUENT COLD FRONT
PASSAGE. ENERGETIC UPPER-LEVEL PATTERN WITH MEAN TROUGHING ALOFT
WILL FAVOR PERIODIC PRECIPITATION CHANCES IN THE WEST NEXT WEEK,
ESPECIALLY FOR THE PACIFIC NORTHWEST/GREAT BASIN/NORTHERN ROCKIES.
SOME SNOW SHOWERS WILL BE POSSIBLE FOR HIGHER MOUNTAIN ELEVATIONS,
BUT SEASONABLY RISING SNOW LEVELS WILL KEEP THESE CHANCES
ISOLATED. TEMPERATURES WILL REMAIN COOL AND BELOW AVERAGE,
ESPECIALLY ACROSS THE WEST COAST STATES.
PUTNAM/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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
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