129
FXUS02 KWBC 250700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT SUN JUN 25 2023
VALID 12Z WED JUN 28 2023 - 12Z SUN JUL 02 2023
...PROLONGED HEAT WAVE FOCUS FROM TEXAS TO THE MID-LOWER
MISSISSIPPI VALLEY...
...EXCESSIVE RAINFALL THREAT ACROSS THE NORTHEAST AND
NORTH-CENTRAL U.S. STATES INTO MID-LATER WEEK...
..OVERVIEW
AN ANOMALOUSLY STRONG AND PERSISTENT UPPER RIDGE AND HEATWAVE WILL
FOCUS OVER TEXAS AND THE MID/LOWER MISSISSIPPI VALLEY THROUGH THE
HOLIDAY WEEKEND. DOWNSTREAM MEAN UPPER LOW/TROUGHING WILL LINGER
OVER THE STILL WET NORTHEAST AS UPSTREAM UPPER TROUGH ENERGIES
STUCK OVER THE WEST SLUGGISHLY LIFT TO THE NORTHERN ROCKIES AND
NORTH-CENTRAL U.S. OVERTOP THE RIDGE TO FOCUS ROUNDS OF
THUNDERSTORMS WITH HEAVY DOWNPOURS.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
GUIDANCE SOLUTIONS REMAIN REASONABLY CLUSTERED OVERALL, BUT
NONETHELESS HAVE SHOWN GREATER RUN TO RUN VARIANCE THAN EXPECTED
WITH THE TIMING OF THE EJECTION OF THE UPPER TROUGH ENERGIES FROM
THE WEST THROUGH THE ROCKIES INTO THE NORTH-CENTRAL STATES. OPTED
TO LEAN A COMPOSITE MODEL AND ENSEMBLE SOLUTION A BIT TOWARD
PERSISTENCE IN THIS FLOW PATTERN. ACCORDINGLY, THE WPC MEDIUM
RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A BLEND OF
GFS/ECMWF/UKMET/CANADIAN MODELS FOR BEST DETAIL MID-LATE WEEK,
WITH EMPHASIS ON THE 18 UTC GFS. ADDED THE GEFS/ECMWF ENSEMBLE
MEANS TO THE BEST CLUSTERED GFS/ECMWF BY THE HOLIDAY WEEKEND.
..WEATHER/HAZARDS HIGHLIGHTS
ANOTHER ORGANIZED LOW PRESSURE SYSTEM WILL WORK ACROSS THE
NORTHEAST MID-LATE WEEK WITH SOME REINFORCEMENT OVER THE WEEKEND.
WRAPPING MOISTURE TO FUEL WIDESPREAD AND LINGERING PRECIPITATION.
LOCALLY HEAVY RAINFALL WILL BE POSSIBLE WITH POTENTIAL TRAINING
AND EMBEDDED THUNDERSTORMS WITH THIS SLOW MOVING SYSTEM. A WPC
EXCESSIVE RAINFALL OUTLOOK (ERO) "MARGINAL RISK" AREA IS PLANNED
TO BE MAINTAINED OVER THE NORTHEAST FOR WEDNESDAY AND THURSDAY IN
A SLOW-TO-EVOLVE FLOW PATTERN IN AN AREA WITH ANTECEDENT RAINFALL.
MEANWHILE, THE EJECTION OF UPPER TROUGH ENERGIES OUT FROM THE WEST
WILL BRING SCATTERED SHOWERS AND STORM CHANCES, WITH ACTIVITY
LIKELY TO BE ON THE INCREASE AND SPREAD DOWNSTREAM TO THE NORTHERN
ROCKIES AND NORTHERN PLAINS/UPPER MIDWEST, AND HEAVY RAINFALL MAY
BE A CONCERN. THERE IS A PLANNED "MARGINAL RISK" OF EXCESSIVE
RAINFALL FOR PARTS OF THIS REGION WEDNESDAY AND THURSDAY TO
ADDRESS POTENTIAL TRAINING/REPEAT CELL RUNOFF CONCERNS GIVEN
INSTABILITY AND FLOW. PRECIPITATION WILL SPREAD ACROSS THE
MIDWEST/EAST-CENTRAL U.S. LATER WEEK INTO THE HOLIDAY WEEKEND AS
THE SYSTEM PROGRESSES TO THE EAST.
IN TERM OF TEMPERATURES, EXCESSIVE HEAT WILL CONTINUE TO PLAGUE
THE SOUTH-CENTRAL U.S. INTO NEXT WEEK WITH A MID-WEEK EXPANSION
NORTH AND EAST ACROSS PORTIONS OF THE CENTRAL PLAINS AND INTO THE
MID- AND LOWER MISSISSIPPI VALLEY. THE HEAT WILL BE OPPRESSIVE
WITH WIDESPREAD HIGH TEMPERATURES EXCEEDING 100 DEGREES AND HEAT
INDICES AS HIGH AS 120 DEGREES. HEAT INDICES MAY EVEN EXCEED 120
DEGREES IN SOME LOCATIONS IN SOUTH TEXAS. SEVERAL TEMPERATURE
RECORDS ARE IN DANGER OF BEING BROKEN DURING THIS SIGNIFICANT HEAT
WAVE. THE DESERT SOUTHWEST WILL ALSO EXPERIENCE TEMPERATURES WELL
OVER 100 DEGREES NEXT WEEK, BUT THAT IS NOT REALLY ANOMALOUS FOR
THIS TIME OF YEAR. FLORIDA WILL ALSO SEE HOT TO RECORD VALUES.
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, 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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