015
FXUS02 KWBC 280657
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 AM EDT WED JUN 28 2023
VALID 12Z SAT JUL 01 2023 - 12Z WED JUL 05 2023
...MAJOR HEATWAVE EXPANDS FROM TEXAS THROUGH THE MID-LOWER
MISSISSIPPI VALLEY AND SOUTHEAST...
..HEATWAVE DEVELOPS OVER DESERT SOUTHWEST
...EXCESSIVE RAINFALL THREAT FOCUS FROM THE OHIO VALLEY THROUGH
THE NORTHEAST THIS WEEKEND...
...PATTERN OVERVIEW AND GUIDANCE EVALUATION/PREDICTABILITY
ASSESSMENT...
THE UPCOMING WEATHER PATTERN FOR THE FIRST WEEK OF JULY WILL
LIKELY BE HIGHLIGHTED BY AN UPPER RIDGE SLATED TO FURTHER EXPAND
ACROSS THE SOUTHERN TIER OF THE NATION TO EXTEND A MAJOR HEATWAVE
WHILE A MAIN STRONG TO SEVERE CONVECTION/RAINFALL FOCUSING UPPER
TROUGH AND SURFACE SYSTEM PROPAGATES ACROSS THE CENTRAL PLAINS
THROUGH THE OHIO VALLEY AND ONWARD OVER THE HOLIDAY WEEKEND.
ANOTHER UPPER RIDGE WILL AMPLIFY AND HEAT UP THE SOUTHWEST/WEST AS
WELL.
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM THE
WEEKEND INTO EARLY NEXT WEEK FROM A BLEND OF REASONABLY WELL
CLUSTERED MID-LARGER SCALE GUIDANCE FROM THE 18 UTC GFS AND 12 UTC
ECMWF/UKMET/CANADIAN ALONG WITH THE 01 UTC NATIONAL BLEND OF
MODELS. THIS SOLUTION HAS GOOD OVERALL ENSEMBLE SUPPORT, ALBEIT
WITH AMPLE LOCAL CONVECTIVE FOCUS DIFFERNECES. REPLACED THE
UKMET/GFS WITH GEFS/ECMWF ENSEMBLE MEANS BY THE 4TH AMID GROWING
FORECAST SPREAD. THIS REPLACEMENT ALSO REMOVES FROM THE EQUATION
LESS SUPPORTED GFS TROPICAL INTERACTIONS INTO THE GULF OF MEXICO.
OVERALL, WPC PRODUCT CONTINUITY IS FAIRLY WELL MAINTAINED WITH THE
BLENDING PROCESS TENDING TO MITIGATE SMALLER SCALE GUIDANCE
DIFFERENCES CONSISTENT WITH INDIVIDUAL SYSTEM PREDICTABILITY.
LATEST 00 UTC GUIDANCE REMAINS BROADLY IN LINE THROUGH THE HOLIDAY.
..WEATHER/HAZARDS HIGHLIGHTS
THE MAIN EJECTION OF UPPER TROUGH ENERGIES OUT FROM THE
ROCKIES/CENTRAL PLAINS INTO THE HOLIDAY WEEKEND IS EXPECTED TO
FOCUS SHOWERS AND STRONG TO SEVERE STORM CHANCES OUT FROM THE
CENTRAL PLAINS THROUGH THE MID-MISSISSIPPI AND OHIO/TENNESSEE
VALLEYS TO THE APPALACHIANS/NORTHERN MID-ATLANTIC/NORTHEAST ALONG
WITH A THREAT FOR LOCALLY HEAVY RAINFALL AND RUNOFF ISSUES.
"MARGINAL RISKS" OF EXCESSIVE RAINFALL ARE PLANNED GIVEN
INSTABILITY/MOISTURE POOLING AND POTENTIAL FOR REPEAT/TRAINING OF
CELLS MAINLY WITH A DEVELOPING WAVE AND FRONTAL SYSTEM. ANTICEDENT
RAINFALL AND ADDITIONAL INFLUENCE FROM NORTHERN STREAM ENERGY ARE
ALSO IN THE MIX. A "SLIGHT RISK" AREA HAS ALSO BEEN INTRODUCED
OVER PORTIONS OF THE OHIO VALLEY FOR SATURDAY GIVEN HIGH POOLED
PRECIPITABLE WATER VALUES. THE OVERALL CONVECTION AND HEAVY RAIN
FOCUS SHOULD SHIFT SOUTHEAST AND BECOME LESS ORGANIZED INTO EARLY
NEXT WEEK WITH WAVE AND TRAILING FRONT PROGRESSION THEN EVENTUAL
STALLING.
EXCESSIVE HEAT WILL CONTINUE TO PLAGUE THE SOUTHERN PLAINS AND
EXPAND NORTH AND EAST THIS WEEKEND TO PORTIONS OF THE CENTRAL
PLAINS AND THE MID-LOWER MISSISSIPPI VALLEY AS WELL AS ACROSS
PORTIONS OF THE SOUTHEAST/FLORIDA. THE HEAT WILL BE OPPRESSIVE
WITH WIDESPREAD HIGH TEMPERATURES EXCEEDING 100 DEGREES AND HEAT
INDICES AS HIGH AS 120 DEGREES OVER THE SOUTH-CENTRAL U.S.. HEAT
INDICES MAY EVEN EXCEED 120 DEGREES IN SOME LOCATIONS IN SOUTH
TEXAS. TENS OF HIGH TEMPERATURE RECORDS ARE IN DANGER OF BEING
BROKEN DURING THIS SIGNIFICANT HEAT WAVE. THE DESERT SOUTHWEST
WILL ALSO EXPERIENCE A NOTABLE HEATING THIS WEEKEND WITH MAX TEMPS
5 TO 10 DEGREES ABOVE NORMAL WHICH MEANS 110 TO 115 DEGREES MAX
TEMPS FOR THESE HOT ENVIRONS SOUTH FROM LAS VEGAS AND WEST FROM
PHOENIX.
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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