124
FXUS02 KWBC 290656
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 AM EDT THU JUN 29 2023
VALID 12Z SUN JUL 02 2023 - 12Z THU JUL 06 2023
...MAJOR HEATWAVE FROM TEXAS THROUGH THE MID-LOWER MISSISSIPPI
VALLEY TO THE SOUTHEAST TO EASE NEXT WEEK...
...HOT TEMPERATURES FROM THE DESERT SOUTHWEST TO INTERIOR
CALIFORNIA...
...EXCESSIVE RAINFALL THREAT FROM THE OHIO VALLEY TO THE
NORTH-CENTRAL APPALACHIANS SUNDAY/MONDAY...
..OVERVIEW AND GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED THROUGH
INDEPENDENCE DAY FROM A BLEND OF REASONABLY WELL CLUSTERED
MID-LARGER SCALE GUIDANCE OF 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. OPTED TO THEN
REPLACE THE UKMET/GFS WITH THE MORE COMPATIBLE GEFS/ECMWF ENSEMBLE
MEANS INTO THE COMPOSITE BLEND AMID GROWING MID-LATER NEXT WEEK
FORECAST SPREAD. THIS REPLACEMENT ALSO REMOVES FROM THE EQUATION
LESS SUPPORTED GFS TROPICAL INTERACTIONS INTO THE GULF OF MEXICO
AND SUBSEQUENT CENTRAL GULF COAST VERY HEAVY RAINFALL. OVERALL,
WPC PRODUCT CONTINUITY IS REASONABLY MAINTAINED WITH THE BLENDING
PROCESS TENDING TO MITIGATE SMALLER SCALE GUIDANCE DIFFERENCES
CONSISTENT WITH INDIVIDUAL SYSTEM PREDICTABILITY. LATEST 00 UTC
GUIDANCE REMAINS GENERALLY IN LINE.
..WEATHER/HAZARDS HIGHLIGHTS
A MAIN EJECTION OF UPPER TROUGH ENERGY FROM THE MIDWEST THROUGH
THE NORTHEAST OVER INTO THE EXTENDED HOLIDAY WEEKEND WILL FOCUS
SHOWERS AND STRONG TO SEVERE STORM CHANCES WITH A WAVY FRONTAL
SYSTEM WITH FOCUS ACROSS THE OHIO VALLEY AND NORTH-CENTRAL
APPALACHIANS ALONG WITH A THREAT FOR LOCALLY HEAVY RAINFALL AND
RUNOFF ISSUES. WPC DAY 4/5 EXCESSIVE RAINFALL OUTLOOK "MARGINAL
RISKS" AREAS SEEM REASONABLE GIVEN INSTABILITY/MOISTURE POOLING
AND POTENTIAL FOR REPEAT/TRAINING OF CELLS. ANTECEDENT RAINFALL
AND ADDITIONAL INFLUENCE FROM NORTHERN STREAM ENERGY ARE ALSO IN
THE MIX. THE OVERALL CONVECTIVE RAIN FOCUS SHOULD SHIFT EAST AND
SINK INTO THE SOUTH/SOUTHEAST AND BECOME LESS ORGANIZED EARLY-MID
NEXT WEEK ALONG A TRAILING/STALLING FRONT THEN RE-EMERGING RETURN
FLOW.
UPSTREAM, ENHANCED INSTABILITY AND CONVECTIVE PRECIPITATION
CHANCES WILL INCREASE AND SHIFT SOUTHEASTWARD ACROSS THE
NORTH-CENTRAL ROCKIES/PLAINS TO THE MID-UPPER MISSISSIPPI VALLEY
THROUGH EARLY TO MID NEXT WEEK AHEAD OF THE NEXT MAIN FRONTAL
SYSTEM SET TO DROP IN FROM CANADA IN APPROACH OF AN AMPLIFIED
WEST-CENTRAL CANADIAN UPPER TROUGH/HEIGHT FALLS.
EXCESSIVE HEAT TO START THE WEEKEND FROM SOUTHERN/SOUTHEAST TEXAS
INTO THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST/FLORIDA WILL
BRIEFLY EXPAND NORTHEASTWARD INTO THE CAROLINAS THROUGH MONDAY
BEFORE A GENERAL DOWNWARD TREND TOWARDS SUMMER AVERAGES OUTSIDE OF
SOUTH TEXAS. THE HEAT WILL BE OPPRESSIVE WITH WIDESPREAD HIGH
TEMPERATURES IN THE MID-90S TO LOW 100S WHICH, WHEN COMBINED WITH
THE HUMIDITY, WILL LEAD TO HEAT INDICES IN THE 110-115 DEGREE
RANGE, LOCALLY EVEN A BIT HIGHER. EXCESSIVE SUMMER HEAT WILL ALSO
OVERSPREAD PORTIONS OF THE WEST THIS WEEKEND, WITH THE CENTRAL
CALIFORNIA VALLEYS SEEING HIGHS OF 105-110 DEGREES, UPWARDS OF
10-15 DEGREES ABOVE AVERAGE. THE DESERT SOUTHWEST WILL EXPERIENCE
A NOTABLE HEATING THIS WEEKEND AS WELL WITH MAX TEMPS 5 TO 10
DEGREES ABOVE AVERAGE WHICH MEANS LOW TO MID 110S FOR THESE HOT
ENVIRONS SOUTH FROM LAS VEGAS AND WEST FROM PHOENIX. ELSEWHERE,
ABOVE AVERAGE HIGH TEMPERATURES IN THE UPPER 80S TO MID 90S ALONG
THE NORTHERN TIER OF THE CENTRAL U.S. THIS WEEKEND WILL SHIFT
EASTWARD INTO THE UPPER MIDWEST/GREAT LAKES REGION AHEAD OF A COLD
FRONT, WHICH WILL BRING MUCH COOLER TEMPERATURES IN THE 70S TO
PORTIONS OF THE CENTRAL/NORTHERN HIGH PLAINS FOR THE JULY 4
HOLIDAY.
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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