580
FXUS02 KWBC 291937
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
336 PM 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 SUN-MON...
..OVERVIEW
STRONG AND PROLONGED HEAT OVER TEXAS/SOUTH WILL START TO RELENT
EARLY NEXT WEEK AS THE PATTERN TAKES ON A MORE ZONAL FLOW. IN A
MORE TYPICAL SUMMERTIME PATTERN, NORTHERN TIER FRONTAL SYSTEMS
WILL PROGRESS SOUTHEASTWARD AND EASTWARD OUT OF THE NORTHERN
PLAINS AND INTO THE EAST WITH DAILY CHANCES OF
SHOWERS/THUNDERSTORMS INTO THE SOUTHEAST.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
ENSEMBLE AGREEMENT WAS AVERAGE TO BETTER THAN AVERGE THROUGH THE
PERIOD, AND A BLEND OF THE RECENT 00Z/06Z GUIDANCE SERVED AS A
REASONABLE STARTING POINT. THE 06Z GFS WAS ON THE QUICKER SIDE
WITH THE FRONT INTO THE GREAT LAKES MIDWEEK NEXT WEEK, WHEREAS THE
MULTI-DAY ENSEMBLE TREND WAS A BIT SLOWER. THE 00Z ECMWF CLUSTERED
BEST WITH THE AGREEABLE GEFS/ECMWF/CANADIAN ENSEMBLE CONSENSUS.
..WEATHER/HAZARDS HIGHLIGHTS
A SYSTEM WILL MOVE EASTWARD THROUGH THE OHIO VALLEY SUN-MON WITH A
SURGE IN MOISTURE FROM THE SOUTH THROUGH THE WARM SECTOR. RAINFALL
COULD BE LOCALLY HEAVY PER SOME OF THE GUIDANCE, AND HAVE
MAINTAINED A MARGINAL RISK FOR EXCESSIVE RAINFALL THERE FOR
SUNDAY, AND INTO THE NORTHERN MID-ATLANTIC ON MONDAY AS THE SYSTEM
PUSHES TO THE COAST WHERE IT HAS BEEN RECENTLY QUITE WET.
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. LOCALLY HEAVY RAIN IS PROBABLE
BUT WITH LIMITED CONFIDENCE IN PLACEMENT.
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 MORE TYPICAL MID-SUMMER
AVERAGES. THE HEAT WILL CONTINUE TO 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 (AND 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 IS
FORECAST TO SEE HIGH TEMPERATURES INTO THE 110S (5 TO 10 DEGREES
ABOVE AVERAGE) FROM LAS VEGAS INTO THE CO RIVER VALLEY EASTWARD TO
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. THIS AREA OF BELOW NORMAL
TEMPERATURES WILL SLIDE EASTWARD INTO THE PLAINS BY NEXT THURSDAY.
FRACASSO/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
HAZARDS:
- HEAVY RAIN ACROSS PORTIONS OF THE GREAT LAKES, THE CENTRAL
APPALACHIANS, AND THE OHIO VALLEY,
SUN, JUL 2.
- FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHERN PLAINS.
- FLOODING LIKELY ACROSS PORTIONS OF THE NORTHERN PLAINS.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE CENTRAL GREAT BASIN,
CALIFORNIA, AND THE SOUTHWEST,
SUN-MON, JUL 2-JUL 3.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY,
THE TENNESSEE VALLEY, CALIFORNIA,
THE SOUTHEAST, THE SOUTHERN APPALACHIANS, AND THE SOUTHERN PLAINS,
SUN, JUL 2.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY
AND THE SOUTHERN PLAINS, SUN-THU,
JUL 2-JUL 6.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE SOUTHEAST AND THE
MID-ATLANTIC, SUN-TUE, JUL 2-JUL 4.
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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