204
FXUS02 KWBC 260612
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
212 AM EDT FRI JUN 26 2026
VALID 12Z MON JUN 29 2026 - 12Z FRI JUL 03 2026
...SIGNIFICANT, DANGEROUS HEAT WAVE EXPECTED NEXT WEEK FOR THE
CENTRAL TO EASTERN U.S...
..PATTERN OVERVIEW
THE PATTERN DURING THE UPCOMING MEDIUM RANGE LOOKS TO BE HIGHLY
AMPLIFIED WITH A STRONG UPPER HIGH/RIDGE OVER THE EASTERN HALF OF
THE U.S. AND A DEEP TROUGH OVER THE WEST. THIS TROUGH WILL BE
REINFORCED THROUGH THE PERIOD BY A SERIES OF SHORTWAVES, WITH SNOW
POSSIBLE AT THE HIGHEST ELEVATIONS OF THE NORTHERN ROCKIES
ASSOCIATED WITH ONE COMPACT UPPER LOW EARLY IN THE PERIOD. IN THE
EAST, A SPRAWLING UPPER HIGH WILL RESULT IN INCREASINGLY DANGEROUS
HEAT AND HUMIDITY THROUGH MUCH OF NEXT WEEK (AND POSSIBLY BEYOND
INTO THE JULY 4TH HOLIDAY WEEKEND). SHOWERS AND THUNDERSTORMS WILL
BE MOST LIKELY ACROSS THE GULF COAST/FLORIDA REGION, THE SOUTHERN
ROCKIES, AND THE UPPER MIDWEST TO GREAT LAKES/NORTHEAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE LARGE
SCALE FORECAST, BUT PLENTY OF UNCERTAINTY STILL IN THE DETAILS. OUT
WEST, GUIDANCE IS SHOWING BETTER AGREEMENT NOW ON AN INITIAL UPPER
LOW OVER MONTANA ON MONDAY LIFTING MORE NORTHWARD, KEEPING THE
UPPER RIDGE OVER THE EAST IN TACT. THIS SYSTEM SHOULD SPIN UP DEEP
LEE CYCLOGENESIS OVER THE NORTHERN/CENTRAL PLAINS, WITH THE
PROGRESS OF THIS SYSTEM SLOW TO MOVE EASTWARD DUE TO THE POTENT
UPPER-HIGH/RIDGE OVER THE EAST. ENERGY AND SHORTWAVES INTO THE
WESTERN TROUGH WILL ACT TO REINFORCE THIS TROUGH THROUGH NEXT WEEK.
THE GUIDANCE SHOWS ANOTHER UPPER LOW DROPPING INTO THE PACIFIC
NORTHWEST LATE WEEK, BUT UNCERTAINTY ON THE EVOLUTION AND DETAILS
OF THIS. WPC WAS ABLE TO USE A MOSTLY DETERMINISTIC/AI GUIDANCE
BLEND FOR THE FIRST HALF OF THE PERIOD, TRANSITIONING TO A 50/50
BLEND OF THE ENSEMBLE MEANS WITH THE EC/EC-AIFS BY DAY 7. GENERALLY
MAINTAINED GOOD AGREEMENT WITH THE PREVIOUS WPC FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
THE MOST IMPACTFUL WEATHER HAZARD DURING THE MEDIUM RANGE PERIOD
WILL BE A LONG LASTING HEAT WAVE AFFECTING MUCH OF THE CENTRAL TO
EASTERN U.S. BEGINNING THIS WEEKEND AND LASTING THROUGH NEXT WEEK,
AND LIKELY INTO THE JULY 4TH HOLIDAY WEEKEND AS WELL. WIDESPREAD
TEMPERATURES INTO THE 90S TO LOW 100S, COMBINED WITH HIGH HUMIDITY,
WILL RESULT IN HEAT INDICES APPROACHING OR EXCEEDING 105-110 IN
MANY PLACES. THIS EQUATES TO WIDESPREAD MAJOR HEATRISK ACROSS THE
ENTIRE REGION, WITH AREAS OF EXTREME HEATRISK IN PARTS OF THE
MIDWEST AND OHIO VALLEY UNDERNEATH THE CORE OF THE UPPER HIGH.
OVERNIGHT LOWS WILL ALSO BE QUITE WARM, WITH SOME RECORD HIGH
MINIMUMS POSSIBLE, BRINGING LITTLE TO NO RELIEF FROM THE HEAT IN
THE NIGHTTIME HOURS.
RAIN AND MOUNTAIN SNOW WILL BE ONGOING INTO MONDAY FOR MUCH OF THE
NORTHERN ROCKIES, WITH SEVERAL INCHES OF SNOW ACCUMULATION FOR THE
HIGHEST MOUNTAIN RANGES. AHEAD OF THIS, RAIN AND THUNDERSTORMS MAY
DEVELOP ACROSS PARTS OF THE UPPER MIDWEST AND GREAT LAKES INTO
TUESDAY AHEAD/NORTH OF A LIFTING WARM FRONT THROUGH THE REGION.
WHILE MUCH OF THIS SHOULD BE FAIRLY PROGRESSIVE, MOISTURE ANOMALIES
AND INSTABILITY MAY SUPPORT A LOCALIZED FLASH FLOOD THREAT. WPC
HIGHLIGHTS PARTS OF THE UPPER MIDWEST AND THE INTERIOR NORTHEAST
WITH MARGINAL RISKS ON THE DAY 5/TUESDAY EXCESSIVE RAINFALL
OUTLOOK.
ELSEWHERE, MOISTURE FUNNELING BETWEEN THE WESTERN TROUGH AND THE
EASTERN RIDGE SHOULD SUPPORT SHOWERS AND THUNDERSTORMS ACROSS PARTS
OF THE SOUTHERN ROCKIES AND SOUTHERN HIGH PLAINS FOR AT LEAST THE
EARLY PART OF THE WEEK. DIURNALLY DRIVEN SHOWERS AND STORMS ARE
ALSO EXPECTED FROM THE CENTRAL GULF COAST TO FLORIDA WITH MOISTURE
INCREASING SOUTH OF THE UPPER RIDGE.
SANTORELLI
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 FORECAST, 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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page