368
FXUS02 KWBC 191856
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT THU JUN 19 2025
VALID 12Z SUN JUN 22 2025 - 12Z THU JUN 26 2025
...FIRST SIGNIFICANT AND EXTREMELY DANGEROUS HEAT WAVE OF THE
SEASON EXPECTED FOR THE CENTRAL PLAINS, MIDWEST, AND MID-
ATLANTIC/NORTHEAST THIS WEEKEND INTO NEXT WEEK...
...MULTI-DAY HEAVY RAIN THREAT WITH POTENTIAL FOR FLASH FLOODING
ACROSS THE CENTRAL PLAINS/UPPER MIDWEST AS WELL AS THE SOUTHERN
ROCKIES/HIGH PLAINS NEXT WEEK...
..GENERAL OVERVIEW
A SIGNIFICANT AND EXTREMELY DANGEROUS HEAT WAVE IS EXPECTED TO
START THE SUMMER ACROSS MUCH OF THE CENTRAL/EASTERN U.S. THIS
WEEKEND THROUGH AT LEAST THE MIDDLE OF NEXT WEEK UNDER A STRONG
UPPER-LEVEL RIDGE. A DEEP UPPER TROUGH IS FORECAST TO MOVE ACROSS
THE NORTHWEST AND PROMOTE WAVES OF LOW PRESSURE ALONG A WAVY
FRONTAL BOUNDARY THROUGH THE CENTRAL/NORTHERN PLAINS. THIS BOUNDARY
WILL ACT AS A FOCUS FOR MULTIPLE DAYS OF HEAVY RAINFALL, EMBEDDED
SEVERE WEATHER, AND FLASH FLOODING. LARGE CLOCKWISE CIRCULATION
CENTERED OVER THE CENTRAL APPALACHIANS WILL HELP DRAW IN TROPICAL
MOISTURE FROM THE SOUTH ON ITS WESTERN PERIPHERY ("RING OF FIRE")
INTO THE SOUTHERN ROCKIES/HIGH PLAINS, SETTING UP THE HEAVY RAIN
THREAT NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE HAS REMAINED IN ABOVE AVERAGE AGREEMENT ON THE OVERALL
LARGER-SCALE PATTERN THROUGH THE MEDIUM RANGE PERIOD AS AN
AMPLIFYING UPPER-LEVEL RIDGE OVER THE CENTRAL/EASTERN U.S. AND
UPPER-LEVEL TROUGH OVER THE WESTERN U.S. TAKE HOLD THIS WEEKEND AND
THROUGH THE MIDDLE OF NEXT WEEK. THE LATEST 00Z/06Z GUIDANCE
CONTINUES TO COME INTO BETTER AGREEMENT OVERALL BUT EXPECT SOME
WAVINESS IN THE FRONTAL LOCATION DUE TO DAILY CONVECTIVE EPISODES.
INTO THE MIDDLE PART OF NEXT WEEK, THE CANADIAN AND ITS ENSEMBLES
ARE QUICKER TO ERODE THE UPPER HIGH DUE TO STRONGER HEIGHT FALLS
INTO THE WEST. THE GFS/ECMWF/ECMWF-AIFS AND THEIR ENSEMBLES
GENERALLY HOLD ONTO THE UPPER RIDGE LONGER AND FAVOR WEAKER
TROUGHING INTO THE WEST BY NEXT WED/THU, AND IS THE PREFERRED
CLUSTER. USED THIS LARGER CONSENSUS FOR THE 2ND HALF OF THE
FORECAST, AND THE NBM FOR MUCH OF THE SENSIBLE WEATHER GRIDS.
..WEATHER/HAZARDS HIGHLIGHTS
FOR SUN/MON, SUBTROPICAL MOISTURE WILL START TO PUSH NORTHWARD
INTO THE SOUTHERN ROCKIES, LEADING TO SOME INCREASE IN RAINFALL
POTENTIAL OVER NEW MEXICO. INTRODUCED A MARGINAL RISK IN THE
EXCESSIVE RAINFALL OUTLOOK AS THERE WAS A BIT OF AN UPTICK IN
HEAVIER AMOUNTS OVER SOME SENSITIVE AREAS/TERRAIN. BY MONDAY, THE
CONTINUED FEED OF MOISTURE NORTHWARD WILL INTERACT WITH THE FRONTAL
BOUNDARY AND COULD LEAD TO A WIDER EXPANSE OF HEAVIER RAINFALL ALL
THE WAY NORTHWARD/NORTHEASTWARD THROUGH THE PLAINS TO THE CORN
BELT AND UPPER MIDWEST. MAINTAINED A SLIGHT RISK OVER IOWA TO
ACCOUNT FOR THE HIGHEST CHANCE OF HEAVIER RAIN BUT THERE IS TYPICAL
MODEL SPREAD IN EXACT LOCATION. THEREAFTER, EXPECT ROUNDS OF
RAINFALL OVER MUCH OF THE SAME AREA (NEW MEXICO TO NEBRASKA TO THE
UPPER MIDWEST) WHICH WILL CONTINUE THE FLASH FLOODING THREAT.
FARTHER WEST, TROUGHING INTO THE NORTHWEST WILL BE STRONG ENOUGH TO
BRING IN COLDER AIR THIS WEEKEND AND SOME SNOW TO THE HIGHEST
ELEVATIONS AROUND GLACIER NATIONAL PARK.
FARTHER EAST, THE STRONG UPPER HIGH WILL FAVOR DRY CONDITIONS
EXCEPT FOR ALONG THE GULF COAST AND NORTHERN NEW ENGLAND THOUGH
SOME INCREASE IN ISOLATED SHOWERS/STORMS IS POSSIBLE IN THE EAST AS
THE HIGH STARTS TO FADE LATER IN THE WEEK. TEMPERATURES WILL BE
WELL ABOVE NORMAL AND APPROACH/EXCEED DAILY RECORDS AT A FEW DOZEN
LOCATIONS IN TOTAL BETWEEN SUNDAY AND AT LEAST WEDNESDAY. THIS
TRANSLATES INTO HIGHS WELL INTO THE 90S TO AROUND 100F WITH HEAT
INDICES TO NEAR 110F AS DEW POINTS WILL BE IN THE 60S TO
LOW/MID-70S. OVERNIGHT LOWS WILL ONLY DROP INTO THE LOW/MID 70S FOR
MANY AREAS BUT MAY STAY AROUND 80F IN THE URBAN CENTERS LIKE
WASHINGTON, D.C., BALTIMORE, PHILADELPHIA, AND NEW YORK CITY. MANY
LOCATIONS MAY EXCEED DAILY OR PERHAPS EVEN MONTHLY RECORD HIGH
MINIMUM TEMPERATURES. SOME RELIEF IS EXPECTED TOWARD THE END OF
NEXT WEEK.
HEAT RISK VALUES WILL BE MAJOR TO EXTREME FOR MUCH OF THE MIDWEST
TO EASTERN STATES -- LEVELS 3 AND 4 ON A SCALE FROM 1 TO 4 (4 BEING
EXTREME). THIS INDICATES AN INTENSITY AND DURATION OF HEAT THAT IS
EXTREMELY DANGEROUS TO ANYONE WITHOUT ADEQUATE COOLING OR
HYDRATION. SUCCESSIVE OVERNIGHT READINGS IN THE MID 70S TO AROUND
80F WILL BRING LITTLE RELIEF FROM THE HEAT AND CAN POSE A
SIGNIFICANT DANGER. EXTREME HEAT IS THE NUMBER 1 WEATHER-RELATED
KILLER.
HIGHS WILL BE COOLER AND BELOW AVERAGE BY AS MUCH AS 10-20 DEGREES
ACROSS PORTIONS OF THE PACIFIC NORTHWEST, GREAT BASIN, AND
NORTHERN ROCKIES/HIGH PLAINS THIS WEEKEND WITH A DEEP- UPPER LEVEL
TROUGH OVERHEAD. TEMPERATURES WILL MODERATE CLOSER TO AVERAGE
THROUGH EARLY/MID NEXT WEEK.
FRACASSO/PUTNAM
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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