144
FXUS02 KWBC 270710
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
310 AM EDT FRI JUN 27 2025
VALID 12Z MON JUN 30 2025 - 12Z FRI JUL 04 2025
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL AND ENSEMBLE GUIDANCE IN THIS GENERALLY PROGRESSIVE
SUMMERTIME PATTERN SEEMS REASONABLY WELL CLUSTERED FOR MID-LARGER
SCALE FEATURES THROUGH THE UPCOMING MEDIUM-RANGE TIMEFRAME IN A
PATTERN WITH SEEMINGLY ABOVE NORMAL PREDICTABILITY. A BLEND OF
THE GFS/ECMWF/CANADIAN/UKMET MODELS AND GEFS/ECMWF ENSEMBLE MEANS
TENDS TO MITIGATE MORE WIDESPREAD SMALLER SCALE DIFFERENCES AS
CONSISTENT WITH INDIVIDUAL SYSTEM PREDICTABILITY. THE CANADIAN
ENSEMBLE MEAN WAS NOT AVAILABLE DUE TO COMPUTER ISSUES AT CMC.
..WEATHER/HAZARDS HIGHLIGHTS
WIDESPREAD THUNDERSTORMS WITH FAVORABLE MOISTURE/INSTABILITY AND
RIGHT ENTRANCE REGION UPPER JET LIFT WILL FUEL LOCALLY STRONG/HEAVY
CONVECTIVE DOWNPOURS LIKELY TO FORM AHEAD OF THE BROAD BUT SHALLOW
UPPER TROUGH AND A SURFACE FRONTAL BOUNDARY WORKING SOUTHEASTWARD
OVER THE MIDWEST MONDAY. AN ELONGATED WPC MARGINAL RISK EXCESSIVE
RAINFALL OUTLOOK AREA (ERO) IS LOCATED ALONG AND AHEAD OF THE FRONT
FROM THE OHIO/TENNESSEE VALLEYS, MID/LOWER MISSISSIPPI VALLEY, AND
THE SOUTH-CENTRAL PLAINS DAY 4/MONDAY. THE FRONT WILL CONTINUE TO
PUSH ONWARD TUESDAY, LEADING TO A WET DAY FROM THE NORTHEAST/MID-
ATLANTIC BACK THROUGH THE APPALACHIANS AND INTO THE SOUTH TUESDAY
WHERE A DAY 5 MARGINAL RISK ERO HAS BEEN INTRODUCED. THESE AREAS
WILL DRY OUT AND AND MODERATE POST-FRONTAL, BUT ACTIVITY WILL
LINGER AS THE FRONT SLOWS ACROSS THE SOUTH/SOUTHEAST INTO MID-LATE
NEXT WEEK. EVEN BEFORE THE FRONT APPROACHES, SCATTERED
THUNDERSTORMS ARE LIKELY FARTHER SOUTH IN THE BROAD WARM SECTOR AS
WELL. THERE WILL BE LESS FORCING FOR ORGANIZATION AND SUSTAINING OF
STORMS ACROSS THE SOUTHERN TIER AWAY FROM THE UPPER JET, BUT
INSTABILITY COULD ALLOW FOR HEAVY RAIN RATES THAT MAY CAUSE NON-
ZERO CHANCES OF LOCALIZED FLASH FLOODING, BUT THAT ARE LIKELY
DEPENDENT ON SMALLER SCALE BOUNDARIES AND ARE LESS PREDICTABLE AT
THIS POINT. ONE AREA OF FOCUS WITH A GROWING MODEL SIGNAL FOR SOME
HEAVIER RAIN IS ACROSS THE CENTRAL TO EASTERN GULF COAST REGION.
WILL MONITOR IF THERE WILL BE FLASH FLOODING CONCERNS THERE, BUT IT
WOULD HAVE TO BATTLE WITH VERY HIGH FLASH FLOOD GUIDANCE.
MONSOONAL MOISTURE WITH SOME CONNECTION TO POSSIBLE EASTERN
TROPICAL PACIFIC TROPICAL DEVELOPMENT IS LIKELY TO INCREASE NEXT
WEEK IN THE SOUTHERN/CENTRAL ROCKIES AND HIGH PLAINS WITH SOUTHERLY
FLOW UNDER THE UPPER RIDGE, THUS INCREASING COVERAGE OF AND RAIN
AMOUNTS IN STORMS. MARGINAL RISKS ARE PLANNED FOR THE SOUTHERN
ROCKIES/HIGH PLAINS DAY 4/MONDAY AND DAY 5/TUESDAY. AREAS LIKE THE
SACRAMENTO MOUNTAINS, WHERE THE STEEP TERRAIN AND BURN SCARS CAUSE
THE AREA TO BE PARTICULARLY SENSITIVE TO RAIN, SEEM LIKELY MOST
VULNERABLE TO RAIN CAUSING POTENTIAL FLASH FLOODING, ESPECIALLY
WITH WET ANTECEDENT CONDITIONS THERE.
ELSEWHERE, SHOWERS AND STORMS MAY DEVELOP OVER PARTS OF THE GREAT
BASIN MONDAY AND TOWARD THE NORTHERN ROCKIES BY TUESDAY. DOWNSTREAM
SHORTWAVE ENERGY TRANSLATIONS SUPPORT INCREASING RAIN/CONVECTION
CHANCES OVER THE NORTH-CENTRAL U.S. WEDNESDAY INTO THURSDAY AS
MOISTURE/INSTABILITY POOL ALONG/OVERTOP A RETREATING FRONT.
TEMPERATURES ARE FORECAST TO BE AROUND 5-10 DEGREES ABOVE AVERAGE
ACROSS THE MIDWEST/GREAT LAKES EARLY NEXT WEEK, WHILE THE SOUTHERN
HALF OF THE PLAINS TO SOUTHEAST CAN EXPECT TYPICAL SUMMER HEAT.
HEATRISK SHOWS SOME MAJOR (LEVEL 3 OF 4) AREAS IN THESE REGIONS,
INDICATING HEAT LEVELS THAT AFFECT ANYONE WITHOUT EFFECTIVE COOLING
AND/OR ADEQUATE HYDRATION. TEMPERATURES AND DEWPOINTS WILL
DECREASE BEHIND THE COLD FRONT AS IT PROGRESSES SOUTHEAST. FARTHER
WEST, BUILDING HEAT IS EXPECTED NEXT WEEK AS AN UPPER RIDGE TAKES
HOLD. TEMPERATURES IN THE NORTHWEST ARE LIKELY TO BE 10-15 (LOCALLY
20) DEGREES ABOVE NORMAL, FOR HIGHS NEARING 100F. IN THE DESERT
SOUTHWEST, TEMPERATURES A FEW DEGREES ABOVE ALREADY HIGH AVERAGES
WILL EQUATE TO 100S AND 110S. MODERATE TO MAJOR HEATRISK IS SHOWN
FOR MUCH OF THE INTERIOR WEST PEAKING MONDAY-TUESDAY.
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 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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