627
FXUS02 KWBC 271806
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
206 PM EDT FRI JUN 27 2025
VALID 12Z MON JUN 30 2025 - 12Z FRI JUL 04 2025
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL AND ENSEMBLE GUIDANCE FOR TODAY CONTINUES TO SHOW
RELATIVELY GOOD AGREEMENT THROUGH MUCH OF THE PERIOD ON WHAT LOOKS
LIKE A GENERALLY PROGRESSIVE SUMMERTIME PATTERN. THERE REMAIN SOME
DIFFERENCES IN THE DETAILS OF SMALLER SCALE SYSTEMS THOUGH. THE CMC
AND UKMET ARE A BIT SHARPER/FARTHER SOUTH WITH A WEAK SHORTWAVE
THROUGH THE GREAT LAKES NEXT WEDNESDAY-THURSDAY, AND THE MODELS ARE
UNSURE ON THE DETAILS AND EVOLUTION OF WAVE ENERGY INTO THE
NORTHWEST. THE GFS IS A LITTLE STRONGER WITH LEADING ENERGY INTO
THE CENTRAL U.S. LATE WEEK, WHICH ERODES THE CENTRAL/SOUTHERN U.S.
RIDGE MORESO THAN THE OTHER GUIDANCE. THE WPC FORECAST FOR TODAY
WAS BASED ON A BLEND OF THE DETERMINISTIC GUIDANCE THE FIRST HALF
OR SO OF THE PERIOD, WITH A 50/50 BLEND OF THE ENSEMBLE MEANS AND
THE DETERMINISTIC ECMWF AND CMC FOR THE SECOND HALF. THIS
MAINTAINED GOOD CONTINUITY WITH THE PREVIOUS WPC FORECAST AS WELL.
..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 ON MONDAY. AN ELONGATED WPC MARGINAL RISK
EXCESSIVE RAINFALL OUTLOOK (ERO) AREA 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 IS DRAWN. 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 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 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.
SANTORELLI/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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