789
FXUS02 KWBC 120549
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
149 AM EDT THU JUN 12 2025
VALID 12Z SUN JUN 15 2025 - 12Z THU JUN 19 2025
...BROAD HEAVY RAIN/FLASH FLOOD THREAT FROM THE SOUTH-CENTRAL U.S.
TO THE TENNESSEE/OHIO VALLEYS AND MID-ATLANTIC INTO SUNDAY...
..GENERAL OVERVIEW
A SLOW MOVING SHORTWAVE TROUGH ALOFT MAY BE GRADUALLY LIFTING OUT
OF THE SOUTH-CENTRAL U.S. THIS WEEKEND AND THEN MAY ALSO BE SLOW TO
MOVE OUT OF THE OHIO VALLEY/MID-ATLANTIC REGION WITH PERIODIC
RELOADING FROM IMPULSE ENERGY DIGGING TO THE LEE OF AN AMPLIFIED
UPSTREAM RIDGE. THIS WILL KEEP THE WEATHER UNSETTLED THROUGH MUCH
OF THE PERIOD WITH WIDESPREAD SHOWERS AND THUNDERSTORMS TO INCLUDE
HARD TO PINPOINT, BUT VIABLE THREATS FOR HEAVY TO EXCESSIVE
RAINFALL OVER A BROAD AREA. SHORTWAVE ENERGY ORIGINATING FROM
TROUGHING OVER THE WEST COAST WILL MEANWHILE SLIDE OVER THE
NORTHERN TIER STATES WITH ACCOMPANYING SHOWERS AND STORMS. A TROUGH
OVER THE WEST WILL MOVE INTO THE SOUTHWEST AND WEAKEN BY MID-NEXT
WEEK, WITH ANOTHER TROUGH TAKING SHAPE OVER THE WEST THEREAFTER.
UPPER RIDGING WILL FOCUS HIGH HEAT OVER THE SOUTHWEST MAINLY JUST
SUNDAY AND MONDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE GUIDANCE SHOWS GOOD AGREEMENT ON THE OVERALL PATTERN EVOLUTION
THROUGH MUCH OF THE PERIOD, BUT WITH PLENTY OF UNCERTAINTY IN THE
DETAILS. THE MAIN SOURCE OF UNCERTAINTY DURING THE PERIOD WILL BE
WITH TROUGHING ENTERING THE WEST COAST ON MONDAY AND SLIDING INTO
THE SOUTHWEST BY TUESDAY. TIMING AND STRENGTH OF THIS BECOMES AN
ISSUE QUICKLY, WITH THE UKMET/CMC THE SLOWEST AND THE GFS FASTER
AND MUCH STRONGER. AFTER TUESDAY, THE GFS CONTINUES TO LIFT THE
ENERGY/SHORTWAVE INTO THE CENTRAL PLAINS, WITH SOME INTERACTION
WITH ADDITIONAL NORTHERN STREAM ENERGY. THE BETTER CONSENSUS OF
GUIDANCE SUGGESTS MORE SEPARATION OF STREAMS AND SHOWS THE
SOUTHWEST SHORTWAVE WEAKENING AS THE ENERGY TRACKS INTO THE CENTRAL
STATES. AS A RESULT, GFS SHOWS A SLIGHTLY MORE AMPLIFIED PATTERN
(CENTRAL U.S. TROUGH, EASTERN RIDGE), WHILE THE MAJORITY OF THE
REST OF THE GUIDANCE SHOWS MORE ZONAL FLOW WITH WEAK SYSTEMS
THROUGH THE NORTHERN TIER AND UPPER RIDGING DOMINATING ACROSS THE
SOUTH.
THE WPC FORECAST WAS ABLE TO USE A BLEND OF THE DETERMINISTIC
GUIDANCE FOR THE FIRST FEW DAYS OF THE PERIOD. QUICKLY TRANSITIONED
TO MOSTLY ENSEMBLE MEANS BY THE SECOND HALF TO HELP MITIGATE SOME
OF THE ISSUES DESCRIBED ABOVE. MAINTAINED SOME ECMWF FOR A LITTLE
SYSTEM DEFINITION WHICH WAS CLOSEST TO THE ENSEMBLE MEAN SOLUTIONS.
..WEATHER/HAZARDS HIGHLIGHTS
DAILY SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BE WIDESPREAD FROM
THE GULF COAST TO THE OHIO VALLEY/MID-ATLANTIC AND INTO THE
NORTHEAST ASSOCIATED WITH PERSISTENT AND PESKY UPPER LEVEL
IMPULSE/TROUGH ENERGIES IMPACTING THE BROAD REGION. THERE REMAINS A
LOT OF UNCERTAINTY IN THE DETAILS, BUT THERE IS SOME GENERAL
AGREEMENT THAT HEAVIER RAINS MAY FOCUS ALONG/NEAR A SLOW MOVING A
WAVY FRONTAL BOUNDARY DRAPED ACROSS THE MID-ATLANTIC AND WESTWARD.
A MOIST AND UNSTABLE SURROUNDING ENVIRONMENT FROM THE CENTRAL TO
EASTERN U.S. NECESSITY THE CONTINUATION OF A VERY BROAD WPC
MARGINAL RISK AREA ON THE DAY 4 EXCESSIVE RAINFALL OUTLOOK (ERO)
FOR AT LEAST SUNDAY. WAS ABLE TO TRIM THAT BACK TO JUST THE MID-
ATLANTIC STATES ON MONDAY, THE DAY 5 ERO, BUT SHOWERY CONDITIONS
WILL CONTINUE FARTHER SOUTH AND WEST. OVERALL SIGNAL IS FOR A WET
PATTERN, AND IT'S LIKELY EMBEDDED SLIGHT RISK AREAS WILL BE NEEDED
ONCE GUIDANCE SIGNALS BECOME MORE DEFINED WITH TIME. FARTHER NORTH,
SHORTWAVE ENERGY THROUGH THE NORTHERN TIER WILL SUPPORT SHOWERS
AND STORMS, WITH MARGINAL RISKS HIGHLIGHTED ON BOTH THE DAY 4 AND 5
EROS FOR CONVECTIVE COMPLEX POTENTIAL OVER THE NORTHERN PLAINS.
MODERATE TO HEAVIER RAIN MAY TRY TO MATERIALIZE MORESO ON
MONDAY/DAY 5 ACROSS PARTS OF THE NORTH- CENTRAL U.S. AS A STRONGER
SHORTWAVE MOVES INTO THE PLAINS, WITH THE MARGINAL RISK EXPANDED
ACCORDINGLY.
TEMPERATURES WILL REMAIN SLIGHTLY ABOVE NORMAL FOR MUCH OF THE
INTERMOUNTAIN WEST INTO NEXT WEEK UNDER THE INFLUENCE OF A MEAN
UPPER RIDGE, WITH SOME DAILY MODERATION IN SPOTS WITH SYSTEMS
MOVING THROUGH. TEMPERATURES SHOULD BE CLOSER TO NORMAL ALONG THE
COAST. TO THE SOUTH, HAZARDOUS HEAT WILL CONTINUE THROUGH ABOUT
MONDAY FOR THE DESERT SOUTHWEST WITH HIGHS MAKING A RUN AT 110
DEGREES FOR THE LOWER ELEVATIONS OF SOUTHERN ARIZONA AND SOUTHEAST
CALIFORNIA, WITH HEAT RISK LIKELY REACHING THE MAJOR CATEGORY.
SHORTWAVE ENERGY THROUGH THE REGION SHOULD MODERATE TEMPERATURES
AFTER MONDAY. MEANWHILE, SLIGHTLY BELOW AVERAGE TEMPERATURES ARE
LIKELY FROM THE UPPER MIDWEST TO THE GREAT LAKES AND NORTHERN NEW
ENGLAND GOING INTO THE WEEKEND AS THIS REGION WILL BE NORTH OF THE
MAIN FRONTAL BOUNDARY.
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 (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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