941
FXUS02 KWBC 150636
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 AM EDT FRI AUG 15 2025
VALID 12Z MON AUG 18 2025 - 12Z FRI AUG 22 2025
..OVERVIEW
AN EXPANSIVE RIDGE ACROSS THE SOUTHERN TIER STATES WILL RETROGRADE
AND FOCUS ACROSS THE FOUR CORNERS REGION BY MID-WEEK. THE JET
STREAM WILL MAINTAIN A FAIRLY ACTIVE WEATHER PATTERN ACROSS THE
NORTH-CENTRAL STATES THROUGH THE START OF THE WEEK BEFORE IT SHIFTS
FARTHER SOUTHEAST AS TROUGHING BUILDS OVER THE EAST. THIS
TROUGHING SHOULD HELP STEER ERIN MORE NORTHERLY AWAY FROM THE EAST
COAST. VERY WARM TEMPERATURES INITIALLY ACROSS THE MIDWEST WILL
MODERATE THE REST OF THE WEEK AS MUCH OF THE WEST WILL SEE WARMING
TEMPERATURES THROUGH THE WEEK. RAINFALL LOOKS TO FOCUS OVER THE
UPPER MIDWEST/GREAT LAKES INTO THE MIDWEST AND NORTHEAST/MID-
ATLANTIC, AND BACK TOWARDS THE SOUTHWEST/SOUTHERN ROCKIES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLE GUIDANCE CONTINUE TO SHOW ABOVE AVERAGE
AGREEMENT ON THE OVERALL MEDIUM RANGE PATTERN. SHORTWAVE ENERGY
EJECTING FROM AN INITIAL TROUGH OVER THE NORTHWEST INTO CANADA WILL
HELP FLATTEN THE FLOW OVER THE NORTHERN TIER ALLOWING FOR A MORE
PROGRESSIVE TROUGH ACROSS EASTERN CANADA/THE NORTHEAST. THIS SHOULD
HELP PICK UP WHAT SHOULD BE HURRICANE ERIN AND STEER IT AWAY FROM
THE EAST COAST QUICKLY. THERE REMAIN SOME DIFFERENCES IN THE
DETAILS OF THE NORTHEAST TROUGH, WHICH OF COURSE COULD IMPACT HOW
CLOSE OR FAR AWAY ERIN IS FROM THE COAST BEFORE IT MAKES A
NORTHWARD TURN BACK OUT INTO THE ATLANTIC. PLEASE SEE THE NHC
WEBSITE FOR THE MOST UP-TO- DATE INFORMATION AS ERRORS IN POSITION
5+ DAYS CAN BE SIGNIFICANT. THE WPC FORECAST FOR TONIGHT USED A
GENERAL DETERMINISTIC MODEL CONSENSUS FOR DAYS 3-5, INCREASING
WEIGHTING OF THE ENSEMBLE MEANS TO 40 PERCENT OF THE BLEND BY DAY
7.
..WEATHER/HAZARDS HIGHLIGHTS
A GENERALLY EAST-WEST ORIENTED AND SLOW MOVING FRONTAL BOUNDARY
WILL BE THE FOCUS FOR HEAVY RAINFALL THE FIRST PART OF THE PERIOD
FROM THE GREAT LAKES INTO THE MIDWEST AND OHIO VALLEY. ABOVE NORMAL
PW VALUES AND AMPLE INSTABILITY WILL SUPPORT INSTANCES OF HEAVY TO
EXCESSIVE RAINFALL. ON MONDAY/DAY 4, MAINTAINED A MARGINAL RISK
ERO ACROSS THE UPPER MIDWEST/GREAT LAKES, BUT AN UPGRADE TO A
SLIGHT RISK MAY EVENTUALLY BE NEEDED IF MODELS CONVERGE ON WHERE
THE HEAVIEST QPF WILL FOCUS. RAINFALL COVERAGE WILL EXPAND AND
SHIFT SOUTH WITH A BROAD MARGINAL RISK DEPICTED ON THE TUESDAY/DAY
5 ERO FROM THE MID-MISSISSIPPI VALLEY INTO THE OHIO VALLEY AND
INTERIOR NORTHEAST/LOWER GREAT LAKES. THE FRONT WILL SAG INTO THE
SOUTHEAST AS WEAKEN BY LATER IN THE WEEK WITH INCREASED CONVECTION
FROM THE SOUTHERN PLAINS TO THE SOUTHEAST LATER IN THE WEEK.
ELSEWHERE, A CONTINUED SURGE OF MOISTURE INTO THE SOUTHWEST
COMBINED WITH DIURNAL HEATING MAY TRIGGER STORMS CAPABLE OF
PRODUCING HEAVIER RAINFALL THAT MAY FALL OVER MORE SENSITIVE AREAS
(STEEP TERRAIN, IN/AROUND BURN SCARS, ETC.). A MARGINAL RISK ERO IS
DEPICTED FOR BOTH DAYS 4-5. RAINFALL SHOULD DECREASE IN COVERAGE
BY THE SECOND HALF OF THE WEEK AS THE RIDGE SHIFTS MORE INTO THE
REGION. SOME LINGERING MOISTURE WILL BE PRESENT ACROSS THE FLORIDA
PENINSULA EARLY WEEK BUT OPTED TO REMOVE THE MARGINAL RISK FROM THE
ERO ON MONDAY DUE TO LACK OF QPF SUPPORT. THE HEAVIEST RAINFALL
ASSOCIATED WITH ERIN SHOULD REMAIN WELL OFFSHORE BY MID TO LATE
WEEK, BUT INCREASED MOISTURE MAY GET DRAWN FROM ERIN INTO THE
SOUTHEAST FRONTAL BOUNDARY WITH SOME POTENTIAL, BUT LOTS OF
UNCERTAINTY, FOR MODERATE TO HEAVIER RAINFALL ALONG THE EAST COAST.
ABOVE NORMAL TEMPERATURES AND MAJOR TO EXTREME HEATRISK WILL
CONTINUE THROUGH TUESDAY FOR MUCH OF THE MIDWEST. HEAT WILL
MODERATE ACROSS THIS REGION BY MID WEEK WITH LOWER HEIGHTS ALOFT,
BUT WILL INCREASE FARTHER WEST INTO THE FOUR CORNERS REGION.
TEMPERATURES FOR THE LOWER DESERTS OF THE SOUTHWEST MAY EXCEED 110F
BY LATER IN THE WEEK WITH WIDESPREAD MODERATE TO MAJOR HEATRISK
ACROSS THE SOUTHWEST, SOUTHERN/CENTRAL ROCKIES AND PARTS OF THE
CENTRAL HIGH PLAINS.
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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