347
FXUS02 KWNH 050728
PREEPD
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
327 AM EDT FRI JUN 5 2026
VALID 12Z MON JUN 08 2026 - 12Z FRI JUN 12 2026
..OVERVIEW
AN AMPLIFIED RIDGE WILL DOMINATE MUCH OF EASTERN U.S. WHILE A
SHORTWAVE ENERGY WILL MOVE ACROSS NORTHERN U.S. SUPPORTING MULTIPLE
ROUNDS OF SHOWERS AND THUNDERSTORMS ACROSS THE PLAINS INTO THE
MISSISSIPPI VALLEY AND ACROSS THE OHIO/TENNESSEE VALLEY. MEANWHILE,
TROUGHING OVER THE PACIFIC NORTHWEST WILL MAINTAIN A CORRIDOR OF
MOISTURE ACROSS THE NORTHERN TIER, WHILE BRINGING COOLER
TEMPERATURES TO PARTS OF WESTERN U.S. ANOMALOUS WARMTH FROM THE
PLAINS THROUGH THE GREAT LAKES AND MUCH OF THE EAST WILL CONTINUE
TO BUILD THROUGH THE WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS CONTINUE TO SHOW DECENT CLUSTER WITH THE TROUGH OVER THE
WEST AND BROAD RIDGING ACROSS MUCH OF EASTERN U.S. BY MID-PERIOD,
THE SHORTWAVE ENERGIES EMBEDDED IN THE TROUGH OVER THE WEST COAST
BEGIN TO DIVERGE WITHIN THE MODELS, ESPECIALLY WITH THE GFS, AS IT
EJECTS EASTWARD. THESE SUBTLE IMPULSES WILL LIKELY DETERMINE THE
PLACEMENT AND INTENSITY OF MESOSCALE CONVECTIVE SYSTEMS ACROSS THE
NORTHERN PLAINS, UPPER MIDWEST, AND GREAT LAKES. THE ENSEMBLE
SPREAD REMAINS RELATIVELY SMALL AFTER DAY 5. THEREFORE, THE
FORECAST FAVORED A BLEND BETWEEN ECMWF/GFS/CMC/EC-AIFS/UKMET, WITH
LESS WEIGHT TOWARDS THE GFS. TOWARDS THE LATTER PORTION OF THE
FORECAST, THE ENSEMBLE MEANS WERE INCORPORATED TO SMOOTH OUT
TIMING AND PLACEMENT DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
AT THE SURFACE, A SERIES OF LOW PRESSURE SYSTEMS AND FRONTAL
BOUNDARIES MOVING ACROSS THE PLAINS INTO THE UPPER GREAT LAKES
WILL SUPPORT SCATTERED SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE
MISSISSIPPI VALLEY AND UPPER GREAT LAKES ON MONDAY INTO TUESDAY.
SEVERAL SHORTWAVE DISTURBANCES EMBEDDED WITHIN THE WEST-NORTHWEST
FLOW ALOFT WILL SUPPORT CLUSTERS OF THUNDERSTORMS. INCREASING
MOISTURE TRANSPORT FROM THE GULF COMBINED WITH SUFFICIENT
INSTABILITY ALONG THE BOUNDARY COULD BRING CHANCES FOR HIGH
RAINFALL RATES. THEREFORE, DAY 4/MONDAY SLIGHT RISK OF EXCESSIVE
RAINFALL ARE IN PLACE TO ACCOUNT FOR FLASH FLOODING CONCERNS ACROSS
PARTS OF TENNESSEE/OHIO VALLEY INTO THE MISSISSIPPI VALLEY, WHILE
THE MARGINAL RISK CONTINUES TO HIGHLIGHT PARTS OF THE CENTRAL
PLAINS, THE UPPER GREAT LAKES, UPPER MIDWEST, AND SOUTHEAST.
THE FRONTAL PASSAGE WILL SLOWLY MOVE INTO THE OHIO/TENNESSEE
VALLEY AND PARTS OF THE MID-ATLANTIC BY TUESDAY, BRINGING CHANCES
FOR SHOWERS AND THUNDERSTORMS EASTWARD, WHILE SOUTHERLY FLOW
CONTINUES TO POOL WARM MOISTURE ALONG THE BOUNDARY. THEREFORE, A
MARGINAL RISK WAS PLACED FOR DAY 5/TUESDAY EXCESSIVE RAINFALL
OUTLOOK ACROSS PARTS OF THE GREAT LAKES INTO PARTS OF SOUTHEAST. IN
ADDITION, A SECONDARY MARGINAL RISK IS PLACED OVER THE NORTHERN
PLAINS, WHERE INCREASED INSTABILITY MAY INTERACT WITH A SECONDARY
FRONTAL BOUNDARY PRODUCING ORGANIZED CONVECTION AND HEAVY RAINFALL
RATES.
OVER INTO THE SOUTHEAST, PERSISTENT WARM MOISTURE COMBINED WITH
SEA- BREEZE INTERACTION WILL MAINTAIN DAILY THUNDERSTORM CHANCES
ACROSS FLORIDA AND PORTIONS OF THE GULF COAST, WHICH MAY LEAD TO
LOCALLY HEAVY RAINFALL.
TROUGHING OVER THE PACIFIC NORTHWEST AND A SURFACE LOW WITH
A TRAILING COLD FRONT WILL BRING COOLER CONDITIONS AND CHANCES FOR
SCATTERED SHOWERS AND THUNDERSTORMS ON MONDAY INTO TUESDAY. BY
MIDWEEK, THE FRONTAL BOUNDARY PUSHES FURTHER SOUTHEASTWARD AND WILL
INTERACT WITH A SECOND FRONTAL BOUNDARY OVER NORTHERN
ROCKIES/PLAINS. THE FRONTAL BOUNDARY WILL GRADUALLY DRAPE INTO THE
UPPER MIDWEST, BRINGING ADDITIONAL SHOWERS AND THUNDERSTORMS
ACROSS THE NORTHERN TIER THROUGH THURSDAY.
TEMPERATURES WILL TREND BELOW NORMAL OVER THE PACIFIC NORTHWEST AND
ALONG THE WEST COAST AS THE TROUGH CONTINUES TO MOVE INLAND. THE
REMAINDER OF CONUS WILL EXPERIENCE ABOVE SEASONAL TEMPERATURES WITH
NORTH-CENTRAL U.S. SEEING THE GREATEST ANOMALY WITH 15-25 DEGREES
ABOVE NORMAL TEMPERATURES.
OUDIT
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY MESSAGES
ARE AT:
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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