798
FXUS02 KWBC 051848
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
248 PM EDT SAT JUL 5 2025
VALID 12Z TUE JUL 8 2025 - 12Z SAT JUL 12 2025
...HAZARDOUS HEAT AND HUMIDITY OVER PARTS OF THE EAST; BUILDING
HEAT OVER THE WEST...
19Z UPDATE: THE OVERALL FORECAST HAS NOT CHANGED VERY MUCH FROM THE
OVERNIGHT ISSUANCE, WITH MAINLY MINOR ADJUSTMENTS TO QPF BASED ON
THE NEW NBM AND DETERMINISTIC MODEL GUIDANCE. IN TERMS OF THE
MODELS, THE 00Z CMC STRAYED FROM THE CONSENSUS AND THE AIFS ACROSS
THE NORTH- CENTRAL U.S. BY THE END OF THE WEEK WITH A MUCH
STRONGER TROUGH/CLOSED LOW DROPPING SOUTH ACROSS THE DAKOTAS, SO
THE FORECAST TRANSITIONED TO MORE OF THE GFS/ECMWF AND THEIR
ENSEMBLE MEANS FOR THURSDAY-SATURDAY. THERE IS STILL VERY GOOD
AGREEMENT WITH THE BUILDING UPPER RIDGE ACROSS THE SOUTHWEST, SO
THAT REMAINS THE MOST CONFIDENT PART OF THE FORECAST. ACROSS THE
EAST COAST REGION, A MARGINAL RISK IS PLANNED FOR PORTIONS OF
SOUTHERN VIRGINIA AND EASTERN NORTH CAROLINA FOR WEDNESDAY WITH A
MORE CONCENTRATED AXIS OF QPF NOTED IN THE GUIDANCE SOUTH OF A
STATIONARY FRONTAL BOUNDARY. THE PREVIOUS FORECAST DISCUSSION IS
APPENDED BELOW FOR REFERENCE. /HAMRICK
----------------
..PATTERN OVERVIEW
QUASI-ZONAL FLOW OVER MOST OF THE CONUS TO START THE WEEK WILL
TRANSITION TOWARD AN UPPER HIGH STARTING TO TAKE RESIDENCE NEAR LAS
VEGAS AND INCREASED TROUGHING INTO THE NORTHEAST. THIS WILL FAVOR
A FAIRLY TYPICAL SUMMERTIME PATTERN BUT WITHOUT MUCH, IF ANY,
MONSOON SIGNAL INTO THE SOUTHWEST.
...GUIDANCE/PREDICTABILITY ASSESSMENT
THE LARGE SCALE PATTERN REMAINS IN GOOD AGREEMENT THROUGH THE
EXTENDED PERIOD. LIKE ITS PREVIOUS RUNS, THE GFS AND THE GEFS MEAN
WERE PERSISTENT IN BEING THE FASTER SOLUTIONS FROM THE NORTHEAST
PACIFIC INTO WESTERN NORTH AMERICA THAN THE OTHER MODELS THEREFORE
HAD LIMITED INCLUSION IN THE FORECAST. THE PREFERRED BLEND WAS A
COMPRISE OF THE 12Z ECMWF/CANADIAN/UKMET/ECMWF ENSEMBLE MEAN AND
THE NBM.
..WEATHER/HAZARDS HIGHLIGHTS
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BE FOCUSED IN PROXIMITY
TO PROGRESSIVE COLD FRONTS, STALLED BOUNDARIES AND ROUND THE UPPER
HIGH IN THE SOUTHERN ROCKIES. THE WAVY FRONT INTO THE EASTERN U.S.
MAY BE A FOCUS FOR HEAVIER RAIN AND THUNDERSTORMS. THIS INCLUDES
AREAS FROM THE CORN BELT INTO THE MIDWEST AND OHIO VALLEY,
APPALACHIANS, MID-ATLANTIC, AND NORTHEAST. THERE ARE MARGINAL RISKS
IN PLACE (LEVEL 1 OF 4) FOR THE SOUTHWEST, CENTRAL PLAINS/MIDWEST
TO THE UPPER MISSISSIPPI VALLEY/UPPER GREAT LAKES REGION AND
PORTIONS OF THE NORTHEAST FOR DAY 4, AND FOR THE MID-MISSISSIPPI
VALLEY/MIDWEST AND PORTIONS OF THE MID-ATLANTIC FOR DAY 5 FOR AN
AXIS OF HEAVIER RAINFALL POSSIBLE SOUTH OF A FRONTAL BOUNDARY.
HEIGHTS ACROSS THE NORTHEAST AND MID-ATLANTIC REGIONS WILL
GRADUALLY LOWER AS TROUGHING MOVES IN. WITH THE HIGHER HEIGHTS
SHIFTING SOUTHWARD THE HEAT WILL INCREASE AS WELL AS BEGIN TO BUILD
TO THE WEST AS THE UPPER HIGH STRENGTHENS OVER THE SOUTHWEST. MANY
LOCATIONS WILL HAVE DAILY MAXIMUMS CLIMBING WELL INTO THE 100S AT
LOWER ELEVATIONS WHICH WILL GREATLY LIMIT RAIN EXCEPT FOR PERHAPS
FAR SOUTHEASTERN AZ INTO NM EARLY IN THE WEEK. EXPERIMENTAL
HEATRISK VALUES MAY RISE TO MAJOR OR EXTREME LEVELS (3 OUT OF 4 OR
4 OUT OF 4) FROM THE CALIFORNIA DESERTS INTO SOUTHERN NEVADA, UTAH,
AND ARIZONA.
CAMPBELL/FRACASSO
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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