237
FXUS02 KWBC 250659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT FRI JUL 25 2025
VALID 12Z MON JUL 28 2025 - 12Z FRI AUG 01 2025
...MAJOR AND PERSISTENT HEAT WAVE CONTINUES ACROSS THE MID-SOUTH
AND SOUTHEAST THROUGH MUCH OF NEXT WEEK...
..OVERVIEW
A LARGE AND STRONG UPPER HIGH MEANDERING OVER THE CENTRAL/SOUTHERN
PLAINS INTO THE MID-SOUTH WILL CAUSE A PERSISTENT AND MAJOR HEAT
WAVE FOR THOSE AREAS THROUGH MUCH OF NEXT WEEK. DANGEROUS HEAT IS
FORECAST TO EXTEND NORTH THROUGH THE MIDWEST AND OHIO VALLEY EARLY
NEXT WEEK BUT GRADUALLY GET PRESSED SOUTHWARD BEHIND A COLD FRONT
AS THE WEEK PROGRESSES. COMPLEXES OF SHOWERS AND STORMS ARE LIKELY
ALONG THE NORTHERN PERIPHERY OF THE RIDGE, ACROSS THE
SOUTHERN/CENTRAL HIGH PLAINS EASTWARD INTO THE MIDWEST. SCATTERED
THUNDERSTORMS ARE POSSIBLE FARTHER EAST AT TIMES, ESPECIALLY NEAR
THE FRONT AS IT PUSHES SOUTH. ADDITIONALLY, SOUTHERLY FLOW WILL
BRING MONSOONAL MOISTURE INTO THE SOUTHWEST STATES FOR POSSIBLY
HEAVY RAIN.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL AGREEMENT IS EXCELLENT FOR THE OVERALL PATTERN NEXT WEEK.
MODELS ARE UNIFIED IN SHOWING AN EXPANSIVE UPPER HIGH OF 2+
STANDARD DEVIATIONS ABOVE NORMAL, WITH WIDESPREAD 594+ DM 500MB
HEIGHTS BUT WITH LOW CHANCES OF REACHING 600 DM. GUIDANCE SHOWS THE
HIGH LARGEST MONDAY-TUESDAY AS IT ENCOMPASSES THE SOUTH-CENTRAL
ROCKIES EAST ACROSS THE MISSISSIPPI AND OHIO VALLEYS AND SOUTHEAST,
BEFORE SHRINKING IN SCOPE AND BEING CENTERED OVER THE SOUTHERN
PLAINS BY LATER NEXT WEEK. MEANWHILE THE RIDGE AXIS WILL SHIFT WEST
AND BUILD NORTH ACROSS THE NORTHERN ROCKIES INTO WESTERN CANADA
STARTING TUESDAY, COINCIDENT WITH THE UPPER TROUGH EDGING INTO THE
NORTH-CENTRAL TO NORTHEASTERN U.S. ANCHORED BY A LARGE HUDSON BAY
TO EASTERN CANADA UPPER LOW.
REGARDLESS OF THE LARGE SCALE AGREEMENT, SHORTWAVES RIDING AROUND
THE RIDGE WILL CAUSE MORE DIFFERENCES IN SENSIBLE WEATHER LIKE
FRONTAL PLACEMENT, AND CONVECTION WILL HAVE FURTHER UNCERTAINTIES
DUE TO SMALL BOUNDARIES LIKE OUTFLOWS INTERACTING. THESE TEND NOT
TO BECOME CLEARER UNTIL THE SHORT RANGE OR NEAR TERM, SO THE
DETAILS OF QPF REMAIN UNCERTAIN, BUT AT LEAST THE OVERALL PATTERN
SEEMS SET.
THE WPC FORECAST WAS INITIALLY BASED ON A BLEND OF THE 12Z ECMWF,
18Z GFS, 12Z CMC, AND 12Z UKMET FROM MOST TO LEAST. USED SOME GEFS
AND EC ENSEMBLE MEANS BY THE LATTER PART OF THE PERIOD, BUT WAS
ABLE TO MAINTAIN A MAJORITY OF DETERMINISTIC GUIDANCE WITH THE GOOD
GENERAL AGREEMENT.
..WEATHER/HAZARDS HIGHLIGHTS
THE PERSISTENT AND STRONG UPPER RIDGE WILL LEAD TO CONTINUED
DANGEROUS HEAT THAT WILL BE LONGEST LASTING ACROSS THE TENNESSEE
VALLEY/MID-SOUTH AND SOUTHEAST INTO THE CAROLINAS NEXT WEEK.
HEATRISK IS IN THE MAJOR (LEVEL 3/4) TO EXTREME (LEVEL 4/4)
CATEGORIES FOR THESE AREAS THROUGH WEDNESDAY OR THURSDAY. HIGH
TEMPERATURES WILL BE IN THE UPPER 90S AND 100S WITH HEAT INDICES
POTENTIALLY EXCEEDING 110 TO 115 DEGREES, WHILE MORNING LOWS WELL
INTO THE 70S AND NEARING 80 WILL NOT PROVIDE MUCH RELIEF. THIS IS
LIKELY TO SET SCATTERED DAILY RECORDS FOR MAXIMUM TEMPERATURES AND
PERHAPS MORE WIDESPREAD RECORDS FOR MINIMUM TEMPERATURES. FARTHER
NORTH, THE MIDWEST AND OHIO VALLEY INTO THE MID-ATLANTIC CAN EXPECT
HOTTER THAN NORMAL TEMPERATURES INTO THE 90S WITH MAJOR HEATRISK
EARLY NEXT WEEK, BUT THESE AREAS ARE LIKELY TO COOL BY WEDNESDAY OR
THURSDAY BEHIND A COLD FRONT.
RAIN AND THUNDERSTORMS ARE LIKELY TO FOCUS ON THE PERIPHERY OF THE
RIDGE. SOME UPPER JET AND SHORTWAVE FORCING COMBINED WITH
SUFFICIENT MOISTURE AND HIGH TO EXTREME INSTABILITY SHOULD LEAD TO
CONVECTION ACROSS THE NORTHERN TIER MONDAY AND TUESDAY. THERE ARE
SOME UNCERTAINTIES IN THE AXIS OF STORMS AND PLACEMENT OF HEAVIEST
RAIN, SO WILL MAINTAIN MARGINAL RISKS IN THE DAY 4/MONDAY AND DAY
5/TUESDAY EXCESSIVE RAINFALL OUTLOOKS, BUT WILL BE ON THE LOOKOUT
FOR HEAVY RAIN RATES AND RAIN AMOUNTS THAT COULD EVENTUALLY WARRANT
SLIGHT RISKS FOR FLASH FLOODING. MEANWHILE TO THE WEST OF THE
RIDGE, MONSOONAL MOISTURE WILL BE INCREASING OVER THE SOUTHWEST.
MARGINAL RISKS ARE IN PLACE IN THE DAYS 4 AND 5 EROS FOR THE
SOUTHWEST, AND REACHING INTO THE CENTRAL ROCKIES/HIGH PLAINS
ESPECIALLY BY DAY 5/TUESDAY AS THE MONSOONAL MOISTURE MEETS THE
FRONTAL SYSTEM TO THE NORTH. THE NORTH-CENTRAL ROCKIES AND PLAINS
LOOK TO BE AREAS OF FOCUS FOR HEAVY RAIN INTO WEDNESDAY AND
THURSDAY AS WELL.
ELSEWHERE, MOISTURE AND INSTABILITY COULD LEAD TO SCATTERED
THUNDERSTORMS IN PARTS OF THE EASTERN HALF OF THE U.S. FROM DAY TO
DAY. THERE MAY BE SOME FOCUS FOR STORMS ALONG THE COAST OF THE
CAROLINAS ON MONDAY, AND THEN OVER THE CENTRAL/EASTERN GULF COAST
ON TUESDAY AND WEDNESDAY WHERE THERE IS A TROUGH/WEAK LOW. WILL
HOLD OFF ON ANY ERO RISK AREAS FOR THESE AREAS DUE TO MODEL
UNCERTAINTIES AND HIGH FLASH FLOOD GUIDANCE VALUES. BY WEDNESDAY
AND ESPECIALLY THURSDAY THE COLD FRONTS SLOWLY PUSHING SOUTH COULD
PROVIDE A FOCUS FOR ENHANCED RAIN AMOUNTS IN THE EAST, WHICH WILL
BE REFINED IN FUTURE FORECASTS.
TATE
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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