679
FXUS02 KWBC 230653
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
253 AM EDT WED JUL 23 2025
VALID 12Z SAT JUL 26 2025 - 12Z WED JUL 30 2025
***MAJOR HEAT WAVE CONTINUES FROM THE SOUTHEAST TO THE CENTRAL U.S.
THIS WEEKEND INTO NEXT WEEK***
..GENERAL OVERVIEW
AN UPPER LEVEL RIDGE WILL BE LARGE AND IN CHARGE FOR THIS FORECAST
PERIOD FROM THE WESTERN HIGH PLAINS TO THE SOUTHEAST STATES. THE
UPPER HIGH IS INITIALLY CENTERED NEAR THE SOUTHEAST COAST ON
SATURDAY, BUT BUILDS BACK FARTHER TO THE WEST ACROSS THE PLAINS
GOING INTO EARLY NEXT WEEK AS THE OVERALL PATTERN STARTS TO BECOME
MORE AMPLIFIED. AN UPPER TROUGH OVER CENTRAL CANADA WILL LIKELY
AMPLIFY FURTHER DOWNSTREAM OF THIS UPPER RIDGE ACROSS THE NORTHEAST
BY THE MIDDLE OF THE WEEK AND BEYOND, SIGNALING A RETURN TO COOLER
CONDITIONS BY THE END OF THE FORECAST PERIOD. SHORTWAVE ENERGY
TRACKING AROUND THE NORTHERN PERIPHERY OF THE UPPER RIDGE WILL FUEL
THE DEVELOPMENT OF MULTIPLE THUNDERSTORM COMPLEXES FROM THE
NORTHERN PLAINS TO THE GREAT LAKES AND THE NORTHEAST STATES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GOOD MODEL AGREEMENT EXISTS AMONG THE 00Z GUIDANCE SUITE REGARDING
THE MAIN UPPER LEVEL AND SURFACE PRESSURE PATTERN ACROSS THE
NATION FOR THIS WEEKEND. LOOKING AHEAD TO EARLY NEXT WEEK, THE
EXPANSIVE UPPER RIDGE/HIGH IS THE MOST CONFIDENT ASPECT OF THE
FORECAST WITH THE BEST MODEL AGREEMENT. THERE HAS BEEN A TREND IN
THE GUIDANCE FOR A MORE AMPLIFIED UPPER TROUGH DEVELOPING OVER
ONTARIO AND QUEBEC THAT WILL BEGIN TO EXERT ITS INFLUENCE ACROSS
THE NORTHEAST STATES STARTING MID-WEEK, IN RESPONSE TO THE UPPER
RIDGE RETROGRADING TO THE WESTERN HIGH PLAINS. A GENERAL MODEL
BLEND WORKED FOR THE WEEKEND, WITH A TRANSITION TO ABOUT 40-50%
ENSEMBLE MEANS BY NEXT WEDNESDAY.
..WEATHER/HAZARDS HIGHLIGHTS
THE OVERALL WEATHER PATTERN IS EXPECTED TO REMAIN RATHER ACTIVE
ACROSS THE NORTHERN TIER STATES AS STORM SYSTEMS TRAVERSE THE
NORTHERN PERIPHERY OF THE UPPER HIGH. THE FIRST AREA OF CONCERN
WILL BE FROM THE NORTHERN OHIO VALLEY AND SOUTHERN MICHIGAN TO THE
NORTHEAST U.S. WITH A FRONTAL BOUNDARY SLOWLY DROPPING SOUTHWARD.
SCATTERED TO NUMEROUS SHOWERS AND STORMS ARE LIKELY ON SATURDAY
WITH THE POTENTIAL FOR SOME CONVECTIVE TRAINING, AND A MARGINAL
RISK WILL REMAIN VALID GOING INTO THE NEW DAY 4 OUTLOOK. THIS
REACHES THE NORTHEAST ON SUNDAY AND THIS IS WHERE THE NEW DAY 5
MARGINAL RISK WILL BE VALID. THE OTHER AREA OF CONCERN WILL BE
ACROSS THE UPPER MIDWEST, WITH THE HEAVIEST RAINFALL LIKELY ON
SUNDAY AS A SURFACE LOW DEVELOPS ALONG A COLD FRONT AND INTERCEPTS
AN ANOMALOUSLY HUMID AIRMASS ACROSS MUCH OF MINNESOTA. GIVEN GOOD
MODEL QPF AGREEMENT FOR THIS TIME RANGE AND THE RECENT HEAVY
RAINFALL, A SLIGHT RISK AREA WILL BE VALID FROM EXTREME EASTERN
NORTH DAKOTA TO AND ACROSS NORTHERN MINNESOTA FOR THE NEW DAY
5/SUNDAY EXCESSIVE RAINFALL OUTLOOK.
ELSEWHERE ACROSS THE NATION, THE POSITION OF THE UPPER HIGH/RIDGE
OVER THE WESTERN HIGH PLAINS BY EARLY NEXT WEEK WILL RESULT IN
DEEPER MONSOONAL MOISTURE BEING ADVECTED NORTHWARD ACROSS THE
DESERT SOUTHWEST. THIS FIRST BECOMES NOTICEABLE ACROSS SOUTHERN NEW
MEXICO ON SUNDAY, BUT BECOMES MORE WIDESPREAD AND ENCOMPASSES MORE
OF NEW MEXICO AND INTO MUCH OF CENTRAL/EASTERN ARIZONA AND COLORADO
BY MONDAY AND TUESDAY. THEREFORE, THE DAY 5/SUNDAY ERO WILL FEATURE
A MARGINAL RISK AREA CENTERED OVER SOUTHWESTERN NEW MEXICO. HEAVY
SHOWERS AND STORMS FROM SEA BREEZE CONVERGENCE OVER FLORIDA IS
LIKELY DURING THE AFTERNOON HOURS EARLY NEXT WEEK, AND SCATTERED
STORMS WILL ALSO BE POSSIBLE ACROSS PORTIONS OF THE NORTHERN
ROCKIES AND THE CASCADES.
IN THE TEMPERATURE DEPARTMENT, HEAT WILL CONTINUE TO MAKE WEATHER
HEADLINES ACROSS A LARGE EXPANSE OF THE CENTRAL AND EASTERN U.S.
GIVEN THE SIZE OF THE UPPER RIDGE AND THE JET STREAM WELL TO THE
NORTH. HEAT INDICES OF 100 TO 110 DEGREES ARE LIKELY FROM THE
DELMARVA PENINSULA TO FLORIDA THIS WEEKEND, AND ALSO ACROSS MUCH OF
THE CENTRAL AND SOUTHERN PLAINS. THERE WILL LIKELY BE SOME
ABATEMENT IN THE HEAT FOR THE MID-ATLANTIC AND NORTHEAST FOR EARLY
TO MID NEXT WEEK AS AN UPPER TROUGH BEGINS TO AMPLIFY ACROSS
EASTERN CANADA AND INTO NEW ENGLAND. HOWEVER, THE HEAT LIKELY
BECOMES EVEN WORSE FOR THE MIDWEST TO THE DEEP SOUTH WITH HEAT
INDICES OF 105 TO 115 DEGREES FOR MANY AREAS, WITH HEAT ADVISORIES
AND EXTREME HEAT WARNINGS LIKELY TO CONTINUE INTO NEXT WEEK.
HAMRICK
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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