586
FXUS02 KWNH 240637
PREEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 AM EDT THU JUL 24 2025
VALID 12Z SUN JUL 27 2025 - 12Z THU JUL 31 2025
***MAJOR AND PERSISTENT HEAT WAVE CONTINUES FROM THE SOUTHEAST TO
THE CENTRAL U.S. THIS WEEKEND INTO NEXT WEEK***
..GENERAL OVERVIEW
A MAJOR HEATWAVE WILL CONTINUE TO MAKE WEATHER HEADLINES ACROSS A
LARGE EXPANSE OF THE CENTRAL AND EASTERN U.S. GOING INTO NEXT
WEEK. THIS IS IN RESPONSE TO A SPRAWLING UPPER RIDGE THAT WILL
INITIALLY BE CENTERED OVER THE SOUTHEAST STATES, AND THEN BUILDS
BACK TO THE WEST ACROSS THE CENTRAL AND SOUTHERN PLAINS BY THE
MIDDLE OF THE WEEK. COMPLEXES OF SHOWERS AND STORMS ARE LIKELY FROM
THE NORTHERN PLAINS TO THE MIDWEST, AND MONSOONAL MOISTURE MAKES A
RETURN TO THE SOUTHWEST STATES. A PATTERN CHANGE IS LIKELY TO
EVOLVE BY THE END OF THE FORECAST PERIOD AS THE UPPER LEVEL FLOW
BECOMES MORE AMPLIFIED, WITH THE RIDGE BUILDING NORTH ACROSS THE
ROCKIES AND A TROUGH FROM CANADA BUILDING SOUTHWARD ACROSS THE
GREAT LAKES AND THE NORTHEAST, BRINGING A RETURN TO MUCH MORE
PLEASANT CONDITIONS BEHIND A COLD FRONT BY THURSDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
EXCELLENT OVERALL MODEL AGREEMENT EXISTS AMONG THE 00Z GUIDANCE
SUITE REGARDING THE MAIN UPPER LEVEL AND SURFACE PRESSURE PATTERN
ACROSS THE NATION FOR SUNDAY AND MONDAY. LOOKING AHEAD TO THE
MIDDLE OF NEXT WEEK, THE EXPANSIVE UPPER RIDGE/HIGH IS THE MOST
CONFIDENT ASPECT OF THE FORECAST WITH THE BEST MODEL AGREEMENT.
THERE ARE SOME MESOSCALE DIFFERENCES WITH THE SHORTWAVES THAT CROSS
THE NORTH-CENTRAL U.S., BUT NOTHING MAJOR. 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 SUNDAY INTO TUESDAY, WITH A TRANSITION TO ABOUT
40% ENSEMBLE MEANS BY NEXT THURSDAY.
..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 MAIN AREA OF CONCERN IN
TERMS OF HEAVY RAINFALL POTENTIAL EARLY THIS PERIOD 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 REMAIN VALID FOR THE DAY
4/SUNDAY PERIOD FROM EXTREME EASTERN NORTH DAKOTA, ACROSS NORTHERN
MINNESOTA, AND INTO FAR NORTHWEST WISCONSIN.
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 4/SUNDAY ERO
FEATURES A MARGINAL RISK AREA CENTERED OVER CENTRAL AND SOUTHERN
NEW MEXICO, AND THE DAY 5/MONDAY OUTLOOK HAS THE MARGINAL RISK AREA
EXTENDING INTO EASTERN ARIZONA AND SOUTHERN COLORADO. EVEN GREATER
COVERAGE OF SHOWERS AND STORMS IS LIKELY BY THE MIDDLE OF NEXT WEEK
AS DEEPER LOW-MID LEVEL MOISTURE ENTERS THE REGION. SCATTERED
STORMS WILL ALSO BE POSSIBLE ACROSS PORTIONS OF THE NORTHERN
ROCKIES AND THE CASCADES. SOME LOCALLY HEAVY RAINFALL WILL ALSO BE
POSSIBLE ACROSS THE NORTHEAST ON SUNDAY, AND A MARGINAL RISK AREA
IS VALID HERE AS WELL.
IN THE TEMPERATURE DEPARTMENT, HEAT WILL CONTINUE TO BE A MAJOR
PROBLEM FROM THE CENTRAL PLAINS TO THE SOUTHEAST STATES GIVEN THE
SIZE OF THE UPPER RIDGE AND THE JET STREAM WELL TO THE NORTH.
DANGEROUS HEAT INDICES ON THE ORDER OF 105 TO 115 DEGREES WILL
LIKELY BE COMMON FOR THE PIEDMONT AND COASTAL PLAIN OF THE
SOUTHEAST U.S. AND INCLUDING NORTHERN FLORIDA, WITH HEAT RISK IN
THE MAJOR TO EXTREME CATEGORY FOR MUCH OF NEXT WEEK. THE HEAT THEN
BUILDS ACROSS THE MIDWEST AND EXTENDING SOUTH TO THE GULF COAST AS
THE UPPER RIDGE RETROGRADES TO THE WEST FOR THE FIRST HALF OF THE
WORK WEEK, WITH HEAT INDICES ALSO REACHING 110 DEGREES AT TIMES FOR
SOME OF THESE AREAS, WITH HEAT ADVISORIES AND EXTREME HEAT
WARNINGS LIKELY TO CONTINUE. WARM AND HUMID OVERNIGHT LOWS WON'T
PROVIDE MUCH RELIEF EITHER. SOME GOOD NEWS TO REPORT IS THAT A COLD
FRONT IS EXPECTED TO DROP SOUTH FROM THE GREAT LAKES TO THE OHIO
VALLEY AND EVENTUALLY THE MID-ATLANTIC AND NORTHEAST TOWARDS THE
END OF THE WEEK, PROVIDING SOME BADLY NEEDED RELIEF AS A HIGHER
QUALITY AIRMASS BUILDS IN BEHIND THE FRONT.
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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