131
FXUS02 KWBC 241927
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
327 PM EDT TUE JUN 24 2025
VALID 12Z FRI JUN 27 2025 - 12Z TUE JUL 01 2025
...TAIL END OF HEAT WAVE LINGERS OVER THE EASTERN OHIO VALLEY
FRIDAY...
..OVERVIEW
HEAT RELIEF ARRIVES FRIDAY FOR MUCH OF THE MID-ATLANTIC, BUT
THE HEAT WAVE LINGERS OVER PORTIONS OF THE EASTERN OHIO VALLEY.
MOISTURE CONTINUES TO ADVECT NORTH AND THEN EAST AROUND THE BROAD
SOUTHEASTERN U.S. RIDGE IN A "RING OF FIRE" SETUP INTO SATURDAY. A
WAVY FRONTAL BOUNDARY INTERACTING WITH THE ABOVE AVERAGE MOISTURE
SHOULD ALLOW FOR LOCALIZED HEAVY RAIN AND FLASH FLOODING IN THE
SACRAMENTO MOUNTAINS OF NEW MEXICO, NORTHERN PLAINS AND NORTHEAST
FRIDAY- SATURDAY. ADDITIONAL SCATTERED THUNDERSTORMS ACROSS MUCH
OF THE CENTRAL AND EASTERN U.S. THIS THE WEEKEND AND EARLY NEXT
WEEK COULD HAVE FLOODING POTENTIAL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE CONTINUES TO BE AGREEABLE IN SHOWING
WEAKENING/WIDENING RIDGING ACROSS THE SOUTHEASTERN U.S. THROUGH
THIS WEEKEND WITH A TROUGH DEVELOPING ALONG THE WEST COAST FOR
EARLY NEXT WEEK. THIS CREATES A MORE ZONAL PATTERN EAST OF THE
GREAT BASIN WITH THE JET STREAM OVER THE NORTHERN TIER WITH
EMBEDDED SHORTWAVES. THE FRIDAY SHORTWAVE AND WEAK SURFACE LOW
ATOP THE GREAT LAKES CONTINUES TO HAVE CONVECTIVE QPF DIFFERENCES
OVER THE NORTHEAST INTO FRIDAY NIGHT WITH THE MAIN CONCERN OF
WHETHER THE QPF MAX WILL BE IN CANADA OR NORTHERN NEW ENGLAND. THE
NEXT TROUGH COMES ACROSS THE NORTHWEST FRIDAY AND REACHES THE
NORTH- CENTRAL U.S. BY SUNDAY. A STRIPE OF HEAVY RAIN SHOULD
DEVELOP OVER THE NORTHERN PLAINS/UPPER MIDWEST WITH 12Z GUIDANCE IN
BETTER AGREEMENT THAN PRIOR RUNS. MEANWHILE RIDGING IS FORECAST TO
BUILD WITH ITS AXIS ALONG THE ROCKIES.
THE WPC FORECAST IS NEARLY ALL BASED ON A COMPOSITE BLEND OF THE
00Z/06Z DETERMINISTIC GUIDANCE WITH ONLY SOME ENSEMBLE MEANS FOR
DAYS 6/7 AS NECESSITY BEYOND THE RANGE OF THE UKMET.
..WEATHER/HAZARDS HIGHLIGHTS
MOISTURE ADVECTION AROUND THE SOUTHEASTERN U.S. UPPER RIDGE
COMBINED WITH SHORTWAVES ALOFT AND A WAVY FRONTAL BOUNDARY WILL
PROVIDE A FAVORABLE ENVIRONMENT FOR CONVECTION FOR PORTIONS OF THE
NORTHERN TIER FRIDAY/SATURDAY. AN INITIAL WAVE MOVING ACROSS THE
LOWER GREAT LAKES AND NORTHEAST FRIDAY-SATURDAY WILL ALLOW FOR SOME
POSSIBLY HEAVY RAIN IN THE INTERIOR NORTHEAST ON THE CUSP OF THE
INSTABILITY GRADIENT AND WHERE A WEAK SURFACE LOW TRACKS ALONG THE
FRONT. A MARGINAL RISK REMAINS IN EFFECT FOR DAYS 4 AND 5 OVER
PORTIONS OF THE NORTHEAST (AND THE CENTRAL APPALACHIANS FOR DAY 4).
HIGH QPF MAXES ON FRIDAY MAY ALLOW AN UPGRADE AT SOME POINT.
DELINEATED IN THE DAY 4/FRIDAY AND DAY 5/SATURDAY EROS FOR
LOCALIZED FLASH FLOODING WITH THIS ACTIVITY.
ANOTHER SHALLOW UPPER TROUGH AND FRONTAL SYSTEM WILL PUSH THROUGH
THE NORTH-CENTRAL U.S. FRIDAY NIGHT INTO SUNDAY, PROVIDING FORCING
FOR THUNDERSTORMS. INSTABILITY IS LIKELY TO BE HIGH (MUCAPE OF
3000-5000 J/KG ALREADY SHOWN BY THE GLOBAL MODELS. THE DAY 4
MARGINAL RISK IS MAINTAINED FOR ND/MN WITH MORE EAST-WEST EXPANSION
TO THE DAY 4 MARGINAL RISK FROM SD INTO THE U.P. OF MICHIGAN BASED
ON CONVERGENCE ALONG A FRONTAL ZONE. CONVECTION IS FORECAST TO
SHIFT SOUTHEAST ACROSS THE MIDWEST AND CENTRAL PLAINS/MIDDLE
MISSISSIPPI VALLEY EARLY NEXT WEEK AHEAD OF THE TROUGH AND FRONT.
RING OF FIRE MOISTURE ADVECTION OVER THE SOUTHERN ROCKIES/ADJACENT
HIGH PLAINS CONTINUES WITH ELEVATED MOISTURE THROUGH SATURDAY. DAY
4 AND 5 MARGINAL RISKS ARE NOW IN EFFECT FOR THE SACRAMENTO
MOUNTAINS FOR DIURNALLY DRIVEN ISOLATED FLASH FLOODING. MONSOONAL
MOISTURE LOOKS TO INCREASE EARLY NEXT WEEK, BRINGING RAIN AND
THUNDERSTORM CHANCES TO THE SOUTHERN AND CENTRAL ROCKIES AND HIGH
PLAINS.
THE CENTRAL GULF COAST MAY SEE A FEW DAYS OF MORE FOCUSED
CONVECTION, WITH HEAVIER AMOUNTS POSSIBLE EARLY NEXT WEEK (AFTER
THE ERO PERIOD, AND WOULD HAVE TO BATTLE AGAINST HIGH FLASH FLOOD
GUIDANCE TO SEE FLOODING CONCERNS THERE).
WEAKENING/SUPPRESSION OF THE EAST-CENTRAL RIDGE FRIDAY INTO
SATURDAY WILL ALLOW MODERATION OF TEMPERATURES WITH A BACKDOOR COLD
FRONT OVER MUCH OF THE MID-ATLANTIC FRIDAY, THOUGH WARMING IS
EXPECTED EARLY NEXT WEEK. THE NORTH-CENTRAL U.S. CAN EXPECT
TEMPERATURES TO BE 5-10 DEGREES ABOVE AVERAGE FRIDAY- SATURDAY AND
THEN COOL BEHIND A COLD FRONT. TEMPERATURES IN THE INTERIOR NORTHWEST
WILL WARM BY EARLY NEXT WEEK UNDER AN UPPER RIDGE AND NORTH OF THE
TROUGH ALONG THE COAST. THE DESERT SOUTHWEST CAN EXPECT A RETURN TO
ABOVE NORMAL TEMPERATURES STARTING SUNDAY FROM ADVECTION EAST OF
THE WEST COAST TROUGH.
JACKSON
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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