999
FXUS02 KWBC 281835
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
235 PM EDT WED MAY 28 2025
VALID 12Z SAT MAY 31 2025 - 12Z WED JUN 04 2025
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE CONTINUES TO MAINTAIN DECENTLY GOOD AGREEMENT
WITH THE LARGE SCALE PATTERN THROUGH MOST OF THE MEDIUM RANGE TIME
PERIOD. HOWEVER, SOME SOURCES OF UNCERTAINTY REMAIN, LARGELY STEM
FROM THE TIMING OF AN AMPLIFYING TROUGH ACROSS THE WEST AND A
DEPARTING TROUGH ACROSS THE NORTHEAST EARLY TO MID NEXT WEEK. MOST
OF THESE TIMING DIFFERENCES STEM FROM SHORTER WAVELENGTHS EMBEDDED
IN THE LARGER SCALE FEATURES, WHICH INHERENTLY HAVE LESS
PREDICTABILITY AT LONGER LEAD TIMES. THAT BEING SAID, THE 00Z RUNS
OF THE ECMWF/CMC/UKMET AND THE 00Z/06Z RUNS OF THE GFS PROVIDED A
GOOD COMPOSITE STARTING POINT FOR THE WPC FORECAST, WHICH BECAME
MORE HEAVILY WEIGHTED TOWARDS THE 00Z EPS AND THE 06Z GEFS BY DAY 6
AND ESPECIALLY DAY 7 FOR STABILITY AND SMOOTHING OF DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
THE FLOW PATTERN ACROSS THE CONTINENTAL U.S. WILL TRANSITION FROM
PROGRESSIVE TO MORE AMPLIFIED THIS WEEKEND INTO EARLY NEXT WEEK. A
SERIES OF LEADING SHORTWAVES AND SECONDARY SYSTEMS WILL DIG INTO AN
AMPLIFIED UPPER TROUGH OVER A COOLED AND UNSETTLED EAST. THIS
OCCURS AS A TRAILING, RAINFALL-FOCUSING FRONT WORKS OFFSHORE INTO
THE WESTERN ATLANTIC, FLORIDA, AND THE GULF WHERE SOME HEAVY
DOWNPOURS MAY LINGER INTO NEXT WEEK WITH DEEPENED MOISTURE TO
MONITOR. THE BULK OF THE ENERGY ASSOCIATED WITH THE UPPER TROUGH
LIFTS OUT EARLY NEXT WEEK. PRIOR TO ITS EXIT, A TRAILING,
DEEPENING, SURFACE LOW WILL LIFT FROM NEW ENGLAND INTO EASTERN
CANADA THIS WEEKEND. WHILE INSTABILITY IS GENERALLY LACKING, THE
QPF FOOTPRINT IS CERTAINLY ENOUGH TO MAINTAIN AND EVEN EXPAND THE
MARGINAL RISK ERO ACROSS NORTHERN NEW ENGLAND FOR DAY 4/SATURDAY.
MEANWHILE, UPPER RIDGING WILL PREVAIL OVER MUCH OF THE WEST INTO
THE WEEKEND, SUPPORTING ANOMALOUS HEAT AND TEMPERATURES RISING
UPWARDS OF 10 TO 20 DEGREES ABOVE NORMAL. THIS POTENTIALLY
HAZARDOUS HEAT WILL FOCUS ACROSS THE CALIFORNIA CENTRAL VALLEY INTO
THE DESERT SOUTHWEST. PARTS OF THE WEST THAT WILL BE SPARED FROM
THE HEAT INCLUDE THE PACIFIC NORTHWEST, WHERE UPPER TROUGH ENERGY
WITH MODEST RAIN WILL KEEP TEMPERATURES COOLER. DESPITE SOME TIMING
DIFFERENCES, GUIDANCE CONTINUES TO TREND IN FAVOR OF SIGNIFICANT
UPPER TROUGH AMPLIFICATION INTO THE WEST EARLY NEXT WEEK, ALONG
WITH THE EJECTION OF THE LEAD SOUTHERN STREAM CLOSED SYSTEM FROM
OFFSHORE BAJA. THIS TRANSITION WILL THEN ACT TO PROVIDE RELIEF FROM
THE HEAT OVER THE WEST WITH THE BUILDING OF A MUCH MORE UNSETTLED
AND INCREASINGLY WET FLOW PATTERN FARTHER INLAND AND DOWNSTREAM TO
THE INTERMOUNTAIN WEST AND ESPECIALLY THE NORTHERN ROCKIES THROUGH
MIDWEEK. DESPITE THE CALENDAR FLIPPING INTO JUNE, THIS PATTERN WILL
SUPPORT AT LEAST A MINOR THREAT FOR MOUNTAIN SNOW IN THE HIGHEST
ELEVATIONS.
MILLER/SCHICHTEL
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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