196
FXUS02 KWBC 181910
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
310 PM EDT WED MAR 18 2026
VALID 12Z SAT MAR 21 2026 - 12Z WED MAR 25 2026
...IMPRESSIVE EARLY SEASON HEAT WAVE CONTINUES ACROSS THE
SOUTHWESTERN U.S. THROUGH THE WEEKEND WITH NUMEROUS RECORDS,
GRADUALLY EASING EARLY NEXT WEEK...
..OVERVIEW
THE HIGHLY ANOMALOUS UPPER LEVEL RIDGE OVER THE SOUTHWESTERN U.S.
WILL BEGIN TO BE MORE SUPPRESSED AND A LITTLE WEAKER GOING INTO THE
WEEKEND, WITH THE EARLY SEASON HEATWAVE LIKELY PEAKING LATE WEEK.
A QUASI- ZONAL UPPER FLOW PATTERN SHOULD BE IN PLACE ACROSS MOST OF
THE COUNTRY BY SUNDAY, WITH BROAD CYCLONIC FLOW ALOFT OVER THE
GREAT LAKES AND NORTHEAST. THERE SHOULD STILL BE A BROAD UPPER
TROUGH SITUATED OVER THE EASTERN U.S. THROUGH EARLY NEXT WEEK, AND
THE RIDGE MAY TRY TO BUILD BACK IN SOME ACROSS THE DESERT SOUTHWEST
BY NEXT TUESDAY/WEDNESDAY, BUT NOT TO THE SAME LEVEL AS THIS WEEK.
MORE RAIN AND MOUNTAIN SNOW IS EXPECTED TO RETURN TO THE PACIFIC
NORTHWEST BY THAT TIME AS A TROUGH BUILDS IN FROM THE NORTHEASTERN
PACIFIC.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL GUIDANCE HAS DECENT AGREEMENT ON THE LARGE SCALE
PATTERN EVOLUTION ACROSS THE CONUS FOR THE MEDIUM RANGE PERIOD
FEATURING A SOUTHWESTERN U.S. RIDGE AND MULTIPLE SHORTWAVES OVER
THE TOP OF IT HELPING TO REINFORCE MEAN TROUGHING OVER THE EAST
THROUGH THE PERIOD. SOME UNCERTAINTY IN THE DETAILS AND TIMING OF
THESE INDIVIDUAL SHORTWAVES, WHICH HAS IMPLICATIONS FOR SENSIBLE
WEATHER. WITH NO MAIN OUTLIERS, A BLEND OF THE ECMWF, GFS, AND AIFS
SEEMED TO SERVE AS A GOOD STARTING POINT FOR THE 500MB AND SURFACE
PROGS. BY NEXT TUESDAY AND ESPECIALLY WEDNESDAY, THE ECMWF REMAINS
STRONGER/MORE AMPLIFIED WITH THE RIDGE BUILDING BACK ACROSS THE
WEST, SO TRENDED MORE TOWARDS THE ENSEMBLE MEANS WHICH WERE MORE IN
LINE WITH THE WEAKER GFS AND AIFS SOLUTIONS (AS WELL AS WPC
CONTINUITY).
..WEATHER/HAZARDS HIGHLIGHTS
THE RECORD-BREAKING HEATWAVE WILL LIKELY BE REACHING ITS PEAK BY
SATURDAY ACROSS THE SOUTHWESTERN U.S. WITH A HIGHLY ANOMALOUS UPPER
RIDGE IN PLACE. THE LOWER ELEVATIONS OF ARIZONA AND EASTERN
CALIFORNIA ARE EXPECTED TO HAVE TEMPERATURES EASILY EXCEED 100
DEGREES, AND THIS WILL SET MULTIPLE ALL TIME MARCH TEMPERATURE
RECORDS. EXTREME HEAT WARNINGS ARE NOW IN EFFECT GIVEN THE
MAGNITUDE AND HOW EARLY IN THE SEASON THIS IS HAPPENING, GIVEN MANY
ARE NOT YET ACCLIMATED TO THESE CONDITIONS. WIDESPREAD HIGHS
20-30+ DEGREES ABOVE LATE MARCH AVERAGES WILL ALSO BE EXPERIENCED
FROM THE INTERMOUNTAIN WEST TO THE CENTRAL/SOUTHERN PLAINS, WITH
NUMEROUS RECORDS BROKEN HERE AS WELL. THERE WILL LIKELY BE SOME
ABATEMENT IN THE HEAT GOING INTO EARLY NEXT WEEK, ESPECIALLY FOR
THE PLAINS AS A COLD FRONT SETTLES IN FROM THE NORTH, AND A MODEST
IMPROVEMENT FOR THE SOUTHWEST ALTHOUGH STILL WELL ABOVE NORMAL.
THERE WILL LIKELY BE A BRIEF WARM-UP FOR THE EAST COAST REGION
THIS WEEKEND AHEAD OF A STRONG COLD FRONT, WITH HIGHS EXPECTED TO
BE WELL INTO THE 60S AND 70S FOR MANY AREAS. HIGHS SHOULD RETURN TO
SLIGHTLY BELOW NORMAL LEVELS BY MONDAY AND TUESDAY AS A CANADIAN
SURFACE HIGH BUILDS IN FROM THE NORTH. THERE MAY BE SOME LIGHT RAIN
AND APPALACHIAN WINTRY PRECIPITATION FROM THE EASTERN OHIO VALLEY
TO THE MID-ATLANTIC BY TUESDAY INTO WEDNESDAY AS A POTENTIAL LOW
DEVELOPS ALONG A FRONTAL BOUNDARY, BUT UNCERTAIN ON SPECIFICS.
THE ATMOSPHERIC RIVER THAT WILL BE IN PLACE ACROSS WASHINGTON
STATE LATE THIS WEEK IS EXPECTED TO WEAKEN AND MOVE INLAND ACROSS
THE NORTHERN ROCKIES BY THE WEEKEND, AND THEREFORE NO EXCESSIVE
RAINFALL RISK AREAS ARE CURRENTLY WARRANTED FOR BOTH THE DAY
4/SATURDAY AND DAY 5/SUNDAY TIME PERIODS. HOWEVER, MORE RAIN AND
MOUNTAIN SNOW IS LIKELY TO MAKE A RETURN TO THIS REGION ON TUESDAY
AS THE NEXT STORM SYSTEM FROM THE PACIFIC APPROACHES, AND MORE SNOW
FOR THE HIGHER ELEVATIONS OF THE NORTHERN ROCKIES.
SANTORELLI/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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