031
FXUS02 KWBC 171819
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
219 PM EDT TUE MAR 17 2026
VALID 12Z FRI MAR 20 2026 - 12Z TUE MAR 24 2026
...IMPRESSIVE EARLY SEASON HEAT WAVE CONTINUES ACROSS THE
SOUTHWESTERN U.S. THROUGH THE WEEKEND WITH NUMEROUS RECORDS,
GRADUALLY EASING EARLY NEXT WEEK...
..OVERVIEW
IT GENERALLY REMAINS THE CASE THAT A HIGHLY AMPLIFIED AND
ANOMALOUS UPPER LEVEL RIDGE OF HIGH PRESSURE WILL CONTINUE TO
DOMINATE THE WEATHER PATTERN ACROSS THE WESTERN HALF OF THE COUNTRY
THROUGH THE WEEKEND, BRINGING CONTINUED SUMMERLIKE HEAT THAT
SHOULD SET NUMEROUS DAILY AND MONTHLY TEMPERATURE RECORDS FOR
PORTIONS OF THE DESERT SOUTHWEST, THE INTERMOUNTAIN WEST, AND THE
PLAINS. THIS REGION SHOULD GRADUALLY MODERATE AS THE RIDGE BRIEFLY
BECOMES MORE SUPPRESSED, BUT SHOULD STILL REMAIN PLENTY WARM INTO
EARLY NEXT WEEK. JUST NORTH OF THE RIDGE, THE TAIL END OF A
PERSISTENT ATMOSPHERIC RIVER WILL CONTINUE TO BRING PERIODS OF
MODERATE TO HEAVY RAIN TO PARTS OF THE PACIFIC NORTHWEST THROUGH
FRIDAY BEFORE DRYING OUT OVER THE WEEKEND. DOWNSTREAM, UPPER
TROUGHING ACROSS THE EAST WILL LEAD TO REINFORCING BOUTS OF NEAR TO
COOLER THAN NORMAL TEMPERATURES FROM THE UPPER MIDWEST TO THE
NORTHEAST ALONG WITH THE POTENTIAL FOR OCCASIONAL RAIN AND SNOW.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST AVAILABLE MODEL GUIDANCE CONTINUES TO SHOW GOOD OVERALL
AGREEMENT WITH THEIR DEPICTIONS OF THE LARGE SCALE PATTERN THROUGH
MOST OF THE MEDIUM RANGE PERIOD, WITH TYPICAL TIMING AND AMPLITUDE
DIFFERENCES OF VARIOUS SHORTWAVES EMBEDDED IN FAST QUASI-ZONAL
FLOW ACROSS THE NORTHERN TIER LATE IN THE PERIOD LEADING TO THE
MOST UNCERTAINTY IN THE RESULTING SURFACE PRESSURES, FRONTAL
PLACEMENT, AND QPF, ESPECIALLY ACROSS THE EAST. A GENERAL COMPOSITE
BLEND OF THE 000UTC AND 06 UTC DETERMINISTIC GUIDANCE PROVIDED A
GOOD STARTING POINT TO THE WPC FORECAST STILL FAVORS A STOUT 594DM
RIDGE ACROSS THE SOUTHWEST BECOMING SUPPRESSED LATE THIS WEEKEND
AS A RESULT OF THE ENERGETIC JET WITH EMBEDDED WAVES IMPINGING DOWN
FROM THE NORTH. THE LATTER PORTION OF THE WPC FORECAST THEN
UTILIZED INCREASING WEIGHT FROM THE ECMWF/CANADIAN AND GEFS
ENSEMBLE MEANS, ALONG WITH THE EC-AIFS, TO REDUCE THE EFFECTS OF
THE AFOREMENTIONED TIMING AND AMPLITUDE DIFFERENCES OF THOSE WAVES.
THIS RESULTED IN A FORECAST THAT DEPICTED THE OVERALL TROUGH AXIS
ACROSS THE EASTERN U.S., WHICH IS A FAIR COMPROMISE AT THIS STAGE
OF THE GAME ALONG WITH A MIDDLE OF THE ROAD TIMING OF THE MAIN/WAVY
FRONTS AND QPF AXIS TIMINGS MAINLY IN LINE WITH THE 13 UTC NBM.
HOWEVER, SURFACE SYSTEM CONTINUITY IS NOT AS STELLAR AS FLOW ALOFT.
..WEATHER/HAZARDS HIGHLIGHTS
UNSEASONABLY HOT AND SUMMERLIKE TEMPERATURES WILL CONTINUE
UNDERNEATH A LARGE DOME OF UPPER LEVEL HIGH PRESSURE THROUGH THE
WEEKEND, WITH FORECAST HIGHS POISED TO BREAK NUMEROUS DAILY AND
MONTHLY RECORDS ACROSS MUCH OF THE SOUTHWESTERN U.S. HIGHS ARE
FORECAST TO SOAR WELL PAST 100 DEGREES THROUGH AT LEAST SUNDAY AND
POSSIBLY MONDAY ACROSS THE LOWER DESERT VALLEYS OF CALIFORNIA AND
ARIZONA, RESULTING IN WIDESPREAD EXTREME HEAT WARNINGS. WHILE NOT
QUITE AS HOT, TEMPERATURES 20 TO 30 DEGREES ABOVE NORMAL WILL ALSO
BE A CONCERN ACROSS MUCH OF THE INTERMOUNTAIN WEST AND FROM THE
CENTRAL TO SOUTHERN PLAINS INTO THE WEEKEND. HIGH TEMPERATURES WILL
CLIMB WELL INTO THE 80S ACROSS MUCH OF THE GREAT BASIN AND
INTERMOUNTAIN WEST, INTO THE MID/UPPER 80S TO NEAR 90 IN THE
CENTRAL PLAINS, AND INTO THE MID/UPPER 90S TO NEAR 100 IN THE
SOUTHERN PLAINS. THE MOST INTENSE HEAT WILL BEGIN TO WANE SOMEWHAT
AS THE RIDGE BRIEFLY BREAKS DOWN EARLY NEXT WEEK, BUT HIGHS ARE
EXPECTED TO STILL REMAIN WELL ABOVE NORMAL COMPARED TO MARCH
CLIMATOLOGY.
NORTH OF THE RIDGE ACROSS THE PACIFIC NORTHWEST, THE TAIL END OF A
PERSISTENT ATMOSPHERIC RIVER WILL CONTINUE TO BRING MODERATE TO
HEAVY RAIN TO COASTAL LOCATIONS OF WESTERN WASHINGTON AND HIGH
ELEVATION SNOW TO THE WASHINGTON CASCADES THROUGH THE DAY ON FRIDAY
BEFORE GRADUALLY DRYING OUT ON SATURDAY AND SUNDAY. GIVEN SIMILAR
CONDITIONS AND A WET PATTERN IN THE DAYS LEADING UP TO FRIDAY,
DECIDED TO ADD A MARGINAL RISK TO THE EXCESSIVE RAINFALL OUTLOOK
(ERO) FOR DAY 4 FRIDAY TO ACCOUNT FOR THE ATMOSPHERIC RIVER STAYING
IN PLACE FOR ONE MORE DAY. BY DAY 5 SATURDAY, ANY REMAINING
SHOWERS ACROSS THE NORTHWEST WILL BE MOSTLY LIGHT, AND THE REST OF
THE CONUS LOOKS MOSTLY DAY. AS A RESULT, NO RISK AREAS WILL BE
OUTLINED FOR THE DAY 5 SATURDAY ERO.
ACROSS THE EASTERN HALF OF THE COUNTRY, ABOVE NORMAL WARMTH FROM
THE CENTRAL U.S. WILL SPREAD ACROSS THE SOUTHEAST, WHILE
PERSISTENT UPPER TROUGHING AND A SERIES OF FRONTAL SYSTEMS WILL
KEEP TEMPERATURES NEAR TO SLIGHTLY COOLER THAN NORMAL. THE EXACT
TIMING OF THE TROUGH(S) AND RELATED SURFACE LOW/FRONTAL SYSTEMS
REMAIN UNCERTAIN, BUT A FAIRLY UNSETTLED PATTERN FEATURING
OCCASIONAL RAIN AND SNOW ARE POSSIBLE ACROSS THE GREAT LAKES,
NORTHEAST, AND MID- ATLANTIC AT TIMES INTO EARLY NEXT WEEK.
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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