088
FXUS02 KWBC 050700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT WED JUN 5 2024
VALID 12Z SAT JUN 08 2024 - 12Z WED JUN 12 2024
...WARMER THAN AVERAGE TEMPERATURES CONTINUE FOR THE WEST INTO THE
WEEKEND AND EARLY NEXT WEEK, THOUGH LESS EXTREME THAN THE SHORT
RANGE PERIOD...
..OVERVIEW
A RELOADING UPPER TROUGH WILL BE PRESENT IN THE EASTERN U.S. THIS
WEEKEND INTO EARLY NEXT WEEK, WHILE MEAN UPPER RIDGING IS FORECAST
FOR THE WESTERN U.S. (THOUGH DISRUPTED AT TIMES BY SHORTWAVE
ENERGIES). WARM TO HOT TEMPERATURES WILL CONTINUE ACROSS THE WEST
DURING THE MEDIUM RANGE PERIOD, THOUGH MODERATED A BIT COMPARED TO
THE SHORT RANGE. THE FORECAST PATTERN SHOULD SUPPORT MULTIPLE
ROUNDS OF SHOWERS/STORMS OVER THE CENTRAL OR SOUTH-CENTRAL ROCKIES,
PLAINS, AND MISSISSIPPI VALLEY AS SYSTEMS RIDE THE RIDGE AND
FRONTAL BOUNDARIES HELP TO FOCUS MOISTURE. RAIN CHANCES SHOULD
EVENTUALLY REACH THE SOUTHEAST INTO NEXT WEEK. MEANWHILE, PERIODS
OF LIGHT TO MODEST RAIN ARE LIKELY IN THE NORTHEASTERN U.S.
UNDERNEATH THE SLOW-MOVING TROUGH/LOW.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE GENERALLY AGREES WITH THE WEEKEND PATTERN OF UPPER
RIDGING IN THE WEST (WITH A COUPLE OF SHORTWAVE DISRUPTIONS) AND
TROUGHING IN THE EAST, BUT CONTINUE TO SEE DIFFERENCES IN THE
DETAILS EVEN IN THE EARLY-MID PERIOD THAT WILL AFFECT SENSIBLE
WEATHER. BY SUNDAY-MONDAY, NOTABLE DIFFERENCES ARISE WITH POTENTIAL
FOR ENERGY TO ROUND THE WESTERN SIDE OF THE TROUGH AND DIG
TROUGHING INTO THE EAST-CENTRAL CONUS. GFS RUNS WERE STRONG ENOUGH
WITH THIS SHORTWAVE TO CLOSE OFF A SMALL LOW; THE 18Z RUN WAS NOT
TOO FAR OFF FROM THE ECMWF/CMC IN PLACEMENT OVER THE MID-
MISSISSIPPI TO OHIO VALLEYS MONDAY, BUT THE 12Z GFS SEEMED TOO
SLOW. NOW 00Z GUIDANCE HAS TRENDED AWAY FROM THIS DIGGING ENERGY
FOR THE MOST PART, THOUGH THE 00Z ECMWF KEEPS IT AND THUS MAINTAINS
TROUGHING ACROSS THE EAST INTO TUESDAY-WEDNESDAY. THE TIMING OF
THE TROUGH MOVING OUT OF THE EAST (OR REBUILDING) IS ALSO AFFECTED
BY A COUPLE OF UNCERTAIN UPSTREAM FEATURES THAT MAY OR MAY NOT
COMBINE OR INTERACT--NAMELY, SHORTWAVE TROUGHING EXPECTED TO COME
INTO THE NORTHWEST SUNDAY MOVING EAST AND ENERGY MOVING SOUTHEAST
FROM WEST-CENTRAL CANADA. MODELS (BOTH DYNAMICAL AND AI/MACHINE
LEARNING) SHOW A VARIETY OF SOLUTIONS WITH THESE TRACKS AND
EVOLUTION, KEEPING CONFIDENCE LOW. ELSEWHERE, ECMWF RUNS HAVE BEEN
STRONG WITH AN UPPER LOW DROPPING INTO THE EASTERN PACIFIC SUNDAY-
MONDAY AND STALLING THROUGH THE FIRST HALF OF THE WEEK. THE 00Z GFS
AND CMC DO SHOW THIS FEATURE NOW, BUT WEAKER THAN THE ECMWF.
THE WPC FORECAST WAS BASED ON A BLEND OF DETERMINISTIC MODELS
FAVORING THE 18Z GFS AND 12Z ECMWF EARLY IN THE PERIOD, BUT
INCREASED THE PROPORTION OF ENSEMBLE MEANS IN THE BLEND TO HALF DAY
6 AND MORE DAY 7 GIVEN THE INCREASING UNCERTAINTY.
..WEATHER/HAZARDS HIGHLIGHTS
AMPLE MOISTURE FROM THE GULF AND PACIFIC MOISTURE ADVECTING AROUND
THE UPPER RIDGE WILL COMBINE ACROSS THE SOUTHERN/CENTRAL ROCKIES
AND PLAINS THIS WEEKEND, WITH ONE OR MORE SURFACE BOUNDARIES
HELPING TO FOCUS MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS IN AN
ENVIRONMENT WITH PLENTY OF INSTABILITY. WHILE THERE IS STILL SOME
UNCERTAINTY IN THE EXACT PLACEMENT OF CONVECTION ON ANY GIVEN DAY,
THE INGREDIENTS ARE IN PLACE FOR HEAVY RAIN AMOUNTS AND RAIN RATES
THAT COULD CAUSE FLOODING CONCERNS. FOR DAY 4/SATURDAY, A SLIGHT
RISK IN THE ERO REMAINS IN PLACE ACROSS THE
OKLAHOMA/KANSAS/MISSOURI/ARKANSAS INTERSECTION AND EXPANDED TO THE
EAST, AS MODELS CONTINUE TO SHOW A HEAVY RAINFALL AXIS OF 3-5
INCHES IN THESE AREAS. THE MARGINAL RISK EXPANDS BACK INTO THE
CENTRAL HIGH PLAINS. BY SUNDAY, THE COLD FRONT SHOULD PRESS SOUTH A
BIT AND SHIFT THE FLOODING RISK SOUTH WITH IT. AS A FIRST TAKE AT
THE DAY 5/SUNDAY ERO, HAVE A BROAD MARGINAL RISK FROM THE
SOUTHERN/CENTRAL ROCKIES EAST INTO THE SOUTHERN PLAINS AND INTO THE
MID-SOUTH. SOUTHERN PARTS OF THE ROCKIES AND HIGH PLAINS AROUND
NORTHEASTERN NEW MEXICO OR SO HAVE SHOWN THE GREATEST CONSISTENCY
IN MODERATE TO HEAVY RAIN AMOUNTS, BUT WAS NOT CONFIDENT THAT THE
IMPACTS WOULD RISE TO THE SLIGHT RISK LEVEL THERE. FARTHER EAST,
THE PLACEMENT OF EMBEDDED HEAVIER CONVECTION REMAINS UNCERTAIN AS
THERE IS NOT A LOT OF RUN-TO-RUN CONTINUITY. BUT AN EMBEDDED SLIGHT
RISK IS POSSIBLE SOMEWHERE ACROSS THE SOUTH-CENTRAL U.S. ON SUNDAY
IF MODELS CONVERGE BETTER ON A LOCATION OF FOCUS, AND IF IT
OVERLAPS AREAS THAT HAVE SEEN SIGNIFICANT RAINS RECENTLY. THE FRONT
SHOULD CONTINUE TO PRESS SOUTHEAST INTO MONDAY AND COULD SPREAD
RAIN CHANCES TO THE GULF COAST AND SOUTHEAST. AFTER SOME LIGHT
SHOWERS IN THE INTERIOR WEST SATURDAY, WEAK UPPER TROUGHING FARTHER
NORTH WILL BRING IN MODEST RAIN TO THE NORTHERN ROCKIES SUNDAY AND
CONTINUE RAIN CHANCES ACROSS THE CENTRAL/SOUTHERN ROCKIES MONDAY.
MEANWHILE, ROUNDS OF RAIN AND POSSIBLE THUNDERSTORMS ARE EXPECTED
ACROSS THE LOWER GREAT LAKES TO THE NORTHEAST UNDERNEATH THE UPPER
TROUGH. THESE RAINFALL AMOUNTS LOOK TO BE SUB-MARGINAL RISK LEVELS.
THE MEAN RIDGE IN THE WEST WILL CONTINUE TO CAUSE MUCH WARMER THAN
AVERAGE TEMPERATURES THERE, BUT BY THE WEEKEND SOME SOUTHERN
STREAM TROUGHING DISRUPTING THE RIDGE SHOULD MODERATE TEMPERATURES
(AND HEATRISK) SOMEWHAT IN THE SOUTHWEST COMPARED TO THE SHORT
RANGE PERIOD. HIGHER TEMPERATURE ANOMALIES OF 15-20F ABOVE NORMAL,
LOCALLY HIGHER, WILL BE IN THE NORTHWEST SATURDAY AND JUST A TOUCH
BELOW THAT BY EARLY NEXT WEEK WHEN A NORTHERN STREAM SHORTWAVE
MOVES THROUGH. BY TUESDAY-WEDNESDAY THE WARM ANOMALIES LOOK TO
EXPAND BACK SOUTH AS WELL AS EAST INTO THE NORTHERN PLAINS THOUGH.
MEANWHILE, MOST AREAS EAST OF THE ROCKIES SHOULD TREND TO SLIGHTLY
BELOW NORMAL BEHIND THE COLD FRONT. THIS WILL EVENTUALLY INCLUDE
TEXAS AND FLORIDA (WHERE HIGHS SEVERAL DEGREES ABOVE NORMAL MAY
LEAD TO SOME DAILY RECORDS) AFTER A HOT WEEKEND.
TATE
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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