479
FXUS02 KWBC 031928
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
327 PM EDT MON JUL 03 2023
VALID 12Z THU JUL 06 2023 - 12Z MON JUL 10 2023
...MAJOR SOUTHERN TIER HEAT WAVE TO EASE THIS WEEK, BUT MAY
REBUILD OVER THE SOUTHERN HIGH PLAINS AND VICINITY DURING THE
WEEKEND...
...STRONG TO SEVERE STORMS ALONG WITH A HEAVY RAIN/RUNOFF THREAT
TO FOCUS OVER THE CENTRAL PLAINS THURSDAY/FRIDAY...
..OVERVIEW
IT REMAINS THE CASE THAT THE MOST STABLE UPPER FEATURES DURING THE
PERIOD WILL BE A SOUTHERN ROCKIES/HIGH PLAINS CENTERED RIDGE
(POSSIBLY STRENGTHENING SOME BY SUNDAY OR MONDAY) AND A CENTRAL
CANADA MEAN TROUGH THAT WILL EXTEND INTO AT LEAST NORTHERN PARTS
OF THE LOWER 48. SHORTWAVE ENERGY ON THE LEADING SIDE OF THE
TROUGH WILL HELP TO PUSH A COLD FRONT AND ITS ASSOCIATED
SHOWERS/THUNDERSTORMS FROM THE GREAT LAKES THROUGH SOUTHERN PLAINS
EASTWARD TO THE EAST COAST. UPSTREAM SHORTWAVES EMBEDDED WITHIN
PROGRESSIVE FLOW BETWEEN THE UPPER RIDGE AND TROUGH WILL LIKELY
INTERACT WITH THE WESTERN END OF THE FRONT (INITIALLY STALLED AND
THEN RETURNING AS A WARM FRONT) TO PRODUCE MULTIPLE CENTRAL U.S.
CONVECTIVE SYSTEMS WHOSE FOCUS SHOULD SHIFT GRADUALLY EASTWARD
WITH TIME. GUIDANCE CONTINUES TO SUGGEST THAT ANOTHER FRONT MAY
DROP INTO THE CENTRAL U.S. DURING THE WEEKEND AND EARLY NEXT WEEK
WITH SUPPORT FROM SOME COMBINATION OF ENERGY EJECTING FROM THE
WEST AND/OR AMPLIFICATION OF THE CANADIAN/NORTHERN TIER U.S. UPPER
TROUGH. MEANWHILE EXPECT A WEAK TROUGH WITH ONE OR MORE EMBEDDED
UPPER LOWS TO EVOLVE ALONG THE WEST COAST FROM LATE THIS WEEK INTO
THE WEEKEND, WITH SOME QUESTION AS TO ITS PERSISTENCE OR RELOADING
BY THE START OF NEXT WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
GUIDANCE SOLUTIONS SEEM REASONABLY WELL CLUSTERED FOR THE MAIN
THEMES OF THE MID-LARGE SCALE PATTERN, BUT CONTINUE TO EXHIBIT
MORE NUMEROUS SMALLER-MID SCALE EMBEDDED SYSTEM DIFFERENCES OVER
TIME. A COMPOSITE BLEND OF LATEST GFS/ECMWF/UKMET/CANADIAN SEEMS
TO PROVIDE A GOOD SUMMERTIME DEPICTION OF THE PATTERN AND MAIN
WEATHER FOCUSING SYSTEMS FOR LATER THIS WEEK INTO SATURDAY SEEMS
OVERALL CONSISTENT WITH WPC PRODUCT CONTINUITY AND THE NATIONAL
BLEND OF MODELS. THIS SOLUTION ALSO HAS GOOD MULTI-MODEL ENSEMBLE
SUPPORT. ADDED SUBSTANTIAL INPUT FROM THE GEFS/ECMWF ENSEMBLE
MEANS ALONG WITH THE GENERALLY COMPATIBLE GFS/ECMWF BY DAYS 6/7
(SUNDAY/NEXT MONDAY) FOR A BIT MORE DETAIL, ALBEIT AMID GROWING
MODEL FORECAST SPREAD. THE LAST FEW RUNS OF THE CANADIAN OFFER
LESS THAN STELLAR RUN TO RUN CONTIUITY AT THESE LONGER TIME
FRAMES, ESPECIALLY WITHIN NORTHERN STREAM FLOW. THIS GENERAL PLAN
TENDS TO SMOOTH DETAIL CONSISTENT WITH INDIVIDUAL SYSTEM
PREDICTABILITY THROUGH MEDIUM RANGE TIME SCALES. OVERALL,
PREDICTABILITY SEEMS NEAR AVERAGE FOR A EARLY WARM SEASON PATTERN.
..WEATHER/HAZARDS HIGHLIGHTS
THE WAVY COLD FRONT PROGRESSING EASTWARD FROM THE GREAT LAKES
THROUGH SOUTHERN PLAINS THURSDAY ONWARD WILL LIKELY PRODUCE
MULTIPLE EPISODES OF SHOWERS AND THUNDERSTORMS, WITH SOME LOCALLY
HEAVY. THE DAYS 4-5 EXCESSIVE RAINFALL OUTLOOKS COVERING THE
THURSDAY THROUGH FRIDAY NIGHT TIME FRAME DEPICT A BROAD MARGINAL
RISK AREA WITH THIS ACTIVITY, FROM THE OHIO VALLEY SOUTH-SOUTHWEST
TO THE GULF COAST (DAY 4) AND FROM THE NORTHEAST INTO THE
SOUTHEAST (DAY 5). THERE IS STILL NOT SUFFICIENT AGREEMENT FOR
LOCATION AND INTENSITY OF RAINFALL TO MERIT ANY EMBEDDED SLIGHT
RISK AREAS AT THIS TIME, BUT SHORTER-TERM GUIDANCE MAY EVENTUALLY
RESOLVE BETTER DEFINED AREAS OF FOCUS. DAY 4 CONTINUES TO DEPICT
A MARGINAL RISK AREA OVER PARTS OF THE CAROLINAS/EASTERN GEORGIA
WITH LINGERING MOISTURE AND INSTABILITY ALONG/SOUTH OF A STALLED
FRONT. MEANWHILE THE COMBINATION OF A STALLED HIGH
PLAINS/SOUTHERN PLAINS FRONT EVENTUALLY RETURNING AS A WARM FRONT
ALONG WITH PROGRESSIVE WEAK SHORTWAVES ALOFT WILL FAVOR A
MULTI-DAY PATTERN OF CENTRAL U.S. CONVECTIVE SYSTEMS WHOSE FOCUS
SHOULD DRIFT EASTWARD WITH TIME. THE DAY 4 OUTLOOK COVERING
THURSDAY-THURSDAY NIGHT INTRODUCED A SLIGHT RISK AREA CENTERED
OVER/NEAR THE WESTERN TWO-THIRDS OF KANSAS, REFLECTING THE BEST
OVERLAP OF GUIDANCE SIGNALS. THE DAY 5 OUTLOOK WILL DEPICT A
BROAD MARGINAL RISK AREA AS THERE IS A REASONABLE SIGNAL FOR MORE
LOCALLY HEAVY CONVECTION BUT POOR AGREEMENT FOR LOCATION. IT
APPEARS LIKELY THAT EVENTUAL GUIDANCE CLUSTERING WOULD SUPPORT ONE
OR MORE EMBEDDED SLIGHT RISK AREAS AT SOME POINT. BEYOND FRIDAY
NIGHT, THIS CENTRAL U.S. CONVECTION SHOULD CONTINUE THROUGH THE
EAST-CENTRAL PLAINS AND INTO THE MISSISSIPPI VALLEY WHILE ANOTHER
FRONT APPROACHING FROM THE NORTH/WEST MAY ALSO PRODUCE SOME
SHOWERS/THUNDERSTORMS. AREAS ALONG THE EAST COAST SHOULD ALSO
CONTINUE TO SEE EPISODES OF SHOWERS/STORMS AT LEAST INTO THE
WEEKEND. THE LATEST VERSION OF ALL THESE ERO PRODUCTS ONLY TEND TO
SLIGHTLY DECREASE AREAL COVERAGE OF THE PRIOR THREAT AREAS AS
GUIDANCE SIGNALS/PREDICTABILITY BECOMES STEADILY MORE FOCUSED OVER
TIME.
THE HIGHEST HEAT INDEX VALUES ACROSS THE SOUTHERN TIER DURING THE
PERIOD SHOULD BE FOCUSED OVER SOUTHERN/EASTERN TEXAS WITH MAXIMUM
DAILY VALUES LIKELY REACHING 110F OR HIGHER, WITH SLIGHTLY LESS
EXTREME VALUES EXTENDING OVER OTHER PARTS OF TEXAS INTO THE
CENTRAL GULF COAST REGION. THE FAR SOUTHEAST/FLORIDA MAY SEE SOME
HEAT INDEX VALUES REACH AS HIGH AS 105-110F OR SO. MEANWHILE THE
UPPER RIDGE OVER THE SOUTHERN ROCKIES/HIGH PLAINS WILL KEEP THAT
REGION HOT THROUGH THE PERIOD, WITH SOME EXPANSION OF HIGHS 5-15F
ABOVE NORMAL BY SATURDAY-MONDAY AS THE UPPER RIDGE STRENGTHENS A
BIT. PACIFIC NORTHWEST HIGHS OF 10-15F ABOVE NORMAL ON THURSDAY
WILL LIKELY MODERATE THEREAFTER AS THE UPPER TROUGH DEVELOPS NEAR
THE COAST. MULTIPLE DAYS OF UPSLOPE FLOW OVER THE
NORTHERN-CENTRAL HIGH PLAINS SHOULD SUPPORT BELOW NORMAL HIGH
TEMPERATURES, WITH COOLEST READINGS UP TO 10-15F BELOW NORMAL ON
THURSDAY. THE NORTHEAST WILL SEE VERY WARM TO HOT TEMPERATURES OF
5-15F ABOVE NORMAL LATE THIS WEEK, ERODING FROM THE WEST AS THE
COLD FRONT APPROACHES. MUCH OF THE EASTERN U.S. SHOULD SEE NEAR
TO SLIGHTLY BELOW NORMAL TEMPERATURES AFTER FRONTAL PASSAGE.
SCHICHTEL/RAUSCH
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
HAZARDS:
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS AND THE
SOUTHERN PLAINS, THU, JUL 6.
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE
MISSISSIPPI VALLEY, THE LOWER
MISSISSIPPI VALLEY, AND THE SOUTHERN PLAINS, FRI-SAT, JUL 7-JUL 8.
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE
CENTRAL PLAINS, THE SOUTHERN PLAINS,
AND THE NORTHERN PLAINS, THU, JUL 6.
- FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHERN PLAINS.
- HAZARDOUS HEAT ACROSS PORTIONS OF CALIFORNIA AND THE SOUTHWEST,
THU-MON, JUL 6-JUL 10.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE SOUTHERN ROCKIES, THE
SOUTHEAST, THE LOWER MISSISSIPPI
VALLEY, THE SOUTHERN PLAINS, AND THE SOUTHWEST, SAT-MON, JUL 8-JUL
10.
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND
KEY MESSAGES ARE AT:
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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