047
FXUS02 KWBC 081900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SAT JUL 08 2023
VALID 12Z TUE JUL 11 2023 - 12Z SAT JUL 15 2023
...HEAT EXPECTED TO REBUILD FROM THE SOUTHWEST TO THE GULF COAST
NEXT WEEK...
...HEAVY RAIN CONCERNS LIKELY TO FOCUS OVER PARTS OF THE MIDWEST
AND MID-MISSISSIPPI VALLEY...
..OVERVIEW
THE UPPER-LEVEL PATTERN OVER THE CONUS NEXT WEEK REMAINS RATHER
UNCHANGED AS A DEEP UPPER LOW REMAINS ENTRENCHED OVER HUDSON BAY,
AND UPPER RIDGING EXPANDS ACROSS THE SOUTHERN TIER STATES.
MULTIPLE WAVES OF ENERGY WILL ROTATE AROUND THE SOUTHERN PERIPHERY
OF THE LOW AND DRIVE ROUNDS OF SHOWERS AND STORMS THAT COULD
RESULT IN AREAS OF HEAVY RAINFALL AND FLOODING ACROSS THE MIDWEST
AND NORTHEAST. UNDERNEATH THE RIDGE, HAZARDOUS HEAT WILL BUILD
OVER THE SOUTHWEST AND TEXAS AND EXPAND EASTWARD TO THE GULF COAST
REGION THROUGH NEXT WEEK. HAZARDOUS HEAT WILL LIKELY PERSIST INTO
THE WEEK TWO TIME FRAME AS WELL, PER THE LATEST FORECAST FROM THE
CLIMATE PREDICTION CENTER.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
GUIDANCE IS IN REASONABLE AGREEMENT REGARDING THE BROAD SCALE
EVOLUTION OF THE SYNOPTIC PATTERN DURING THE MEDIUM RANGE PERIOD.
A GENERAL MODEL BLEND CONSISTING OF THE 00Z EC/CMC/UKMET AND 06Z
GFS WAS USED THROUGH DAY 4. THE GFS WAS GIVEN LESS WEIGHTING ON
DAY 3 DUE TO TO AN INCONSISTENCY BETWEEN IT AND THE 00Z GUIDANCE
WITH RESPECT TO THE SHORTWAVE TROUGH MOVING THROUGH THE NORTHEAST.
THE 00Z ECE AND 06Z GEFS WERE INTRODUCED ON DAY 5 WHILE THE
CANADIAN AND UKMET WERE REMOVED DUE TO FAILURE TO IDENTIFY A
SOUTHERN STREAM RIDGE AND OVER AMPLIFICATION OF SHORTWAVE ENERGY
OVER THE GREAT LAKES, RESPECTIVELY. THE 00Z CMCE WAS INTRODUCED ON
DAY 6 AND THE ENSEMBLE GUIDANCE MADE UP MUCH OF THE BLEND THROUGH
THE REMAINDER OF THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
A FRONT SETTLING FROM THE CENTRAL PLAINS INTO THE MIDWEST SHOULD
PROVIDE THE BEST FOCUS FOR DAILY ROUNDS OF SHOWERS AND STORMS
THROUGH MUCH OF THE MEDIUM RANGE PERIOD, WITH AREAS OF HEAVY
RAINFALL INCREASINGLY LIKELY IN SOME AREAS. FOR THE DAY 4
EXCESSIVE RAINFALL OUTLOOK, THERE WAS ENOUGH MODEL AGREEMENT FOR
THE ADDITION OF A SLIGHT RISK AREA FROM EASTERN SOUTH DAKOTA INTO
FAR NORTHWEST IOWA GIVEN HIGH MOISTURE AND INSTABILITY AND THAT
SOME OF THIS REGION HAS SEEN ABOVE NORMAL RAINFALL OVER THE PAST
WEEK OR TWO. A MARGINAL RISK SURROUNDS THIS AREA INTO THE UPPER
MIDWEST AS WELL AS BACK INTO THE NORTHERN HIGH PLAINS. BY DAY
5/WEDNESDAY, THE HEAVY RAINFALL AXIS SHOULD SHIFT EAST WITH THE
BOUNDARY FROM THE MID-MISSISSIPPI VALLEY INTO THE UPPER GREAT
LAKES. IT SEEMS LIKELY THERE WILL BE HEAVY TO EXCESSIVE RAINFALL
SOMEWHERE WITHIN THIS REGION, BUT THERE IS STILL A CONSIDERABLE
AMOUNT OF UNCERTAINTY ON WHERE. FOR THIS REASON, THE DAY 5 ERO AT
THIS POINT ONLY DEPICTS A BROAD MARGINAL RISK, BUT FUTURE UPGRADES
TO A SLIGHT RISK ARE POSSIBLE AS MODELS COME INTO BETTER FOCUS.
ELSEWHERE, SHOWERS AND STORMS WILL CONTINUE ACROSS PARTS OF THE
SOUTHEAST AND CENTRAL GULF COAST INTO WEDNESDAY NEAR A LINGERING
FRONTAL BOUNDARY. WEAK LOW PRESSURE LIFTING ALONG THE NORTHEAST
COAST WILL ALSO CONTINUE TO BRING WRAP AROUND SHOWERS ACROSS PARTS
OF THE NORTHEAST. A SLIGHT RISK AREA WAS ADDED WITH THIS
AFTERNOON'S UPDATE OVER PORTIONS OF NORTHERN/CENTRAL MAINE ON DAY
4 AS WELL, DUE TO SENSITIVE SURFACES CAUSED BY THE PREVIOUS DAY'S
HEAVY RAINFALL THREAT. ADDITIONAL RAINFALL LOOKS TO IMPACT THIS
REGION AND SOUTH INTO THE MID-ATLANTIC LATER IN THE WEEK AS WELL.
HAZARDOUS HEAT IS EXPECTED TO RETURN AND EXPAND ACROSS THE
SOUTHERN TIER THROUGH AT LEAST NEXT WEEK (AND LIKELY EXTENDING
BEYOND PER LATEST CPC FORECASTS) AS THE UPPER RIDGE STRENGTHENS
OVER THE SOUTH. THE GREATEST HIGH TEMPERATURE ANOMALIES (OF 10-15F
ABOVE AVERAGE) ARE FORECAST UNDER THE CENTER OF THE UPPER HIGH
OVER WEST TEXAS AND NEW MEXICO, WITH A BROADENING AREA OF ABOVE
NORMAL TEMPERATURES ELSEWHERE. INCREASING HUMIDITY WILL RESULT IN
OPPRESSIVE HEAT INDICES POSSIBLY EXCEEDING 110F FROM THE EASTERN
HALF OF TEXAS TO THE GULF COAST, AND HAZARDOUSLY HIGH HEAT INDICES
COULD EXPAND TO THE FLORIDA PENINSULA AS WELL LATE NEXT WEEK.
HUMIDITY WILL BE NATURALLY LOWER BACK INTO THE SOUTHWEST, THOUGH
AIR TEMPERATURES COULD STILL REACH 110-115F IN SOME PLACES. LITTLE
RELIEF IS EXPECTED IN THESE AREAS OVERNIGHT WITH ANOMALOUSLY WARM
NIGHTTIME LOWS IN THE FORECAST. ABOVE NORMAL TEMPERATURES WILL
ALSO EXPAND INTO THE WEST COAST STATES LATE NEXT WEEK. ELSEWHERE,
A COLD FRONT DROPPING SOUTH FROM CANADA SHOULD BRING TEMPERATURES
DOWN TO 5-10F BELOW AVERAGE OVER PARTS OF THE NORTHERN AND CENTRAL
PLAINS, WHILE THE SOUTHEAST AND UP THE EAST COAST SHOULD STAY NEAR
NORMAL FOR THIS TIME OF THE YEAR.
KEBEDE/SANTORELLI
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST, 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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