632
FXUS02 KWBC 071941
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
340 PM EDT FRI JUL 07 2023
VALID 12Z MON JUL 10 2023 - 12Z FRI JUL 14 2023
...HEAT EXPECTED TO REBUILD FROM THE SOUTHWEST TO THE GULF COAST
NEXT WEEK...
...HEAVY RAIN CONCERNS LIKELY TO FOCUS OVER PORTIONS OF THE GULF
COAST AND THE NORTHEAST ON MONDAY, AND BACK INTO THE MIDWEST AND
MID-MISSISSIPPI VALLEY BY MID-WEEK...
..OVERVIEW
LITTLE CHANGE IS ANTICIPATED IN THE UPPER LEVEL PATTERN NEXT WEEK,
WHICH WILL FEATURE A DEEP UPPER LEVEL LOW ANCHORED NEAR THE HUDSON
BAY AND AN UPPER LEVEL RIDGE OVER THE SOUTHWEST. MULTIPLE WAVES OF
ENERGY WILL ROTATE AROUND THE LOW ACROSS THE MIDWEST AND NORTHEAST
AND DRIVE ROUNDS OF SHOWERS AND STORMS THAT COULD RESULT HEAVY
RAINFALL AND FLOODING. UNDERNEATH THE RIDGE, HAZARDOUS HEAT WILL
BUILD OVER THE SOUTHWEST AND TEXAS AND EXPAND EASTWARDS TO THE
GULF COAST REGION THROUGH NEXT WEEK. HAZARDOUS HEAT WILL LIKELY
PERSIST INTO THE WEEK TWO TIMEFRAME AS WELL PER THE LATEST
FORECAST FROM THE CLIMATE PREDICTION CENTER.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODELS SHOW VERY GOOD AGREEMENT ON THE OVERALL LARGE SCALE PATTERN
ACROSS THE CONUS THROUGH NEXT WEEK. AS IS TYPICAL FOR THESE TIME
FRAMES, THERE REMAINS PLENTY OF UNCERTAINTIES IN THE DETAILS
REGARDING A COUPLE OF SHORTWAVES MOVING THROUGH MEAN TROUGHING
FROM THE MIDWEST INTO THE NORTHEAST, WHICH HAS IMPLICATIONS FOR
SURFACE FEATURES AND SENSIBLE WEATHER. THIS IS RELATED TO RATHER
SIGNIFICANT UNCERTAINTIES IN THE PLACEMENT OF THE PARENT UPPER LOW
NEAR HUDSON BAY LATER NEXT WEEK. THE UKMET IS THE FURTHEST NORTH
WITH THE LOW, THE CMC IS THE FURTHEST SOUTH, AND THE GFS AND ECMWF
LIE IN BETWEEN THE OTHER TWO. THE ENSEMBLE MEANS SUPPORT A
SOLUTION CLOSE TO THE GFS AND ECMWF, SO THEY WERE FAVORED IN THE
MODEL BLEND FOR THIS AFTERNOON'S FORECAST. A BLEND OF
DETERMINISTIC SOLUTIONS WAS USED FOR THE FIRST HALF OF THE
FORECAST PERIOD, AND ENSEMBLE MEANS WERE INCLUDED IN THE BLEND FOR
THE SECOND HALF OF THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
18Z UPDATE: THE DAY 4 EXCESSIVE RAINFALL OUTLOOK REMAINS MOSTLY
UNCHANGED IN THE SOUTH AND CENTRAL U.S., BUT AN ADDITIONAL SLIGHT
RISK AREA WAS INTRODUCED IN THE NORTHEAST OVER NORTHEASTERN NEW
YORK AND WESTERN NEW ENGLAND. A SLOW MOVING LOW PRESSURE SYSTEM
WILL PRODUCE A PROLONGED PERIOD OF RAINFALL OVER THIS AREA THIS
WEEKEND INTO EARLY NEXT WEEK, AND REPEATED ROUNDS OF HEAVY
RAINFALL ARE FORECAST EACH DAY. THE HIGHEST RAINFALL AMOUNTS ARE
FORECAST OVER THE TERRAIN WHERE UP-SLOPING WILL CONTRIBUTE TO
HEAVY RAINFALL THAT COULD RESULT IN SCATTERED INSTANCES OF FLASH
FLOODING. THE DAY 5 EXCESSIVE RAINFALL OUTLOOK REMAINS VERY
SIMILAR TO THE PREVIOUS FORECAST WITH ONLY SLIGHT SOUTHWARD AND
EASTWARD ADJUSTMENTS TO THE MARGINAL RISK AREAS OVER THE NORTHEAST
AND NORTH-CENTRAL U.S. TO ACCOUNT FOR TRENDS IN MODEL GUIDANCE.
LOOKING AHEAD AT LATE NEXT WEEK, THE HEAVIEST RAINFALL WILL LIKELY
FOCUS ALONG A FRONTAL BOUNDARY MEANDERING OVER THE MID-MISSISSIPPI
VALLEY.
A SURFACE FRONT DRAPED ACROSS THE SOUTHERN U.S. SHOULD HELP FOCUS
AREAS OF HEAVY RAINFALL EARLY IN THE WEEK, PARTICULARLY NEAR THE
CENTRAL GULF COAST, WHERE A SLIGHT RISK IS HIGHLIGHTED ON THE DAY
4/MONDAY EXCESSIVE RAINFALL OUTLOOK ALONG WITH A MARGINAL RISK ON
DAY 5/TUESDAY. GUIDANCE CONTINUES TO TREND SOUTH WITH THE HEAVIEST
RAINFALL AND THIS IS REFLECTED IN THIS LATEST UPDATE. THERE ARE
ALSO SIGNALS FOR A POSSIBLE BAND OF CONVECTION EXTENDING BACK
NORTHWEST INTO THE CENTRAL PLAINS WITHIN AN AXIS OF FAVORABLE
MOISTURE AND INSTABILITY AND TO THE NORTH OF THE WESTERN EDGE OF
THE FRONT WHICH SHOULD LIFT BACK NORTH AS A WARM FRONT. MAINTAINED
THE MARGINAL RISK FOR THIS REGION ON DAY 4 AS THERE IS STILL A
FAIR BIT OF UNCERTAINTY IN THE SPECIFICS OF WHERE THE BEST HEAVY
RAINFALL WILL SET UP. A WEAK SURFACE LOW LIFTING ALONG THE
NORTHEAST COAST SHOULD FOCUS RAINFALL TO THE NORTH OF IT ACROSS
NORTHERN NEW ENGLAND/MAINE AND A MARGINAL RISK WAS MAINTAINED ON
MONDAY'S OUTLOOK AND CONTINUED INTO THE TUESDAY AS WELL.
ELSEWHERE, A COLD FRONT SAGGING SOUTH ACROSS THE NORTHERN
U.S./MIDWEST SHOULD ALSO FOCUS SHOWERS AND STORMS TUESDAY AND
BEYOND. THE NEW DAY 5/TUESDAY EXCESSIVE RAINFALL OUTLOOK
HIGHLIGHTS A MARGINAL RISK ALONG THIS BOUNDARY, WITH POTENTIAL FOR
AN UPGRADE TO A SLIGHT EVENTUALLY ESPECIALLY IF HEAVY RAIN FALLS
WITHIN A REGION FROM SOUTHEAST NEBRASKA INTO ILLINOIS WHICH HAS
SEEN ABOVE NORMAL PRECIPITATION AS OF LATE. ENOUGH UNCERTAINTY
STILL TO PRECLUDE THAT INCLUSION FOR NOW.
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 SOUTHWEST. 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 THE NORTHERN
TO CENTRAL PLAINS NEXT WEDNESDAY-FRIDAY. THE SOUTHEAST AND UP THE
EAST COAST MAY SEE SLIGHTLY COOLER THAN AVERAGE TEMPERATURES ON
MONDAY, BUT TEMPERATURES WILL MODERATE BACK TO NEAR NORMAL THROUGH
THE REST OF THE WEEK.
DOLAN/SANTORELLI
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 NORTHEAST, MON, JUL 10.
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST AND THE LOWER
MISSISSIPPI VALLEY, MON-TUE, JUL 10-JUL 11.
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS, THE
MIDDLE/LOWER MISSISSIPPI VALLEY, THE OHIO VALLEY, AND THE
TENNESSEE VALLEY, WED-FRI, JUL 12-JUL 14.
- FLOODING POSSIBLE ACROSS PORTIONS OF THE PLAINS.
- HAZARDOUS HEAT ACROSS PORTIONS OF CALIFORNIA, THE SOUTHWEST, THE
SOUTHERN ROCKIES, THE SOUTHERN PLAINS, AND THE LOWER MISSISSIPPI
VALLEY, MON-FRI, JUL 10-JUL 14.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE MIDDLE/LOWER MISSISSIPPI
VALLEY, THE SOUTHEAST, AND THE TENNESSEE VALLEY, WED-FRI, JUL
12-JUL 14.
- HAZARDOUS HEAT ACROSS PORTIONS OF FLORIDA, THU-FRI, JUL 13-JUL
14.
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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