584
FXUS02 KWBC 231932
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
331 PM EDT FRI JUN 23 2023
VALID 12Z MON JUN 26 2023 - 12Z FRI JUN 30 2023
...PROLONGED HEAT WAVE CONTINUES ACROSS TEXAS AND SOUTHEASTERN NEW
MEXICO AND WILL EXPAND NORTHEAST NEXT WEEK...
..OVERVIEW
LITTLE CHANGE TO THE UPPER PATTERN IS FORECAST DURING THE MEDIUM
RANGE PERIOD. A STRONG RIDGE WILL PERSIST OVER THE SOUTH-CENTRAL
U.S. WHILE MEAN UPPER LOW/TROUGHING REMAINS IN PLACE OVER THE EAST
AND WEST COASTS. THE RIDGE IS RESPONSIBLE FOR EXCESSIVE HEAT IN
THE SOUTHERN PLAINS, AND HEAT WILL EXPAND NORTH AND EAST INTO
PARTS OF THE LOWER AND MIDDLE MISSISSIPPI VALLEY AND CENTRAL
PLAINS NEXT WEEK. SHOWERS AND THUNDERSTORMS ARE EXPECTED TO IMPACT
THE EASTERN THIRD OF THE COUNTRY AND THE NORTH-CENTRAL U.S.
THROUGH THE PERIOD.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODEL SOLUTIONS ARE IN GOOD AGREEMENT FOR THE THE FIRST HALF OF
THE PERIOD, AFTER WHICH SOLUTIONS BEGIN TO DIVERGE. A GENERAL
DETERMINISTIC MODEL BLEND WAS USED FOR DAYS 3 AND 4, THEN ENSEMBLE
GUIDANCE WAS INTRODUCED TO THE BLEND FOR DAYS 5, 6, AND 7. THE
MAIN DIFFERENCES BETWEEN THE SOLUTIONS WERE ASSOCIATED WITH A
SHORTWAVE TROUGH THAT IS FORECAST TO MOVE THROUGH THE WESTERN
TROUGH, ROUND THE TOP OF THE RIDGE, THEN DIVE SOUTHEAST ACROSS THE
NORTHERN PLAINS AND UPPER MIDWEST. UNCERTAINTY IS QUITE LARGE ON
THE STRENGTH AND POSITION OF THIS FEATURE, WHICH IN TURNS CREATES
UNCERTAINTY IN THE SENSIBLE WEATHER FORECAST. UNCERTAINTY ALSO
REMAINS ON THE STRENGTH OF THE WESTERN RIDGE IN THE WAKE OF THIS
FEATURE AND HOW THE RIDGE PLACEMENT WILL BE AFFECTED. THE GFS AND
CMC MAINTAIN A STRONGER TROUGH THAT SHIFTS THE CENTER OF THE RIDGE
SLIGHTLY EAST FROM OVER TEXAS TO LOUISIANA. HOWEVER, THE ECMWF
SIGNIFICANTLY WEAKENS THE TROUGH AND KEEPS THE RIDGE POSITION
NEARLY STATIONARY. FOR THIS FORECAST, A BLEND WAS USED TO CREATE A
MIDDLE GROUND SCENARIO.
..WEATHER/HAZARDS HIGHLIGHTS
THE FRONTAL SYSTEM CURRENTLY BRINGING PRECIPITATION TO THE EASTERN
U.S. WILL MOVE OFFSHORE AND DISSIPATE MONDAY MORNING, THEN THE
NEXT SYSTEM WILL FOLLOW HOT ON ITS HEELS. THE SECOND SYSTEM WILL
PUSH ACROSS THE EASTERN U.S. EARLY IN THE WEEK ACCOMPANIED BY
AMPLE MOISTURE THAT WILL SUPPORT WIDESPREAD PRECIPITATION.
MOISTURE WILL FOCUS AHEAD OF AND ALONG THE COLD FRONT AND WRAP
AROUND THE LOW PRESSURE CENTER IN THE GREAT LAKES REGION. SEVERE
WEATHER WILL BE POSSIBLE IN THE WARM SECTOR AND ALONG THE COLD
FRONT, AND THE STORM PREDICTION CENTER HAS HIGHLIGHTED AN AREA OF
POTENTIAL SEVERE WEATHER ON MONDAY FROM THE CHESAPEAKE BAY TO THE
INTERIOR CAROLINAS. LOCALLY HEAVY RAINFALL WILL BE POSSIBLE AS
WELL WITH POTENTIAL TRAINING/REPEAT ACTIVITY ASSOCIATED WITH THIS
SYSTEM. FOR MONDAY, THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL
FOR PARTS OF THE UPPER MIDWEST, NORTHEAST, MID-ATLANTIC, AND
INTERIOR SOUTHEAST. FOR TUESDAY, THERE IS ANOTHER MARGINAL RISK
FOR PARTS OF THE NORTHEAST AND MID-ATLANTIC WHERE HEAVY RAINFALL
POTENTIAL WILL LINGER. EMBEDDED SLIGHT RISK AREAS MAY BE POSSIBLE
FOR THE NORTHEAST AND/OR MID-ATLANTIC IN FUTURE ERO UPDATES WHEN
CONFIDENCE IN THE LOCATION OF HEAVIER RAINFALL TOTALS INCREASES.
FOR NOW, TOO MUCH UNCERTAINTY REMAINS IN THE FORECAST TO HIGHLIGHT
A SPECIFIC AREA. THE SYSTEM WILL SLOW DOWN AS IS APPROACHES THE
EAST COAST, AND PRECIPITATION CHANCES WILL LINGER ALONG THE
EASTERN SEABOARD THROUGH THE END OF THE PERIOD.
IN THE WEST, THE EJECTION OF THE SPLITTING/LEAD UPPER TROUGH
ENERGIES WILL BRING SCATTERED SHOWERS AND STORM CHANCES ACROSS THE
NORTHERN GREAT BASIN AND NORTHWEST EARLY NEXT WEEK. ACTIVITY WILL
INCREASE AND SPREAD DOWNSTREAM TO THE NORTHERN ROCKIES AND
NORTHERN PLAINS, AND HEAVY RAINFALL MAY BE A CONCERN. THERE IS A
MARGINAL RISK OF EXCESSIVE RAINFALL FOR PARTS OF THIS REGION ON
TUESDAY TO ADDRESS POTENTIAL TRAINING/REPEAT CELL RUNOFF CONCERNS.
PRECIPITATION WILL SPREAD INTO THE UPPER MIDWEST AND OHIO AND
TENNESSEE VALLEYS MID-TO-LATE NEXT WEEK AS THE SYSTEM PROGRESSES.
IN TERM OF TEMPERATURES, EXCESSIVE HEAT IS FORECAST TO CONTINUE TO
PLAGUE THE SOUTH-CENTRAL U.S. THROUGH AT LEAST NEXT WEEK WITH A
MID-WEEK EXPANSION NORTH AND EAST INTO THE CENTRAL PLAINS AND
MIDDLE AND LOWER MISSISSIPPI VALLEY. THE HEAT WILL BE OPPRESSIVE
WITH WIDESPREAD HIGH TEMPERATURES EXCEEDING 100 DEGREES AND HEAT
INDICES AS HIGH AS 120 DEGREES. HEAT INDICES MAY EVEN EXCEED 120
DEGREES IN SOME LOCATIONS IN SOUTH TEXAS. SEVERAL TEMPERATURE
RECORDS ARE IN DANGER OF BEING BROKEN DURING THIS SIGNIFICANT HEAT
WAVE. THE DESERT SOUTHWEST WILL ALSO EXPERIENCE TEMPERATURES WELL
OVER 100 DEGREES NEXT WEEK, BUT THAT IS NOT REALLY ANOMALOUS FOR
THIS TIME OF YEAR. ELSEWHERE IN THE COUNTRY, NEAR NORMAL HIGH
TEMPERATURES ARE FORECAST WITH BELOW NORMAL HIGHS LIKELY IN AREAS
OF PRECIPITATION EACH DAY.
DOLAN/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
HAZARDS:
- SEVERE WEATHER ACROSS PORTIONS OF THE SOUTHEAST, THE
MID-ATLANTIC, AND THE CENTRAL APPALACHIANS,
MON, JUN 26.
- FLOODING POSSIBLE ACROSS PORTIONS OF THE CENTRAL PLAINS.
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE CENTRAL
PLAINS.
- FLOODING LIKELY ACROSS PORTIONS OF THE CENTRAL PLAINS, THE
SOUTHEAST, THE NORTHERN PLAINS, AND
THE NORTHERN ROCKIES.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY,
THE SOUTHERN ROCKIES, CALIFORNIA,
THE SOUTHEAST, THE SOUTHERN PLAINS, AND THE SOUTHWEST, MON-FRI,
JUN 26-JUN 30.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE SOUTHERN ROCKIES, THE
LOWER MISSISSIPPI VALLEY, AND THE
SOUTHERN PLAINS, TUE-FRI, JUN 27-JUN 30.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE
MISSISSIPPI VALLEY, THE LOWER
MISSISSIPPI VALLEY, AND THE SOUTHERN PLAINS, WED-THU, JUN 28-JUN
29.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE SOUTHEAST, THE MIDDLE
MISSISSIPPI VALLEY, THE LOWER
MISSISSIPPI VALLEY, AND THE TENNESSEE VALLEY, THU-FRI, JUN 29-JUN
30.
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
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