364
FXUS02 KWBC 290649
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
248 AM EDT SAT JUL 29 2023
VALID 12Z TUE AUG 01 2023 - 12Z SAT AUG 05 2023
...HOT TEMPERATURES AND HIGH HEAT INDICES ARE LIKELY ACROSS THE
SOUTH-CENTRAL PLAINS AND MISSISSIPPI VALLEY INTO THE SOUTHEAST
NEXT WEEK...
..OVERVIEW
THE UPPER HIGH THAT HAS BEEN ANCHORING OVER THE
SOUTHWEST/SOUTH-CENTRAL U.S. FOR WEEKS NOW IS FINALLY FORECAST TO
DRIFT EASTWARD NEXT WEEK, FINALLY BRINGING TEMPERATURES IN THE
DESERT SOUTHWEST CLOSER TO NORMAL (THOUGH STILL HOT). RIDGING
STRETCHING NORTH FROM THE UPPER HIGH WILL ALSO PROMOTE ABOVE
NORMAL TEMPERATURES ACROSS THE CENTRAL PLAINS TO MID-MISSISSIPPI
VALLEY WITH THE SOUTHEAST ALSO LIKELY TO WARM ABOVE NORMAL, WITH
HIGH HEAT INDICES. A "RING OF FIRE" TYPE OF PATTERN IS LIKELY IN
THE PRECIPITATION FORECAST, AS MONSOONAL MOISTURE LEADS TO
DIURNALLY DRIVEN CONVECTION IN THE FOUR CORNERS STATES AND
VICINITY, SHORTWAVES PUSH THROUGH NORTHWEST FLOW AND SPARK STRONG
TO SEVERE THUNDERSTORMS IN THE NORTH-CENTRAL U.S., AND A
WELL-DEFINED COLD FRONT PRESSING UNUSUALLY FAR SOUTH INTO THE
MID-SECTION OF THE COUNTRY WITH A RISK OF HEAVY RAINFALL OVER THE
NORTHERN ROCKIES TO THE CENTRAL HIGH PLAINS MIDWEEK, AND PERHAPS
ACROSS THE NORTHEAST LATE NEXT WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
COMPOSITE BLEND OF BEST CLUSTERED MID-LARGER SCALE GUIDANCE FROM
THE 18 UTC GFS/GEFS, 12 UTC ECMWF/ECMWF ENSEMBLE MEAN AND
GENERALLY COMPATIBLE 01 UTC NATIONAL BLEND OF MODELS. THE 12 UTC
CANADIAN/UKMET SOLUTIONS ARE ALSO IN LINE EARLY-MID NEXT WEEK
BEFORE DIVERGING WITH SEEMINGLY LESS LIKELY BUT PLAUSIBLE TRENDS.
THIS FORECAST PLAN MAINTAINS GOOD WPC PRODUCT CONTINUITY IN A
PATTERN WITH NEAR TO ABOVE AVERAGE OVERALL PREDICTABILITY. A
COMPOSITE OF THE LATEST 00 UTC GUIDANCE OVERALL REMAINS IN LINE.
WHILE THE LARGER SCALE FLOW SIGNAL FOR THE CONVECTIVE PATTERN
REMAINS DECENT FOR MID-SUMMER, THERE REMAINS LINGERING
UNCERTAINTIES THROUGH THESE MEDIUM RANGE TIME SCALES WITH THE MORE
LOCAL FOCUS OF THUNDERSTORMS AND ASSOCIATED HEAVY DOWNPOURS.
..WEATHER/HAZARDS HIGHLIGHTS
A LEAD COLD FRONT SHOULD PUSH UNSEASONABLY FAR SOUTH TO OFFER A
MORE DEFINED THAN NORMAL SUMMERTIME CONVECTIVE FOCUS OVER THE
SOUTHEAST. A MARGINAL RISK HAS BEEN DRAWN UP IN THE DAY 4/5 EROS
FOR PORTIONS OF GEORGIA AND FLORIDA AS THERE COULD BE HIGH RAIN
RATES POSSIBLY CAUSING EXCESSIVE RAINFALL GIVEN STALLING MOISTURE
POOLING/INSTABILITY FOCUS AND UPPER SUPPORT. THE COMBINATION OF AN
ADDITIONAL FRONTAL PASSAGE AS WELL AS THE LINGERING/WAVY SOUTHERN
FRONT IS THEN LIKELY TO FAVOR PERIODIC ACTIVITY THROUGH MID-LATER
NEXT WEEK.
MEANWHILE, THE NORTH-CENTRAL U.S. CAN ALSO EXPECT SCATTERED STORMS
AS SHORTWAVES TRACK THROUGH THE REGION. A HEAVY RAIN/FLASH
FLOODING THREAT WILL LIKELY BE TIED TO THE POTENTIAL FOR ORGANIZED
CONVECTIVE SYSTEMS IN THE NORTHWESTERLY FLOW. DAY TO DAY POSITIONS
OF HEAVY RAIN AND MCSS ARE UNCERTAIN AT THIS POINT, BUT THE
PATTERN IS THERE. MARGINAL RISKS HAVE BEEN INCLUDED ON BOTH DAYS 4
AND 5 TO COVER THIS POTENTIAL, WITH EVENTUAL MORE CONCENTRATED
SLIGHT RISK AREAS POSSIBLE. THE FOUR CORNERS STATES AND INTO
WYOMING ARE LIKELY TO SEE DIURNALLY DRIVEN CONVECTION EACH DAY AS
MONSOONAL MOISTURE COMES IN. AS THE UPPER HIGH SHIFTS EASTWARD
WITH TIME, THIS MAY INCREASE MOIST SOUTHERLY FLOW AND ALLOW FOR
ADDITIONAL SHORTWAVE ENERGY TO WORK INTO THE REGION. THE RISK
AREAS ATTEMPT TO REFLECT CHANNELS WITH BEST MOISTURE/INSTABILITY.
BY THE END OF NEXT WEEK, AN ORGANIZED LOW PRESSURE SYSTEM WILL
TRACK EASTWARD ACROSS CANADA WITH A COLD FRONT TRAILING BACK INTO
THE CENTRAL PLAINS. SUSPECT AN AREA OF RAINFALL WITH POSSIBLY
LOCALLY HEAVY RAIN MAY FOCUS FROM NORTH-CENTRAL ROCKIES TO THE
CENTRAL HIGH PLAINS WHERE THE MONSOONAL MOISTURE APPEARS TO
INTERACT WITH THE TRAILING FRONT AND WITH ANOTHER FRONTAL WAVE
OVER THE CENTRAL PLAINS. LEAD FLOW SHOULD ALSO FUEL AN EXPANDING
AREA OF PRECIPITATION FROM THE OHIO VALLEY THROUGH THE
APPALACHIANS/MID-ATLANTIC AND THE PREVIOUSLY SOGGY NORTHEAST.
THE HOT UPPER HIGH THAT HAS BEEN CENTERED OVER THE
SOUTHWEST/SOUTH-CENTRAL U.S. WILL RE-POSITION EASTWARD INTO
EARLY-MID NEXT WEEK, ALLOWING FOR HIGH TEMPERATURES IN THE DESERT
SOUTHWEST TO FINALLY EASE TO NEAR NORMAL. HIGHS SHOULD STILL BE
OVER 100F IN MANY AREAS BUT AT LEAST THERE SHOULD BE MINOR RELIEF
COMPARED TO THE PAST FEW WEEKS. THE MOST PERSISTENT/GREATEST
ANOMALIES SHOULD MOVE FROM THE CENTRAL PLAINS TO THE
MID-MISSISSIPPI VALLEY, WHERE ABOVE NORMAL TEMPERATURES BY 5 TO 15
DEGREES ARE LIKELY AS ACTUAL TEMPERATURES NEAR OR EXCEED 100F. THE
SOUTHERN PLAINS TO LOWER MISSISSIPPI VALLEY AND SOUTHEAST MAY SEE
SLIGHTLY LOWER ANOMALIES OF 5-10F ABOVE NORMAL, BUT THE HEAT
COMBINED WITH HIGH DEWPOINTS WILL LEAD TO HEAT INDICES SOARING
ABOVE 105F, EVEN ABOVE 110-115F IN SOME AREAS. RECORD HOT HIGHS
AND WARM MINIMUM TEMPERATURES ARE WIDELY POSSIBLE IN THESE REGIONS
NEXT WEEK. THERE IS HOPE FOR SOME RELIEF TO SLOWLY WORK INTO THIS
HEAT DOME FROM THE NORTH THROUGH LATER NEXT WEEK WITH POSSIBLE
COLD FRONTAL APPROACH.
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
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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