029
FXUS02 KWBC 281901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT FRI JUL 28 2023
VALID 12Z MON JUL 31 2023 - 12Z FRI AUG 04 2023
...HOT TEMPERATURES AND HIGH HEAT INDICES ARE LIKELY ACROSS THE
SOUTH-CENTRAL PLAINS AND MISSISSIPPI VALLEY INTO THE SOUTHEAST
NEXT WEEK...
..OVERVIEW
IT REMAINS EVIDENT THAT THE PERSISTENT 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
MODELS AND ENSEMBLE AGREE THAT AS THE UPPER HIGH SLIDES EASTWARD
INTO THE MID-SECTION OF THE COUNTRY, A DEEP SOUTHERLY FLOW FROM
THE SUBTROPICS WILL BRING MONSOONAL MOISTURE INTO AND ACROSS THE
WESTERN U.S. EARLY TO MIDWEEK NEXT WEEK. HOWEVER, THERE ARE
NOTABLE DIFFERENCES IN HOW MUCH MOISTURE WILL BE PRECIPITATED AND
HOW FAR NORTH THE MOISTURE WILL GET. THE ECMWF IS OVERALL THE
DRIEST AND DOES NOT BRING THE MOISTURE AS FAR NORTH AS THE GFS,
WHICH IS ALSO THE WETTEST. THE CMC IS IN BETWEEN THESE TWO
EXTREMES.
BY THE END OF NEXT WEEK, THERE IS GOOD MODEL INDICATIONS OF A LOW
PRESSURE SYSTEM TO TRACK EASTWARD INTO QUEBEC PROVINCE OF CANADA
WITH A COLD FRONT TRAILING BACK INTO THE CENTRAL PLAINS. THERE
APPEARS A CONSISTENT MODEL AGREEMENT FOR AN AREA OF RAINFALL WITH
POSSIBLY LOCALLY HEAVY RAIN FROM NORTHERN 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. MEANWHILE OVER THE NORTHEAST, THERE IS ALSO GOOD MODEL
AGREEMENT ON MODERATE TO HEAVY RAINFALL LATE NEXT WEEK AS A WARM
FRONT LIFTS ATLANTIC MOISTURE INTO THE REGION AHEAD OF THE LOW
PRESSURE SYSTEM MOVING INTO QUEBEC, CANADA.
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
COMPOSITE BLEND OF REASONABLY CLUSTERED MID-LARGER SCALE GUIDANCE
FROM THE 06 UTC GFS/GEFS, 00 UTC ECMWF/EC MEAN, AND 00 UTC
CANADIAN/CMC MEAN, WHICH APPEARS GENERALLY COMPATIBLE WITH THE
NATIONAL BLEND OF MODELS. THIS SOLUTION MAINTAINS DECENT PRODUCT
CONTINUITY IN A PATTERN WITH NEAR TO ABOVE AVERAGE OVERALL
PREDICTABILITY. WHILE THE LARGER SCALE FLOW/FEATURE/GUIDANCE
SIGNAL FOR THE CONVECTIVE PATTERN REMAINS DECENT FOR MID-SUMMER,
THERE IS, AS USUAL, LINGERING UNCERTAINTIES THROUGH THESE MEDIUM
RANGE TIME SCALES WITH THE MORE LOCAL FOCUS OF THUNDERSTORMS AND
ASSOCIATED HEAVY DOWNPOURS.
..WEATHER/HAZARDS HIGHLIGHTS
SHORTWAVE ENERGY IN NORTHWEST FLOW ALOFT FROM THE NORTH-CENTRAL
U.S. TO THE EASTERN U.S. WILL CARRY SHOWERS AND THUNDERSTORMS
EARLY TO MID-NEXT WEEK. 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 AND MOISTURE INCREASES. 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. THERE IS ALSO A NOTABLE TREND OF QPF BECOMING MORE
WIDESPREAD AND LOCALLY HEAVIER AS THE WEEK PROGRESSES, AND
MARGINAL RISKS ARE IN PLACE AND BECOME BROADER WITH TIME. THE
LATEST RISK AREAS ATTEMPT TO REFLECT CHANNELS WITH BEST POTENTIAL
MOISTURE AND INSTABILITY.
BY EARLY NEXT WEEK, THE PERSISTENT UPPER HIGH THAT HAS BEEN
CENTERED OVER THE SOUTHWEST/SOUTH-CENTRAL U.S. WILL START DRIFTING
EASTWARD, 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. MEANWHILE WITH THE CORE OF THE UPPER
HIGH/RIDGE TRACKING EAST, TEMPERATURES ARE LIKELY TO INCREASE TO
ABOVE NORMAL. THE MOST PERSISTENT/GREATEST ANOMALIES SHOULD BE IN
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
POSSIBLE IN THESE REGIONS.
KONG/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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