101
FXUS02 KWBC 141904
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT WED JUN 14 2023
VALID 12Z SAT JUN 17 2023 - 12Z WED JUN 21 2023
***EARLY SEASON HEAT WAVE TO PERSIST ACROSS MUCH OF THE
SOUTH-CENTRAL U.S. INTO EARLY NEXT WEEK AND BEYOND***
..SYNOPTIC OVERVIEW
FOR THE BEGINNING OF THE FORECAST PERIOD THIS WEEKEND, A WELL
DEFINED NORTHEASTERN PACIFIC/GULF OF ALASKA TROUGH WITH EMBEDDED
UPPER LOW WILL BUILD SOUTHEASTWARD ACROSS THE WESTERN U.S. AND
SOUTHWESTERN CANADA, WHILE CENTRAL U.S. INTO CANADA RIDGING
EVENTUALLY REBUILDS AFTER INITIAL WESTERN U.S. SHORTWAVE ENERGY
PROGRESSES THROUGH THE PLAINS AND SETTLES INTO THE LONG-TERM
EASTERN U.S. MEAN TROUGH. THE CORE OF THE UPPER RIDGE OVER TEXAS
AND THE WESTERN GULF OF MEXICO WILL PERSIST THROUGH THE FORECAST
PERIOD, MAINTAINING A SOUTH-CENTRAL U.S. HEAT WAVE THAT SHOULD
EXTEND BEYOND NEXT TUESDAY BASED ON CLIMATE PREDICTION CENTER
OUTLOOKS. MEANWHILE, THE PATTERN EVOLUTION SHOULD FAVOR AN AREA
OF ENHANCED RAINFALL FROM THE NORTHERN-CENTRAL PLAINS INTO
SOUTHEAST/MID-ATLANTIC, WITH PORTIONS OF THE DEEP SOUTH LIKELY
HAVING THE HIGHEST TOTALS OVERALL. THE NORTHWESTERN U.S./NORTHERN
ROCKIES SHOULD SEE PRECIPITATION INCREASE EARLY NEXT WEEK AS THE
WESTERN SYSTEM MOVES IN, AND THE INITIAL UPPER TROUGH/LOW OVER THE
NORTHEAST WILL ALSO SUPPORT PERIODS OF RAINFALL THERE.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
LATEST GUIDANCE MAINTAINS THE GENERAL THEME OF GOOD AGREEMENT FOR
THE LARGE SCALE PATTERN EVOLUTION THROUGH THE PERIOD, AND AT LEAST
INTO DAY 6 TUESDAY GUIDANCE HAS IMPROVED ITS CLUSTERING FOR THE
VIGOROUS SYSTEM REACHING THE NORTHWEST. HOWEVER THERE IS
CONTINUED SPREAD FOR SHORTWAVE ENERGY PROGRESSING FROM THE
ROCKIES/PLAINS INTO THE EAST AND SOME DETAIL DIFFERENCES REMAIN
FOR LINGERING NORTHEAST MEAN TROUGHING BEHIND AN UPPER LOW THAT
DEPARTS AFTER THE WEEKEND. IN GENERAL, UKMET RUNS HAVE GENERALLY
COMPARED MOST POORLY TO OTHER GUIDANCE FOR VARIOUS ASPECTS OF THE
EASTERN U.S./WESTERN ATLANTIC FORECAST. AS OF THE 12Z CYCLE THE
MODEL IS NOW GETTING CLOSER TO CONSENSUS FOR THE EASTERN U.S.
ALOFT BUT IS NOW USING LEADING SHORTWAVE ENERGY TO DEVELOP A
TROPICAL-LOOKING WESTERN ATLANTIC SURFACE LOW. BY THE END OF ITS
RUN IT STRAYS SOUTHEASTWARD WITH ITS AXIS OF THE NORTHEAST UPPER
TROUGH. MEANWHILE GFS RUNS CONTINUE TO EXTEND ITS PLAINS/MIDWEST
SHORTWAVE TROUGH FARTHER SOUTHEAST THAN CONSENSUS (INCLUDING THE
GEFS MEAN) FROM SUNDAY ONWARD. THIS RESULTS IN THE ASSOCIATED
SURFACE PATTERN OVER THE EAST BEING MORE SUPPRESSED THAN MOST
OTHER SOLUTIONS FOR A PERIOD OF TIME. GUIDANCE HAS MAINTAINED A
SIGNAL FOR AN EMBEDDED UPPER LOW THAT WOULD MOST LIKELY TRACK
APPROXIMATELY FROM THE MIDDLE MISSISSIPPI VALLEY INTO OHIO
VALLEY/APPALACHIANS DURING MONDAY-WEDNESDAY. THERE ARE TYPICAL
LOW-PREDICTABILITY DETAIL DIFFERENCES FOR HOW ENERGY WITHIN
NORTHEASTERN U.S. TROUGHING WILL LOOK BY LATE IN THE PERIOD.
00Z/06Z GUIDANCE COMPARISONS FAVORED STARTING WITH THE 00Z ECMWF,
A SPLIT OF THE 06Z GFS/GEFS MEAN (TO DOWNPLAY LESS DESIRABLE GFS
SPECIFICS IN THE EAST), AND 00Z CMC FOR ABOUT THE FIRST HALF OF
THE PERIOD AND THEN TRENDING TO A NEARLY EVEN WEIGHT OF MODELS AND
GEFS/ECMWF MEANS BY DAY 7 WEDNESDAY.
..WEATHER/HAZARDS HIGHLIGHTS
FOR THE DAY 4 PERIOD SATURDAY-SATURDAY NIGHT, THERE IS A BROAD
SIGNAL FOR SCATTERED HEAVY SHOWERS AND STORMS FROM PARTS OF THE
NORTH-CENTRAL THROUGH SOUTH-CENTRAL PLAINS INTO THE DEEP SOUTH
NEAR A FRONTAL BOUNDARY AND SHORTWAVE ALOFT. THE EXCESSIVE
RAINFALL OUTLOOK MAINTAINS A MARGINAL RISK AREA BUT WITH SOME
ONGOING ADJUSTMENTS ON ITS PERIPHERY TO REFLECT LATEST GUIDANCE
TRENDS, INCLUDING A SOMEWHAT DRIER TREND OVER ALABAMA/GEORGIA AND
AN INCREASED POTENTIAL FOR A BAND OF ENHANCED RAINFALL EXTENDING
BACK INTO THE CENTRAL HIGH PLAINS. IT IS LIKELY THAT SOME
LOCATIONS WITHIN THIS OVERALL AREA MAY EVENTUALLY QUALIFY FOR A
SLIGHT RISK AS FUTURE MODEL RUNS COME INTO BETTER AGREEMENT ON THE
MAIN QPF AXIS. MEANWHILE THIS AFTERNOON'S UPDATE PLANS TO ADD A
DAY 4 MARGINAL RISK AREA OVER PORTIONS OF THE NORTHEAST, AS
GUIDANCE IS SUGGESTING POTENTIAL FOR LOCALLY HEAVY MAXIMA UNDER
THE REGION'S UPPER LOW. MOST OF THIS AREA SHOULD HAVE FAIRLY WET
GROUND CONDITIONS BY THAT TIME, WHETHER FROM RECENT RAINFALL
(ESPECIALLY IN MAINE) OR WHAT IS EXPECTED IN THE SHORT TERM.
GOING INTO THE DAY 5 PERIOD SUNDAY, THE GUIDANCE SUGGESTS THE CORE
OF THE HEAVIEST RAINFALL WILL LIKELY SETTLE ACROSS INTERIOR
PORTIONS OF THE DEEP SOUTH AND POSSIBLY EXTENDING A BIT TO THE
NORTHWEST WITH THE POTENTIAL FOR 2-4 INCH RAINFALL TOTALS ON A
LOCALIZED BASIS, BUT MODELS VARY IN THE PLACEMENT OF THE HEAVIEST
QPF MAXIMA. ALTHOUGH A BROAD MARGINAL RISK AREA IS CURRENTLY
MAINTAINED IN THE DAY 5 OUTLOOK, JUST A LITTLE MORE IMPROVEMENT IN
GUIDANCE CLUSTERING WILL BE NEEDED TO MERIT AN EMBEDDED SLIGHT
RISK. ANOTHER ASPECT TO MONITOR WILL BE HOW MUCH OVERLAP THERE
WILL BE BETWEEN DAY 5 ACTIVITY AND WHAT OCCURS IN THE DAYS LEADING
UP TO THAT POINT. THE DAY 5 OUTLOOK ALSO MAINTAINS A MARGINAL
RISK OVER PARTS OF THE NORTHERN ROCKIES WITH THE STRONG SYSTEM AND
LEADING FRONT APPROACHING THE REGION.
ELSEWHERE ACROSS THE U.S., THE MIDWEST INTO SOUTH RAINFALL WILL
LIKELY EXTEND FARTHER NORTHEAST INTO THE OHIO
VALLEY/MID-ATLANTIC/SOUTHEAST FROM LATE WEEKEND INTO THE
EARLY-MIDDLE PART OF NEXT WEEK, WITH SOME LOCALLY MODERATE TO
HEAVY TOTALS POSSIBLE. LOCALLY ENHANCED RAINFALL WITH LATE-DAY
SHOWERS/STORMS OVER THE NORTHEAST WITH THE UPPER LOW OVERHEAD
SHOULD BEGIN TO TREND LIGHTER AND MORE SCATTERED ON SUNDAY.
MEANWHILE, THE VIGOROUS UPPER TROUGH/LOW REACHING THE WEST WILL
LIKELY INCREASE THE COVERAGE AND INTENSITY OF PRECIPITATION OVER
THE PACIFIC NORTHWEST AND ESPECIALLY THE NORTHERN ROCKIES FROM
SUNDAY INTO EARLY NEXT WEEK. SOME LOCALLY HEAVY RAIN MAY FALL
OVER AREAS IN THE NORTHERN ROCKIES THAT COULD BE SENSITIVE DUE TO
WELL ABOVE NORMAL RAINFALL RECENTLY. THE DAY 5 EXCESSIVE RAINFALL
OUTLOOK MAINTAINS A MARGINAL RISK OVER PARTS OF THE NORTHERN
ROCKIES WITH THIS ACTIVITY AND ADDITIONAL RAINFALL IS LIKELY INTO
TUESDAY. THE DEPTH AND TRACK OF THE UPPER SYSTEM COULD ALSO
SUPPORT SOME SNOW AT THE HIGHEST ELEVATIONS. THEN THE NORTHERN
PLAINS MAY SEE A BAND OF RAINFALL BY MIDWEEK AS THE LEADING FRONT
PUSHES INTO THE REGION.
THE EXCESSIVE HEAT WILL CONTINUE THROUGH THE REMAINDER OF THIS
WEEK AND INTO NEXT WEEK ACROSS MUCH OF TEXAS AND INTO MUCH OF
LOUISIANA AND OKLAHOMA, WITH WIDESPREAD 100S ACROSS CENTRAL AND
SOUTHERN PORTIONS OF TEXAS, AND 90S COVERING MUCH OF THE DEEP
SOUTH AND THE CENTRAL PLAINS (MAINLY MONDAY ONWARD FOR THE
LATTER). SOME DAILY RECORD HIGH TEMPERATURES AND HEAT INDICES ON
THE ORDER OF 105 TO 115 DEGREES ARE LIKELY DURING THE HOTTEST
PARTS OF THE DAY FOR MANY OF THESE AREAS, AND SOME ISOLATED
INSTANCES OF HEAT INDICES UP TO 120 DEGREES ARE POSSIBLE FOR PARTS
OF DEEP SOUTH TEXAS WHERE THE GREATEST COMBINATION OF HIGH
DEWPOINTS AND THE HEAT WILL LIKELY EXIST. THERE IS STRONG MODEL
SUPPORT FOR THIS EVENT TO HAVE ADDITIONAL STAYING POWER INTO MUCH
OF NEXT WEEK AS WELL. ON THE OTHER END OF THE SPECTRUM, THE UPPER
TROUGH DIGGING INTO THE NORTHWESTERN U.S. WILL HERALD THE ARRIVAL
OF NOTICEABLY COOLER TEMPERATURES BY SUNDAY AND ESPECIALLY INTO
EARLY NEXT WEEK ACROSS MUCH OF CALIFORNIA, NEVADA, WASHINGTON,
OREGON, AND IDAHO. AFTERNOON HIGHS SHOULD GENERALLY BE 5 TO 20
DEGREES BELOW AVERAGE, WITH THE GREATEST ANOMALIES OVER THE
NORTHERN GREAT BASIN. A FEW PLACES COULD CHALLENGE DAILY RECORDS
FOR COOL HIGHS. ELSEWHERE, THE CENTRAL ROCKIES WILL BE ON THE
COOL SIDE INTO SATURDAY BEFORE MODERATING, WHILE PARTS OF THE
UPPER MIDWEST/NORTHERN PLAINS WILL BE RATHER WARM WITH HIGHS 5 TO
15 DEGREES ABOVE AVERAGE. MOST OF THE EAST COAST REGION SHOULD BE
NEAR OR SLIGHTLY BELOW CLIMATOLOGICAL MID-JUNE LEVELS.
RAUSCH/HAMRICK
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, 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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