300
FXUS02 KWBC 131900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM EDT TUE JUN 13 2023
VALID 12Z FRI JUN 16 2023 - 12Z TUE JUN 20 2023
***EARLY SEASON HEAT WAVE TO PERSIST ACROSS MUCH OF THE
SOUTH-CENTRAL U.S. INTO EARLY NEXT WEEK AND BEYOND***
..SYNOPTIC OVERVIEW
EXPECT A WEAK OMEGA BLOCK UPPER PATTERN TO BE IN PLACE ACROSS
SOUTHERN CANADA AND THE NORTHERN TIER OF THE U.S. AS THE FORECAST
PERIOD STARTS AT THE END OF THIS WEEK. THEN FROM THE WEEKEND INTO
NEXT WEEK, A NORTHEASTERN PACIFIC/GULF OF ALASKA TROUGH WITH
EMBEDDED UPPER LOW WILL DIG INTO THE WESTERN U.S. AND WESTERN
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 RAINFALL FROM THE
NORTHERN-CENTRAL PLAINS INTO SOUTHEAST/MID-ATLANTIC, WITH THE
SOUTHEAST 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
FROM A DETAIL PERSPECTIVE, THE MOST AMBIGUOUS PART OF THE FORECAST
INVOLVES THE SHORTWAVE ENERGY THAT PROGRESSES OUT OF THE
WESTERN/CENTRAL STATES AND EVENTUALLY SETTLES INTO THE LONGER TERM
MEAN TROUGH OVER THE EAST, ALONG WITH NORTHERN STREAM EASTERN
TROUGH ENERGY THAT COULD INTERACT AS WELL. RECENT GFS RUNS HAVE
BEEN LEANING ON THE FASTER SIDE OF THE SPREAD WITH PROGRESSION OF
THE CENTRAL U.S. ENERGY, THOUGH THE 12Z UKMET HAS COME IN WITH A
SOLUTION DIFFERENT FROM OTHER GUIDANCE AS IT HAS A DEFINED
SHORTWAVE THAT IS EVEN FASTER THAN THE GFS WHILE ALSO DEPICTING A
TRAILING SHORTWAVE MORE IN LINE WITH THE ECMWF/CMC. BY NEXT
MONDAY-TUESDAY THE MODELS AND ENSEMBLES HAVE DIFFERED OVER WHETHER
THIS ENERGY, WITH POSSIBLE INPUT OF NORTHERN STREAM FLOW, MAY FORM
AN UPPER LOW OVER THE EAST. LATEST MODELS HAVE LEANED A BIT MORE
IN THE UPPER LOW DIRECTION VERSUS AN OPEN TROUGH WHILE THE
GEFS/ECMWF MEANS SHOW A LITTLE MORE SEPARATION BY TUESDAY. THE
UPDATED BLEND, INCORPORATING A 00Z/06Z OPERATIONAL MODEL COMPOSITE
EARLY AND THEN A COMBINATION OF MODELS AND 06Z GEFS/00Z ECMWF
MEANS, REFLECTS THIS TREND BUT CONFIDENCE IN SPECIFICS AT ANY
SPECIFIC VALID TIME REMAINS FAIRLY LOW.
WITH THE SYSTEM DIGGING INTO THE WEST, THE 06Z GFS WAS NOTABLE IN
BRINGING ITS UPPER LOW INTO THE NORTHWEST ABOUT 12-24 HOURS
EARLIER THAN MOST OTHER SOLUTIONS. THE NEW 12Z GFS HAS SLOWED
DOWN AND IN FACT IS A TAD SLOWER THAN THE MODEL/MEAN AVERAGE. THE
12Z UKMET TRACKS ITS EMBEDDED UPPER LOW NORTH OF OTHER MODELS AND
LATEST GEFS/ECMWF MEANS. THE AFOREMENTIONED BLEND REFLECTS THE
BEST GUIDANCE CLUSTERING WELL INTO DAY 6 MONDAY. NEW 12Z GUIDANCE
THUS FAR IS SUGGESTING THAT THE UPPER LOW COULD BE A LITTLE SLOWER
TO EJECT NORTHEASTWARD BY TUESDAY, THOUGH ALSO WITH INCREASING
UNCERTAINTY OVER WHETHER SOME OF THE UPPER LOW'S ENERGY COULD
SPLIT.
..WEATHER/HAZARDS HIGHLIGHTS
THERE WILL LIKELY BE TWO MAIN AREAS FOR HEAVY RAINFALL POTENTIAL
FOR THE FRIDAY TO SATURDAY TIME PERIOD. THE FIRST AREA SHOULD BE
ACROSS PORTIONS OF MISSISSIPPI AND ALABAMA WHERE THE DETERMINISTIC
GUIDANCE INDICATES A CORRIDOR OF ENHANCED QPF, LIKELY AS THE
RESULT OF MCS ACTIVITY WITH NORTHWEST FLOW ALOFT. THE POTENTIAL
EXISTS FOR 2-4 INCH TOTALS DURING THE DAY 4 PERIOD FRIDAY-FRIDAY
NIGHT, BUT THE MODELS CONTINUE TO DISAGREE ON THE PLACEMENT OF THE
MAIN QPF AXIS, SO THIS PRECLUDES ANYTHING HIGHER THAN A MARGINAL
RISK AT THIS TIME. THE SECOND AREA OF POTENTIAL CONCERN WILL BE
JUST EAST OF THE FRONT RANGE OF THE ROCKIES WHERE ADDITIONAL HEAVY
SHOWERS AND STORMS MAY OCCUR OVER AREAS THAT HAVE RECEIVED COPIOUS
RAINFALL OVER THE PAST WEEK. CURRENT PLAN IS TO MAINTAIN A
MARGINAL RISK AREA FOR NOW, WHILE AN EMBEDDED SLIGHT RISK MAY BE
WARRANTED IN THE NEAR FUTURE IF SHORTER-TERM GUIDANCE REFINES THE
BEST REGION OF FOCUS. FOR THE DAY 5 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 OUTLOOK AGAIN MAINTAINS A MARGINAL RISK AREA WITH ONLY
MINOR ADJUSTMENTS FOR LATEST GUIDANCE, WITH THE EXPECTATION THAT
ONE OR MORE SLIGHT RISK AREAS COULD ARISE IF GUIDANCE CLUSTERING
IMPROVES. SOME OF THIS RAINFALL MAY EXTEND FARTHER EAST/NORTH
INTO THE OHIO VALLEY/MID-ATLANTIC/SOUTHEAST FROM LATE WEEKEND INTO
EARLY NEXT WEEK. THE NORTHEAST SHOULD SEE PERIODS OF RAINFALL
WITH POSSIBLE LATE-DAY THUNDERSTORMS ESPECIALLY FROM LATE WEEK
INTO THE WEEKEND WITH THE UPPER TROUGH/LOW OVER THE REGION.
MEANWHILE THE VIGOROUS UPPER TROUGH/LOW REACHING THE WEST WILL
LIKELY INCREASE THE COVERAGE AND INTENSITY OF PRECIPITATION OVER
THE PACIFIC NORTHWEST AND ESPECIALLY NORTHERN ROCKIES FROM SUNDAY
ONWARD. SOME LOCALLY HEAVY RAIN MAY FALL OVER AREAS IN THE
NORTHERN ROCKIES THAT COULD BE SENSITIVE DUE TO WELL ABOVE NORMAL
RAINFALL RECENTLY. THE DEPTH AND TRACK OF THE UPPER SYSTEM COULD
ALSO SUPPORT SOME SNOW AT THE HIGHEST ELEVATIONS.
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-TUESDAY 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 FRIDAY-SATURDAY BEFORE MODERATING WHILE PARTS OF THE
UPPER MIDWEST/NORTHERN PLAINS WILL BE RATHER WARM WITH HIGHS 5 TO
15 DEGREES ABOVE NORMAL. 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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