458
FXUS02 KWBC 191930
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
330 PM EDT WED JUN 19 2024
VALID 12Z SAT JUN 22 2024 - 12Z WED JUN 26 2024
...HEAT WAVE PERSISTS FOR MID-ATLANTIC SUNDAY WITH ELEVATED HEAT
OVER THE SOUTH/PLAINS THROUGH MUCH OF NEXT WEEK...
...HEAVY RAINFALL THREAT FROM THE UPPER GREAT LAKES TO NORTHERN
NEW ENGLAND SATURDAY-SUNDAY...
..OVERVIEW
FLOW PATTERN BECOMES MORE ZONAL OVER THE CONUS THIS WEEKEND WITH
THE JET FOCUS OVER SOUTHERN CANADA AND SUBTROPICAL RIDGING OVER THE
SOUTHERN STATES. A SHORTWAVE TROUGH CROSSING THE FAR NORTHERN
PLAINS TO QUEBEC SATURDAY THROUGH SUNDAY NIGHT BRINGS A HEAVY
RAINFALL THREAT FROM THE UPPER GREAT LAKES TO NORTHERN NEW ENGLAND
DURING THE WEEKEND WHICH WILL ALSO MODERATE THE AREA OF HAZARDOUS
HEAT EXTENDING FROM THE MIDWEST INTO THE MID- ATLANTIC THROUGH
SUNDAY. HOWEVER HEIGHTS OVER THE SOUTHERN TIER WILL REMAIN SOMEWHAT
ABOVE NORMAL, LEADING TO FAIRLY BROAD COVERAGE OF ABOVE NORMAL
TEMPERATURES OVER THE CENTRAL/SOUTHERN STATES NEXT WEEK. THERE
REMAINS POTENTIAL FOR SECOND WESTERN GULF FEATURE (AFTER ALBERTO)
THAT COULD BRING ADDITIONAL RAINFALL INTO FAR SOUTHERN TEXAS THIS
WEEKEND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
DECENT AGREEMENT AMONG 00Z/06Z GLOBAL GUIDANCE ON THE NORTHERN
STREAM SHORTWAVE TROUGH MOVING FROM THE NORTHERN PLAINS TO QUEBEC
SATURDAY THROUGH SUNDAY NIGHT AND THE NEXT WAVE OFF BC MONDAY
WARRANTED A GENERAL DETERMINISTIC MODEL BLEND FOR PREFERENCES
THROUGH DAY 5. THE BREAKDOWN CAME WITH THE BC WAVE BEING FASTER IN
THE 00Z CMC, THOUGH THE 12Z IS MUCH MORE IN LINE WITH THE 12Z
GFS/ECMWF. A BLEND OF THE 00Z ECMWF/06Z GFS WITH THEIR ENSEMBLES
WAS USED FOR DAY 6/7 GIVEN THEIR SIMILARITIES. THAT SAID, THE ZONAL
FLOW PATTERN DOES MAKE FOR INHERENT UNCERTAINTY IN WHAT IS SURE TO
BE IMPULSES TRACKING WITH THE FLOW NEAR THE U.S./CANADIAN BORDER.
DAYS 4-7 QPF WAS GENERALLY DERIVED FROM A BLEND OF THE 13Z
NATIONALBLEND WITH THE 00Z ECMWF/06Z GFS WITH LOCAL ENHANCEMENTS
FROM THE 00Z GDPS AND UKMET. 13Z NBM TEMPERATURES IN THE MID-
ATLANTIC ON SUNDAY WERE GENERALLY TEMPERED A BIT USING A GLOBAL
BIAS CORRECTED BLEND.
..WEATHER/HAZARDS HIGHLIGHTS
FOCUS FOR HEAVY RAIN AHEAD OF THE NORTHERN PLAINS SHORTWAVE TROUGH
SATURDAY HAS FOCUSED A BIT SOUTH IN THE GLOBAL GUIDANCE CONSENSUS
WHICH WARRANTS FOCUSING THE DAY 4 EXCESSIVE RAINFALL OUTLOOK SOUTH
OF LAKE SUPERIOR WITH CENTRAL WISCONSIN THE MOST LIKELY SPOT FOR A
SECOND ROUND OF HEAVY RAIN AFTER A FIRST ROUND ON FRIDAY. THE
MARGINAL RISKS INTO THE CENTRAL PLAINS WHERE MERELY TRIMMED A BIT
FOR TIMING.
PROGRESSIVE, BUT POSSIBLY REPEATING ACTIVITY LOOKS TO
BE MORE FOCUSED OVER NORTHERN NEW ENGLAND SUNDAY, SO THE DAY 5
SLIGHT RISK WAS TRIMMED A BIT FROM EASTERN MAINE. THE MARGINAL
RISKS WERE MAINTAINED OVER THE UPPER OHIO VALLEY AND NORTHEAST.
THE ENHANCED MOISTURE INTO FAR SOUTHERN TEXAS ALLOWS THE DAY 4/5
MARGINALS TO BE FOCUSED OVER THE LOWER RIO GRANDE VALLEY SOUTH OF
THE SAND SHEET. MEANWHILE SOME SCATTERED DIURNAL CONVECTION LOOKS
TO PERSIST OVER PARTS OF THE FOUR CORNERS STATES. ANOMALOUSLY HIGH
PRECIPITABLE WATER VALUES SUGGEST SOME ACTIVITY COULD BE LOCALLY
HEAVY BUT SO FAR GUIDANCE HAS NOT BEEN QUITE ORGANIZED ENOUGH TO
MERIT A RISK AREA. PARTS OF THE SOUTHEAST/FLORIDA MAY ALSO SEE
LOCALLY HEAVY RAINFALL BUT AGAIN WITHOUT ENOUGH ORGANIZATION TO
FAVOR A RISK AREA. DURING THE EARLY- MIDDLE PART OF NEXT WEEK THE
NEXT FRONTAL SYSTEM REACHING THE PLAINS/MISSISSIPPI VALLEY MAY
PRODUCE SHOWERS AND THUNDERSTORMS OF VARYING INTENSITY.
THE MID-ATLANTIC SHOULD CONTINUE TO HAVE TEMPERATURES 10-15F ABOVE
NORMAL SUNDAY WITH A DOZEN OR TWO DAILY RECORDS FOR MAX/WARM MIN
TEMPERATURES FORECAST. THE FRONT PROGRESSING INTO THE EAST WILL
SUPPRESS THE HEAT SOUTHWARD MONDAY WITH MAX TEMPERATURES AROUND 10
DEGREES ABOVE NORMAL PERSISTING THROUGH MIDWEEK OVER THE SOUTHERN
PLAINS, MIDWEST AND INTO THE SOUTHEAST. TEMPERATURES 5-10F ABOVE
NORMAL OVER THE DESERT SOUTHWEST IS ALSO SIGNIFICANT.
JACKSON
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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