507
FXUS02 KWBC 211852
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
252 PM EDT WED JUN 21 2023
VALID 12Z SAT JUN 24 2023 - 12Z WED JUN 28 2023
...PROLONGED HEAT WAVE CONTINUES ACROSS TEXAS AND SOUTHEASTERN NEW
MEXICO AND WILL EXPAND NORTHEAST NEXT WEEK...
...HEAVY RAIN AND FLOODING ARE POSSIBLE ACROSS THE NORTH-CENTRAL
U.S. INTO SATURDAY WITH A LOW PRESSURE SYSTEM...
..OVERVIEW
THE MEDIUM RANGE PERIOD WILL BEGIN SATURDAY WITH A COUPLE OF UPPER
TROUGHS/LOWS HELPING TO PRODUCE RAIN AND THUNDERSTORMS, ONE OVER
THE NORTH-CENTRAL U.S. AND ANOTHER CENTERED NEAR THE LOWER GREAT
LAKES REGION. THESE FEATURES LOOK TO COMBINE LATER IN THE PERIOD
TO ONE MAIN TROUGH OVER THE EASTERN U.S., WHILE ADDITIONAL
TROUGHING/CLOSED LOW MOVES FROM THE EASTERN PACIFIC INTO THE WEST.
MEANWHILE, IN BETWEEN THESE TROUGHS, AN UPPER HIGH CENTERED OVER
TEXAS WILL CONTINUE TO BRING PERSISTENT EXCESSIVE HEAT TO MUCH OF
THE SOUTHERN PLAINS, WITH SOME EXPANSION AT TIMES INTO THE LOWER
MISSISSIPPI VALLEY AND OKLAHOMA/KANSAS.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE LATEST MODEL GUIDANCE WAS IN GOOD ENOUGH AGREEMENT FOR A
GENERAL BLEND OF THE DETERMINISTIC SOLUTIONS THROUGH DAY 5. MODELS
SHOW EXCELLENT AGREEMENT THROUGH AT LEAST THE MIDDLE OF NEXT WEEK
THAT THE STUBBORN UPPER LEVEL HIGH SHOULD HANG AROUND THE
SOUTH-CENTRAL U.S. WITH MAYBE SOME SLIGHT ADJUSTMENT WESTWARD.
THERE ARE SOME QUESTIONS IN THE DETAILS AS THE INITIAL UPPER LOW
OVER THE LOWER GREAT LAKES BECOMES ABSORBED INTO THE COMPACT LOW
ACROSS THE NORTH-CENTRAL U.S. EARLY NEXT WEEK. BY TUESDAY, THE GFS
AND CMC ARE NOTABLY FASTER WITH THE BROADER RESULTING TROUGH OVER
THE EAST COAST THAN THE ECMWF. ENSEMBLES MAY SUPPORT A SLOWER
PROGRESSION, CLOSER TO THE ECMWF. THERE IS OVERALL GOOD AGREEMENT
THROUGH EVEN DAY 7 ON THE UPPER LOW/SHORTWAVE DROPPING DOWN THE
WEST COAST AND INTO CALIFORNIA, WITH SOME DIFFERENCES IN THE
DETAILS WHICH MAY TAKE UNTIL THE SHORT RANGE PERIOD TO RESOLVE.
WPC USED A BLEND OF THE ENSEMBLE MEANS WITH THE ECMWF FOR THE
LATTER HALF OF THE PERIOD. TODAY'S WPC FORECAST REMAINS CONSISTENT
AND VERY SIMILAR TO THE OVERNIGHT FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
AS THE UPPER TROUGHING IN THE EAST LIFTS NORTH AND WEAKENS, IT
WILL STILL PROVIDE SOME SUPPORT FOR RAIN AND THUNDERSTORMS BUT
LIKELY WITH REDUCED WIDESPREAD HEAVY AMOUNTS COMPARED TO THE SHORT
TERM. SCATTERED THUNDERSTORMS COULD PRODUCE LOCALIZED HEAVY RAIN
RATES GIVEN THE INSTABILITY IN PLACE. THERE MAY BE A SOMEWHAT
FOCUSED AXIS OF RAINFALL ACROSS THE NORTHERN MID-ATLANTIC REGION
INTO THE INTERIOR NORTHEAST THIS WEEKEND, SO MARGINAL RISKS ARE IN
PLACE THERE FOR SATURDAY AND SUNDAY, WITH AREAS OF LOW FLASH FLOOD
GUIDANCE OF PARTICULAR CONCERN. FARTHER WEST, A CONSOLIDATING LOW
PRESSURE SYSTEM AT THE SURFACE AND COUPLED JETS (RIGHT
ENTRANCE/LEFT EXIT REGION COMBINATION) ALOFT WILL LIKELY PRODUCE
HEAVY RAINFALL (LIKELY AROUND 2-4" WITH LOCALLY HIGHER AMOUNTS)
ACROSS THE NORTH-CENTRAL U.S. ON SATURDAY. A BROAD SLIGHT RISK OF
EXCESSIVE RAINFALL IS FOCUSED ON NORTH DAKOTA AND NORTHERN/CENTRAL
MINNESOTA FOR THIS POTENTIAL, WITH A MARGINAL RISK FOR LINGERING
RAINFALL CENTERED ON THE ARROWHEAD OF MINNESOTA ON SUNDAY. SHOWER
AND STORM CHANCES WILL LIKELY ALSO EXTEND SOUTHWARD ACROSS THE
MISSOURI AND MISSISSIPPI VALLEYS THIS WEEKEND AHEAD OF THE FRONTAL
SYSTEM WITH SPC HIGHLIGHTING AN AREA FOR POTENTIAL SEVERE WEATHER
AS WELL. ALONG A DISSIPATING WARM FRONT AND AHEAD OF THE
APPROACHING COLD FRONT, THERE COULD BE AN ADDITIONAL AREA OF
ENHANCED ORGANIZED CONVECTION ON SUNDAY. HIGH RAIN RATES AND
SUFFICIENT INSTABILITY SHOULD CREATE AT LEAST A LOCALIZED FLASH
FLOOD THREAT AND SO A MARGINAL RISK IS IN PLACE FOR THIS AREA ON
THE DAY 5/SUNDAY EXCESSIVE RAINFALL OUTLOOK. ADDITIONAL ROUNDS OF
RAIN AND STORMS ARE LIKELY INTO THE EAST AS THIS SYSTEM CONTINUE
TO PROGRESS EASTWARD EARLY NEXT WEEK. THE NEXT SYSTEM INTO THE
WEST WILL ALSO ALLOW SCATTERED SHOWERS AND STORM CHANCES TO RETURN
ACROSS PARTS OF THE NORTHWEST AND INTO THE NORTHERN ROCKIES/HIGH
PLAINS NEXT MONDAY-TUESDAY.
IN TERMS OF TEMPERATURES, THERE IS REALLY NO END IN SIGHT FOR THE
EXCESSIVE HEAT THAT HAS PLAGUED PARTICULARLY SOUTH AND WESTERN
TEXAS/SOUTHEASTERN NEW MEXICO IN RECENT DAYS. IN FACT, FOR THE
WEEKEND AND INTO NEXT WEEK, TEMPERATURES OVER 100F AND HEAT
INDICES MUCH HIGHER WILL EXTEND FARTHER EAST INTO THE DALLAS-FORT
WORTH AND HOUSTON METROS BY SATURDAY AND THEN INTO THE LOWER
MISSISSIPPI VALLEY AS WELL. SEVERAL RECORD TEMPERATURES COULD BE
SET OR TIED. THE DESERT SOUTHWEST STARTS TO SEE TEMPERATURES WELL
OVER 100F BY THE WEEKEND AND NEXT WEEK TOO, THOUGH NOT REALLY
ANOMALOUS FOR THIS TYPICALLY HOTTEST TIME OF THE YEAR THERE. AS
MEAN UPPER RIDGING EXPANDS FARTHER NORTH, HIGHS IN THE 90S ARE
LIKELY ACROSS MUCH OF THE PLAINS AND MISSISSIPPI VALLEY, WITH
CURRENT FORECASTS SHOWING TEMPERATURES EXCEEDING 100F INTO
OKLAHOMA/KANSAS/ARKANSAS BY NEXT WEDNESDAY. MEANWHILE THE WEST
SHOULD SEE COOLER THAN NORMAL TEMPERATURES PARTICULARLY FOR HIGHS
WITH THE BOUTS OF UPPER TROUGHING ALOFT. THE EAST LOOKS TO BE
WITHIN A FEW DEGREES OF AVERAGE FOR EARLY SUMMER.
SANTORELLI/TATE
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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