202
FXUS02 KWBC 160700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT FRI AUG 16 2024
VALID 12Z MON AUG 19 2024 - 12Z FRI AUG 23 2024
...HAZARDOUS HEAT LIKELY ACROSS THE SOUTHERN PLAINS AND CENTRAL
GULF COAST STATES INTO NEXT WEEK...
..OVERVIEW
GUIDANCE STILL AGREES THAT A SLOW-MOVING UPPER PATTERN WILL BE IN
PLACE NEXT WEEK. AN UPPER HIGH CENTERED OVER THE SOUTHERN HIGH
PLAINS WILL PROMOTE HAZARDOUS HEAT OVER THE SOUTHERN PLAINS TO THE
CENTRAL GULF COAST. AN UPPER LOW/TROUGH IS FORECAST TO MEANDER
JUST OFF THE WEST COAST, LEADING TO A COOLER AND WETTER PATTERN FOR
THE NORTHWEST. MEANWHILE, AN UPPER TROUGH WILL TAKE HOLD FROM THE
GREAT LAKES AND SOUTHWARD AND SLOWLY MOVE EAST AND BE PERIODICALLY
REINFORCED BY SHORTWAVE ENERGIES AS NEXT WEEK PROGRESSES. THIS
TROUGH AND A SURFACE LOW PRESSURE/FRONTAL SYSTEM WILL PROMOTE
SCATTERED TO WIDESPREAD THUNDERSTORMS WITH THE POTENTIAL FOR HEAVY
RAIN ACROSS THE NORTHEAST U.S. INTO EARLY NEXT WEEK. HURRICANE
ERNESTO IS FORECAST TO TRACK NORTH OVER THE WESTERN ATLANTIC AND
REMAIN OFFSHORE OF THE U.S. EAST COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLES CONTINUE TO OFFER A REASONABLY SIMILAR FLOW
PATTERN EVOLUTION OVER THE COMING WEEK. FORECAST SPREAD AND CYCLE
TO CYCLE CONTINUITY HAS NOW IMPROVED, GENERALLY BOLSTERING
FORECAST CONFIDENCE TO ABOVE NORMAL LEVELS. A COMPOSITE OF THE
18 UTC GFS AND 12 UTC ECMWF/UKMET/CANADIAN MODELS ALONG WITH THE
01 UTC NATIONAL BLEND OF MODELS SEEMS TO PROVIDE A SOLID MID-
LARGER SCALE FORECAST BASIS AND RESULTANT SMALLER SCALE DETAIL
THAT SEEMS CONSISTENT WITH LOCAL SYSTEM PREDICTABILITY VALID FOR
MONDAY INTO WEDNESDAY. ADDED TO THE MIX THE 12 UTC ECMWF/CANADIAN
ENSEMBLE MEANS AS UNCERTAINTIES GROW THROUGH LONGER FRAMES. THESE
ENSEMBLES OFFER A SLIGHTLY MORE AMPLIFIED AND LESS PROGRESSIVE
PATTERN THAN THE 18 UTC GEFS MEAN. UPSTREAM FLOW AMPLITUDE AND
A SLOW TO DISLODGE PATTERN HISTORY SEEMS IN LINE WITH THIS PLAN.
BLOCKY PATTERNS TEND TO LINGER.
..WEATHER/HAZARDS HIGHLIGHTS
IT REMAINS THAT CASE THAT GREAT LAKES/EASTERN U.S. UPPER TROUGHING
AND A SURFACE LOW PRESSURE/FRONTAL SYSTEM WILL PROVIDE FORCING FOR
RAIN AND THUNDERSTORMS ACROSS THE EASTERN U.S. INTO EARLY NEXT
WEEK. INSTABILITY AND ABOVE NORMAL MOISTURE WILL BE IN PLACE AND
COULD LEAD TO LOCALLY HEAVY RAIN. A WPC MARGINAL RISK OF EXCESSIVE
RAINFALL REMAINS IN PLACE OVER THE NORTHEAST DAY 4/MONDAY. WHILE
WIDESPREAD HEAVY RAIN IS NOT PARTICULARLY LIKELY, EMBEDDED HEAVY
TOTALS COULD CAUSE FLOODING CONCERNS ESPECIALLY CONSIDERING WET
ANTECEDENT CONDITIONS IN MUCH OF THE REGION AND THE MULTIPLE DAYS
IN A ROW OF RAIN. RAIN IS EXPECTED TO TAPER OFF IN THE NORTHEAST
TUESDAY-WEDNESDAY AS SURFACE HIGH PRESSURE BUILDS IN BEHIND THE
COLD FRONT(S) AND IN THE WAKE OF ERNESTO LIFTING WELL OFFHORE. HOWEVER,
TRAILING FRONTS SLATED TO STALL FARTHER SOUTH ACROSS FLORIDA WILL
MAINTAIN SEVERAL DAYS OF THUNDERSTORM CHANCES THERE. FLOODING
ISSUES ARE A POSSIBILITY IF HEAVY RAIN FALLS IN URBAN AREAS. THIS
FRONT MOVES SLOWLY AS IT BENDS BACK TO THE WEST ATOP THE CENTRAL
GULF COAST AND BACK NORTH INTO THE PLAINS. SCATTERED STORMS ARE
POSSIBLE NEAR THE FRONT AS IMPULSES "RIDE THE RIDGE" ALOFT, BUT
WITH GENERALLY LOW CONFIDENCE IN PLACEMENT STILL AT THIS TIME.
MONSOONAL CONVECTION WILL AFFECT THE FOUR CORNERS STATES NORTHWARD
INTO EARLY NEXT WEEK WITH MOIST SOUTHERLY FLOW WEST OF THE UPPER
RIDGE AXIS. MARGINAL RISKS ARE SLOWLY SPREAD MONDAY-TUESDAY OVER
PORTIONS OF ARIZONA, UTAH, SOUTHEAST CALIFORNIA, SOUTHERN
NEVADA AND COLORADO. STORMS WITH EMBEDDED HEAVY RAIN COULD CAUSE
ISOLATED FLOODING, PARTICULARLY IN VULNERABLE AREAS LIKE THE SLOT
CANYONS OF SOUTHERN UTAH. MONSOONAL CONVECTION LOOKS TO GRADUALLY
REDUCE IN SCOPE INTO MIDWEEK. SOME RAIN IS ALSO FORECAST TO MOVE
ACROSS THE NORTHERN TIER AS THE WEEK PROGRESSES.
UPPER RIDGING OVER THE SOUTH-CENTRAL U.S. WILL MAINTAIN ABOVE
NORMAL TEMPERATURES BY 5-15 DEGREES FROM THE HIGH PLAINS EAST INTO
THE CENTRAL GULF COAST. HIGHS WELL INTO THE 100S IN MUCH OF TEXAS
COULD SET DAILY RECORDS. FROM EASTERN TEXAS INTO THE LOWER
MISSISSIPPI VALLEY, HOT TEMPERATURES AND HIGH DEWPOINTS SHOULD
PRODUCE HEAT INDICES LIKELY ABOVE 110 DEGREES. LOW TEMPERATURES IN
THE UPPER 70S TO LOW 80S WILL EXACERBATE HEAT STRESS AND COULD SET
RECORDS FOR WARM MINIMUM TEMPERATURES. EXPERIMENTAL HEATRISK
CONTINUES TO SHOW MAJOR TO EXTREME IMPACTS FROM THIS LENGTHY HEAT
WAVE. NORTH OF THIS REGION, MOST AREAS SHOULD SEE NEAR TO SLIGHTLY
BELOW NORMAL HIGHS, WITH SOME BELOW NORMAL LOWS AS WELL FOR THE
OHIO VALLEY, WHILE THE INTERMOUNTAIN WEST CAN EXPECT ABOVE AVERAGE
LOWS. THE PACIFIC NORTHWEST INTO NORTHERN CALIFORNIA SHOULD SEE
TEMPERATURES A BIT BELOW NORMAL IN RESPONSE TO THE LOW ALOFT.
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 (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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