079
FXUS02 KWBC 281910
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
310 PM EDT SUN JUL 28 2024
VALID 12Z WED JUL 31 2024 - 12Z SUN AUG 04 2024
...HAZARDOUS HEAT TO SHIFT FROM THE SOUTH-CENTRAL PLAINS EARLY
PERIOD TO THE NORTHWEST LATER THIS WEEK...
..OVERVIEW
GUIDANCE CONTINUES TO SHOW A PATTERN EVOLVING FROM A SOUTHERN
ROCKIES/PLAINS UPPER RIDGE THROUGH MIDWEEK TO AN AMPLIFYING
RIDGE IN THE WEST LATER IN THE WEEK. THIS WOULD HELP SET UP A
PROLONGED PERIOD OF HOT WEATHER OVER MANY AREAS WITH THE MOST
ANOMALOUS HEAT EXPECTED OVER CENTRAL PARTS OF THE PLAINS THROUGH
MIDWEEK. WARMER THAN NORMAL TEMPERATURES ARE FORECAST TO EXPAND
NORTH TOWARD THE U.S./CANADIAN BORDER LATER IN THE WEEK, DESPITE
SHORTWAVE ENERGY MOVING THROUGH THE MIDWEST AND EVENTUALLY
DEVELOPING MEAN TROUGHING OVER THE EASTERN U.S. THAT WILL SUPPORT A
BROAD AREA OF SHOWERS/THUNDERSTORMS DRIFTING ACROSS THE EASTERN
HALF OF THE COUNTRY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODELS AND ENSEMBLES CONTINUE TO SHOW GOOD AGREEMENT ON
THE LARGE SCALE REGARDING THE INITIAL SOUTHERN TIER RIDGE SHIFTING
AND BUILDING OVER THE WEST. THE MAIN MODEL UNCERTAINTIES STILL LIE
NORTH OF THE RIDGE, PARTICULARLY WITH THE TIMING AND STRENGTH OF A
SHORTWAVE THROUGH THE NORTHERN TIER. ECMWF RUNS HAVE BEEN ON THE
SLOWER SIDE OF THE ENVELOPE WITH THE TROUGH'S TRACK THROUGH THE
MIDWEST/GREAT LAKES/OHIO VALLEY LATE WEEK. HAVE BEEN LEANING AWAY
FROM SOLUTIONS THIS SLOW BECAUSE THE ECMWF-BASED AI/ML MODELS WERE
MUCH FASTER, BUT THE 06Z GFS SEEMED OVERLY FAST SO A MIDDLE GROUND
SEEMED MORE REASONABLE. THE 12Z GFS HAS SINCE SLOWED DOWN CLOSER TO
THE ECMWF THOUGH. THIS ALSO AFFECTS THE TIMING OF A SURFACE LOW
MOVING THROUGH THE MIDWEST. MODEL GUIDANCE IS QUITE UNCERTAIN WITH
THE PATTERN IN THE NORTHEASTERN PACIFIC NEXT WEEKEND, WHICH COULD
AFFECT THE NORTHWESTERN U.S., WHICH WILL HAVE TO BE RESOLVED IN
FUTURE FORECASTS.
GUIDANCE AND ENSEMBLES CONTINUE TO HINT AT POSSIBLE TROPICAL
DEVELOPMENT IN THE ATLANTIC, WHICH THE LATEST OUTLOOK FROM THE
NATIONAL HURRICANE CENTER IS HIGHLIGHTING. THE OPERATIONAL ECMWF
AND ITS ENSEMBLES SHOW A MORE EASTERN TRACK (OWING TO STRONGER
RIDGING INTO THE GULF), BRINGING A LOW NORTHWARD OFF THE COAST OF
FL NEXT WEEKEND. THE CMC AND NOW THE 12Z GFS (WITH SOME SUPPORT
FROM THEIR ENSEMBLES AS WELL) SHOWS A MORE SOUTHERLY TRACK SOUTH OF
FL INTO THE GULF. A LOT OF UNCERTAINTY STILL ON THE TRACK OR EVEN
ITS EXISTENCE AS A DEFINED TROPICAL SYSTEM, BUT THIS FEATURE WILL
NEED TO BE WATCHED.
THE WPC FORECAST USED A BLEND OF 00Z/06Z DETERMINISTIC GUIDANCE
EARLY IN THE PERIOD, RAMPING UP THE PROPORTION OF ENSEMBLE MEANS TO
60 PERCENT BY DAY 7. OVERALL, THIS MAINTAINED GOOD CONTINUITY WITH
THE PREVIOUS WPC FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
A WET PATTERN IS LIKELY FROM THE MIDWEST TO THE EASTERN SEABOARD
NEXT WEEK WITH AMPLE MOISTURE AND INSTABILITY IN PLACE AS WELL AS
MEAN TROUGHING ALOFT AND SURFACE FRONTAL SYSTEMS ALL SUPPORTING
SCATTERED THUNDERSTORMS. THUS THE DAYS 4-5 EXCESSIVE RAINFALL
OUTLOOKS COVERING WEDNESDAY-THURSDAY NIGHT SHOW FAIRLY BROAD
MARGINAL RISKS ACROSS PARTS OF THE MIDWEST TO OHIO VALLEY AND THE
NORTHEAST. MODEL GUIDANCE HAS BEEN HINTING AT A LIKELY MESOSCALE
CONVECTIVE SYSTEM WITH HEAVY RAIN RATES MOVING ON THE CUSP OF THE
INSTABILITY GRADIENT IN NORTHWEST MEAN FLOW THAT SHOULD AFFECT
PARTS OF THE MIDWEST WEDNESDAY-WEDNESDAY NIGHT. THERE IS SOME
PLACEMENT SPREAD WITH THIS, BUT ANTECEDENT WET CONDITIONS AND THE
HEAVY RAINFALL POTENTIAL SEEMS TO WARRANT A DAY 4/WEDNESDAY SLIGHT
RISK ACROSS THE MIDWEST, THOUGH THE AREA WILL LIKELY BE ADJUSTED IN
FUTURE FORECASTS IF/WHEN MODELS CONVERGE. THIS ROUND AND
POTENTIALLY ADDITIONAL ROUNDS OF STORMS MAY FOCUS IN LOWER MICHIGAN
AND VICINITY BY THURSDAY. HELD OFF AN EMBEDDED SLIGHT RISK FOR DAY
5 THOUGH, AS THERE IS ADDITIONAL SPREAD IN PLACEMENT OF HEAVIEST
RAIN AMOUNTS (AND WHETHER THEY AFFECT AREAS WITH WET ANTECEDENT
CONDITIONS OR NOT) AND UNCERTAINTY IF MULTIPLE ROUNDS OVERLAP EACH
OTHER. MUCH OF THE NORTH-CENTRAL U.S. TO THE EASTERN THIRD OF THE
COUNTRY SHOULD REMAIN GENERALLY UNSETTLED THROUGH LATE WEEK AS A
UPPER TROUGH IS SLOW TO BUDGE OUT OF THE REGION.
ELSEWHERE, MONSOONAL CONVECTION OVER THE SOUTHWEST SHOULD STAY
CONFINED TO SOUTHERN AREAS THROUGH MIDWEEK, AND A MARGINAL RISK
REMAINS REASONABLE FOR THE DAY 4 ERO FROM EASTERN ARIZONA THROUGH
MUCH OF NEW MEXICO. CHANCES FOR CONVECTION MAY EXPAND NORTHEASTWARD
INTO LATER WEEK DEPENDING ON THE SHAPE OF THE SOUTHERN
ROCKIES/PLAINS RIDGE AND UPPER LEVEL ENERGY ROTATING AROUND ITS
WESTERN PERIPHERY. AS SUCH THE DAY 5/THURSDAY MARGINAL EXPANDS A
BIT NORTHWARD INTO SOUTHERN COLORADO, AND RAIN CHANCES INCREASE
INTO THE CENTRAL HIGH PLAINS BY FRIDAY.
THE FORECAST PATTERN EVOLUTION WILL SUPPORT AREAS OF WARMER THAN
AVERAGE TEMPERATURES ACROSS THE LOWER 48 INTO NEXT WEEKEND. THE
MOST SIGNIFICANT HIGH TEMPERATURE ANOMALIES SHOULD BE OVER THE
CENTRAL PLAINS EARLY ON, WHERE SOME LOCATIONS SHOULD SEE MULTIPLE
DAYS WITH HIGHS 10-15F OR SO ABOVE NORMAL AND HIGH TEMPERATURES
NEAR 105F. THE EXPERIMENTAL HEATRISK LIKEWISE REFLECTS AN EXPANDING
AREA OF MAJOR TO EVEN EXTREME RISKS OF HEAT-RELATED IMPACTS
THROUGH WEDNESDAY. AN INCOMING FRONT WILL CAUSE SOME
EASING/SOUTHWARD SHIFT OF THE HEAT LATE THIS WEEK IN THAT REGION,
WITH SOME HEAT BUILDING ACROSS PARTS OF THE SOUTHEAST AS WELL.
RECORD WARM MINIMUM TEMPERATURES IN THE SOUTHEAST WILL EXACERBATE
HEAT STRESS. MEANWHILE, MUCH OF THE WEST WILL TREND WARMER AFTER
WEDNESDAY, WITH LOWER ELEVATIONS SEEING 100F+ HIGH TEMPERATURES.
SCATTERED DAILY RECORD HIGHS ARE POSSIBLE. PERIODS OF ABOVE NORMAL
TEMPERATURES ARE ALSO LIKELY FOR THE MIDWEST TO OHIO VALLEY TO THE
MID-ATLANTIC/NORTHEAST LATE THIS WEEK, WITH PERHAPS SOME MODERATION
NEXT WEEKEND AFTER COLD FRONTS PASS THROUGH.
TATE/SANTORELLI
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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