729
FXUS02 KWBC 111857
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 PM EDT FRI APR 11 2025
VALID 12Z MON APR 14 2025 - 12Z FRI APR 18 2025
..OVERVIEW
GUIDANCE AGREES RATHER WELL FOR A LEADING NORTHERN STREAM UPPER
TROUGH AND SURFACE LOW/FRONTAL SYSTEM THAT WILL AFFECT THE CENTRAL
THROUGH EASTERN U.S. DURING THE FIRST HALF OF NEXT WEEK. THIS
SYSTEM WILL BRING MOSTLY LIGHT TO MODERATE PRECIPITATION ON MONDAY
ALONG WITH POTENTIALLY SEVERE STORMS IN THE UPPER OHIO VALLEY, WITH
A PERIOD OF BRISK WINDS FROM THE PLAINS INTO THE NORTHEAST. THE
WESTERN RIDGE/EASTERN TROUGH PATTERN EARLY-MID WEEK SHOULD PROMOTE
WARM TEMPERATURES OVER THE WEST AND COOL WEATHER OVER THE EAST.
FROM ABOUT WEDNESDAY ONWARD THERE IS RAPIDLY INCREASING SPREAD FOR
THE EVOLUTION OF THE NEXT SHORTWAVE TROUGH IN THE SERIES. SOMEWHAT
MORE GUIDANCE SHOWS THIS ENERGY FEEDING INTO YET ANOTHER AMPLIFIED
EASTERN UPPER TROUGH BY NEXT FRIDAY, LEADING TO ANOTHER ROUND OF
RAIN SPREADING ACROSS THE CENTRAL AND EASTERN U.S. MID- LATE WEEK,
WHILE MEAN RIDGING PERSISTS OVER THE WEST. HOWEVER THERE IS A
MEANINGFUL MINORITY THAT SHOWS THE ENERGY DIGGING INTO THE WEST
INSTEAD OF FARTHER EASTWARD, OBVIOUSLY WITH MAJOR DIFFERENCES IN
THE SURFACE/PRECIPITATION PATTERN AND TEMPERATURE ANOMALIES.
MEANWHILE A WEAKENING SOUTHERN STREAM UPPER LOW SHOULD REACH THE
SOUTHWEST BY TUESDAY WITH A LARGER SCALE UPPER LOW LURKING OFFSHORE
SOUTHERN CALIFORNIA FOR THE REST OF THE WEEK (DEPENDING ON FLOW
DETAILS OVER THE WESTERN U.S.).
..GUIDANCE/PREDICTABILITY ASSESSMENT
WITH THE LATEST GUIDANCE CLUSTERING WELL IN PRINCIPLE FOR THE
LEADING CENTRAL-EASTERN U.S. UPPER TROUGH AND ASSOCIATED SYSTEM,
THE PRIMARY FOCUS OF DECISION-MAKING TODAY REGARDS THE SIGNIFICANT
GUIDANCE DIVERGENCE THAT TAKES PLACE BEHIND THE FIRST TROUGH.
LOOKING AT AVAILABLE DATA THROUGH THE 00Z/06Z CYCLES, THERE WAS A
PRONOUNCED TREND IN GFS/GEFS RUNS TOWARD RECENT ECMWF/ECENS
SOLUTIONS DEPICTING A MORE AMPLIFIED EASTERN U.S. UPPER TROUGH BY
LATE IN THE WEEK WITH LOW PRESSURE GRAVITATING TOWARD THE
CENTRAL/UPPER GREAT LAKES AS OF EARLY FRIDAY. THE 00Z CMC WAS A BIT
WESTWARD BUT SIMILAR IN PRINCIPLE WHILE THE 00Z CMCENS AND UKMET
MEANS FIT INTO THIS THEME ALBEIT IN SLIGHTLY WEAKER FASHION. SOME
CMC/ECENS ENSEMBLE MEMBERS PROVIDED A FIRST SUGGESTION OF A VERY
DIFFERENT EVOLUTION HOWEVER, WITH A HANDFUL OF EACH DIGGING A LOT
MORE TROUGH ENERGY INTO THE WEST. THE 00Z ICON ALSO FIT INTO THIS
SCENARIO. 00Z/06Z ML (MACHINE LEARNING) MODELS SHOWED A DRAMATIC
SPLIT AS WELL, WITH A COUPLE (INCLUDING MULTIPLE ECMWF AIFS RUNS)
OPTING FOR MORE WESTERN TROUGHING VERSUS THE OTHER ML MODELS PLUS
THE 00Z AIFS MEAN FAVORING THE EASTERN TROUGH.
BASED ON THE RELATIVELY GREATER PROPORTION OF GUIDANCE DEPICTING
THE EASTERN TROUGH SCENARIO BY LATE WEEK, WHICH WOULD ALSO
REPRESENT SOME PERSISTENCE OF THE OVERALL MEAN PATTERN, FORECAST
PREFERENCES BY THE LATTER HALF OF NEXT WEEK TRENDED TO A BLEND OF
THE 00Z ECMWF/CMC AND THEIR ENSEMBLE MEANS. THIS LED TO AN EARLY
FRIDAY GREAT LAKES SURFACE SYSTEM CLOSE TO THE DEPTH RECOMMENDED BY
THE CLUSTER OF ML MODELS WITH THAT SOLUTION. 00Z/06Z GFS RUNS AND
THE GEFS MEAN DIFFERED ENOUGH FROM OTHER SOLUTIONS IN THE CLUSTER
FOR DETAILS TO EXCLUDE FROM THE FORECAST. AN OPERATIONAL MODEL
BLEND PROVIDED A GOOD STARTING POINT EARLIER IN THE WEEK.
NEW 12Z GUIDANCE ADDS FURTHER CONFUSION TO THE LATE-WEEK FORECAST,
WITH THE ECMWF AND CMC BOTH FLIPPING TO THE WESTERN TROUGH
SCENARIO BUT THE ICON ADJUSTING TO AN INTERMEDIATE IDEA OF A
PLAINS/CENTRAL ROCKIES UPPER TROUGH BY NEXT FRIDAY. ON THE OTHER
HAND THE 12Z GFS HAS ADJUSTED VERY CLOSE TO THE PREFERRED FORECAST
DESCRIBED ABOVE AND THE GENERAL SURFACE PATTERN OF THE 12Z GEFS/06Z
UKMET MEANS ARE SIMILAR TO OR A BIT SLOWER VERSUS PREFERENCE.
..WEATHER/HAZARDS HIGHLIGHTS
A SURFACE LOW TRACKING FROM THE UPPER GREAT LAKES MONDAY THROUGH
SOUTHEASTERN CANADA TUESDAY AND ITS TRAILING COLD FRONT WILL
SUPPORT SOME PRECIPITATION ACROSS THE EAST-CENTRAL AND EASTERN U.S.
MONDAY-TUESDAY. AN UPPER TROUGH WILL PROVIDE DYNAMICAL SUPPORT AND
SOME INSTABILITY SHOULD POOL IN THE UPPER OHIO VALLEY TO
POTENTIALLY PRODUCE SEVERE THUNDERSTORMS, WITH DAMAGING WINDS AS
THE PRIMARY THREAT, PER THE STORM PREDICTION CENTER. RAIN RATES
COULD POSSIBLY REACH AN INCH PER HOUR AROUND OHIO/WEST
VIRGINIA/PENNSYLVANIA, BUT THESE SHOULD BE SHORT-LIVED AS THESE
STORMS ARE FAST MOVING AND NORTH/EAST OF WHERE HEAVIEST RAINFALL
HAS OCCURRED IN RECENT WEEKS. HOWEVER SOME NON-GFS MODELS ARE
SHOWING A LITTLE MORE OF A SIGNAL NOW FOR LOCALLY ENHANCED
RAINFALL. THIS IS A VERY SMALL-SCALE AREA AND A FEW DAYS OUT IN
TIME SO THE DAYS 4-5 EROS MAINTAIN NO RISK AREAS, BUT TYPICAL
TERRAIN SENSITIVITY AND TRENDS SEEM TO MERIT SOME MONITORING OVER
FUTURE CYCLES INTO THE SHORT RANGE. ON THE BACKSIDE OF THE LOW,
TEMPERATURES COULD BE COLD ENOUGH FOR SNOW IN THE U.P. OF MICHIGAN
MONDAY AND INTO HIGHER ELEVATIONS OF THE ADIRONDACKS AND GREEN AND
WHITE MOUNTAINS INTO TUESDAY. FLOW BEHIND THE NORTHERN TIER STORM
SHOULD PRODUCE STRONG AND GUSTY WINDS OVER THE NORTHERN/CENTRAL
PLAINS INTO MONDAY, WITH SOME BRISK WINDS REACHING INTO THE GREAT
LAKES/NORTHEAST THEREAFTER.
A WEAKENING UPPER LOW REACHING THE SOUTHWEST BY TUESDAY MAY
PRODUCE SOME VERY SCATTERED AND LIGHT PRECIPITATION. THEN AS
SURFACE LOW PRESSURE DEVELOPS IN THE CENTRAL HIGH PLAINS AND MOVES
EAST, RAIN IS FORECAST TO SPREAD ACROSS THE CENTRAL PLAINS TO
MIDDLE MISSISSIPPI VALLEY FOR MIDWEEK. THERE IS STILL UNCERTAINTY
WITH HOW HEAVY THIS RAINFALL WILL BE AND THE FORECAST WILL CONTINUE
TO BE REFINED WITH TIME. NORTHERN STREAM ENERGY COULD ALSO PRODUCE
LIGHT PRECIPITATION OVER THE GREAT LAKES REGION WEDNESDAY, AND
THESE FEATURES MAY COMBINE TO PRODUCE AN EXPANDING AREA OF RAINFALL
WITH VARYING INTENSITY OVER THE EASTERN HALF OF THE COUNTRY
THURSDAY- FRIDAY. DEPENDING ON HOW DEEP THE SUPPORTING UPPER TROUGH
AND POSSIBLE EMBEDDED LOW BECOME TOWARD THE END OF THE WEEK, IT
COULD BECOME COLD ENOUGH TO PRODUCE SOME SNOW OVER THE UPPER GREAT
LAKES. NOTE THAT THERE IS A MINORITY POTENTIAL FOR AN ALTERNATE
PATTERN EVOLUTION WHICH MAY LEAD TO LESS SOUTHWARD EXTENT OF
PRECIPITATION OVER THE EAST AND AT THE SAME TIME GREATER COVERAGE
OF RAIN AND HIGHER ELEVATION SNOW OVER PARTS OF THE WEST/ROCKIES
(VERSUS THE CURRENT RELATIVELY DRY FORECAST). CONTINUE TO MONITOR
FORECAST UPDATES FOR ANY SIGNIFICANT TRENDS IN THE MOST LIKELY
SCENARIO.
MEAN RIDGING ALOFT WILL FAVOR WARMER THAN AVERAGE TEMPERATURES
OVER THE WEST AND EXPANDING INTO THE PLAINS EARLY-MID NEXT WEEK (UP
TO PLUS 10-20F OR SO ANOMALIES FOR HIGHS), WHILE THE UPPER TROUGH
MOVING INTO THE EAST WILL BRING COOLER TEMPERATURES OVER THAT PART
OF THE COUNTRY (HIGHS UP TO 10-15F BELOW NORMAL OVER PARTS OF THE
GREAT LAKES INTO APPALACHIANS). WARMER THAN NORMAL TEMPERATURES ARE
ALSO LIKELY FROM SOUTHERN TEXAS INTO THE EASTERN U.S. ON MONDAY
AHEAD OF THE LEADING COLD FRONT. FORECAST CONFIDENCE RAPIDLY
DECLINES BY THURSDAY-FRIDAY. CURRENT FORECAST PREFERENCES WOULD
MAINTAIN VERY WARM TEMPERATURES OVER THE WEST, AS WELL AS THE
SOUTHERN HALF OF THE PLAINS INTO THURSDAY BEFORE FRONTAL PASSAGE,
WHILE THE EAST WOULD TREND BELOW NORMAL AGAIN BY NEXT FRIDAY.
HOWEVER THERE IS SOME POTENTIAL FOR A COOLER TREND OVER PARTS OF
THE WEST AND LESS COOLING FARTHER EAST.
RAUSCH/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 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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