442
FXUS02 KWBC 110700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT FRI APR 11 2025
VALID 12Z MON APR 14 2025 - 12Z FRI APR 18 2025
..OVERVIEW
NEXT WEEK, A COUPLE OF NORTHERN STREAM UPPER TROUGHS WILL TRAVERSE
THE NORTH-CENTRAL TO NORTHEASTERN U.S. AND SUPPORT A COUPLE OF
ROUNDS OF PRECIPITATION. MORE SPECIFICALLY, LIGHT TO MODERATE
PRECIPITATION LOOKS TO IMPACT THE EAST-CENTRAL U.S. ON MONDAY ALONG
WITH POTENTIALLY SEVERE STORMS IN THE UPPER OHIO VALLEY, WITH THE
NEXT ROUND OF RAIN SPREADING INTO THE CENTRAL U.S. WEDNESDAY AND
THE EAST-CENTRAL U.S. THURSDAY. MEANWHILE, MEAN UPPER RIDGING
SHOULD BE IN PLACE ACROSS THE INTERIOR WEST, BUT A COUPLE OF
SOUTHERN STREAM UPPER LOWS ARE FORECAST TO SPIN ATOP THE EASTERN
PACIFIC AND APPROACH CALIFORNIA. OTHER THAN SOME WARMER THAN NORMAL
TEMPERATURES ON MONDAY IN THE EAST, THIS PATTERN WILL SUPPORT
COOLER THAN AVERAGE TEMPERATURES IN THE EAST AND WARMER THAN
AVERAGE TEMPERATURES FROM THE WEST INTO THE PLAINS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS IN GOOD AGREEMENT WITH UPPER TROUGHING MOVING
FROM THE NORTH-CENTRAL U.S. ACROSS THE EAST AROUND MONDAY TO
WEDNESDAY, ALONG WITH THE SURFACE LOW TRACKING FROM THE GREAT LAKES
INTO SOUTHEASTERN CANADA. A MULTI-MODEL BLEND WORKED WELL FOR THESE
SYSTEMS. MEANWHILE, THERE IS MUCH MORE SPREAD IN THE DETAILS FOR
SOUTHERN STREAM TROUGHING/EMBEDDED UPPER LOWS IN THE EASTERN
PACIFIC EVEN AT THE START OF THE PERIOD MONDAY. INITIALLY, AN UPPER
LOW MAY BE NEAR THE CALIFORNIA COAST MONDAY, WHICH IS ESPECIALLY
SHOWN BY NON-NCEP GUIDANCE, WHILE GFS RUNS HAVE BEEN FOCUSING ON AN
UPPER LOW FARTHER SOUTHWEST WELL OFFSHORE. TO BE FAIR, THIS MAY BE
A DOUBLE-BARRELED LOW ESPECIALLY PER AI/ML MODELS. BUT GENERALLY
FAVORED THE 12Z ECMWF DEPICTION AND THE NEWER 00Z EC SEEMS SIMILAR.
MODELS SHOW THIS ENERGY TRACKING EASTWARD TUESDAY WHILE ADDITIONAL
ENERGY DIVES SOUTH THROUGH THE EASTERN PACIFIC TO FORM ANOTHER
UPPER LOW THAT BECOMES DOMINANT. MODELS SHOW TIMING SPREAD IN ITS
SLOW APPROACH TOWARD CALIFORNIA, WITH THE 12Z CMC ONE OF THE
FASTEST MODELS TO BRING THE UPPER LOW EAST COMPARED TO CONSENSUS.
MEANWHILE IN THE NORTHERN STREAM, THERE HAS BEEN A MARKED CHANGE IN
THE 00Z GUIDANCE COMPARED TO THE 12/18Z GUIDANCE CYCLE THAT WAS
USED FOR THE FORECAST. THE NEWER CYCLE SHOWS MORE TROUGHING DIGGING
INTO THE NORTHERN PLAINS BY THURSDAY, IMPACTING SURFACE LOW
PRESSURE AND PRECIPITATION. INTERESTINGLY SOMETHING SIMILAR WAS
INDICATED BY THE 18Z AIFS, THOUGH THE AIFS WAS EVEN MORE AGGRESSIVE
WITH THE TROUGHING. SO EXPECT TIMING AND PLACEMENT DIFFERENCES IN
THE FRONTAL FORECASTS IN FUTURE FORECASTS. THUS THE WPC FORECAST
BEGAN WITH A MULTI-MODEL BLEND FAVORING THE ECMWF EARLY IN THE
FORECAST PERIOD, WITH SOME ENSEMBLE MEAN INCLUSION INCREASING TO
HALF BY DAY 6 AND MORE BY DAY 7 GIVEN THE INCREASING SPREAD.
..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. THESE STORMS
DO NOT LOOK LIKE MUCH OF A FLASH FLOODING THREAT, AS 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 AND EAST OF WHERE HEAVY RAINFALL
HAS OCCURRED IN RECENT WEEKS. THUS THE DAY 4-5 EROS SHOW NO RISK
AREAS. 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 MODEST
RAINFALL IN THE EAST-CENTRAL U.S. THURSDAY.
PERSISTENT WARMER THAN AVERAGE TEMPERATURES WILL BE IN PLACE IN THE
WEST UNDER MEAN RIDGING. AS THE WEEK PROGRESSES, WARMER THAN NORMAL
TEMPERATURES WILL SPREAD INTO THE PLAINS. THE REGION FROM THE GREAT
BASIN TO THE NORTHERN/CENTRAL HIGH PLAINS SHOULD BE PARTICULARLY
ABOVE NORMAL BY 15-20 DEGREES. FARTHER EAST, WARMER THAN NORMAL
TEMPERATURES ARE LIKELY FROM SOUTHERN TEXAS INTO THE EASTERN U.S.
ON MONDAY, BUT COLD FRONTS SHOULD COOL THE EASTERN THIRD OF THE
U.S. TO BELOW NORMAL AROUND MIDWEEK, WITH SOME MODERATION CLOSER TO
AVERAGE LATER WEEK.
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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