453
FXUS02 KWBC 121859
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM EDT SAT APR 12 2025
VALID 12Z TUE APR 15 2025 - 12Z SAT APR 19 2025
..OVERVIEW
INITIALLY, AN UPPER LEVEL TROUGH WILL BE MOVING ACROSS THE EASTERN
U.S. AND A CLOSED UPPER LOW WILL BE POSITIONED OFFSHORE OVER THE
EASTERN PACIFIC, WITH RIDGING IN BETWEEN OVER THE INTERMOUNTAIN
WEST. BY THE SECOND HALF OF NEXT WEEK, THE EASTERN TROUGH WILL
SHIFT INTO THE ATLANTIC FOLLOWED BY THE UPPER RIDGE, MAKING WAY FOR
AN ENERGETIC UPPER LOW THAT IS EXPECTED TO DIVE SOUTH ACROSS THE
WEST. THIS LOW IS FORECAST TO INTERACT WITH THE LOW/TROUGH OVER THE
EASTERN PACIFIC AND EJECT ENERGY NORTHEAST TOWARDS THE PLAINS. AT
THE SURFACE, A COUPLE OF COLD FRONTS WILL PUSH ACROSS THE EAST
TUESDAY INTO WEDNESDAY, SUPPORTING PRECIPITATION CHANCES FROM THE
GREAT LAKES TO THE MID-ATLANTIC AND NORTHEAST, THEN THE FOCUS FOR
PRECIPITATION WILL SHIFT TO THE WESTERN AND CENTRAL U.S. AS A
STRONG FRONTAL SYSTEM MOVES SOUTHEAST ACROSS THESE REGIONS.
PORTIONS OF THE ROCKIES COULD SEE NOTABLE SNOWFALL FROM THIS SYSTEM
WEDNESDAY THROUGH FRIDAY. THEN BY NEXT WEEKEND, THIS FRONTAL SYSTEM
IS EXPECTED TO BECOME ELONGATED, STRETCHING FROM THE SOUTHWEST TO
THE NORTHEAST, AND THERE MAY BE A RISK OF HEAVY RAINFALL FROM THE
SOUTHERN PLAINS TO THE OHIO VALLEY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE HAD BEEN SPLIT ON THE EVOLUTION OF NORTHERN STREAM
ENERGY IN THE WEST NEXT WEEK, WITH SOME SOLUTIONS BRINGING ENERGY
SOUTH AND SOME PUSHING IT TO THE EAST. TODAY, ALL AVAILABLE
DETERMINISTIC, ENSEMBLE, AND AI MODEL GUIDANCE ARE DEPICTING THE
ENERGY TAKING A SOUTHWARD TRACK INTO THE WESTERN U.S., WHICH HAS
RESULTED IN SIGNIFICANT CHANGES TO THE FORECAST SINCE YESTERDAY
AFTERNOON. THE FRONTAL EVOLUTION THURSDAY THROUGH SATURDAY HAS
CHANGED DRAMATICALLY, WHICH WILL RESULT IN LARGE CHANGES TO THE
SENSIBLE WEATHER FORECAST. MOST NOTABLY, THE PROBABILITY OF
SNOWFALL IN THE ROCKIES HAS INCREASED WEDNESDAY THROUGH FRIDAY, AND
A WETTER PATTERN IS FAVORED LATE NEXT WEEK FROM THE SOUTHERN
PLAINS TO THE OHIO VALLEY.
FOR WPC'S AFTERNOON FORECAST, A BLEND OF THE DETERMINISTIC 06Z GFS
AND 00Z ECMWF/CMC/UKMET WAS USED FOR THE FIRST TWO DAYS, THEN
ENSEMBLE MEANS FROM THE 06Z GEFS AND 00Z ECENS WERE ADDED IN
INCREASING AMOUNTS THROUGH THE REST OF THE PERIOD. THE GFS AND
ECMWF WERE FAIRLY AGREEABLE WITH THE EXCEPTION OF TIMING AND
PLACEMENT OF SOME FEATURES LATE IN THE PERIOD, AND THEY WERE ALSO
IN LINE WITH AVAILABLE AI GUIDANCE. THE CMC AND UKMET ALSO SHOWED
GOOD AGREEMENT, BUT DEVIATED A BIT FROM THE GENERAL CONSENSUS ON
HOW TO HANDLE NORTHERN STREAM ENERGY ACROSS THE NORTHERN TIER LATE
NEXT WEEK. FOR THIS REASON, THE GFS AND ECMWF WERE GIVEN STRONGER
WEIGHT IN THE WPC FORECAST BLEND THAN THE CMC AND UKMET.
..WEATHER/HAZARDS HIGHLIGHTS
AT THIS TIME, NO RISK AREAS WERE INTRODUCED TO THE DAY 4 (TUESDAY)
AND DAY 5 (WEDNESDAY) EXCESSIVE RAINFALL OUTLOOKS. PRECIPITATION
AMOUNTS ARE FORECAST TO BE MODEST EARLY NEXT WEEK, WITH LITTLE TO
NO RISK OF FLASH FLOODING.
A SURFACE LOW TRACKING THROUGH SOUTHEASTERN CANADA AND ITS
TRAILING COLD FRONT WILL SUPPORT SOME PRECIPITATION FROM THE GREAT
LAKES TO THE MID-ATLANTIC AND NORTHEAST ON TUESDAY, SOME OF WHICH
MAY LINGER INTO WEDNESDAY FOR THE INTERIOR NORTHEAST. TEMPERATURES
ON THE BACKSIDE OF THE LOW COULD BE COLD ENOUGH FOR SNOW AT HIGHER
ELEVATIONS OF THE ADIRONDACKS AND GREEN AND WHITE MOUNTAINS. GUSTY
WINDS WILL ALSO BE POSSIBLE WITH THIS SYSTEM FROM THE
MIDWEST/GREAT LAKES TO THE NORTHEAST AND NORTHERN/CENTRAL
APPALACHIANS. CONDITIONS WILL DRY OUT ACROSS THE EAST MID-WEEK AS
HIGH PRESSURE MOVES IN BEHIND THE SYSTEM.
A WEAKENING UPPER LOW WILL BE POSITIONED OVER THE EASTERN PACIFIC
ON TUESDAY WITH TROUGHING EXTENDING INTO THE SOUTHWEST, WHICH MAY
SUPPORT ISOLATED TO SCATTERED PRECIPITATION FOR THE FOUR CORNERS
STATES. MORE SIGNIFICANT PRECIPITATION CHANCES WILL ARRIVE ON
WEDNESDAY AS THE ENERGETIC UPPER LOW DIVES SOUTHWARD INTO THE WEST.
PRECIPITATION WILL SPREAD FROM THE NORTHERN ROCKIES ON WEDNESDAY,
TO THE GREAT BASIN AND CENTRAL ROCKIES ON THURSDAY, AND INTO THE
FOUR CORNERS REGION BY FRIDAY. THE PROBABILITY OF ACCUMULATING SNOW
HAS INCREASED ACROSS THE ROCKIES WITH THIS FORECAST, AND SOME
LOCATIONS COULD RECEIVE NOTABLE SNOWFALL FROM THIS SYSTEM.
AS THE ENERGETIC UPPER LOW DIVES SOUTH, A SMALLER PORTION OF THE
NORTHERN STREAM ENERGY WILL CONTINUE EAST, TRAILING ALONG THE
NORTHERN TIER OF THE NATION. THIS WILL SUPPORT PRECIPITATION
CHANCES FROM THE NORTHERN PLAINS TO THE MIDWEST AND GREAT LAKES
THURSDAY AND FRIDAY. BY SATURDAY, AN ELONGATED FRONTAL SYSTEM IS
EXPECTED TO STRETCH FROM THE SOUTHWEST TO THE NORTHEAST WITH SHOWER
AND THUNDERSTORM CHANCES SPANNING THE ENTIRE LENGTH OF THE
BOUNDARY. SOUTHERLY FLOW AHEAD OF THE BOUNDARY SHOULD PUSH WARM,
MOIST AIR INTO THE SOUTH-CENTRAL U.S., WHICH COULD CREATE A THREAT
OF HEAVY RAIN FROM THE SOUTHERN PLAINS TO THE MID-MISSISSIPPI AND
OHIO VALLEYS NEXT WEEKEND. DUE TO INCREASED SENSITIVITY TO RAINFALL
ACROSS THE MISSISSIPPI AND OHIO VALLEYS, RAINFALL NEXT WEEK COULD
CAUSE ADDITIONAL FLOODING ISSUES FOR THESE REGIONS. HOWEVER, AT
THIS TIME, THIS WETTER SOLUTION IS STILL UNCERTAIN. THE FORECAST
DETAILS WILL LIKELY CHANGE OVER THE NEXT FEW DAYS AND SHOULD BE
CLOSELY MONITORED TO ASSESS ANY POSSIBLE IMPACTS.
INITIAL MEAN RIDGING ALOFT WILL ALLOW FOR ABOVE NORMAL TEMPERATURES
IN THE WEST, SPREADING INTO THE PLAINS BY MID-WEEK. GENERALLY,
TEMPERATURES ARE FORECAST TO BE 10-20 DEGREES ABOVE AVERAGE, WITH
HIGHS IN THE 90S IN THE DESERT SOUTHWEST TUESDAY AND WEDNESDAY AND
IN THE CENTRAL AND SOUTHERN PLAINS ON THURSDAY. COOLER THAN AVERAGE
TEMPERATURES ARE LIKELY IN THE GREAT LAKES AND OHIO VALLEY ON
TUESDAY AND INTO THE EASTERN U.S. ON WEDNESDAY AND THURSDAY. LOWS
SHOULD BE 5-10 DEGREES BELOW AVERAGE AND HIGHS 10-15 BELOW AVERAGE.
AFTER THAT, BELOW AVERAGE TEMPERATURES ARE EXPECTED TO DEVELOP
SOUTHWARD ACROSS THE WEST UNDERNEATH THE UPPER LOW WHILE ABOVE
NORMAL TEMPERATURES GRADUALLY SHIFT TOWARDS THE EAST AND SOUTHEAST.
DOLAN/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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