259
FXUS02 KWBC 131858
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 PM EDT SUN APR 13 2025
VALID 12Z WED APR 16 2025 - 12Z SUN APR 20 2025
..OVERVIEW
AS THE MEDIUM RANGE PERIOD BEGINS WEDNESDAY, AN UPPER LOW WILL BE
MOVING ACROSS SOUTHEASTERN CANADA WITH TROUGHING EXTENDING SOUTH
ACROSS THE EASTERN U.S. AND UPPER RIDGING WILL BE IN POSITION
ACROSS THE PLAINS. UPSTREAM, AN ENERGETIC TROUGH OVER WESTERN
CANADA IS EXPECTED TO BEGIN NUDGING INTO THE NORTHWEST WHILE A
PACIFIC UPPER LOW MEANDERS EAST TOWARDS THE COAST OF CALIFORNIA.
THE TROUGH IS FORECAST TO DIVE SOUTHWARDS ACROSS THE WEST DURING
THE SECOND HALF OF NEXT WEEK AND FORM A CLOSED LOW OVER THE
SOUTHWEST. COOLER TEMPERATURES AND INCREASED PRECIPITATION CHANCES
ARE EXPECTED WITH THIS TROUGH/LOW, INCLUDING THE POTENTIAL FOR
HEAVY SNOW IN THE NORTHERN/CENTRAL ROCKIES WEDNESDAY AND THURSDAY.
MEANWHILE, A NORTHERN STREAM TROUGH IS FORECAST TO SWING ACROSS
NORTH-CENTRAL AND NORTHEASTERN U.S., ACCOMPANIED BY A STRENGTHENING
SURFACE LOW PRESSURE SYSTEM AND WIDESPREAD PRECIPITATION CHANCES
FROM THE MIDWEST TO THE NORTHEAST. BY NEXT WEEKEND, THE FRONTAL
SYSTEM WILL BECOME ELONGATED AND SETTLE ACROSS THE SOUTHERN PLAINS
AND MIDDLE/LOWER MISSISSIPPI VALLEY. THIS SET UP COULD RESULT IN
HEAVY RAINFALL, AND WILL CONTINUE TO MONITOR THIS POTENTIAL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
AFTER A SIGNIFICANT PATTERN CHANGE OVER THE PAST COUPLE OF DAYS,
MODELS HAVE NOW STABILIZED ON THE OVERALL PATTERN DESCRIBED ABOVE
FOR MID TO LATE NEXT WEEK. ALL AVAILABLE MODEL GUIDANCE OVER THE
PAST 24 HOURS HAS CONSISTENTLY SHOWN UPPER LEVEL ENERGY DIVING
SOUTH ACROSS THE WEST AND FORMING A CLOSED LOW OVER THE SOUTHWEST.
OVERALL, MODEL AGREEMENT IS GOOD, BUT THERE ARE SOME DIFFERENCES IN
THE DETAILS, SUCH AS HOW THE LOW MOVING SOUTH ACROSS THE WEST WILL
INTERACT WITH ENERGY MOVING EAST FROM THE PACIFIC AND
TIMING/POSITION OF THE LATE WEEK NORTHERN STREAM TROUGH.
FOR THE WESTERN LOW, THE 00Z CMC AND UKMET SOLUTIONS FALL EAST OF
WHERE THE 00Z ECMWF AND 06Z GFS HAVE THE LOW, BUT THE EASTERN
POSITION IS CLOSER TO THE ENSEMBLE MEAN POSITIONS FROM THE LATEST
GEFS/ECENS/CMCE. THE 00Z ECMWF IS ON THE SOUTHERN EDGE OF MODEL
SPREAD, BUT THE 12Z GFS TRENDED SOUTH, CLOSER TO THE ECMWF
SOLUTION. OVERALL, A SOLUTION IN THE MIDDLE OF THE EAST/WEST SPREAD
SEEMED REASONABLE WITH A SLIGHTLY SOUTHWARD BIAS TOWARDS THE ECMWF
SOLUTION. ONCE THE TROUGH/LOW REACHES THE SOUTHWEST IT SHOULD
INTERACT WITH PACIFIC ENERGY FROM THE PACIFIC LOW. MODELS ARE
SHOWING POTENTIAL FOR SOME PACIFIC ENERGY TO BE EJECTED NORTHEAST
ACROSS THE CENTRAL U.S. TOWARDS THE MIDWEST, WHICH COULD ENHANCE
PRECIPITATION FRIDAY INTO SATURDAY.
FOR THE NORTHERN STREAM TROUGH, THERE IS QUITE A BIT OF SPREAD
AMONG THE DIFFERENT MODEL SOLUTIONS. THE 06Z GFS SEEMED TO BE THE
FARTHEST OUTLIER FROM THE GENERAL CONSENSUS, WITH A SLOWER AND MORE
SOUTHWARDS TRACK. THE 00Z GFS WAS CLOSER TO THE ECMWF SOLUTIONS,
WHICH FALLS IN LINE WITH THE ENSEMBLE MEAN SOLUTIONS AS WELL.
HOWEVER, THE 12Z GFS HELD ON TO THE SLOWER AND SOUTHERN TREND. FOR
NOW, A SOLUTION CLOSER THE THE MEANS WAS FAVORED, BUT THERE IS
POTENTIAL FOR THIS TO CHANGE IN FUTURE ITERATIONS OF THE FORECAST.
WPC'S AFTERNOON FORECAST BLEND CONSISTED OF PURELY DETERMINISTIC
GUIDANCE FROM THE 06Z GFS AND 00Z ECMWF/CMC/UKMET FOR THE FIRST TWO
DAYS (WEDNESDAY AND THURSDAY). FOR THE REST OF THE PERIOD, THE 06Z
GFS WAS PHASED OUT AND THE 00Z GFS WAS PHASED IN, AND ENSEMBLE
MEANS FROM THE GEFS AND ECENS WERE ADDED IN INCREASING AMOUNTS.
..WEATHER/HAZARDS HIGHLIGHTS
THERE WILL LIKELY BE SOME LINGERING PRECIPITATION IN THE NORTHEAST
ON WEDNESDAY UNDER THE UPPER TROUGH AXIS, AND A SHORTWAVE COULD
PRODUCE SOME MODEST RAIN ACROSS THE MID-MISSISSIPPI VALLEY.
HOWEVER, A RAINFALL TOTALS SHOULD STAY WELL BELOW EXCESSIVE
RAINFALL THRESHOLDS, SO THERE ARE NO RISK AREAS ON THE DAY 4
EXCESSIVE RAINFALL OUTLOOK.
MORE SIGNIFICANT PRECIPITATION IS EXPECTED ACROSS THE WEST WITH
THE COMBINING ENERGIES FROM THE UPPER LOWS. PRECIPITATION CHANCES
WILL SPREAD FROM THE NORTHERN ROCKIES WEDNESDAY-THURSDAY TO THE
CENTRAL ROCKIES AND SOUTHWEST THURSDAY-FRIDAY. WITH THE COLD UPPER
TROUGH, ACCUMULATING SNOW IN HIGHER ELEVATIONS IS LIKELY, WITH THE
HEAVIEST SNOW EXPECTED IN THE HIGHER ELEVATIONS OF WYOMING AND
SOUTHERN MONTANA. PRECIPITATION AMOUNTS HAVE TRENDED UP SLIGHTLY IN
THE SIERRA NEVADA AND ACROSS THE GREAT BASIN, INCLUDING SOME
HIGHER ELEVATION SNOW IN THE SIERRA AND WASATCH. SOME PRECIPITATION
IS FORECAST TO CONTINUE IN THE FOUR CORNERS STATES INTO NEXT
WEEKEND.
AS THE UPPER LOW DIVES SOUTH IN THE WEST, A SMALLER PORTION OF THE
NORTHERN STREAM ENERGY WILL CONTINUE EAST, TRAILING ALONG THE
NORTHERN TIER OF THE NATION WITH AN ACCOMPANYING SURFACE LOW
PRESSURE SYSTEM. THIS WILL SUPPORT SHOWER AND THUNDERSTORM CHANCES
FROM THE NORTHERN PLAINS TO THE MIDWEST ON THURSDAY. LOCALLY HEAVY
RAIN RATES MAY BE POSSIBLE IN THUNDERSTORMS, BUT STORMS SHOULD BE
MOVING QUICKLY WITH THE PROGRESSIVE LOW PRESSURE SYSTEM WHICH WOULD
LIMIT ANY FLOODING CONCERNS. FOR THIS REASON, THERE ARE NO RISK
AREAS ON THE DAY 5 EXCESSIVE RAINFALL OUTLOOK.
RAIN CHANCES WILL CONTINUE EAST INTO THE GREAT LAKES REGION ON
FRIDAY AND THE NORTHEAST AND MID-ATLANTIC ON SATURDAY. MEANWHILE,
THE TAIL END OF THIS FRONTAL SYSTEM COMBINING WITH A FRONT AHEAD OF
THE SLOW MOVING SOUTHWEST UPPER LOW COULD SUPPORT A FOCUS FOR
HEAVY RAIN FROM THE SOUTHERN PLAINS TO THE MID-MISSISSIPPI VALLEY,
WITH MODEST RAINFALL CHANCES EXTENDING INTO THE OHIO VALLEY AS
WELL. SOME AREAS COULD OVERLAP WITH AREAS OF THE OHIO AND
MISSISSIPPI VALLEYS THAT MAY STILL BE SENSITIVE FROM RECENT
FLOODING, BUT FORTUNATELY THE AXIS OF THE HEAVIEST AMOUNTS THROUGH
SATURDAY IS EXPECTED TO BE TO THE WEST. EVEN SO, RUNOFF FROM THESE
AREAS COULD FLOW INTO THE MISSISSIPPI RIVER, COULD EXACERBATE
ONGOING FLOODING ISSUES IN SOME AREAS. THE FORECAST DETAILS COULD
CHANGE OVER THE NEXT FEW DAYS AND SHOULD BE CLOSELY MONITORED TO
ASSESS ANY POSSIBLE IMPACTS.
INITIAL UPPER RIDGING ACROSS PORTIONS OF THE INTERIOR WEST AND
PLAINS WILL ALLOW FOR ABOVE NORMAL TEMPERATURES THERE. TEMPERATURES
ARE GENERALLY FORECAST TO BE 10-20 DEGREES ABOVE AVERAGE, AND EVEN
UP TO 25 DEGREES ABOVE NORMAL IN THE CENTRAL AND SOUTHERN PLAINS ON
THURSDAY WITH HIGHS IN THE 90S FROM TEXAS TO KANSAS. COOLER THAN
AVERAGE TEMPERATURES ARE LIKELY IN THE EAST ON WEDNESDAY AND
THURSDAY. LOWS SHOULD BE 5-10 DEGREES BELOW AVERAGE AND HIGHS 10-20
DEGREES BELOW AVERAGE. AFTER THAT, BELOW NORMAL TEMPERATURES ARE
EXPECTED TO DEVELOP SOUTHWARD ACROSS THE WEST UNDERNEATH THE UPPER
LOW WHILE ABOVE NORMAL TEMPERATURES GRADUALLY SHIFT TOWARDS THE
EAST, BECOMING MORE LIMITED TO THE SOUTHEAST NEXT WEEKEND.
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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