797
FXUS02 KWBC 130700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT SUN APR 13 2025
VALID 12Z WED APR 16 2025 - 12Z SUN APR 20 2025
..OVERVIEW
AS THE MEDIUM RANGE PERIOD BEGINS WEDNESDAY, UPPER TROUGHING WILL
BE IN PLACE OVER THE EAST, WHILE AN UPPER RIDGE SETS UP OVER THE
HIGH PLAINS JUST AHEAD OF AN ENERGETIC TROUGH OVER WESTERN CANADA
SNEAKING INTO THE NORTHWEST. THIS LATTER TROUGH IS FORECAST TO DIVE
SOUTH ACROSS THE INTERIOR WEST WHILE INTERACTING WITH SOUTHERN
STREAM TROUGHING TRACKING EAST FROM THE EASTERN PACIFIC TO FORM A
LIKELY CLOSED LOW SETTLING OVER THE SOUTHWESTERN U.S. LATE WEEK.
THE TROUGHING WILL BRING COOLER TEMPERATURES AND PRECIPITATION TO
THE WEST, INCLUDING SOME POSSIBLY HEAVY SNOW IN THE
NORTHERN/CENTRAL ROCKIES WEDNESDAY TO FRIDAY. MEANWHILE SOME
NORTHERN STREAM TROUGHING AND A DEVELOPING LOW PRESSURE SYSTEM
SHOULD LEAD TO WIDESPREAD RAIN CHANCES ACROSS PARTS OF THE MIDWEST
BY THURSDAY AND INTO THE GREAT LAKES AND NORTHEAST LATE WEEK. BY
FRIDAY INTO NEXT WEEKEND, THE COLD FRONT ASSOCIATED WITH THE
SURFACE LOW IS FORECAST TO BECOME ELONGATED AND SETTLE ACROSS THE
SOUTH-CENTRAL U.S. WHILE MOISTURE STREAMS IN AHEAD OF THE SOUTHWEST
UPPER LOW. THIS COULD CAUSE HEAVY RAINFALL IN THE SOUTHERN PLAINS
TO MID/LOWER MISSISSIPPI VALLEY, AND WILL CONTINUE TO MONITOR THIS
POTENTIAL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
AFTER A SIGNIFICANT PATTERN CHANGE IN THE LAST COUPLE OF DAYS,
MODELS HAVE NOW STABILIZED BETTER ON THE OVERALL PATTERN DESCRIBED
ABOVE FOR MID TO LATE WEEK INTO NEXT WEEKEND. THERE REMAINS GOOD
MODEL AGREEMENT FOR THE FIRST UPPER TROUGH IN THE EAST TO SHIFT
EASTWARD INTO THE ATLANTIC LATER THIS WEEK AND A GOOD SIGNAL FOR
RIDGING BEHIND IT. THERE IS RELATIVELY MORE SPREAD IN THE EVOLUTION
OF THE WEST TROUGH (THOUGH CERTAINLY MUCH LESS SPREAD THAN A DAY
AGO). A SOUTHERN STREAM UPPER LOW IS FORECAST TO MOVE FROM THE
EASTERN PACIFIC WEDNESDAY INTO CALIFORNIA BY THURSDAY, WHILE
SIGNIFICANT ENERGETIC TROUGHING DIGS SOUTH INTO THE NORTHWEST.
THESE SHOULD FORM A CLOSED UPPER LOW ATOP THE GREAT BASIN AND
SOUTHWEST LATE WEEK. ON THE BROAD SCALE THESE FEATURES LOOK
COMBINED BY FRIDAY OR SO, BUT SOME ENERGY MAY SNEAK AROUND THE BASE
OF THE DEVELOPING UPPER LOW AND EJECT INTO THE CENTRAL U.S.
FRIDAY-SATURDAY AND POSSIBLY ENHANCE RAIN. THE 12Z CMC/UKMET WERE A
BIT NORTHEAST WITH THE CLOSED UPPER LOW POSITION AROUND FRIDAY
COMPARED TO OTHER GUIDANCE, WHILE GFS RUNS (INCLUDING THE NEW 00Z
GFS) WERE FARTHER SOUTHWEST. A POSITION LIKE THE ECMWF SEEMS TO BE
THE BEST MIDDLE GROUND AND BEST ALIGNED WITH THE ENSEMBLE MEANS.
THE SOUTHWEST UPPER LOW LOOKS TO BECOME CUT OFF AS NORTHERN STREAM
ENERGY TRACKS EASTWARD WITHOUT IT. THERE ARE SOME POSITION
DIFFERENCES IN THE SOUTHWEST UPPER LOW BY NEXT WEEKEND AS IT SLOWLY
MOVES EASTWARD. THESE ARE MOSTLY MINOR, AS DETERMINISTIC MODELS
AND EC-BASED AI MODELS ARE IN FAIR ALIGNMENT, THOUGH THE 12Z ECMWF
BECAME NEGATIVELY TILTED BY NEXT SUNDAY. HOWEVER, INTERESTINGLY
MANY OF THE GFS-BASED AI MODELS (ASIDE FROM THE AURORA) STAYED MUCH
FARTHER WEST IN THE EASTERN PACIFIC WITH THE UPPER LOW CENTER,
WHICH WAS NOT FAVORED. THEN REGARDING THE NORTHERN TIER TROUGH,
THERE ARE SOME TIMING DIFFERENCES WITH IT AND THE RESULTING SURFACE
LOW, INCLUDING THE 18Z GFS THAT WAS SLOWER THAN CONSENSUS. NEWER
00Z MODELS LOOK REASONABLY AGREEABLE FOR THE LATE MEDIUM RANGE
PERIOD TIMEFRAME.
THUS THE WPC FORECAST USED A BLEND OF THE DETERMINISTIC MODELS
FAVORING THE ECMWF/GFS EARLY IN THE PERIOD, WITH INCREASING
PROPORTIONS OF THE ENSEMBLE MEANS TO HALF DAY 6 AND MORE DAY 7 AS
MODEL SPREAD INCREASED IN THE DETAILS. THERE WAS BETTER CONTINUITY
WITH THE PREVIOUS FORECAST ISSUANCE COMPARED TO 24 HOURS AGO, SO
HOPEFULLY THE FORECAST WILL CONTINUE TO BE MORE STABLE.
..WEATHER/HAZARDS HIGHLIGHTS
SOME LINGERING RAIN AND SNOW IS FORECAST FOR THE INTERIOR
NORTHEAST MIDWEEK UNDERNEATH THE UPPER TROUGH AXIS. ALSO ON
WEDNESDAY INTO WEDNESDAY NIGHT, A SHORTWAVE COULD PRODUCE SOME
MODEST RAIN ACROSS THE MIDDLE MISSISSIPPI VALLEY, BUT WITHOUT MUCH
INSTABILITY TO WORK WITH, RAIN AMOUNTS SHOULD STAY WELL BELOW ANY
EXCESSIVE RAINFALL CONCERNS.
MEANWHILE, THE COMBINING ENERGIES IN THE WEST WILL SPREAD
SIGNIFICANT PRECIPITATION CHANCES THERE. PRECIPITATION IS LIKELY IN
THE NORTHERN ROCKIES WEDNESDAY-THURSDAY AND SPREADING INTO THE
CENTRAL ROCKIES THURSDAY-FRIDAY. WITH THE COLD UPPER TROUGH,
ACCUMULATING SNOW IN HIGHER ELEVATIONS IS LIKELY, AND SNOW LOOKS TO
BE HEAVIEST IN THE HIGHER ELEVATIONS OF WYOMING PEAKING THURSDAY.
PRECIPITATION AMOUNTS HAVE TRENDED UP SOMEWHAT IN THE SIERRA NEVADA
ACROSS THE GREAT BASIN AS WELL, 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 ENERGETIC UPPER LOW DIVES SOUTH, A SMALLER PORTION OF THE
NORTHERN STREAM ENERGY WILL CONTINUE EAST, TRAILING ALONG THE
NORTHERN TIER OF THE NATION, ALONG WITH A SURFACE LOW PRESSURE
SYSTEM. THIS WILL SUPPORT RAIN AND POSSIBLY THUNDERSTORM CHANCES IN
NORTHERN PLAINS AND MIDWEST ON THURSDAY. LOCALLY HEAVY RAIN RATES
MAY BE POSSIBLE IN THUNDERSTORMS, BUT CURRENTLY THIS IS NOT LIKELY
TO CAUSE ANY FLOODING CONCERNS AS RAIN TOTALS SHOULD STAY MODEST
AND STORMS WILL BE MOVING QUICKLY. THUS NO EXCESSIVE RAINFALL AREA
WAS DELINEATED IN THURSDAY'S DAY 5 ERO. RAIN CHANCES CONTINUE INTO
THE GREAT LAKES REGION FRIDAY AND THE NORTHEAST/MID-ATLANTIC
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 IN THE SOUTH-CENTRAL U.S. AS AMPLE
MOISTURE STREAMS IN. THE CURRENT FORECAST SHOWS THE HEAVIEST RAIN
ACROSS THE SOUTHERN PLAINS AND TOWARD THE LOWER/MIDDLE MISSISSIPPI
VALLEY, WITH MORE MODERATE RAIN EAST INTO THE OHIO VALLEY. SOME
AREAS COULD OVERLAP WITH AREAS OF THE OHIO AND MISSISSIPPI VALLEYS
THAT COULD STILL BE SENSITIVE FROM RECENT FLOODING, BUT FORTUNATELY
THE AXIS OF THE HEAVIEST AMOUNTS THROUGH SATURDAY ARE TO THE WEST.
THE FORECAST DETAILS COULD CHANGE OVER THE NEXT FEW DAYS AND
SHOULD BE CLOSELY MONITORED TO ASSESS ANY POSSIBLE IMPACTS.
INITIAL UPPER RIDGING ACROSS THE INTERIOR WEST TO PLAINS WILL
ALLOW FOR ABOVE NORMAL TEMPERATURES THERE. TEMPERATURES ARE
GENERALLY FORECAST TO BE 10-20 DEGREES ABOVE AVERAGE, AND EVEN 25F
ABOVE NORMAL IN THE CENTRAL PLAINS WEDNESDAY-THURSDAY AS
TEMPERATURES REACH THE 90S FROM TEXAS TO KANSAS. COOLER THAN
AVERAGE TEMPERATURES ARE LIKELY IN THE EAST 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.
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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