414
FXUS02 KWBC 160659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT WED APR 16 2025
VALID 12Z SAT APR 19 2025 - 12Z WED APR 23 2025
...HEAVY RAINFALL/FLOODING AND SEVERE WEATHER IN PARTS OF THE
CENTRAL U.S. THIS WEEKEND...
..OVERVIEW
AT THE START OF THE MEDIUM RANGE PERIOD SATURDAY, POSITIVELY TILTED
UPPER TROUGHING WILL BE IN PLACE FROM THE NORTH-CENTRAL U.S. TO THE
FOUR CORNERS, PIVOTING EAST INTO SUNDAY. AMPLE MOISTURE INFLOW
AHEAD OF THIS TROUGH AND AN ELONGATED FRONTAL SYSTEM WILL ALLOW FOR
HEAVY RAIN WITH POTENTIAL FLOODING AS WELL AS STRONG TO SEVERE
THUNDERSTORM CHANCES STRETCHING FROM THE SOUTHERN PLAINS INTO THE
LOWER/MIDDLE MISSISSIPPI VALLEY AND PORTIONS OF THE OHIO VALLEY
THIS WEEKEND. SNOW IS LIKELY TO LINGER IN THE COLORADO AND NEW
MEXICO ROCKIES SATURDAY ON THE BACKSIDE OF THE SYSTEM, WHILE WARM
TEMPERATURES ARE LIKELY IN THE EAST AHEAD OF THE COLD FRONT. MODEST
RAINFALL SHOULD SHIFT INTO THE EAST-CENTRAL U.S. BY MONDAY AS THE
FRONT MOVES THROUGH, AND BY TUESDAY SOME MOISTURE MAY RETURN TO THE
CENTRAL U.S. FOR ADDITIONAL RAIN.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE STARTS REASONABLY AGREEABLE ON SATURDAY WITH THE
NORTH-CENTRAL TO SOUTHWESTERN U.S. TROUGHING. HOWEVER, MODELS
QUICKLY DIVERGE WITH THE TIMING OF THE TROUGH(S) PIVOTING EAST EVEN
BY SUNDAY. INTERACTIONS OF ENERGY IN THE NORTHERN AND SOUTHERN
STREAMS OF THE TROUGH PLAY A PART IN THIS. FOR EXAMPLE, THE 12Z
ECMWF WAS QUITE AGGRESSIVE IN SHOWING A SMALL CLOSED LOW IN THE
NORTHERN STREAM TROUGH BY SUNDAY ATOP NORTHERN MINNESOTA, SHAPING
THE TROUGH DIFFERENTLY AND SPEEDING UP THE SURFACE LOW TRACK A BIT.
MEANWHILE THE 12/18Z GFS ARE FAST TO PIVOT THE TROUGH AND
RESULTANT SURFACE LOW (AND QPF). DESPITE THE DYNAMICAL GFS AND
ECMWF ON THE FASTER SIDE, THE AI MODELS CONTINUE TO BE CONSIDERABLY
SLOWER. SOMEWHAT UNUSUALLY, PREFERRED THE CMC/UKMET UPPER TROUGH
AND SURFACE LOW TRACK IN TERMS OF THE DETERMINISTIC MODELS, AS THEY
TENDED TO AGREE WITH THE ENSEMBLE MEANS THE BEST, AND WERE IN
BETWEEN THE FASTER EC/GFS AND SLOWER AI MODELS. THE 18Z GFS IN
PARTICULAR THEN SHOWED THE UPPER TROUGH CENTER/POSSIBLE CLOSED LOW
TRACKING FARTHER EAST ACROSS THE OHIO VALLEY BY MONDAY RATHER THAN
THE PIVOT NORTHEAST THAT NON-NCEP GUIDANCE SHOWED. THE NEWER 00Z
GFS REMAINS FAST AND THEN FARTHER EAST THAN CONSENSUS WITH THE
UPPER AND SURFACE LOW, THOUGH IT EVOLVES THAT WAY SOMEWHAT
DIFFERENTLY WITH A NORTHERN STREAM CONNECTION. THE 00Z CMC AND
UKMET STILL SEEM REASONABLE, WHILE THE 00Z ECMWF LOOKS BETTER THAN
THE 12Z RUN WITH THE TROUGH AND LOW SINCE IT NO LONGER HAS THE
UNUSUAL NORTHERN STREAM UPPER LOW.
MOST GUIDANCE SHOWS THESE FEATURES LIFTING NORTH AND WEAKENING
INTO THE WORKWEEK. THE UPPER PATTERN LOOKS TO FLATTEN OUT OVERALL,
BUT THERE COULD BE SOME TROUGHING IN THE NORTHWEST BY MONDAY WITH
SOME MODEL SPREAD IN ITS EVOLUTION OF TRACKING MORE SOUTH OR MORE
EAST INTO TUESDAY-WEDNESDAY. THE 12Z CMC WAS THE STRONGEST WITH
DIVING ENERGY SOUTHWARD COMPARED TO CONSENSUS THAT SKIRTED THE
TROUGH EASTWARD. SO DID NOT PREFER THE 12Z CMC IN THE WEST, AND THE
00Z CMC LOOKS MORE CONSISTENT WITH OTHER MODELS.
THE WPC FORECAST USED A MULTI-MODEL BLEND FAVORING THE CMC FOR THE
EARLY PART OF THE PERIOD, BUT QUICKLY INCREASED THE PROPORTION OF
GEFS/EC ENSEMBLE MEANS AS THE PERIOD PROGRESSED. THE BLEND WAS HALF
MEANS BY DAY 5 AND ALL MEANS BY DAY 7 AS MODEL SPREAD INCREASED.
..WEATHER/HAZARDS HIGHLIGHTS
ON SATURDAY, THE SLOW PIVOT OF THE BASE OF THE UPPER TROUGH, A
CONSOLIDATING FRONTAL SYSTEM WITH SOME WEST-EAST ORIENTATION TO
PROMOTE POSSIBLE TRAINING STORMS, AND PRECIPITABLE WATER ANOMALIES
OVER THE 90TH PERCENTILE ARE LIKELY TO CAUSE WIDESPREAD HEAVY RAIN
OF 3+ INCHES, WITH LOCALLY HIGHER AMOUNTS. A SLIGHT RISK OF
EXCESSIVE RAINFALL STRETCHES FROM NORTH-CENTRAL TEXAS ACROSS
PORTIONS OF OKLAHOMA, ARKANSAS, MISSOURI, AND FAR SOUTHEAST KANSAS
AND SOUTHWESTERN ILLINOIS IN THE DAY 4/SATURDAY ERO. THIS IS
CONSIDERED A HIGHER END SLIGHT RISK IN EASTERN OKLAHOMA TO THE
OZARKS WHERE THE HEAVIEST RAIN IS CURRENTLY FORECAST. A BROADER
MARGINAL RISK SURROUNDS THE SLIGHT AND IS DRAWN ACROSS MUCH OF THE
OHIO RIVER WHERE STREAMFLOWS REMAIN HIGH. THE STORM PREDICTION
CENTER FORECASTS SEVERE THUNDERSTORM POTENTIAL ACROSS THE SOUTHERN
PLAINS THROUGH ARKANSAS INTO THE LOWER OHIO VALLEY ON SATURDAY AS
WELL. BY SUNDAY THERE REMAINS SOME MODEL SPREAD IN THE TIMING AND
PLACEMENT OF THE UPPER AND SURFACE LOWS AND THUS WHERE RAINFALL
WILL FOCUS, BUT BROADLY RAIN AND THUNDERSTORM CHANCES ARE LIKELY
FROM THE SOUTHERN AND CENTRAL PLAINS INTO MUCH OF THE MISSISSIPPI
VALLEY. HAVE DELINEATED A MARGINAL RISK CENTERED OVER MISSOURI AND
SURROUNDING STATES FOR THE DAY 5/SUNDAY ERO PERIOD, BUT STAY
ATTUNED TO THE FORECAST AS THIS COULD SHIFT AROUND IF AND WHEN
MODELS CONVERGE BETTER ON HEAVY RAINFALL PLACEMENT. AT LEAST IT
SEEMS LIKELY THAT RAINFALL TOTALS WILL BE LOWER ON SUNDAY COMPARED
TO SATURDAY AS THE LOW/FRONTAL SYSTEM START TO MOVE MORE. SEVERE
WEATHER IS POSSIBLE FROM EASTERN TEXAS INTO THE LOWER MISSISSIPPI
VALLEY ON SUNDAY PER SPC. WITH THIS WEEKEND'S RAIN EVENT, THE
HEAVIEST RAINFALL TOTALS ARE LIKELY TO BE WEST OF THE MOST
SENSITIVE AREAS OF THE MISSISSIPPI VALLEY AND OHIO VALLEY FROM
RECENT FLOODING. HOWEVER, SOME RAIN ATOP RECENTLY FLOODED AREAS,
AND RUNOFF FROM OTHER AREAS INTO THESE RIVERS, COULD EXACERBATE
ONGOING FLOODING ISSUES IN SOME AREAS, SO CONTINUE TO MONITOR. BY
MONDAY, RAIN CHANCES ARE FORECAST TO SPREAD INTO THE EAST-CENTRAL
U.S. AS THE FRONT PUSHES EAST, BUT WITH GENERALLY LOWER AMOUNTS.
THEN BY TUESDAY, THERE REMAINS UNCERTAINTY IN THE PATTERN, BUT
GENERALLY AN INCREASE IN RAIN CHANCES SEEMS POSSIBLE IN THE CENTRAL
U.S. AGAIN IN THE VICINITY OF FRONTS.
FARTHER WEST, SNOW IS LIKELY TO CONTINUE IN THE CENTRAL/SOUTHERN
ROCKIES ON SATURDAY BEFORE PRECIPITATION PULLS EAST ON SUNDAY.
FARTHER NORTH, A POSSIBLE UPPER TROUGH COULD SUPPORT PRECIPITATION
IN THE NORTHWEST THIS WEEKEND AND PERSISTING INTO MONDAY, INCLUDING
HIGHER ELEVATION SNOW IN THE NORTHERN ROCKIES.
ABOVE NORMAL TEMPERATURES BY 10-20 DEGREES WILL BE LIKELY FROM THE
SOUTHEAST INTO THE EASTERN SEABOARD ON SATURDAY WITH UPPER RIDGING
AHEAD OF THE MAIN TROUGH, RAISING TEMPERATURES WELL INTO THE 70S
INTO PARTS OF NEW ENGLAND. ON THE OTHER HAND, COLDER THAN NORMAL
TEMPERATURES ESPECIALLY IN TERMS OF HIGHS ARE EXPECTED FOR THE FOUR
CORNERS STATES INTO THE CENTRAL PLAINS SATURDAY. TEMPERATURES
SHOULD WARM CLOSER TO NORMAL SUNDAY IN THE CENTRAL U.S., AND
MEANWHILE COOL IN THE NORTHEAST WHERE A COLD FRONT COMES THROUGH.
ABOVE AVERAGE TEMPERATURES COULD CONTINUE ACROSS THE SOUTHEASTERN
U.S. INTO EARLY NEXT WEEK THOUGH. PERIODS OF SLIGHTLY BELOW NORMAL
TEMPERATURES IN THE NORTHWEST AND SLIGHTLY ABOVE NORMAL
TEMPERATURES FROM THE CENTRAL GREAT BASIN TO CENTRAL U.S. ARE
POSSIBLE INTO NEXT WEEK, BUT TEMPERATURES IN MOST PLACES SHOULD BE
PRETTY CLOSE TO AVERAGE.
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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