118
FXUS02 KWBC 161855
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 PM 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 REMAINS IN REASONABLY GOOD AGREEMENT THROUGH DAY
3/SATURDAY BEFORE GREATER THAN TYPICAL SPREAD INCREASES THROUGH THE
REMAINDER OF THE MEDIUM RANGE PERIOD, PARTICULARLY BEYOND DAYS
4/SUNDAY AND 5/MONDAY. REGARDING THE EVOLUTION OF THE FOUR
CORNERS/CENTRAL U.S. SYSTEM THIS WEEKEND INTO EARLY NEXT WEEK,
QUITE A BIT OF VARIABILITY FROM CYCLE TO CYCLE CONTINUES TO STEM
FROM SMALL SCALE CHANGES WITHIN SEVERAL LOW PREDICTABILITY NORTHERN
STREAM SHORTWAVES ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST.
HOW MODELS HANDLE THESE WAVES AND THEIR INTERACTION WITH THE
TROUGH/CLOSED LOW EJECTING OUT OF THE FOUR CORNERS AND SOUTHERN
PLAINS LATE SATURDAY INTO SUNDAY IS DIRECTLY IMPACTING THE
DOWNSTREAM PLACEMENT/TRACK OF A SURFACE LOW/FRONTAL SYSTEM AND ITS
RESULTING QPF. THE 00Z CMC, ECMWF, AND UKMET ACTUALLY SHOWED DECENT
AGREEMENT WITH THE LARGE SCALE PATTERN WHILE THE 00Z AND 06Z GFS
(AND EVEN TO SOME DEGREE THE GEFS) WERE DISTANT OUTLIERS. AFTER DAY
5/MONDAY, THE PATTERN LARGELY BECOMES QUASI-ZONAL AND DOMINATED BY
MORE FAST-MOVING SHORTWAVE TROUGHS IN THE NORTHERN STREAM, WHICH
AGAIN LENDS TO LOWER PREDICTABILITY THAN USUAL. THUS, FOR THE FIRST
FEW DAYS OF THE MEDIUM RANGE PERIOD, A MULTI-MODEL BLEND
CONSISTING MOSTLY OF THE NON-NCEP DETERMINISTIC GUIDANCE FROM THE
00Z/16 CYCLE WAS FAVORED BEFORE TRANSITIONING TO A MAJORITY OF NON-
NCEP ENSEMBLE MEANS FOR THE LATTER HALF OF THE PERIOD.
..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 FROM EASTERN OKLAHOMA TO THE
OZARKS, TO EXTREME NORTHEAST TEXAS WHERE THE HEAVIEST RAIN IS
CURRENTLY FORECAST. ONLY MINOR ADJUSTMENTS WERE MADE TO THE SLIGHT
WITH THIS PACKAGE GIVEN AT LEAST MODEST AGREEMENT OF WHERE THE
HEAVIEST RAIN IS EXPECTED TO FALL. OTHERWISE, 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 A FAIR AMOUNT OF 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. GIVEN THE CONTINUED UNCERTAINTY, DECIDED TO MAINTAIN THE
MARGINAL RISK CENTERED OVER MISSOURI AND SURROUNDING STATES FOR THE
DAY 5/SUNDAY ERO PERIOD AS THE DELINEATED AREA IS STILL A SOLID
COMPROMISE UNTIL MODELS COME INTO BETTER AGREEMENT. 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.
MILLER/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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page