544
FXUS01 KWBC 300732
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
331 AM EDT SUN APR 30 2023
VALID 12Z SUN APR 30 2023 - 12Z TUE MAY 02 2023
...HEAVY RAINFALL AND SEVERE THUNDERSTORMS LIKELY ACROSS NORTHEAST
AND MID-ATLANTIC ON SUNDAY...
...LOCALLY SIGNIFICANT, MULTI-DAY SNOWFALL EVENT FOR U.P. OF
MICHIGAN THROUGH EARLY WORK WEEK; WELL-BELOW-AVERAGE TEMPERATURES
ACROSS GREAT LAKES AND OHIO VALLEY SUNDAY THROUGH TUESDAY...
...ABOVE-AVERAGE TEMPERATURES TO CONTINUE ACROSS INTERIOR PACIFIC
NORTHWEST, GREAT BASIN, AND INTERMOUNTAIN WEST, AS COOLER WEATHER
ARRIVES ON SUNDAY FOR IMMEDIATE COAST...
THE MAIN WEATHER HEADLINE FOR THE LAST DAY OF APRIL WILL BE THE
HEAVY RAINFALL POTENTIAL THROUGHOUT THE MID-ATLANTIC AND NORTHEAST
AS A STRENGTHENING STORM SYSTEM TRACKS ALONG THE EASTERN SEABOARD.
SUNDAY WILL BE A WET AND CHILLY DAY FOR THE ENTIRETY OF THE
REGION, AS THE SURFACE LOW TRACKS JUST INLAND, ALLOWING FOR
ANOMALOUSLY MOIST AIR ORIGINATING FROM AS FAR SOUTH AS FLORIDA TO
PUSH ONSHORE, INCREASING THE CHANCES FOR HEAVY RAINFALL AND
PRODUCING REGION-WIDE RAINFALL TOTALS OF 1"+. THE HEAVIEST TOTALS
WILL BE CONFINED TO COASTAL AND INTERIOR NORTHERN NEW ENGLAND,
WHERE UPWARDS OF 3-5" OF RAIN, IN ADDITION TO RAINFALL RATES
APPROACHING 1"/HR WILL BE POSSIBLE, RESULTING IN THE ISSUANCE OF A
SLIGHT RISK OF EXCESSIVE RAINFALL FOR NORTHERN MASSACHUSETTS, NEW
HAMPSHIRE, AND SOUTHERN MAINE. FURTHER SOUTH, A SECOND SLIGHT RISK
IS IN EFFECT FOR NEW JERSEY, EASTERN PENNSYLVANIA, SOUTHERN NEW
YORK, AND THE BALTIMORE/WASHINGTON D.C. URBAN CORRIDOR, AS
ALTHOUGH RAINFALL TOTALS WILL NOT BE AS EXCESSIVE AS IN PREVIOUSLY
MENTIONED AREAS, THE COMBINATION OF 1-2" OF RAIN AND SATURATED
SOILS, GIVEN THE RECENT RAINFALL, MAY LEAD TO AREAS OF FLOODING AS
SHOWERS AND THUNDERSTORMS DEVELOP ON SUNDAY. SEVERE THUNDERSTORMS
WILL ALSO BE OF CONCERN ACROSS THE CAROLINAS AND MID-ATLANTIC
AHEAD OF THE FRONTAL PASSAGE DURING THE EARLY TO MIDDAY SUNDAY
HOURS, WITH DAMAGING WINDS AND ISOLATED TORNADOES POSSIBLE,
RESULTING IN THE STORM PREDICTION CENTER PLACING MUCH OF THE
REGION UNDER A SLIGHT RISK FOR SEVERE THUNDERSTORMS. CONDITIONS
WILL IMPROVE FROM SOUTH TO NORTH, WITH THE HEAVIEST AXIS OF
PRECIPITATION PUSHING THROUGH NORTHERN NEW ENGLAND DURING THE
EARLY MONDAY MORNING HOURS, ALTHOUGH THE WEATHER WILL REMAIN DAMP
AND COOL THROUGH TUESDAY.
MEANWHILE, A DEEPENING, HIGHLY ANOMALOUS, AND NEARLY STATIONARY
UPPER-LOW PRESIDING OVER THE GREAT LAKES WILL LEAD TO MUCH
BELOW-AVERAGE TEMPERATURES AND LOCALIZED HEAVY SNOWFALL ACROSS
NORTHERN WISCONSIN AND THE UPPER PENINSULA (U.P.) OF MICHIGAN
THROUGH MONDAY. SHORTWAVE ENERGY TRAVELING AROUND THE BASE OF THE
UPPER LOW WILL LEAD TO A RAPID DEEPENING OF A SURFACE LOW OVER
LAKE SUPERIOR AND THE ONTARIO PROVINCE LATE SUNDAY INTO MONDAY,
WITH SEVERAL LOCATIONS POTENTIALLY APPROACHING BOTH APRIL AND MAY
MONTHLY LOW-PRESSURE RECORDS. STRONG NORTHWESTERLY WINDS ON THE
BACKSIDE OF THE STRENGTHENING SURFACE LOW, IN CONJUNCTION WITH
COLD AIR ADVECTING SOUTHWARD AND OROGRAPHIC LIFTING, WILL LEAD TO
A LOCALIZED SWATH OF 1-2FT OF SNOW ACROSS HIGHER ELEVATIONS OF THE
INTERIOR U.P. OF MICHIGAN. GIVEN THE LATE-SEASON SNOW, SURFACE
TEMPERATURES HOVERING AROUND FREEZING DURING THE EVENT WILL LEAD
TO VERY HEAVY WET SNOW, WHICH MAY RESULT IN DOWNED TREES AND
POWERLINES. THE SNOW WILL DIMINISH ON TUESDAY AS THE SYSTEM
WEAKENS AND SLOWLY PUSHES EASTWARD AS HIGH PRESSURE BUILDS IN.
FURTHERMORE, A BROADER AREA OF MUCH-BELOW-AVERAGE TEMPERATURES
(10-20 DEGREES F BELOW AVERAGE), ENCOMPASSING MUCH OF THE MIDWEST,
GREAT LAKES REGION, AND OHIO VALLEY, WILL BE POSSIBLE THROUGH
TUESDAY, AS DAYTIME HIGHS STRUGGLE TO REACH 50F, AND NUMEROUS
LOCATIONS APPROACH OR BREAK DAILY RECORD LOW MAXIMUM TEMPERATURES.
ELSEWHERE, ABOVE-AVERAGE TEMPERATURES ACROSS THE INTERMOUNTAIN
WEST, GREAT BASIN, AND INTERIOR PACIFIC NORTHWEST WILL CONTINUE
THROUGH THE FORECAST TIMEFRAME AS PERSISTENT UPPER-LEVEL RIDGING
SUPPORTS TEMPERATURES 15-25 DEGREES ABOVE NORMAL. WIDESPREAD HIGH
TEMPERATURES IN THE 80S ARE EXPECTED THROUGHOUT INTERIOR SECTIONS
OF THE PACIFIC NORTHWEST, WHILE LOCATIONS FURTHER SOUTH, INCLUDING
CALIFORNIA'S CENTRAL VALLEY AND THE MOJAVE/SONORAN DESERTS, REACH
THE 90S AND EVEN 100S IN LOCALIZED AREAS ON SUNDAY. HOWEVER, A
STORM SYSTEM AND ATTENDANT COLD FRONT PUSHING ONSHORE EARLY SUNDAY
WILL RESULT IN MORE SEASONABLE TEMPERATURES RETURNING TO THE
IMMEDIATE COAST, WITH COOLER TEMPERATURES SPREADING INLAND ON
MONDAY AND TUESDAY. FURTHERMORE, SCATTERED SHOWERS, THUNDERSTORMS,
AND HIGH-ELEVATION SNOW WILL ALSO BE POSSIBLE ACROSS THE WEST AND
NORTHERN/CENTRAL ROCKIES DURING THE START OF THE WORK WEEK.
RUSSELL
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