754
FXUS21 KWNC 111807
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT APRIL 11 2025
SYNOPSIS: A SHOT OF MUCH BELOW NORMAL TEMPERATURES BRINGING FROST AND FREEZE
CHANCES TO PORTIONS OF THE MID-ATLANTIC IS POSSIBLE AT THE ONSET OF WEEK-2.
ASSOCIATED WITH THIS COLD AIR IS AN AREA OF SURFACE LOW PRESSURE FORECAST TO
DEVELOP IN THE NORTHEAST AND SOUTHEASTERN CANADA BRINGING INCREASED CHANCES FOR
HIGH WINDS TO PARTS OF THE REGION. BY THE MIDDLE OF THE PERIOD, AN AREA OF
MID-LEVEL LOW PRESSURE OVER THE WEST WILL BEGIN TO BRING INCREASED CHANCES FOR
HEAVY PRECIPITATION AND HIGH WINDS TO PORTIONS OF THE SOUTH-CENTRAL CONTIGUOUS
U.S. (CONUS). FLOODING REMAINS POSSIBLE INTO WEEK-2 ALONG PORTIONS OF THE
MIDDLE AND LOWER MISSISSIPPI RIVER.
HAZARDS
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE GREAT LAKES,
OHIO, TENNESSEE, AND MIDDLE MISSISSIPPI VALLEY, SOUTHEAST, AND MID-ATLANTIC,
SAT-SUN, APR 19-20.
SLIGHT RISK OF HIGH WINDS FOR THE NORTHEAST, SAT-SUN, APR 19-20.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE CENTRAL AND SOUTHERN
PLAINS AND MIDDLE AND LOWER MISSISSIPPI VALLEY, SUN-WED, APR 20-23.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS, AND
SOUTHERN ROCKIES, SUN-WED, APR 20-23.
FLOODING POSSIBLE FOR THE MIDDLE AND LOWER MISSISSIPPI, AND LOWER OHIO RIVERS.
DETAILED SUMMARY
FOR MONDAY APRIL 14 - FRIDAY APRIL 18:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY APRIL 19 - FRIDAY APRIL 25: A MID-LEVEL TROUGH IS FORECAST TO BE
OVER THE NORTHEASTERN CONUS AT THE ONSET OF THE PERIOD WITH AN ASSOCIATED
SURFACE LOW PRESSURE SYSTEM OVER THE MARITIME PROVINCES OF CANADA. THIS SURFACE
LOW PRESSURE HAS GROWN STRONGER IN THE ENSEMBLE GUIDANCE TODAY RELATIVE TO
PRIOR FORECASTS. THEREFORE, A SLIGHT RISK OF HIGH WINDS REMAINS POSTED FOR THIS
FEATURE FOR APR 19-20. THE ADDITIONAL STRENGTH OF THIS SYSTEM INCREASES THE
COLD AIR ADVECTION INTO THE EASTERN CONUS BRINGING A BROADER RISK FOR ANOTHER
SHOT OF MUCH BELOW NORMAL TEMPERATURES INTO PORTIONS OF THE EAST EARLY IN
WEEK-2. TEMPERATURES ARE FORECAST BY DETERMINISTIC MODEL RUNS AND THE
PROBABILISTIC EXTREMES TOOLS (PETS) AND SOME ENSEMBLE GUIDANCE TO FALL BELOW 40
DEG F. ACROSS PORTIONS OF THE MIDDLE MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS,
SOUTHERN GREAT LAKES, MID-ATLANTIC, AND INTO PARTS OF THE UPPER SOUTHEAST EARLY
IN WEEK-2, INCREASING CHANCES FOR FROST AND FREEZES. THEREFORE, AN ASSOCIATED
MUCH BELOW NORMAL TEMPERATURES HAZARD IS FORECAST FOR SAT-SUN, APR 19-20.
A MID-LEVEL TROUGH IS FORECAST TO DEVELOP ACROSS THE WEST DURING THE FIRST HALF
OF THE WEEK-2 PERIOD. THIS TROUGH INCREASES THE CHANCES FOR A LEE-SIDE
CYCLOGENESIS IN THE SOUTHERN AND CENTRAL PLAINS. FURTHER, THE SURFACE PATTERN
FROM THE GEFS, ECENS, AND CANADIAN ENSEMBLE ALL SUPPORT STRONG RETURN FLOW OFF
OF THE GULF. THE RAW ENSEMBLE GUIDANCE REMAINS DIFFUSE WITH RELATIVELY LOW
RAINFALL AMOUNTS ACROSS A FAIRLY BROAD REGION OF THE PLAINS AND MISSISSIPPI
VALLEY. HOWEVER, BOTH THE GEFS AND ECENS PETS HIGHLIGHT THIS AREA FOR
PRECIPITATION EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE. FURTHER,
DETERMINISTIC GUIDANCE FROM THE GFS, ECENS, AND EC-AIFS ALL SUPPORT DEVELOPMENT
OF PRECIPITATION AND WINDS ACROSS THIS REGION SOMETIME DURING THE WEEK-2
PERIOD. WHILE UNCERTAINTY REMAINS HIGH ON TIMING AND PLACEMENT, THE GUIDANCE
SUGGESTS DEVELOPMENT OF ENHANCED PRECIPITATION AT SOME POINT DURING THE PERIOD.
SCATTERED FLASH FLOODING MAY BE A CONCERN IN THESE AREAS AS PRECIPITATION IS
LIKELY TO BE CONVECTIVE IN NATURE. THEREFORE, A SLIGHT RISK OF HEAVY
PRECIPITATION IS FORECAST FOR THE CENTRAL AND SOUTHERN PLAINS, AND MIDDLE AND
LOWER MISSISSIPPI VALLEY FOR APR 20-23. SECONDLY, A SLIGHT RISK OF HIGH WINDS
IS FORECAST FOR THE HIGH CENTRAL AND SOUTHERN PLAINS AND PARTS OF THE SOUTHERN
ROCKIES FOR THE SAME PERIOD.
IN THE CENTRAL CONUS, GIVEN THE COPIOUS ANTECEDENT RAINFALL AND RECURRING
FLOODING CONCERNS IN THIS REGION, A FLOODING POSSIBLE HAZARD REMAINS POSTED FOR
PORTIONS OF THE LOWER OHIO, MIDDLE AND LOWER MISSISSIPPI VALLEYS DUE TO THE
POTENTIAL FOR NEW AND RENEWED RISES IN RIVER LEVELS. WHILE MAIN CHANNELS ARE
ALREADY VERY HIGH, AND THUS LIKELY WON’T RESPOND TOO MUCH TO ADDITIONAL
PRECIPITATION, TRIBUTARIES AND STREAMS WILL BE MORE SUSCEPTIBLE TO RENEWED
FLOODING OR FLASH FLOODING IF ADDITIONAL RAINFALL OCCURS.
IN ALASKA, AS SPRING CONTINUES AND DAILY INCOMING SOLAR RADIATION FLUX TOTALS
INCREASE, ICE-BOUND RIVERS WILL BEGIN TO BREAK UP. THERE IS NO ASSOCIATED
HAZARD POSTED AT THIS TIME BUT THIS SITUATION WILL BE CLOSELY MONITORED IN THE
COMING DAYS AND WEEKS AS CONDITIONS CAN QUICKLY CHANGE, LEADING TO THE
POTENTIAL FOR ICE JAMS AND ASSOCIATED FLOODING.
FORECASTER: RYAN BOLT
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