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Official 90-day Outlooks are issued once each month near mid-month at 8:30am Eastern Time. Please consult the schedule of 30 & 90-day outlooks for exact release dates.

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    0.5mn AMJ 2018
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    4.5mn ASO 2018
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    6.5mn OND 2018
    7.5mn NDJ 2018
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    9.5mn JFM 2019
   10.5mn FMA 2019
   11.5mn MAM 2019
   12.5mn AMJ 2019
    0.5mn Apr 2018


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HOME> Outlook Maps>Seasonal Forecast Discussion
 
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SAT MAR 31 2018


30-DAY OUTLOOK DISCUSSION FOR APRIL 2018

THE UPDATED MONTHLY OUTLOOK FOR APRIL 2018 IS BASED PRIMARILY ON SHORT- AND
EXTENDED-RANGE TEMPERATURE AND PRECIPITATION OUTLOOKS FROM WPC AND CPC, CFS
30-DAY FORECASTS OF TEMPERATURE AND PRECIPITATION, MJO-BASED CONSIDERATIONS,
RECENT SOIL MOISTURE OBSERVATIONS, THE CONSTRUCTED ANALOG BASED ON SOIL
MOISTURE (CAS), SEVERAL RUNS OF THE GFS TOTAL PRECIPITATION FORECASTS FOR THE
NEXT TWO WEEKS, SSTS NEAR THE SOUTHWEST COAST OF ALASKA, AND APRIL CLIMATOLOGY.

THE UPDATED TEMPERATURE OUTLOOK FOR APRIL 2018 DEPICTS ENHANCED ODDS OF BELOW
NORMAL TEMPERATURES FROM ABOUT THE NORTHERN AND CENTRAL CONTINENTAL DIVIDE
EASTWARD ACROSS THE NORTHERN AND CENTRAL GREAT PLAINS, THE UPPER AND MIDDLE
MISSISSIPPI VALLEY, THE GREAT LAKES REGION, THE OHIO VALLEY, THE NORTHERN AND
CENTRAL APPALACHIANS, THE NORTHEAST, AND THE MID-ATLANTIC. THE SPATIAL EXTENT
OF THIS COLD ANOMALY IS PREDICTED AT EACH TIME-SCALE OUT THROUGH THE NEXT
30-DAYS. THE PAST 9 RUNS OF THE CFS MODEL ARE REMARKABLY STABLE IN PREDICTING
THIS AREA OF ANOMALOUS COLD FOR APRIL. ENHANCED CONVECTION ASSOCIATED WITH THE
MADDEN-JULIAN OSCILLATION (MJO) OVER THE WESTERN PACIFIC AND WESTERN HEMISPHERE
DURING WEEK-1, AND THE WESTERN HEMISPHERE AND AFRICA DURING WEEK-2, CORRELATES
WELL WITH BELOW NORMAL TEMPERATURES ACROSS THE NORTH-CENTRAL CONUS ABOUT TWO
WEEKS INTO THE FUTURE. PROBABILITIES TOP 70% IN PARTS OF THE NORTHERN PLAINS,
WHERE TEMPERATURE DEPARTURES OF 12 TO 24 DEGREES F BELOW NORMAL ARE PREDICTED
BY WPC WITHIN THE FIRST WEEK TO TEN DAYS OF APRIL. ENHANCED ODDS OF ABOVE
NORMAL TEMPERATURES ARE PREDICTED FOR MOST OF THE SOUTHERN HALF OF CALIFORNIA,
THE CENTRAL AND SOUTHERN GREAT BASIN, THE SOUTHERN ROCKIES, MUCH OF TEXAS, AND
THE FLORIDA PENINSULA. THE GULF COAST STATES ARE ANTICIPATED TO BE NEAR TO
BELOW NORMAL DURING THE FIRST TWO WEEKS OF APRIL, AND NEAR TO ABOVE NORMAL FOR
THE SECOND HALF OF THE MONTH. WITH A VARIABLE MIX OF TEMPERATURES EXPECTED, AND
A MIX OF NEAR TO BELOW NORMAL SOIL MOISTURE, IT WAS DECIDED THAT EQUAL CHANCES
(EC) IS THE BEST BET FOR THIS REGION. ABOVE NORMAL TEMPERATURES ARE ALSO
FAVORED FOR MUCH OF ALASKA, WITH THE EXCEPTION OF THE PANHANDLE REGION, AND
NORTHEASTERN ALASKA, WHERE OCCASIONAL COLD AIR INTRUSIONS ARE ANTICIPATED.
PROBABILITIES FOR ABOVE NORMAL TEMPERATURES EXCEED 50% IN EXTREME SOUTHWESTERN
ALASKA, IN PART DUE TO THE PROXIMITY OF RELATIVELY WARM SSTS.

THE UPDATED PRECIPITATION OUTLOOK FOR APRIL 2018 DEPICTS ENHANCED ODDS OF ABOVE
NORMAL PRECIPITATION OVER MUCH OF THE NORTHERN AND EASTERN HALVES OF THE CONUS.
THIS BROAD SWATH OF FAVORED ABOVE NORMAL PRECIPITATION DENOTES, IN A ROUGH
SENSE, THE MEAN EXPECTED POSITIONS OF THE POLAR JET STREAM AND STORM TRACK. THE
CONFLUENCE OF NORTHERN STREAM ENERGY WITH MOISTURE STREAMING UP FROM THE GULF
OF MEXICO OVER THE TENNESSEE AND OHIO VALLEYS FAVORS PEAK PROBABILITIES IN
EXCESS OF 50% FOR THAT AREA. THIS BROAD AREA OF FAVORED ABOVE NORMAL
PRECIPITATION ALSO HAS THE SUPPORT OF PRECIPITATION FORECASTS AND OUTLOOKS AT
LEAST THROUGH MID-APRIL, WITH A DRIER PATTERN ANTICIPATED DURING WEEKS 3,4
ACROSS THE DEEP SOUTH. THE MOST RECENT RUNS OF THE CFS ALSO LEND ADEQUATE
SUPPORT FOR THIS EXPECTED AREA OF ANOMALOUS WETNESS. BELOW NORMAL PRECIPITATION
IS FAVORED OVER THE SOUTHERN HALF OF CALIFORNIA, MUCH OF THE SOUTHERN HALVES OF
THE GREAT BASIN AND ROCKIES, WESTERN OKLAHOMA, AND WESTERN AND SOUTHERN
PORTIONS OF TEXAS. THIS LARGE REGION IS FORECAST TO BE WELL REMOVED FROM THE
ANTICIPATED MEAN STORM TRACK DURING APRIL, AND IS TYPICALLY DRIER AT THIS TIME
OF YEAR. BELOW NORMAL PRECIPITATION IS ALSO FAVORED OVER THE FLORIDA PENINSULA.
THIS IS DUE IN PART TO APRIL TYPICALLY BEING THE HEIGHT OF THE DRY SEASON IN
THIS AREA, AND TO PRE-EXISTING DRY SOILS FOR MANY AREAS. THE STORM TRACK IS
ALSO FORECAST TO REMAIN NORTH OF THE SUNSHINE STATE. FINALLY, THERE ARE
ELEVATED ODDS OF BELOW NORMAL PRECIPITATION FOR THE ALASKA PANHANDLE IN APRIL,
DUE TO RECENT RUNS OF THE CFS MODEL, AND WHAT APPEARS TO BE A SOUTHWARD
DISPLACED JET OVER VANCOUVER ISLAND AND THE U.S. PACIFIC NORTHWEST.

ELSEWHERE, EQUAL CHANCES (EC) OF BELOW, NEAR, AND ABOVE NORMAL TEMPERATURES AND
PRECIPITATION ARE FORECAST, CORRESPONDING TO AREAS WHERE CLIMATE SIGNALS ARE
RATHER WEAK AND INDISTINGUISHABLE FROM NOISE AND/OR WHERE THE VARIOUS MODELS
AND TOOLS EXHIBIT SIGNIFICANT DISAGREEMENT.

----- PREVIOUS DISCUSSION (FOR THE 0.5-MONTH LEAD OUTLOOK) IS SHOWN BELOW -----

THE OUTLOOK FOR APRIL 2018 IS BASED PRIMARILY ON A WIDE RANGE OF DYNAMICAL AND
STATISTICAL MODELS AND TOOLS SUCH AS THE CFS, THE NMME SUITE OF CLIMATE MODELS,
THE CONSTRUCTED ANALOG BASED ON SEA SURFACE TEMPERATURES (CA-SST), AND THE
CONSTRUCTED ANALOG BASED ON SOIL MOISTURE (CAS). OTHER CONSIDERATIONS INCLUDED
DECADAL TEMPERATURE AND PRECIPITATION TRENDS, CURRENT SEA SURFACE TEMPERATURES
ALONG THE WEST COAST OF ALASKA, NEAR-COASTAL SEA ICE CONDITIONS IN NORTHWESTERN
ALASKA, INITIAL CONDITIONS, CLIMATOLOGY AND OBSERVED SOIL MOISTURE CONDITIONS
OVER THE PAST 30-DAYS.

LA NINA CONDITIONS CONTINUE INTO MID-MARCH, WITH NEGATIVE SST ANOMALIES
OBSERVED ACROSS THE CENTRAL AND EASTERN EQUATORIAL PACIFIC OCEAN FROM ABOUT
170W TO THE COAST OF SOUTH AMERICA. BOTH THE LA NINA AND THE COUPLED
ATMOSPHERIC RESPONSE TO THIS COLD EVENT WEAKENED CONSIDERABLY DURING THE PAST
MONTH. THE OUTGOING LONGWAVE RADIATION (OLR) ANOMALY MAP VALID FOR THIS SAME
PERIOD DEPICTS POSITIVE OLR ANOMALIES DUE TO REDUCED CONVECTION NEAR AND JUST
NORTH OF THE EQUATOR IN THE VICINITY OF THE DATE LINE, AND NEGATIVE OLR
ANOMALIES DUE TO ENHANCED CONVECTION OVER PARTS OF THE MARITIME CONTINENT AND
WESTERN PACIFIC. CPC'S ENSO DIAGNOSTIC DISCUSSION (MARCH 8TH) EXPECTS A
TRANSITION FROM LA NINA TO ENSO-NEUTRAL TO BE MOST LIKELY (~55% CHANCE) DURING
THE MARCH-MAY SEASON, WITH NEUTRAL CONDITIONS LIKELY TO CONTINUE INTO THE
SECOND HALF OF THE YEAR. THE MADDEN JULIAN OSCILLATION (MJO) HAS WEAKENED
CONSIDERABLY DURING THE PAST FEW WEEKS, WITH THE ENHANCED CONVECTIVE PHASE
CURRENTLY LOCATED OVER THE EASTERN INDIAN OCEAN. DURING THE NEXT TWO WEEKS, THE
MJO IS PREDICTED TO WEAKEN FURTHER, AND ITS EFFECTS ON THE U.S. TEMPERATURE AND
PRECIPITATION OUTLOOKS FOR APRIL ARE CONSIDERED MINIMAL.

THE TEMPERATURE OUTLOOK FOR APRIL 2018 DEPICTS ELEVATED ODDS FOR BELOW NORMAL
TEMPERATURES OVER SOUTHEASTERN MAINLAND ALASKA AND THE PANHANDLE, AND FROM
WASHINGTON STATE EASTWARD ACROSS THE NORTHERN ROCKIES, THE NORTHERN PLAINS
(PERHAPS AS FAR SOUTH AS NEBRASKA), AND MUCH OF THE UPPER MISSISSIPPI VALLEY.
THIS AREA OF FAVORED BELOW NORMAL TEMPERATURES HAS BROAD SUPPORT FROM THE
CALIBRATED AND UNCALIBRATED NMME ENSEMBLE MEAN, CFS, CA-SST, AND DECADAL
TRENDS. OFTEN DURING THE WANING STAGES OF A LA NINA, THE ANOMALOUS COLD SIGNAL
OVER THE NORTH-CENTRAL CONUS SHIFTS FARTHER WEST INTO THE PACIFIC NORTHWEST,
LENDING ADDITIONAL SUPPORT TO THE TEMPERATURE OUTLOOK. THE GREATEST
PROBABILITIES FOR BELOW NORMAL TEMPERATURES, IN EXCESS OF 50 PERCENT, ARE
FORECAST OVER NORTH DAKOTA AND SMALL PORTIONS OF NEIGHBORING STATES. ABOVE
NORMAL TEMPERATURES ARE FAVORED ACROSS APPROXIMATELY THE SOUTHERN HALF AND
EASTERN THIRD OF THE CONUS, BASED IN LARGE PART ON THE NMME, CFS, DECADAL
TEMPERATURE TRENDS, AND TO A LESSER DEGREE, THE CA-SST. THE NMME (ESPECIALLY
THE CALIBRATED VERSION) AND THE CFS ALSO PREDICT A RELATIVE WEAKNESS IN THE
PREDICTED ANOMALOUS WARMTH FROM APPROXIMATELY THE EASTERN CORN BELT AREA
EASTWARD ACROSS THE OHIO AND TENNESSEE VALLEYS, THE MID-ATLANTIC AND NORTHEAST.
A FEW OF THE MORE RECENT CFS RUNS, INCLUDING TODAY'S SOLUTION, CAST DOUBT ON
HIGHER PROBABILITIES FOR ABOVE NORMAL TEMPERATURES OVER THE NORTHEAST CONUS.
ACCORDINGLY, ONLY MODEST TILTS IN THE PROBABILITIES FOR ABOVE NORMAL
TEMPERATURES ARE FORECAST FOR THE NORTHEAST. ABOVE NORMAL TEMPERATURES ARE ALSO
FAVORED OVER WESTERN ALASKA, SUPPORTED BY THE NMME AND LATEST FEW RUNS OF THE
CFS, CA-SST, RELATIVELY WARM COASTAL SSTS, AND REDUCED SEA ICE COVERAGE
RELATIVE TO NORMAL (NORTHWESTERN ALASKA). THE GREATEST ODDS FOR ABOVE NORMAL
TEMPERATURES ARE INDICATED OVER THE BERING SEACOAST OF ALASKA, AND ALONG THE
SOUTHERN TIER OF THE CONUS (BOTH IN EXCESS OF 50 PERCENT).

THE PRECIPITATION OUTLOOK FOR APRIL 2018 FAVORS ABOVE NORMAL PRECIPITATION OVER
WESTERN AND NORTHERN ALASKA, FROM THE NORTHERN ROCKIES TO MINNESOTA, AND FROM
NORTHEASTERN ARKANSAS NORTHEASTWARD TO SOUTHEASTERN MICHIGAN. THE RELATIVE
WETNESS FAVORED IN WESTERN AND NORTHERN ALASKA IS SUPPORTED PRIMARILY BY THE
LAST 9 RUNS OF THE CFS, AND TO A LESSER EXTENT, THE CA-SST. THE FAVORED ABOVE
NORMAL PRECIPITATION FROM THE NORTHERN ROCKIES EASTWARD TO MINNESOTA, AND FROM
NORTHEASTERN ARKANSAS NORTHEASTWARD TO SOUTHEASTERN MICHIGAN IS SUPPORTED TO
VARIOUS DEGREES BY THE CAS TOOL, THE NMME (ESPECIALLY UNCALIBRATED VERSION),
CFS, CA-SST (OHIO VALLEY AREA), AND OBSERVED SOIL MOISTURE ANOMALIES FOR THE
PAST 30-DAYS FOR MOST OF THESE AREAS. ODDS ARE TILTED TOWARDS BELOW NORMAL
PRECIPITATION ACROSS SOUTHEASTERN MAINLAND ALASKA AND THE PANHANDLE REGION,
MOST OF CALIFORNIA AND NEVADA, SOUTHWESTERN UTAH, ARIZONA, MOST OF NEW MEXICO,
AND APPROXIMATELY THE SOUTHWESTERN HALF OF TEXAS. ODDS OF BELOW NORMAL
PRECIPITATION ARE ALSO ELEVATED OVER MUCH OF THE SOUTHERN ATLANTIC COAST
REGION. SUPPORT FOR THESE REGIONS OF ANTICIPATED BELOW NORMAL PRECIPITATION
COMES FROM THE NMME, CFS, CA-SST (ALASKA COAST ONLY), APRIL CLIMATOLOGY, AND
RECENT SOIL MOISTURE CONDITIONS (CONUS). THE HIGHEST CHANCES (IN EXCESS OF 50
PERCENT) FOR THE PRECIPITATION OUTLOOK ARE DEPICTED OVER CENTRAL AND SOUTHERN
FLORIDA (FOR BELOW NORMAL PRECIPITATION), IN PART DUE TO APRIL BEING THE PEAK
OF THE CLIMATOLOGICAL DRY SEASON FOR THIS AREA.

FORECASTER: ANTHONY ARTUSA

THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING
THE WORLD METEOROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3
COMPLETE DECADES AS THE CLIMATE REFERENCE PERIOD.  THE PROBABILITY ANOMALIES
FOR TEMPERATURE AND PRECIPITATION BASED ON THESE NEW NORMALS BETTER REPRESENT
SHORTER TERM CLIMATIC ANOMALIES THAN THE FORECASTS BASED ON OLDER NORMALS.

THE NEXT MONTHLY OUTLOOK...FOR MAY ... WILL BE ISSUED ON THU APR 19 2018

THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD.
$$

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