588  
FXUS04 KWBC 292123  
QPFPFD  
 
QUANTITATIVE PRECIPITATION FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
522 PM EDT TUE MAY 29 2018  
 
FINAL DAY 1, DAY 2 AND DAY 3 QPF DISCUSSION  
VALID MAY 30/0000 UTC THRU JUN 02/0000 UTC  
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR  
 
DAY 1  
 
FOR THE 00Z QPF ISSUANCE: NO MAJOR CHANGES WERE MADE TO THE 29/18Z  
QPF ISSUANCE. SOME TWEAKS WERE MADE OVER WESTERN  
TN/WESTERN KY IN CONJUNCTION WITH ALBERTO, AS WELL AS A FEW OVER  
THE SOUTHERN APPALACHIANS. BOTH TWEAKS WERE MADE BASED ON RADAR  
TRENDS, AS WELL AS THE TIME LAGGED HRRR.  
 
...ALBERTO / SOUTHEAST U.S. / OHIO AND TENNESSEE VALLEYS/ SOUTHERN  
APPALACHIANS...  
 
BASED ON THE CONSENSUS OF THE 12Z HI-RES MODELS, MADE AN EASTWARD  
ADJUSTMENT TO THE ANTICIPATED AXIS OF HEAVIER AMOUNTS NEAR THE  
TRACK OF THE CENTER. THERE REMAINS A GOOD SIGNAL FOR 1-2 INCH,  
WITH LOCALLY HEAVIER AMOUNTS NEAR THE TRACK OF THE CENTER,  
ESPECIALLY EARLY IN THE PERIOD AS THE SYSTEM MOVES ACROSS WESTERN  
TENNESSEE INTO THE LOWER OHIO VALLEY THIS EVENING. FURTHER TO THE  
SOUTH, THERE IS STILL A GOOD INDICATION AS WELL FOR ADDITIONAL  
LOCALLY HEAVY AMOUNTS ALONG THE TRAILING INFLOW AXIS ACROSS  
ALABAMA, AS WELL AS INTO THE UPSLOPE REGIONS OF THE SOUTHERN  
APPALACHIANS EXTENDING FROM NORTHERN GEORGIA TO SOUTHWEST  
VIRGINIA. THE HREF MEAN WAS UTILIZED AS A STARTING POINT FOR WPC  
QPF ACROSS MUCH OF THE REGION.  
   
..EASTERN KANSAS AND CENTRAL TO EASTERN OKLAHOMA
 
 
STILL A GOOD MODEL SIGNAL FOR CONVECTIVE DEVELOPMENT TO PRODUCE  
MODERATE TO HEAVY RAIN TOTALS AS A PROGRESSIVE SHORTWAVE TROUGH  
MOVES INTO THE CENTRAL PLAINS THIS AFTERNOON. BASED ON THE  
CONSENSUS OF THE HI-RES MODELS, ADJUSTED THE AXIS OF HEAVIER  
AMOUNTS FURTHER TO THE SOUTH ACROSS CENTRAL INTO SOUTHEASTERN  
OKLAHOMA THIS AFTERNOON-EVENING. HERE ALSO, WPC QPF UTILIZED THE  
HREF MEAN AS A STARTING POINT.  
   
..NORTHERN PLAINS AND UPPER MIDWEST
 
 
A NEGATIVELY-TILTED TROUGH COMPRISED OF AN UPPER LOW LIFTING OUT  
OF THE NORTHERN HIGH PLAINS AND SHORTWAVE ENERGY EMANATING FROM  
THE CENTRAL PLAINS IS EXPECTED TO PIVOT ACROSS THE DAKOTAS AND  
NEBRASKA INTO THE UPPER MISSISSIPPI VALLEY ON WED. DEEP  
SOUTHWESTERLY FLOW AHEAD OF THE TROUGH IS EXPECTED TO TAP SOME OF  
THE DEEP MOISTURE ASSOCIATED WITH ALBERTO, SUPPORTING THE  
DEVELOPMENT OF MODERATE TO HEAVY RAINS ACROSS THE UPPER  
MISSISSIPPI VALLEY DURING THE AFTERNOON/EVENING HOURS, WITH  
LIGHTER AMOUNTS FURTHER TO THE WEST IN A DEVELOPING DEFORMATION  
ZONE BACK ACROSS THE DAKOTAS.  
 
DAYS 2/3...  
   
..GREAT LAKES
 
 
REMAINS FROM ALBERTO WILL ADVANCE NORTHEASTWARD FROM THE GREAT  
LAKES INTO ONTARIO OVERNIGHT WEDNESDAY INTO THURSDAY. TROPICAL  
AIR MASS ASSOCIATED WITH ALBERTO WILL HAVE PRECIPITABLE WATER  
VALUES OF 2.00 INCHES THAT WILL WANE TO 1.25 INCHES BY THURSDAY  
AFTERNOON. THE MAXIMUM RAINFALL ASSOCIATED WITH ALBERTO WILL  
RANGE BETWEEN 1.00 AND 1.50 INCHES OVER PARTS OF THE UPPER  
PENINSULA OF MICHIGAN ON WEDNESDAY EVENING INTO THURSDAY EVENING.  
THURSDAY EVENING INTO FRIDAY EVENING, THE QPF OVER THE GREAT LAKES  
WILL BE WITH MAXIMUM QPF AMOUNTS RANGING BETWEEN 0.10 AND 0.25  
INCHES.  
 
WITH A LACK OF A STRONG LOW-LEVEL FOCUSING MECHANISM (OTHER THAN  
ALBERTO'S CENTER), THE EXCESSIVE RAINFALL OUTLOOK FOR DAY 2 SHOWS  
A BROAD SLIGHT RISK FOR MOST OF THE REGION. ALTHOUGH RAIN MAY BE  
FOCUSED MORE ALONG THE TRACK OF THE LOW, FLASH FLOOD GUIDANCE IS  
HIGHER IN THOSE AREAS SUGGESTING THAT ANTECEDENT CONDITIONS MAY  
PREVENT MORE WIDESPREAD FLOODING.  
 
WPC IS ISSUING THE LATEST ADVISORIES ON ALBERTO.  
 
   
..OHIO VALLEY/MID-ATLANTIC SOUTHWARD TO THE SOUTHEAST
 
 
IN THE WAKE OF THE REMAINS OF ALBERTO, DEEP TROPICAL MOISTURE WILL  
EXTEND FROM THE MID-ATLANTIC COAST SOUTHWARD TO FLORIDA WITH  
PRECIPITABLE WATER VALUES OF 2.00 INCHES THAT WILL BEGIN TO MOVE  
OFF THE COAST OVERNIGHT THURSDAY. THE PRECIPITABLE WATER VALUES  
WILL DECREASE TO NEAR 1.75 INCHES BY FRIDAY EVENING. THE MOISTURE  
WILL INTERACT WITH SHORT WAVE OVER THE SOUTHEAST THAT WILL AID IN  
PRODUCING MAXIMUM QPF AMOUNTS RANGING BETWEEN 1.00 AND 1.40 INCHES  
ON WEDNESDAY EVENING INTO THURSDAY EVENING. A SECONDARY MAXIMUM  
WILL BE OVER PARTS OF THE NORTHERN MID-ATLANTIC INTO THE EASTERN  
OHIO VALLEY WITH MAXIMUM QPF AMOUNTS RANGING 0.50 TO 0.85 INCHES.  
ON THURSDAY EVENING INTO FRIDAY EVENING, PRECIPITABLE WATER VALUES  
OVER FLORIDA WILL REMAIN AT OR NEAR 2.00 INCHES. DIURNAL HEATING  
WILL INTERACT WITH THE MOISTURE TO PRODUCE MAXIMUM QPF AMOUNTS  
RANGING FROM 0.50 TO 0.60 INCHES OVER THE CENTRAL PORTION OF THE  
FLORIDA PENINSULA.  
 
   
..CENTRAL PLAINS INTO THE OHIO VALLEY AND NORTHEAST
 
 
DISORGANIZED SHORT WAVE ENERGY OVER THE SOUTHERN ROCKIES WILL MOVE  
EASTWARD INTO THE OHIO VALLEY BY THURSDAY EVENING. A BAROCLINIC  
ZONE OVER CENTRAL CANADA ON THURSDAY MORNING WILL MOVE  
SOUTHEASTWARD TO INTO THE OHIO VALLEY INTO THE NORTHEAST.  
PRECIPITABLE WATER VALUES WILL BE RELATIVELY HIGH OVER THE REGION  
RANGING FROM 1.75 TO 1.50 INCHES. THE ENERGY WILL AID IN  
PRODUCING A MAXIMUM QPF AMOUNTS OVER PARTS OF THE MIDDLE  
MISSISSIPPI VALLEY/CENTRAL PLAINS RANGING FROM 0.75 TO 1.10 INCHES  
ON WEDNESDAY EVENING INTO THURSDAY EVENING. AS THE BAROCLINIC  
ZONE AND UPPER-LEVEL ENERGY MOVE IN ON FRIDAY, MAXIMUM QPF AMOUNTS  
WILL RANGE FROM 0.50 TO 1.10 INCHES OVER PARTS OF THE OHIO AND  
TENNESSEE VALLEYS FROM THURSDAY EVENING INTO FRIDAY EVENING.  
 
MODELS SHOW AN EXPANDING LOW-MID LEVEL THERMAL RIDGE INTO THE  
SOUTHERN PLAINS OVER THE NEXT SEVERAL DAYS, WITH SPORADIC QPF  
ALONG THE PERIPHERY OF THE ELEVATED MIXED LAYER FROM EASTERN  
COLORADO, THROUGH KANSAS, AND INTO THE OZARKS AND MID MISSISSIPPI  
VALLEY REGIONS. FROM A PATTERN RECOGNITION STANDPOINT, THIS SEEMS  
REASONABLE AND ALSO PROVIDES GREATER THAN NORMAL UNCERTAINTY IN  
THE QPF. MODELS CAN STRUGGLE WITH THE TIMING OF MCSS AS THEY ROLL  
IN A GENERALLY EASTERLY DIRECTION AROUND THE PERIPHERY OF A RIDGE,  
AND ALSO STRUGGLE WITH HOW MUCH LATITUDE THEY CAN LOSE AS THEY  
MATURE AND PROPAGATE FURTHER INTO THE HIGHER THETA E AIR MASS.  
GENERALLY FOLLOWED A COMPROMISE OF THE ECMWF AND GFS IN TERMS OF  
TIMING AND POSITION OF QPF MAXIMA IN THIS REGION, WITH A MARKED  
INCREASE IN NOCTURNAL QPF RELATIVE TO THE NBM.  
 
   
..NORTHERN ROCKIES INTO NORTHERN PLAINS
 
 
AN AMPLIFIED TROUGH PUSHING INTO THE NORTHWEST AND EVENTUALLY INTO  
THE ROCKIES SHOULD LEAD TO INCREASINGLY WIDESPREAD CONVECTION, ON  
WEDNESDAY EVENING INTO THURSDAY EVENING OVER MONTANA AND FROM  
THURSDAY EVENING INTO FRIDAY EVENING OVER MONTANA INTO NORTH  
DAKOTA. MAXIMUM QPF AMOUNTS WILL RANGE FROM 1.40 TO 1.00 INCHES  
OVER PARTS OF MONTANA ON WEDNESDAY EVENING INTO THURSDAY EVENING.  
ON THURSDAY EVENING INTO FRIDAY EVENING, THE MAXIMUM QPF AMOUNTS  
WILL RANGE BETWEEN 1.60 TO 1.00 INCHES OVER NORTH DAKOTA WITH A  
SECONDARY MAXIMUM RANGING FROM 1.20 TO 0.90 INCHES OVER WESTERN  
MONTANA.  
 
PEREIRA/ZIEGENFELDER  
 
GRAPHICS AVAILABLE AT WWW.WPC.NCEP.NOAA.GOV/QPF/QPF2.SHTML  
 

 
 
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