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
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