502
FXUS04 KWBC 012049
QPFPFD
QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
448 PM EDT FRI JUN 01 2018
FINAL DAY 1, DAY 2 AND DAY 3 QPF DISCUSSION
VALID JUN 02/0000 UTC THRU JUN 05/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR
FOR THE 02/00Z QPF ISSUANCE: NOT MUCH IN THE WAY OF CHANGE TO THE
01/18Z ISSUANCE. A FEW TWEAKS WERE MADE ACROSS NE AND ND, BASED
MAINLY ON RADAR TRENDS (ND) AND TRENDS IN THE HRRR (NE).
..CENTRAL-NORTHERN PLAINS AND UPPER MIDWEST
THERE REMAINS A GOOD MODEL SIGNAL FOR TWO DISTINCT AREAS OF
MODERATE TO HEAVY RAINFALL DEVELOPING THIS AFTERNOON AND EVENING
ACROSS THE NORTHERN AND CENTRAL PLAINS INTO THE MISSISSIPPI VALLEY
AS STRONG UPPER DYNAMICS, DEEP MOISTURE AND INSTABILITY CONVERGE
ACROSS THE REGION. THE LOW LEVEL JET IS EXPECTED TO AMPLIFY OVER
THE CENTRAL AND NORTHERN PLAINS THIS AFTERNOON-EVENING AS A
NEGATIVELY-TILTED UPPER TROUGH TRANSLATES EAST ACROSS THE NORTHERN
AND CENTRAL ROCKIES. GUIDANCE SHOWS PWS INCREASING IN EXCESS OF
1.5 INCHES ALONG A 40-50+ KT LOW LEVEL JET CENTERED ACROSS
NEBRASKA AND THE DAKOTAS. THIS MOISTURE INTERACTING WITH AMPLE
INSTABILITY AND THE AFOREMENTIONED TROUGH IS FORECAST TO SUPPORT
DEVELOPING STORMS, PRODUCING HEAVY RAINS ACROSS THE DAKOTAS LATER
THIS AFTERNOON. AS NOTED IN THE OVERNIGHT DISCUSSION, WITH THE
STRENGTHENING LOW LEVEL JET, THE HI-RES MODELS CONTINUE TO SHOW A
PERIOD OF SLOWER EASTWARD PROGRESSION/CELL TRAINING - RAISING THE
POTENTIAL FOR HEAVY AMOUNTS FLASH-FLOODING ACROSS THIS REGION.
DURING THE OVERNIGHT HOURS, THE GENERAL MODEL CONSENSUS SHOWED
CONVECTION MOVING MORE PROGRESSIVELY EASTWARD ACROSS EASTERN NORTH
DAKOTA INTO MINNESOTA WITH A GENERAL DOWNWARD TREND IN RAINFALL
RATES AS A DEVELOPING CONVECTIVE COMPLEX TO THE SOUTH BEGINS THE
INTERRUPT THE INFLOW OF DEEPER MOISTURE. WPC QPF LARGELY UTILIZED
THE HREF MEAN AS STARTING POINT ACROSS THIS REGION.
FURTHER TO THE SOUTH, THERE REMAINS A STRONG SIGNAL FOR A
CONVECTIVE COMPLEX DEVELOPING AND TRACKING SOUTHEAST FROM CENTRAL
NEBRASKA TOWARD THE MID MISSISSIPPI AND LOWER MISSOURI VALLEYS
OVERNIGHT. RECENT RUNS OF THE RAP SHOW PWS INCREASING TO AROUND 2
INCHES ON THE NOSE OF 50 KT SOUTHERLY INFLOW. UPON ORGANIZING,
THIS SYSTEM SHOULD BECOME FAIRLY PROGRESSIVE, HOWEVER STRONG
SOUTHWESTERLY INFLOW MAY PROMOTE A PERIOD OF BACKBUILDING/TRAINING
CONVECTION, FURTHER RAISING THE THREAT FOR HEAVY AMOUNTS ACROSS
PORTIONS OF CENTRAL NEBRASKA TO NORTHEAST KANSAS AND NORTHERN
MISSOURI. CONVECTION IS EXPECTED TO WANE AS THE COMPLEX CONTINUES
FURTHER SOUTHEAST TOWARD THE LOWER OHIO AND TENNESSEE VALLEYS
DURING THE MORNING HOURS ON SATURDAY. HOWEVER MODELS SHOW
CONVECTION REDEVELOPING LATER IN THE DAY ALONG AND AHEAD OF COLD
FRONT PUSHING FROM THE PLAINS INTO THE MISSISSIPPI VALLEY. DURING
THE FRI EVENING INTO THE OVERNIGHT HOURS, WPC QPF REFLECTS A
NORTHWARD SHIFT IN HEAVIER AMOUNTS, SIMILAR TO THE HREF MEAN.
HOWEVER, DID NOT GO AS FAR NORTH AS THE HRW-ARW AND NSSL-WRF RUNS,
BUT INSTEAD GAVE MORE WEIGHT TO THE MORE SOUTHERLY HRW-NMMB AND
NAM CONEST SOLUTIONS ACROSS NEBRASKA INTO KANSAS AND MISSOURI
OVERNIGHT.
..EASTERN U.S.
SLOW-MOVING, POSITIVELY-TILTED UPPER TROUGH WILL NUDGE EASTWARD
TOWARD THE ATLANTIC COAST BY SATURDAY. UNTIL THEN, A BROAD AREA OF
MODEST DYNAMICAL FORCING EAST OF THE TROUGH AXIS AND SURFACE FRONT
WILL FAVOR SCATTERED-WIDESPREAD CONVECTION ONCE AGAIN TODAY,
ESPECIALLY DURING THE PEAK HEATING HOURS FROM LATE-AFTERNOON INTO
EARLY EVENING. THIS MAY RAISE ADDITIONAL FLASH FLOODING CONCERNS,
PARTICULARLY ACROSS PORTIONS OF THE CENTRAL APPALACHIAN INTO THE
MID-ATLANTIC REGION WHERE FLASH FLOOD GUIDANCE VALUES ARE QUITE
LOW GIVEN THE RECENT HEAVY RAINS IMPACTING THE REGION.
THEN ON SATURDAY MODELS SHOW ENERGY OVER THE GREAT LAKES DROPPING
SOUTHEAST INTO THE MID-ATLANTIC, SUPPORTING SURFACE LOW
DEVELOPMENT ALONG THE DELARMVA COAST. DEEP MOISTURE POOLING NEAR
THE CENTER WILL FUEL AN INCREASING THREAT FOR DEVELOPING MODERATE
TO HEAVY RAINS ACROSS THE MID-ATLANTIC REGION DURING THE AFTERNOON
INTO THE EVENING HOURS.
DAYS 2
..UPPER MS VALLEY INTO THE GREAT LAKES
FOR DAY 2---MODELS ARE FAIRLY SIMILAR IN TAKING AN INCREASINGLY
NEGATIVELY TILTED TROF EASTWARD FROM THE UPPER MS VALLEY THROUGH
THE GREAT LAKES. THERE ARE SOME TIMING DIFFERENCES THAT BEGIN TO
DEVELOP WITH THIS TROF TOWARD THE END OF DAY 2 THAT HAVE
CONSEQUENCES WITH QPF TIMING AMONG THE MODELS. THE TYPICALLY MORE
PROGRESSIVE GFS IS AMPLIFYING THE SOUTHERN PORTION OF THIS
NEGATIVELY TILTED TROF MORE THAN THE REMAINDER OF THE GUIDANCE AND
IS SUBSEQUENTLY SLOWER. GIVEN ITS OUTLIER STATUS DAY 2---WE
TRENDED MORE PROGRESSIVE WITH THE QPF DETAILS. WITH PW VALUES
EXPECTED TO BE ABOVE AVERAGE ALONG AND AHEAD OF THIS TROF AND THE
ASSOCIATED FRONTAL BOUNDARY---MODERATE TO ISOLATED HEAVY PRECIP
TOTALS POSSIBLE. THE GFS BESIDES BEING SLOW IS ALSO SHOWING A
MORE WIDESPREAD AREA OF HEAVY PRECIP OVER PORTIONS OF THE UPPER MS
VALLEY INTO THE UPPER LAKES. DAY 2 QPF LEANED TOWARD A MORE TONED
DOWN VERSION AND MORE PROGRESSIVE---SHOWING AREAL AVERAGE
.25-.50"+ AMOUNTS ACROSS THESE AREAS. L
..MID TO LOWER MS VALLEY INTO THE SOUTHERN PLAINS
SCATTERED CONVECTION LIKELY SOUTH AND SOUTHWESTWARD ALONG THE
FRONTAL BOUNDARY EXTENDING INTO THE SOUTHERN PLAINS. DYNAMICS ARE
NOT AS STRONG ALONG THIS PORTION OF THE FRONT BUT INSTABILITY IS
MUCH GREATER---ESPECIALLY AT THE BEGINNING OF DAY 2. MODERATE
AREAL AVERAGE TOTALS DEPICTED WITH ISOLATED HEAVY AMOUNTS POSSIBLE
WHERE CONVECTION DOES BECOME ORGANIZED.
...SOUTHERN TO CENTRAL ROCKIES..
THE UPPER TROF THAT MOVES NORTHEASTWARD INTO THE SOUTHWEST DAY 1
WILL CONTINUE TO MOVE NORTHEAST DAY 2 INTO THE FOUR
CORNERS/SOUTHERN TO CENTRAL ROCKIES REGION. THIS SYSTEM WILL HELP
DRAW INCREASING PW VALUES NORTHWARD THROUGH THE SOUTHERN TO
CENTRAL ROCKIES AND SOUTHERN HIGH PLAINS. THIS WILL SUPPORT
INCREASING CONVECTION ACROSS THESE AREA SUNDAY AFTERNOON IN A
REGION OF FAIRLY WELL DEFINED UPPER DIFLUENCE AHEAD OF THESE
HEIGHT FALLS. THE GENERAL MODEL CONSENSUS IS FOR AREAL AVERAGE
MODERATE TOTALS WITH ISOLATED HEAVY AMOUNTS POSSIBLE.
.CENTRAL APPALACHIANS INTO THE MID-ATLANTIC
THE SLOW MOVING MID TO UPPER LEVEL TROF MOVING OUT OF THE CENTRAL
APPALACHIANS INTO THE MID-ATLANTIC DAY 1 WILL CONTINUE TO PRESS
SLOWLY EASTWARD ACROSS THE MID-ATLANTIC DAY 2. WHILE THERE IS A
TYPICAL AMOUNT OF SPREAD FOR DAY 2 WITH THE EXACT AXIS OF THIS
PRECIP AREA---THERE IS CONSENSUS FOR ADDITIONAL MODERATE TO HEAVY
TOTALS ACROSS THESE AREAS AND THE CONTINUATION OF POTENTIAL FOR
LOCAL RUNOFF ISSUES GIVEN LOW FFG VALUES ACROSS THIS AREA.
DAY 3
...EASTERN GREAT LAKES---NORTHERN MID-ATLANTIC INTO SOUTHERN NEW
ENGLAND...
THE DAY 2 ISSUES WITH THE STRENGTH OF THE SOUTHERN PORTION OF THE
ELONGATED TROF OVER THE GREAT LAKES CONTINUES AS THIS TROF PUSHES
EASTWARD ACROSS THE EASTERN GREAT LAKES---NORTHERN MID-ATLANTIC
AND INTO NEW ENGLAND. THE GFS CONTINUES MORE AMPLIFIED AND SLOWER
WITH THE TROF AND HEAVIER WITH THE PRECIP AHEAD OF IT---ESPECIALLY
FROM THE COASTAL NORTHERN MID-ATLANTIC---EASTERN NY STATE INTO
SOUTHERN NEW ENGLAND. THERE ARE A VARIETY OF QPF SOLUTIONS ACROSS
THESE AREAS FROM THE HEAVY GFS TO THE DRY NAM AND SOLUTIONS IN
BETWEEN. NOT WANTING TO FAVOR EITHER OF THE OUTLIER SOLUTIONS
HERE---DAY 3 QPF LEANED FOR LIGHTER PRECIP THAN THE GFS BUT
HEAVIER THAN THE NAM ACROSS THESE AREAS---MORE IN LINE WITH THE
LATEST ECMWF (1200 UTC)---DEPICTING .25-.50"+ AMOUNTS. TIMING
WISE...ALSO TRENDING FASTER THAN THE GFS TOWARD THE LATEST ECMWF.
..SOUTHERN TO CENTRAL HIGH PLAINS
HEIGHT FALLS MOVING INTO THE SOUTHERN TO CENTRAL ROCKIES DAY 2
WILL PRESS EASTWARD INTO THE CENTRAL TO SOUTHERN HIGH PLAINS DAY
3. STRENGTHENING SOUTHERLY LOW LEVEL FLOW AHEAD OF THESE HEIGHT
FALLS WILL SUPPORT INCREASING PW VALUES AND INCREASING CHANCES OF
ORGANIZED CONVECTION MOVING EASTWARD INTO THE SOUTHERN TO CENTRAL
HIGH PLAINS. MODEL ARE SHOWING POTENTIAL FOR BOTH A NORTHERN AND
SOUTHERN AREA OF ORGANIZED PRECIP DAY 3. NOT A LOT OF CONFIDENCE
IN EXACT PLACEMENT---BUT MODERATE TO LOCALLY HEAVY TOTALS POSSIBLE
AS THE HEIGHT FALLS PUSH EAST DAY 3.
PEREIRA/ORAVEC
GRAPHICS AVAILABLE AT WWW.WPC.NCEP.NOAA.GOV/QPF/QPF2.SHTML
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