510  
FXUS04 KWBC 022032  
QPFPFD  
 
QUANTITATIVE PRECIPITATION FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
431 PM EDT SAT JUN 02 2018  
 
FINAL DAY 1, DAY 2 AND DAY 3 QPF DISCUSSION  
VALID JUN 03/0000 UTC THRU JUN 06/0000 UTC  
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR  
 
FOR THE 03/00Z QPF ISSUANCE: NOT MUCH IN THE WAY OF CHANGE TO THE  
02/18Z QPF ISSUANCE. A FEW TWEAKS WERE MADE OVER THE MID ATLANTIC  
FOR THE FIRST PERIOD, BASED IN PART ON RADAR TRENDS AND IN PART ON  
THE MOST RECENT HRRR RUNS.  
   
..EASTERN U.S.
 
 
A MODERATE RISK FOR FLASH FLOODING REMAINS IN PLACE ACROSS  
PORTIONS OF MARYLAND, DELAWARE AND THE VIRGINAS AS A SHORTWAVE  
TROUGH DRIFTING EAST FROM THE VIRGINIAS INTERACTS WITH A DEEP  
MOISTURE POOL -- SUPPORTING HEAVY RAINS ACROSS THE NORTHERN MID  
ALTANTIC, INCLUDING AREAS THAT WERE IMPACTED BY HEAVY RAINS  
EARLIER IN THE WEEK. GUIDANCE SHOWS THE AFOREMENTIONED TROUGH  
DRIFTING SLOWLY EAST FROM THE VIRGINIAS TO THE COAST OVER THE NEXT  
24-36 HOURS, WITH DEEP MOISTURE (PWS AROUND 2 INCHES) POOLING NEAR  
THE ASSOCIATED LOW LEVEL CIRCULATION. EXPANDING COVERAGE OF  
MODERATE TO HEAVY RAINFALL RATES IS EXPECTED TO CONTINUE AS  
INSTABILITY INCREASES THIS AFTERNOON. WEAK FLOW ALOFT IS EXPECTED  
TO SUPPORT SLOW MOVING CELLS WITH HIGH RH THROUGH THE MID LEVELS  
AND TALL 'SKINNY' CAPE SUPPORTING EFFICIENT RAINFALL PROCESSES.  
THREAT FOR HEAVY RAINFALL RATES IS EXPECTED TO PEAK DURING THE  
AFTERNOON INTO THE EVENING HOURS, WITH A DOWNWARD TREND AS  
INSTABILITY DECREASES OVERNIGHT. THE RETURN OF DAYTIME HEATING IS  
EXPECTED TO SUPPORT AN UPWARD TREND IN RAINFALL RATES CLOSER THE  
MID ATLANTIC COAST TOMORROW AFTERNOON. WPC QPF UTILIZED THE HREF  
MEAN AS A STARTING POINT THROUGH MUCH OF THE PERIOD, WITH MODERATE  
TO HEAVY AMOUNTS FROM EASTERN WEST VIRGINIA TO THE MID ATLANTIC  
COAST OVER THE 24-30 HOURS.  
   
..UPPER MIDWEST/GREAT LAKES/OHIO VALLEY
 
 
A NEGATIVELY-TILTED UPPER TROUGH WILL CONTINUE TO PUSH SHOWERS AND  
STORMS EASTWARD ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION  
THIS AFTERNOON/EVENING. THE PROGRESSIVE NATURE OF THE SYSTEM  
ALONG WITH MODEST INSTABILITY SHOULD LIMIT THE POTENTIAL FOR HEAVY  
AMOUNTS, WITH GENERALLY LIGHT TO MODERATE ACCUMULATIONS EXPECTED  
AS THE SYSTEM MOVES ACROSS THE UPPER GREAT LAKES REGION TONIGHT.  
AS THE SYSTEM PUSHES FURTHER EAST ON SUNDAY, INCREASING  
INSTABILITY SUPPORTED BY DAYTIME HEATING IS EXPECTED TO RAISE THE  
THREAT FOR LOCALLY HEAVY RAINS ACROSS THE OHIO VALLEY SUNDAY  
AFTERNOON-EVENING. THE HREF MEAN WAS UTILIZED AS A STARTING POINT  
WITH A SLIGHT SHIFT TOWARD THE MORE PROGRESSIVE MEMBERS, INCLUDING  
THE HRW-NMMB.  
 
   
..MID AND LOWER MISSISSIPPI VALLEY
 
 
DIVERGENT FLOW ALONG OF THE BASE OF THE AFOREMENTIONED TROUGH  
ALONG WITH DEEPENING MOISTURE AHEAD OF THE ASSOCIATED COLD FRONT  
WILL CONTINUE TO SUPPORT DEVELOPING CONVECTION ACROSS FROM THE MID  
MISSISSIPPI VALLEY AND OZARK REGION SOUTHWARD INTO THE LOWER  
MISSISSIPPI VALLEY AND ARKLATEX REGION. DEEP MOISTURE AND  
INSTABILITY ARE EXPECTED TO SUPPORT LOCALLY HEAVY AMOUNTS WITH THE  
HI-RES MODELS CONTINUING TO SHOW A GOOD SIGNAL FOR HEAVIER AMOUNTS  
CENTERED ACROSS ARKANSAS THIS EVENING. HOWEVER THESE STORMS  
SHOULD BE FAIRLY PROGRESSIVE IN NATURE, LIMITING THE THREAT FOR  
MORE WIDESPREAD HEAVY AMOUNTS. THE HREF MEAN WAS UTILIZED AS A  
STARTING POINT, WITH A SLIGHT SHIFT TOWARD THE MORE PROGRESSIVE  
MEMBERS.  
 
   
..SOUTHERN ROCKIES/HIGH PLAINS
 
 
GUIDANCE SHOWS A GOOD SIGNAL FOR DEVELOPING PRECIPITATION, WITH  
LOCALLY HEAVY AMOUNTS POSSIBLE ACROSS PORTIONS OF THE REGION  
TOMORROW. INCREASING SOUTHEASTERLY LOW LEVEL INFLOW AHEAD OF A  
SHORTWAVE TROUGH MOVING ACROSS THE FOUR CORNERS REGION IS EXPECTED  
TO SUPPORT DEVELOPING SHOWERS AND STORMS DURING THE AFTERNOON AND  
EVENING HOURS TOMORROW, WITH SOME SIGNAL FOR MODERATE TO LOCALLY  
HEAVY AMOUNTS ACROSS THE SOUTHERN COLORADO AND THE NEW MEXICO  
RANGES.  
 
DAY 2  
 
..EASTERN GREAT LAKES---UPSTATE/EASTERN NY---COASTAL NORTHERN  
MID-ATLANTIC INTO SOUTHERN TO CENTRAL NEW ENGLAND...  
 
THE NEGATIVELY TILTED MID TO UPPER LEVEL TROF MOVING THROUGH THE  
GREAT LAKES REGION DAY 1 WILL CONTINUE TO PUSH EASTWARD DAY 2 AND  
UNDERGO AMPLIFICATION AS ADDITIONAL UPSTREAM HEIGHT FALLS DIVE  
SOUTHEAST FROM THE UPPER TO EASTERN GREAT LAKES REGION. MODEL  
DIFFERENCES ARE NOT AS ACUTE AS YESTERDAY WITH FAIRLY GOOD OVERALL  
AGREEMENT WITH THIS EVOLUTION. SOME TIMING DIFFERENCES WITH THE  
ASSOCIATED SECONDARY LOW MOVING FROM THE MID-ATLANTIC COAST TO IN  
THE VICINITY OF SOUTHEAST NEW ENGLAND WITH THE NAM FASTEST. SHIED  
AWAY FROM THIS OUTLIER SOLUTION WITH RESPECT TO QPF TIMING DAY  
2--MORE TOWARD IN HOUSE ENSEMBLE MEANS AND THE ECMWF---WHICH AS  
PER THE LATEST PMDHMD IS CLOSEST TO THE EC/GEFS/NAEFS MEANS. A  
BROAD REGION OF MODERATE TO HEAVY RAINS WILL STRETCH AHEAD OF THE  
MID TO UPPER LEVEL CENTER ALONG THE ONTARIO/QB BORDER---SOUTHEAST  
INTO UPSTATE AND EASTERN NY---EASTERN PA---NJ AND INTO CENTRAL TO  
SOUTHERN NEW ENGLAND AHEAD OF THE COASTAL SURFACE WAVE WHICH WILL  
ENHANCE ONSHORE SOUTH SOUTHEASTERLY FLOW. DRIER CONDITIONS  
EXPECTED OVER THE MID-ATLANTIC/CENTRAL APPALACHIANS DAY 2 AS THE  
FOCUS FOR HEAVY PRECIP SHIFTS NORTHEASTWARD.  
 
...SOUTHERN HIGH PLAINS..  
 
THE SOUTHERN TO CENTRAL ROCKIES HEIGHT FALLS WILL BE PUSHING  
EASTWARD DAY 2 INTO THE CENTRAL TO SOUTHERN PLAINS. ORGANIZED  
CONVECTION POSSIBLE AHEAD OF THESE HEIGHT FALLS---ESPECIALLY ALONG  
THE SOUTHERN END OF THEM ACROSS THE SOUTHERN HIGH PLAINS FROM  
SOUTH-CENTRAL TO SOUTHEAST NM INTO SOUTHWEST TX. CONFIDENCE NOT  
GREAT WITH TIMING---BUT THERE IS A MODEL SIGNAL FOR POTENTIALLY  
HEAVY TO ISOLATED EXCESSIVE RAINFALL AMOUNTS ACROSS THESE REGIONS.  
NO CHANGES PLANNED TO THE PREVIOUS DAY 2 MARGINAL RISK AREA ON  
THE EXCESSIVE RAINFALL OUTLOOK ACROSS THIS AREA.  
   
..SOUTHEAST---NORTHERN GULF COAST INTO CENTRAL TX
 
 
SCATTERED CONVECTION LIKELY ALONG AND AHEAD OF THE COLD FRONT  
PRESSING SOUTHWARD OFF THE NORTHERN GULF COAST---INTO NORTH  
FLORIDA AND THROUGH THE SOUTHEAST DAY 2. NOT A LOT OF CONFIDENCE  
WITH QPF IN THIS SCATTERED CONVECTIVE REGIME WITH LIGHT TO  
MODERATE AREAL AVERAGE TOTALS DEPICTED.  
 
DAY 3  
   
.NORTHERN NY STATE INTO NORTHERN NEW ENGLAND
 
 
STRONG SOUTHEAST LOW LEVEL FLOW WILL CONTINUE AHEAD OF THE SURFACE  
LOW MOVING FROM OFF THE SOUTHEAST NEW ENGLAND COAST TO THE SOUTH  
COAST OF NOVA SCOTIA DAY 3. TIMING ISSUES CONTINUE DAY 3 WITH THE  
NAM REMAINING THE MOST PROGRESSIVE. WPC DAY 3 QPF STUCK WITH THE  
EC/GFS IN HOUSE QPF MEAN WHICH WERE MORE SIMILAR AND SHOWED  
MODERATE TO HEAVY PRECIP POTENTIAL ACROSS THESE AREAS WITH THE  
GREATEST HEAVY RAIN THREAT ACROSS CENTRAL TO EASTERN MAINE IN THE  
REGION OF STRONGEST ONSHORE FLOW.  
 
   
..LOWER GREAT LAKES INTO THE NORTHERN MID-ATLANTIC
 
 
ADDITIONAL HEIGHT FALLS ROTATING SOUTHEAST INTO THE MEAN TROF  
POSITION ACROSS SOUTHEAST CANADA DAY 3 WILL HELP PUSH A COLD FRONT  
SOUTH THRU THE GREAT LAKES. THE NAM WAS A NORTHERN OUTLIER WITH  
THE AXIS OF PRECIP ASSOCIATED WITH THIS FRONT. WPC FAVORED THE  
FARTHER SOUTH GFS/EC SOLUTIONS--DEPICTING AREAL AVERAGE .10-.25"+  
AMOUNTS FROM THE LOWER GREAT LAKES INTO THE NORTHERN MID-ATLANTIC.  
THE NAM AXIS WAS ORIENTED FROM THE UPPER GREAT LAKES INTO MUCH OF  
WESTERN TO NORTHERN NY STATE.  
   
.SOUTHERN PLAINS
 
 
CONVECTION MAY FIRE IN THE NORTHWESTERLY MID TO UPPER LEVEL FLOW  
PARALLEL TO THE SURFACE FRONT OVER THE SOUTHERN PLAINS DAY 3. THE  
GFS AND NAM WERE FAIRLY SIMILAR WITH THE POTENTIAL MODERATE TO  
HEAVY QPF AXIS FROM WESTERN TO CENTRAL OK INTO NORTHEAST TX. THIS  
AXIS IS IN BETWEEN THE ECMWF'S DEPICTION OF TWO SEPARATE  
AXES---ONE OVER NW TX AND THE OTHER FROM EASTERN OK INTO WESTERN  
LA. CONFIDENCE IS TYPICALLY LOW FOR A DAY 3 CONVECTIVE QPF AXIS.  
AT THE MOMENT---WE FAVORED THE GFS-EC DEPICTION.  
 
PEREIRA/ORAVEC  
 
GRAPHICS AVAILABLE AT WWW.WPC.NCEP.NOAA.GOV/QPF/QPF2.SHTML  
 

 
 
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