471
FXUS04 KWBC 022023
QPFPFD
QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
422 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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