000
FXUS04 KWBC 100719
QPFPFD
 
QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
318 AM EDT FRI SEP 10 2010
PRELIM DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION
VALID SEP 10/1200 UTC THRU SEP 13/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR
 
...DAY 1...

...SYNOPSIS...
DEEP MID/UPR VORTEX OVR THE NERN U.S. WL GET SHOVED EWD THIS PD FM
THE STG WRN U.S. TROF THAT WORKS INTO THE NCNTRL U.S.. THE FLAT
RDG ACRS THE SRN U.S. WL REMAIN INTACT. SFC REMNANTS OF HERMINE
HAVE BEEN LOST IN THE SFC DATA...BUT THE MIDLVL ENERGY WL CONT TO
SUPPORT PCPN AS IT MOVS SLOLY EWD. MDLS GNRLY ARE ON THE SAME PAGE
WITH THE BULK OF THE PCPN THRU THE CNTRL U.S....BUT AMTS ARE QUITE
DIFF BETWEEN THE MDLS.

...NERN U.S....
VRY COLD MIDLVL TEMPS...ASSOCD WITH THE DEEP VORTEX WL SUPPORT
RATHER UNSTBL CONDS TDA WITH SHWRS XPCTD TO FORM AND PUSH ACRS THE
REGION. RNFL AMTS WL BE LGT.

...FL...
DIURNAL CNVCTN WL FIRE ALNG THE SERN CSTL FNT THIS MRNG AND PUSH
WWD ACRS THE ST WITH SOME ENHANCEMENT THIS AFTN OVR INTERIOR
SECTIONS. MOST LGT RNFL IS XPCTD.

...LWR OH VLY INTO LWR MS VLY...
MIDLVL REMNANTS OF HERMINE WL CONT TO PROGRESS EWD THRU THE LWR OH
VLY. MDLS CONT TO SHOW DEEP MSTR...PWS AOA TWO INCHES...ASSOCD
W/THE MIDLVL CENTER AND LOLVL FLOW WL CONT TO BRING SOME LOLVL
GULF MSTR INTO THE REGION. SFC BNDRY DRAPED ACRS THE REGION WL
HELP FOCUS LIFT WITH SWRLY LOLVL FLOW PROVIDG SOME ISENTROPIC LIFT
OVR THE BNDRY. XPCT A BROAD REGION OF LGT/MOD RNFL WITH ISOLD HVY
AMT PSBL. LGT PCPN SHLD EXTEND INTO THE LWR MS VLY AND TO THE
CNTRL GULF REGION AS MDLS SHOW A RIBBON OF DEEPER MSTR THRU THIS
REGION.

...NRN ROCKIES INTO THE NRN PLNS/UPR MS VLY...
SVRL SHRTWVS EMBEDDED IN THE WRN U.S. TROF ARE FCST TO PHASE INTO
A SHARPENING/NEG TILT TROF THAT WL SWING THRU THE NRN PLNS/UPR MS
VLY LATER TDA/TNGT WITH STG HGT FALLS/UPR JET DYNAMICS. SFC/8H
BNDRY THAT WL MOV OUT OF THE ROCKIES INTO THE PLNS WL BCM BETTER
ORGANIZED/DEFINED THRU TDA WITH STRENGTHENING LOLVL MSTR CVRG AND
A DVLPG LOLVL THETA-E RDG AHD OF THE BNDRYS. TONGUE OF DEEP
MSTR...PWS AOA 1.50 INCHES IS ALRDY IN PLC AND WL FUEL A SWATH OF
MOD/HVY RNFL ACRS THE REGION. XPCT MORE FRACTURED CNVCTN ERLY THIS
MRNG TO BCM BETTER ORGANIZED THIS AFTN AS THE MIDLVL ENERGY EJECTS
INTO THE PLNS WITH THE CNVCTN LIFTG RPDLY NEWD TNGT. HVIER RNFL
SHLD DVLP OVR THE UPR MS VLY UNDER THE STG SPLIT THAT DVLPS IN THE
POLAR JET WITH IMPRVS UPR DIFL/DVRG FLOW. SREF/GEFS/EC ENS
SPAGHETTI PLOTS OF 1-2 INCH RNFL ARE BCMG VRY CLUSTERED OVR NRN
MN.


...SRN PLNS INTO MID MS VLY...
THE SRN PORTION OF THE AFOREMENTIONED MID/UPR TROF SWINGING THRU
THE NCNTRL U.S. WL PROVIDE STGR LRG SCALE LIFT LATER THIS
AFTN/TNGT WITH THE PTNL FOR ORGANIZED HVY RNFL. MDLS CONT TO SHOW
MSTR POOLG THRU THIS REGION...AHD OF THE ADVANCING CDFNT...WITH
PWS LKLY TO EXCEED TWO INCHES BY LATER TDA. STG AFTN HEATG WL HELP
BOOST CAPES TO 2-3K J/KG WITH LIS DROPG TO MINUS 4-6 ACRS PORTIONS
OF ERN KS INTO WRN MO. MDLS SHOW VRY STG BNDRY LYR MSTR CVRG DVLPG
OVR SERN KS WITH THE STGR CVRG SPRDG SWD INTO WRN OK AND EVEN NWRN
TX OVERNIGHT. NOT SURE THIS WL RESULT IN CNVCTN DVLPG THAT FAR
S...BUT IN THESE TYPES OF SCENARIOS...THE CNVCTN USUALLY DOES DVLP
SW OF THE MDL GUID. 8H FCSTS ALSO SHOW VRY STG THETA-E CVRG/ADV
INTO SERN KS/WCNTRL MO THAT WORKS SWWD TNGT INTO OK. CVNCTN SHLD
BCM WELL ORGANIZED ON/AFTR 11/00Z AS A SRN STREAM UPR JET STREAK
DIGS INTO THE REGION AND THEN SPLITS WITH INCRSG UPR DIFL/DVRG
THAT WL INCRS THE LRG SCALE LIFT. MDL PROPAGATION VECTORS SHOW
GNRLY SLOW MOVEMENT THRU MOST OF TNGT AS THE LLJ INCRS AND VEERS
TO A SWRLY DIR. THIS WL ALSO HELP TO BUILD CNVCTN SWWD FM KS INTO
OK. XPCT A LRG AREA OF MOD/HVY RNFL WITH THE PSBLY OF SOME VRY HVY
RNFL OVERNIGHT THRU SERN KS INTO WCNTRL MO AND PSBLY FAR NERN OK.
LATEST SREF/GEFS/EC ENS SPAGHETTI PLOTS OF 1-2 INCH RNFL ARE SHOWG
MORE CLUSTERING OVR SERN KS INTO WCNTRL MO. GFS MOS POPS OF RNFL
EXCEEDING ONE INCH AND TWO INCHES IN SIX HRS SHOWS LRG INCRS FM
11/00Z-12Z ACRS THE REGION. 

...TX...
SCT/SPOTTY CNVCTN IS PSBL ALNG THE WRN EDGE OF THE DEEP MSTR WHERE
WEAK CVRG IS EVIDENT ALNG A SFC BNDRY. OVERALL RNFL AMTS SHLD BE
LGT...BUT SPOTTY HVY AMTS ARE PSBL.

...PAC NW...
NEXT UPSTREAM SHRTWV APRCHG THE REGION WL BRING DECENT HGT
FALLS/ONSHORE FLOW TO THE REGION THAT WL BEGIN TO SUPPORT LGT
SHWRS OVR THE PORTIONS OF WA/ID.
 
DAYS 2 AND 3...

...GREAT LAKES/OHIO VALLEY/TN VALLEY/NORTHEAST/NORTHERN TO CENTRAL
APPALACHIANS/MID ATLANTIC/SOUTHEAST...
A DEEP UPPER-LEVEL TROUGH SHEARS NEWD OVER THE GREAT LAKES FRIDAY
NIGHT AND SATURDAY...WITH LOWER LEVEL CONVERGENCE GRADUALLY
WEAKENING. A REGION OF MID-LEVEL WARM ADVECTION/LIFT UNDERNEATH A
DIVERGENCE MAXIMA ALOFT SUPPORTS SHOWERS/STORMS IN ADVANCE OF THE
ASSOCIATED SFC-H85 COLD FRONT ACROSS THE OHIO AND TN VALLEYS TO
THE CENTRAL APPALACHIANS SAT...WHERE 
OROGRAPHIC LIFT AIDS ASCENT.  PRE-FRONTAL LOW LEVEL CONVERGENCE
REDEVELOPS FURTHER EAST IN THE MID ATLANTIC/SOUTHEAST SUN.  HIGHER
MOISTURE VALUES WITH PW VALUES OF 2 INCHES WILL BE IN PLACE OVER
EAST CAROLINAS/GEORGIA...WHERE HIGHER AMOUNTS ARE FOCUSED SUN
BEFORE THE FRONT PUSHES OFFSHORE SUN NIGHT AND COOLING/DRYING
BEHIND THE FRONT BRING AN END TO THE RAIN.   THE MODELS HAVE MINOR
TIMING DIFFERENCES WITH THE FRONT...LEADING A CONSENSUS BASED
APPROACH. 
HPC QPF BLENDED THE ECMWF/21Z SREF MEAN WITH LESS WEIGHT ON THE
GFS/UKMET.  THE GFS STOOD OUT WITH A WAVE ON THE FRONT IN NEW
ENGLAND ON DAY THREE NOT SHOWN IN OTHER MODELS/OTHER GFS RUNS...SO
CAUTION WAS USED IN ADOPTING THIS.


...GULF COAST/FLORIDA...
A MOIST AIRMASS REMAINS IN PLACE ON DAY TWO BUT LIFT WILL BE WEAK
WITH THE MID-UPPER RIDGE REMAINING IN PLACE.  PWATS AOA 2 INCHES
WILL CONTINUE TO WORK IN TANDEM WITH DIURNAL HEATING AND THE SEA
BREEZE...PRODUCING LOCALIZED CONVECTION ALONG THE FLORIDA
PENINSULA AND THE NORTHERN GULF COAST.  ON DAY 3...THE WEAKENING
FRONT MOVES SOUTH TO THE GULF COAST AND NORTHERN FLORIDA. CYCLONIC
SHEAR DISSIPATES...AS DOES PRE-FRONTAL CONVERGENCE...SO SEA
BREEZES AND LAKES BREEZES REMAIN THE PREDOMINANT LIFTING
MECHANISM.  
Y EVENING WHEN THE UPPER-LEVEL TROUGH WEAKENS/SUPPRESSES THE
MID-LEVEL SUBTROPICAL RIDGE...ALLOWING FOR ISOLATED CONVECTION TO
DEVELOP ALONG THE SEA BREEZE FRONT.


PACIFIC NORTHWEST/NORTHERN ROCKIES...
AFTER A DRY DAY 2....SUFFICIENT HEIGHT FALL COME ONSHORE IN THE
PACIFIC NORTHWEST TO PRODUCE PRE-FRONTAL CONVERGENCE AND ASCENT IN
WESTERN WA BEFORE THE FRONT MOVES INLAND AND GRADUALLY WEAKENS AS
IT CROSSES THE NORTHERN ROCKIES....WHERE MODEST MID LEVEL THETA-E
ADVECTION SUPPORTS LIGHT SHOWERS.  THE MODELS MOSTLY KEEP HIGHER
AMOUNTS IN THE WA CASCADES AND NORTH OF THE BORDER...AND MANUAL
PROGS FOLLOW SUIT.  TIMING DIFFERENCES ON THE SHORTWV NORTH OF THE
BORDER PERSISTS...SO A BLENDED APPROACH AMONG THE ECMWF/GFS/UKMET
WAS USED TO MITIGATE THE DIFFERENCES.  


ECKERT/PETERSEN