Quantitative Precipitation Forecast
Issued by NWS

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992
FXUS04 KWBC 301852
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
251 PM EDT SAT APR 30 2016


PRELIM DAY 1 QPF DISCUSSION
VALID MAY 01/0000 UTC THRU MAY 02/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR



DAY 1

...THE LOWER MS VALLEY/SOUTHEAST/SOUTHERN APPALACHIANS...

THE MODELS/ENSEMBLES INDICATE THE ONGOING CLUSTER OF CONVECTION IN
LA MOVES INTO SOUTHERN MS AND THEN WEAKENS AS THE STRENGTH OF THE
LOW LEVEL JET AND MOISTURE CONVERGENCE WEAKENS WITH TIME...PLUS
THE LOSS OF DIURNAL INSTABILITY.  A FEW OF THE MODELS TRIGGER
SHOWER/STORMS FURTHER NORTH TONIGHT ALONG THE FRONT...CONTINUING
INTO SUNDAY.  THE SPOTTY NATURE OF THE CONVECTION MAKES THIS
ASPECT OF THE FORECAST UNCERTAIN WITH BELOW NORMAL CONFIDENCE.
THE LOW LEVEL JET IS WEAKER THAN TODAY...FINDING A RELIABLE AREA
OF LIFT MORE DIFFICULT THAN TODAY.

THE HIGH RES RUNS STILL INDICATE THE POSSIBILITY OF REGENERATION
OF HEAVY SHOWERS/THUNDERSTORMS OVER SOUTHERN LA SUNDAY. THE WRF
RUNS FROM NSSL/ARW/NMMB AND CANADIAN REGIONAL GEM SHOW A MAXIMUM
IN THIS AREA SUNDAY AFTERNOON...SO THE AREA WILL NEED TO BE
MONITORED.  HOWEVER...WITH A WEAKER FORECAST LOW LEVEL JET AND
EVEN ANTICYCLONICALLY TURNING LOW LEVEL WINDS...LOCAL BOUNDARIES
ARE NEEDED TO GENERATE LIFT...LIKE THE GULF COAST SEA BREEZE.
MANUAL QPF WAS LIGHTER THAN THE HIGH RES RUNS AS THE RESULT OF
LESS FAVORABLE DIAGNOSTICS FOR SUSTAINED LIFT.

THE LOW LEVEL MOISTURE RETURN INT HE SOUTHEAST AND SOUTHERN
APPALACHIANS HAS LED TO DEVELOPING SHOWERS/STORMS IN EASTERN TN/GA
IN THE GENERAL LOW LEVEL WARM ADVECTION PATTERN.  SHOWERS AND
STORMS ARE EXPECTED AS THE MOISTURE RETURN THEN GETS LIFTED INTO
WINDWARD AREAS OF THE SOUTHERN APPALACHIANS WITH ENHANCED TOTALS
OCCURRING AS A RESULT OF TOPOGRAPHIC ENHANCEMENT. MORE WEIGHTING
WAS GIVEN TO THE HIGH RES RUNS..INCLUDING THE CANADIAN REGIONAL
GEM...BUT NOT AS HIGH AS THE 12Z CONUS NEST NAM IN EITHER THE
SOUTHERN APPALACHIANS OR IN MS/LA.

...CENTRAL PLAINS/UPPER MS VALLEY/GREAT LAKES/OH VALLEY INTO THE
CENTRAL APPALACHIANS/MID ATLANTIC/NORTHEAST...

THE MODELS SHOW ONE QPF MAXIMA IN THE LOW-MID LEVEL DEFORMATION
AND CONVERGENCE JUST NORTH OF THE 700 MB CIRCULATION TONIGHT IN
NEBRASKA. FURTHER DOWNSTREAM...LOW-MID LEVEL WARM/MOIST ADVECTION
SUPPORTS SHOWERS/STORMS DEVELOPING IN THE GREAT LAKES TO PA AND
NY.  AS THE MID LEVEL WAVE MOVES EAST...THE SURFACE WARM FRONT
FOCUSES SHOWERS AS IT MOVES NORTH ACROSS THE MID ATLANTIC...WITH A
PEAK IN ACTIVITY IN LONG ISLAND SUNDAY JUST NORTH OF THE WARM
FRONT. THE GLOBAL MODELS AND HIGH RES RUNS CLUSTER NORMALLY WITH
TYPICAL TIMING/AMOUNT DIFFERENCES. A MULTI-MODEL/ENSEMBLE BLEND
WAS USED.

BIGGER DIFFERENCES PERSIST AMONG THE MODELS WITH RESPECT TO THE
AXIS OF THE HEAVIEST TOTALS ACROSS THE OH VALLEY INTO THE CENTRAL
APPALACHIANS DUE TO WHERE/WHEN CONVECTIVE CLUSTERS FORM....AS THE
AIRMASS RECOVERS AFTER THIS AFTERNOONS ACTIVITY.  A MAXIMA IN THE
700 MB CONVERGENCE INT HE GFS FORECAST FOCUSES ENHANCED TOTALS IN
THE CENTRAL APPALACHIANS WITH ISOLATED HEAVY RAINFALL TOTALS
ACROSS THE UPPER OH VALLEY INTO THE CENTRAL APPALACHIANS.  THE CMC
GEM...NSSL WRF AND A MULTI-MODEL/SREF MEAN QPF AMOUNTS WERE USED
PRIMARILY FOR THE QPF AXIS DETAILS.

...CENTRAL-SOUTHERN ROCKIES INTO THE ADJACENT HIGH PLAINS...

THERE IS GOOD AGREEMENT WITH THE EVOLUTION OF THE CLOSED LOW
EJECTING EAST NORTHEAST OUT OF AZ INTO NM SUNDAY.  A COMMA
HEAD/DEFORMATION PRECIPITATION BAND TO THE NORTH AND NORTHEAST OF
THIS CLOSED LOW WILL SUPPORT MODERATE TO ISOLATED HEAVY PRECIP
TOTALS FROM CENTRAL TO NORTHERN AZ ACROSS SOUTHWEST CO AND
NORTHERN NM.  PRECIP IS SUPPORTED BY COUPLED UPPER
DIVERGENCE/LOWER CONVERGENCE MAXIMA WITH ENHANCEMENT IN FAVORED
UPSLOPE AREAS LIKE THE SAN JUANS AND SANGRE DE CRISTO RANGES.
MANUAL PROGS USED A BLEND OF CONTINUITY WITH THE GLOBAL MODELS AND
12Z CANADIAN REGIONAL GEM AND 09Z SREF MEAN QPF.

GRAPHICS AVAILABLE ON THE WEB AT WWW.WPC.NCEP.NOAA.GOV

PETERSEN

24HR QP VT 02/00Z
 0.01 470759 467729 466722 464715 463708 459704 447696 434688
      426686 418682 412678 406674 399669 397672 392673 388675
      384680 380688 374706 371718 366726 359743 356750 353755
      350758 345765 340771 326781 320784 313790 308794 306797
      302806 300810 301815 305825 307830 306837 303846 299853
      295859 287877 282882 279886 277892 274901 271908 268945
      268950 272952 274952 275955 275962 276967 277971 276974
      277984 277989 278993 281003 283007 282013 278020 278023
      280026 285029 290030 304038 313041 318046 323054 326058
      328060 328064 329085 327090 324096 323106 325115 327120
      329122 333124 336128 340135 341140 344141 353142 357141
      358148 353155 353163 358172 359177 353179 353184 356188
      389210 395215 398213 399209 398205 394202 390200 388196
      382188 378180 377175 376170 377166 376160 373157 372151
      377142 382134 387127 393124 400118 403114 407112 410107
      409100 408094 406100 405104 404107 402107 400103 397094
      397091 398088 400084 404077 404072 402068 401065 404064
      407065 415071 418074 421078 422085 422091 423098 421105
      420115 415125 404142 399150 397154 397158 398161 402165
      409161 421150 427146 435141 438139 439130 436121 435115
      435109 437102 441102 444100 449100 453100 452095 449092
      444089 441086 439083 440079 441077 443078 448078 451081
      451075 447067 442062 434055 432050 433044 439025 444001
      446988 447971 448960 449945 448934 447916 447902 448893
      449887 450881 452867 455859 456852 457845 459820 460809
      462800 470779 470767 469761 470759
 0.01 399945 398936 396933 396929 394926 394922 391919 387918
      383919 380920 375923 371924 369925 363929 358932 352934
      337939 326943 323944 321946 316952 313958 310964 309967
      309972 308977 310981 315992 319998 323003 329007 332007
      335006 338005 340003 346998 353989 355987 359986 361984
      366985 371987 374989 378990 384992 390993 394977 397961
      398951 399945
 0.01 275009 274009 274007 273006 271005 271004 271005 269006
      268007 267008 266009 267011 269013 271014 271013 273012
      273011 274009 275009
 0.01 257004 256000 253996 249995 244995 240993 237995 238997
      242999 244002 247006 251007 255006 257004
 0.25 454769 453753 452744 451736 447724 442717 437715 433715
      420717 417715 414711 408705 399710 391718 385726 381734
      375758 371766 368773 362781 358785 354786 349784 345785
      340792 334798 325803 321806 319812 319823 322833 322839
      320845 315852 308858 296872 290879 286887 282896 278906
      276917 276930 279941 281947 285951 288953 293953 301949
      309943 316935 327922 332915 338909 342906 348905 358902
      376891 382887 385886 388891 396896 401898 408898 410901
      410907 410919 408949 408963 409976 410990 411994 415998
      417001 422005 426003 431000 438899 443873 444861 444845
      445820 449794 450787 453781 454769
 0.25 399053 400048 399044 397041 394041 388045 386048 383048
      380041 375037 364029 361023 359020 355019 349022 345027
      341034 338040 333045 331048 331053 333056 337058 343061
      346063 344067 340072 338075 337080 337090 336098 336108
      339123 344128 347130 351131 358129 362125 371114 377110
      381106 382102 383096 384086 385072 382065 382063 384058
      387055 392055 397055 399053
 0.25 312022 313018 313013 311011 309011 305010 302010 300011
      298013 296015 296019 297021 299023 301024 305025 308026
      311024 312022
 0.50 441772 441766 440760 439755 436751 432747 425744 420745
      416747 412746 409744 408740 406735 404731 399729 394731
      391734 386747 381765 376778 372783 366789 360792 356793
      353791 350789 346791 341797 337803 333808 328812 325816
      325817 329824 329831 330838 330850 328857 322861 314862
      308867 298876 293880 290886 283900 279916 278920 279925
      281931 286937 290938 296938 308933 311932 314930 318923
      325911 330905 337901 344890 355879 360876 366873 382870
      390867 395862 406852 411848 418849 425852 429857 432866
      433869 435866 436856 437850 437843 436832 434822 432811
      431807 432802 435795 437789 440780 441772
 0.50 425971 426966 425961 424958 423954 422952 421949 419950
      417953 416956 415959 415963 414968 415973 416975 419976
      422975 424973 425971
 0.50 379085 381080 380075 376069 371066 366066 356073 348073
      345079 344088 345096 347102 346110 346117 350123 355123
      359118 362111 365106 372095 375086 379085
 0.50 370055 371050 371047 367041 362040 357038 353036 351037
      347042 345048 343052 345054 352057 357060 361060 365061
      368061 370057 370055
 1.00 420782 421776 421774 419771 412772 408777 408787 412793
      416800 415804 415809 418813 419811 418806 417801 418797
      420793 420787 420782
 1.00 392796 391792 387790 380791 368799 361802 356806 350810
      346816 343834 345842 350844 355842 358843 363848 369852
      373852 375848 380832 383826 386819 389810 391803 392796
 1.00 316888 315883 311879 306879 302882 295889 291897 286908
      286913 287918 290923 295924 301922 304919 310911 314901
      315895 316888 316888
 1.50 358821 359819 357817 356817 355817 354819 354821 356822
      358821 358821
 1.50 307895 305890 302891 298894 297897 295901 293906 292912
      295915 299914 302909 303905 304901 306897 307895

$$





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