Quantitative Precipitation Forecast
Issued by NWS

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152
FXUS04 KWBC 211847
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
246 PM EDT FRI APR 21 2017


PRELIM DAY 1 QPF DISCUSSION
VALID APR 22/0000 UTC THRU APR 23/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1...

...SOUTHERN-CENTRAL PLAINS EASTWARD THROUGH THE TENNESSEE
VALLEY...LOWER OHIO VALLEY...AND MID ATLANTIC...

A SLOWLY EVOLVING UPPER TROUGH...ONE THAT WILL ELONGATE WITH TIME
AS IT BECOMES INCREASINGLY CONSTRICTED BY RIDGES TO THE NORTH AND
TO THE SOUTH.  FAVORABLE UPPER JET DYNAMICS IN THE FORM OF COUPLED
JET STREAKS WILL AID THE GENERATION OF ADDITIONAL MODERATE TO
HEAVY RAINFALL NORTH OF A SURFACE STATIONARY FRONT. THE SYSTEM
WILL MAKE ITS WAY SLOWLY TOWARDS THE EAST...SPREADING LIGHT TO
MODERATE RAINFALL AMOUNTS AS FAR EAST AS THE TN VALLEY/SOUTHERN
APPALACHIANS AND PARTS OF THE CAROLINAS BY LATE SATURDAY AFTERNOON.

THE BEST AREA FOR HEAVIEST RAIN...THOUGH...STILL LOOKS TO BE
ACROSS PARTS OF THE SOUTHERN/CENTRAL PLAINS INTO THE WESTERN TN
VALLEY TONIGHT.  SOUTHERLY INFLOW WILL INCREASE TO BETWEEN 45 KTS
AND 55 KTS WHICH HELPS INCREASE THE INSTABILITY SOUTH OF THE
FRONTAL BOUNDARY.  BETWEEN THAT AND THE APPROACH OF SHORTWAVE
ENERGY FROM THE WEST SHOULD HELP ENHANCE RAINFALL RATES.  ONE
NEGATIVE AT PLAY IS THE EXPECTED FORWARD SPEED OF THE SYSTEM WHICH
WOULD LIMIT THE TOTAL RAINFALL AMOUNT DESPITE THE ENHANCED
RAINFALL RATES.  EVEN THE 12Z MODEL RUNS WERE NOT HANDLING THE
SHORT TERM QPF WELL...BEING TOO FAR NORTH AND TOO LIGHT WHEN
COMPARED WITH RADAR.  PART OF THE PROBLEM WITH RESPECT TO THE
AMOUNTS MAY BE THE SPIN UP TIME FOR THE MODELS TO GENERATE THE
CONVECTIVE RAINFALL ADEQUATELY.  AS A RESULT...THE 00Z ECMWF/GFS
AND 00Z CONVECTIVE ALLOWING GUIDANCE WAS USED AS A STARTING POINT
AND THEN MODIFIED TO FIT THE SPEED SHOWN BY SATELLITE AND RADAR
IMAGERY THROUGHOUT THE MORNING AND EARLY AFTERNOON.

MUCH LIKE THE PREVIOUS FORECAST...THE HIGHEST AMOUNTS LOOK TO BE
FOCUSED IN PARTS OF MO GIVEN UPSLOPE ENHANCEMENT IN THE LOW
LEVELS.  BEYOND THAT...THE 12Z RUN OF THE HIRES ARW STILL
SUPPORTED THE IDEA OF SOME 3 TO 5 INCH RAINFALL AMOUNTS WITHIN THE
AREA OF BEST INSTABILITY AND THAT MODEL AT LEAST HINTED THAT
CONVECTION WOULD BE PROPAGATING EASTWARD MORE QUICKLY.


...WESTERN UNITED STATES...

A DEEP AREA OF LOW PRESSURE OVER THE EASTERN NORTH PACIFIC WILL
PUSH A FRONT INLAND OVER PARTS OF THE WESTERN UNITED STATES.  THE
FRONT WILL BE THE FOCUS FOR MAINLY LIGHT TO LOCALLY MODERATE
PRECIPITATION AMOUNTS LATER TONIGHT AND ON SATURDAY.  THE HIGHEST
QPF WAS INDICATED IN THE TERRAIN WHICH ARE FAVORED BY A WEST TO
SOUTHWEST FLOW.

BANN


GRAPHICS AVAILABLE ON THE WEB AT
WWW.WPC.NCEP.NOAA.GOV/QPF/QPF2.SHTML

24HR QP VT 23/00Z
 0.01 511281 512274 512268 512254 512249 511243 510237 508234
      499190 496187 492186 485189 479195 475202 469209 461212
      447216 420233 413231 405235 397237 389236 393242 401249
      418257 434268 441274 448279 451282 456284 459287 463287
      471285 476281 480277 482273 484274 486279 492285 496285
      500287 503290 507288 511281
 0.01 531891 531882 531874 529868 527862 522855 518854 515855
      510866 508861 507853 506846 505839 502834 499836 492853
      486871 479890 475902 474912 475917 475921 475928 477935
      477942 480951 481966 480973 481979 483992 486005 488011
      490012 492012 493015 492022 492029 492036 495041 494050
      493057 491060 489063 486062 481062 475059 464057 462052
      460047 457044 452043 444041 439042 436040 433041 428041
      423034 419031 414030 407021 405009 399993 398988 398984
      400974 400968 399963 400958 401951 402946 402938 400926
      397914 397899 397892 398887 398875 400848 401843 401836
      401822 401816 402811 401797 400782 399774 396770 395765
      395759 396749 395745 393743 389741 387735 384731 381729
      370732 365738 363727 360724 356723 352725 349729 347738
      345744 342748 338755 336764 336769 337773 344772 342778
      341784 342791 346802 346814 348826 347831 344835 341843
      341849 342852 343859 340862 334868 320883 314889 309895
      302901 300904 298909 295930 292939 288945 285955 285960
      289962 288980 290983 297984 306979 313976 319976 323979
      341978 345977 351976 359981 365986 370991 381006 387011
      391016 391019 390022 391025 389030 386039 385044 384047
      381047 372045 369049 365047 361049 363052 372052 381057
      383059 388059 394061 395065 394069 396071 398073 399070
      402070 408077 414081 426097 433102 436110 442111 446109
      450118 456123 455117 455112 458108 462111 462115 460119
      460124 470123 478129 483133 484132 483126 482116 481110
      483105 485101 488097 488085 490081 492081 495081 500081
      502079 513063 516059 517052 519035 522010 523999 524983
      524965 524948 523933 523925 525918 531891
 0.01 504717 503710 501703 497691 496683 494677 492669 490665
      485654 478647 474644 471643 465643 462641 455638 449639
      444642 442644 439643 436642 428639 423638 419640 415644
      413649 412661 414672 406678 402682 401683 401688 403694
      405699 407703 411706 419709 423713 425715 424720 423726
      422730 417738 414743 416747 418753 418759 422770 426770
      429767 437761 443759 447756 450746 452733 456730 461730
      463739 463747 464752 465754 469754 478757 486758 492757
      495753 498741 500736 503733 504717
 0.01 463188 463186 460183 455181 450180 445184 441185 442188
      440192 439197 443199 444201 448199 452195 457192 461188
      463188
 0.01 472031 471026 471021 468018 466021 464028 462030 459032
      454034 452037 455039 458040 462038 465038 469036 472031
      472031
 0.01 426072 426070 425070 424069 422068 421069 419071 420074
      422076 424076 425074 426072
 0.01 293805 292799 290797 282793 277793 273791 267786 265784
      259783 255783 250783 241786 234791 231799 230808 232819
      236827 238830 242833 249837 257839 261840 264838 269831
      269826 267823 267816 269812 272809 276808 282808 286808
      291807 293805
 0.25 498266 498259 496255 494248 489242 483242 481239 479234
      477230 473230 467233 463233 459231 452232 447236 444238
      444241 446248 446254 450257 454256 460251 464246 468246
      472248 478251 484250 488254 492263 494266 496267 498266
 0.25 487699 486694 483692 481680 479674 477669 472663 466658
      460655 456656 451658 444661 438664 429666 425669 424674
      425679 428683 439692 443700 447707 460715 464713 469713
      475715 483712 486709 487704 487699
 0.25 459081 458074 454069 450064 445060 440060 437064 434069
      433078 435081 437081 441079 446081 451085 454086 459081
 0.25 425246 427245 426242 425242 424241 422240 421240 420240
      419242 420244 420245 421246 423246 425247 425246
 0.25 417048 417045 417043 417042 415041 415040 413040 412039
      410039 408039 406040 407042 408045 409047 410048 411049
      413050 415050 417048 417048
 0.25 394821 393802 392793 390785 386779 384772 383765 381757
      377751 375750 372751 367754 362755 362758 363763 362769
      359774 354779 352785 352793 354802 357808 356825 354837
      352845 352851 350859 348866 345871 340874 336878 333882
      329887 325890 320894 318898 321902 324902 329901 332897
      336894 338896 339900 339909 339916 336924 327947 323959
      322963 323967 328970 335969 340966 348959 356952 362952
      366956 372969 375974 380976 384975 386974 389967 390960
      391952 391932 392915 393879 394861 394846 394821
 0.25 258801 257796 255794 252793 248794 242798 237804 236810
      236820 241825 247828 252828 255820 255812 257803 258801
 0.50 475684 475677 472673 468673 463674 460676 457682 456686
      456692 458699 462700 466698 470695 472691 474687 475684
 0.50 389808 389800 388794 381785 376777 375769 377764 375757
      372756 370760 368766 366777 364782 360785 358790 358796
      360802 361809 362818 361824 361829 359834 354857 348877
      345888 344894 343901 343908 342914 338923 333947 331960
      332963 334964 338962 353950 358947 361947 366949 368953
      373962 377965 380965 384961 385955 387943 387934 388930
      389921 389913 388897 389886 390829 389816 389808
 0.50 250820 251816 251812 251808 249804 246803 243804 241805
      239807 239811 239815 240819 241822 243823 247824 249822
      250820
 1.00 383800 383799 381798 381796 381795 380796 379797 377798
      376798 376799 374800 373801 372802 371804 372806 373806
      374807 376807 378806 379805 380804 381803 382802 383800
      383800
 1.00 383845 383836 382827 378823 373821 370820 367822 365828
      361841 361847 359855 357861 356868 355874 352881 349892
      348901 348908 346919 342933 342941 345943 348942 359938
      365939 369943 373947 375948 378947 382944 384936 384919
      383904 381897 381889 384875 382857 383845
 1.00 366914 366910 365907 365903 362902 359903 357905 357907
      355911 354914 355917 357920 359921 362923 363923 364921
      365916 366914
 1.50 378848 377839 375834 370835 368829 364838 365845 364852
      360865 361876 359884 360887 361887 367887 370885 374882
      376875 375862 378848
 1.50 379929 379927 379925 379922 378922 377920 377919 375920
      373923 373925 375927 377928 377929 379930 379929
 2.00 374848 374846 374845 373844 372844 371844 370845 369847
      368848 368849 367851 367853 367854 367855 369855 371854
      372853 372852 373851 374849 374848

$$





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