Quantitative Precipitation Forecast
Issued by NWS

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199
FXUS04 KWBC 201857
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT SAT MAY 20 2017


PRELIM DAY 1 QPF DISCUSSION
VALID MAY 21/0000 UTC THRU MAY 22/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...N-CENTRAL US AND E-CENTRAL US...

IT REMAINS THE CASE THAT ANOTHER DAY OF WIDESPREAD HEAVY PRECIP IS
ON TAP AHEAD OF THE STRONG CLOSED LOW LIFTING NORTHEASTWARD FROM
THE CENTRAL PLAINS TO THE NRN PLAINS/UPPER MS VALLEY INTO SUNDAY.
WHILE MODELS OVERALL ARE IN AGREEMENT WITH THE EVOLUTION OF THE
SYSTEM...QPF DETAIL DIFFERENCES AGAIN ABOUND...ESPECIALLY IN THE
MORE CONVECTIVE COMPONENT OF THE PRECIPITATION DISTRIBUTION AHEAD
OF THE ADVANCING COLD FRONT PUSHING FROM THE SRN PLAINS INTO THE
MS/OH/TN VALLEYS AND GREAT LAKES. THERE WILL CONTINUE TO BE AN
OVERALL VERY FAVORABLE PATTERN FOR WIDESPREAD HEAVY RAINS WITH
STRONG LIFT AHEAD OF THE NORTHEASTWARD MOVING CLOSED LOW IN AN
AXIS OF PW VALUES 1 TO 2 STANDARD DEVIATIONS ABOVE THE MEAN. THERE
IS SOMEWHAT BETTER AGREEMENT WITH THE COMMA HEAD/DEFORMATION
PRECIP AREA TO THE NORTH OF THE CLOSED LOW ACROSS THE NRN
PLAINS/UPPER MS VALLEY AND AS MOISTURE WRAPS BACK ACROSS THE GREAT
LAKES. THIS SHOULD LEAD TO GENERAL AREAL AVERAGES OF .25-.50"+.

SIGNIFICANT DIFFERENCES PERSIST WITH THE CONVECTIVE PRECIP ALONG
AND AHEAD OF THE TRAILING FRONTAL BOUNDARY AND AMPLE CONVECTIVE
MESO BOUNDARIES PUSHING FROM THE SRN PLAINS INTO THE MS/OH/TN
VALLEYS AND SERN STATES. VERIFICATION CONTINUES TO SHOW VERY POOR
SHORT TERM MODEL QPF SKILL WITH THE GLOBAL AND MESO MODELS THAT IS
QUITE DISAPPOINTING. THIS SEEMS LIKELY TO CONTINUE DURING THE
UPCOMING DAY 1 PERIOD GIVEN THE LARGE SPREAD IN QPF DETAILS AND
COMPLEX OUTFLOW AND CONVECTIVE MERGER/INTERACTION AND COLD POOL
ISSUES AS EVIDENT ON LATEST RADAR/OBS. CONFIDENCE IS LOW WITH
DETAILS...BUT AGAIN HIGHER OVERALL THAT THERE WILL BE POTENTIAL
FOR WIDESPREAD HEAVY PRECIP IN THE OVERALL FAVORABLE HEAVY PRECIP
PATTERN. THIS IS ESPECIALLY EVIDENT FOR THE VICINITY OF MS/AL/GA
WHERE SATL/RADAR AND TIGHT DEEP MOISTURE AXIS FEED FROM THE GULF
OF MEXICO SEEM TO BE COMING TOGETHER FOR SUBSTANTIAL PCPN/RUNOFF
POTENTIAL.

FOR THE QPF DETAILS...WPC QPF LEANS MOSTLY ON CONTINUITY AND
ESPECIALLY THE HI RES ARW GIVEN OUR OVERALL HIGHER CONFIDENCE IN
THIS MODEL AND SEEMINGLY REASONABLE CONVECTIVE FOCUS TRANSITION
OVER TIME TONIGHT AND INTO SUN. THAT SAID...THE ARW HAS ITSELF
RECENTLY SHOWN SOME VERY LARGE ERRORS RECENTLY WITH THE ONGOING
ORGANIZED CONVECTION. WHILE ARW GUIDANCE IS NOT GREAT THIS
AFTERNOON AT ALL...CONVECTIVE EMPHASIS SEEMS TO
REGROUP/CONSOLIDATE REASONABLY WELL AFTER 00 UTC FOR THIS DAY 1
PERIOD...PROBABLY FOR THE WRONG REASONS.

GIVEN THE OVERALL FAVORABLE HEAVY RAIN PATTERN AHEAD OF THE CLOSED
LOW AND SWEEPING AND COMPLEX LEAD FRONTAL SYSTEM...THERE CONTINUES
TO BE A FAIRLY LARGE THREAT REGION FOR EXCESSIVE RAINFALL AMOUNTS
STRETCHING FROM TX INTO THE LOWER MS VALLEY...TN
VALLEY/SOUTHEAST...AND UP ACROSS THE MIDWEST/GREAT LAKES AND INTO
THE MID-ATLANTIC.

...N-CENTRAL GREAT BASIN/ROCKIES...

SHORTWAVE ENERGY NOW OVER THE PAC NW IS FORECAST TO DROP OVER THE
N-CENTRAL GREAT BASIN/ROCKIES INTO SUN. MODEL CONSENSUS IS FOR
SOME SCATTERED CONVECTION AHEAD OF THESE HEIGHT FALLS...BUT THERE
REMAINS QUITE A BIT OF LOCAL DETAIL UNCERTAINTY WITH ACTIVITY IN
THIS PATTERN. DAY 1 QPF AREAL AVERAGES SHOULD BE LIGHT...ALBEIT
WITH LOCALLY HIGHER EMBEDDED .25-.5" OR SO AMOUNTS...POSSIBLY MOST
LIKELY IN VICINITY OF ERN ID/WRN WY TERRAIN.

ORAVEC/SCHICHTEL

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


24HR QP VT 22/00Z
 0.01 536896 526852 524846 524839 520824 512801 498773 490758
      485751 479744 478741 475738 469736 460740 456741 451740
      441742 429745 419762 415769 410774 404779 398781 394784
      386785 377786 366779 362771 362766 365762 364757 362753
      357747 350742 340737 336738 332741 329744 328749 325753
      325757 324761 324767 325773 327777 329780 332781 337776
      339779 338783 337790 334797 329802 322806 318807 315806
      303808 295810 287806 279800 272793 267787 263787 259788
      256791 254795 255801 253806 252808 252813 255820 259824
      265827 278834 280836 280840 280851 280864 280871 279877
      279884 278890 278902 278924 277934 272943 266954 263960
      261964 260968 237987 235990 234996 236008 254016 260018
      263019 265023 267040 286064 297074 299076 305077 311077
      314075 326064 341052 329047 322045 319043 318039 312024
      311019 307015 306011 308007 317968 325950 340937 366927
      375923 382920 396913 410908 420907 424910 427915 430925
      431933 429940 426945 426950 424955 424959 426962 426969
      424973 421981 420987 419991 419996 420002 420007 421010
      425013 432009 437005 455006 459006 463005 472002 479997
      485988 489987 494983 504983 513983 517978 520968 522963
      523955 530918 534904 534899 536896
 0.01 529060 528055 524053 516058 512062 507065 500073 497072
      493073 487078 473086 470087 468085 466085 466082 465080
      462079 458073 458066 460060 464058 467055 470055 490058
      499059 503057 508058 514053 514050 510045 502038 492033
      483032 478032 474034 469033 467035 464035 459035 455032
      447027 436026 435026 434030 432037 430043 427046 423045
      412044 401046 394050 386049 383053 381058 379063 380067
      380071 381072 385072 388075 392078 395078 398076 401074
      404074 407073 409075 411079 409086 404086 401099 399104
      396108 389112 383116 380120 377123 380126 384125 388125
      396123 405119 409118 412118 415120 418128 414129 411134
      412142 412148 416153 421157 427161 432162 434157 439156
      442157 444159 452166 455174 452177 449183 450190 454194
      458192 463189 465186 466181 462173 459168 459164 462162
      467163 471166 476167 479167 481164 476160 465154 462151
      458145 470134 470130 473124 477122 479119 477116 474113
      473109 474105 477099 481097 483096 486096 490097 492095
      496090 508080 515074 522068 529060
 0.01 234826 233824 232822 230820 228819 228818 227819 226820
      225821 226823 227825 228827 230828 230829 232829 233828
      234826 234826
 0.25 511890 511883 509874 507868 504861 497848 494842 491833
      489820 485808 480795 473785 466778 462775 457773 450775
      444779 439783 433786 422788 410790 405792 399796 390803
      386805 380807 366806 362805 358806 351809 343812 337813
      323814 310815 304815 298817 292823 290828 289833 289841
      287848 286856 287866 288873 287881 286895 286903 288912
      289922 292935 291942 289947 287950 287954 286961 287967
      289974 288978 286980 280983 276980 272978 268982 263985
      253983 248984 245988 244990 241991 239996 247004 252007
      262007 270008 275011 280015 285012 287007 288000 290994
      293991 299984 303975 307961 310956 314951 317943 317935
      317930 320925 324916 332908 339902 343899 348897 358890
      363885 370882 376881 383883 427876 428874 431872 437871
      442875 446878 450883 454889 455898 456911 456920 455925
      455942 454958 455966 456971 460975 464977 470977 476975
      481972 487967 494954 497944 498938 499929 499920 500916
      503914 506910 508903 511890
 0.25 442106 441099 438094 434092 431094 430097 425101 422105
      422110 423112 426117 429115 433111 438109 442106
 0.25 352757 351751 347750 342752 336753 334756 332759 331766
      333767 334763 337761 339762 342764 345766 348767 350764
      351760 352757
 0.25 280821 279821 278819 277819 275818 274818 272820 272821
      272822 274824 276825 278824 279823 280821
 0.25 267802 268800 266798 264797 264798 263800 265802 266802
      267802 267802
 0.50 493876 491871 489867 482862 477859 474854 474845 475837
      476827 476820 476815 476809 474802 469794 464786 460784
      454785 445791 438794 432794 421796 418797 415796 411793
      408794 404797 401799 398808 395812 391812 384812 380815
      373816 368813 362810 357811 353813 343817 338819 332819
      322819 311819 306818 299819 296822 293828 293832 294837
      297840 294843 291847 290852 289856 289862 291872 289884
      289888 290895 291902 293909 295914 295921 297924 300925
      303922 307918 311911 315905 321897 329890 334888 342887
      348884 354879 370869 375862 381854 388845 391842 397838
      401838 404839 406843 405848 404854 401860 403864 407867
      415863 419862 423858 427854 431850 435847 439847 445851
      446855 449860 457864 465863 467863 469858 470858 472860
      471865 469865 467871 465880 465889 466898 467927 467937
      465949 465957 467960 472959 476956 479953 482946 483938
      482930 481916 479910 479901 481899 484900 488893 491890
      491884 493876
 0.50 266999 266992 264989 261987 256986 252986 250988 247992
      243994 243996 246997 249998 253001 256003 260002 264000
      266999
 1.00 463817 463809 462802 458802 455804 452807 449811 447814
      446821 445827 450828 453829 458829 461825 462819 463817
 1.00 408801 408800 406800 405801 406802 408802 408801
 1.00 360823 360819 357818 350821 338825 323824 318823 313826
      313831 319834 323837 323845 322847 318848 312845 305845
      298846 294850 292858 294872 294879 294889 296894 300897
      305897 305902 308904 311899 313896 312892 315887 320883
      325880 332878 345875 350871 353866 354859 357852 359846
      360844 359839 357835 358828 360823
 1.00 261992 260992 260990 259989 257989 256990 255991 254992
      254994 254996 255997 257997 258996 258995 259994 260993
      261992
 1.50 353833 353826 348826 343831 341835 337837 335837 334842
      334848 331852 324857 319857 314855 307850 304848 299848
      296851 295855 296869 295878 296884 299888 307885 321877
      339870 343869 346865 348855 350844 353835 353833
 1.50 334830 334828 333828 331828 329828 327828 326829 326831
      328832 329832 331833 333833 334830
 1.50 321829 321827 320827 319830 320830 321829
 2.00 345860 345858 345855 344854 342854 340855 339856 338857
      337858 335860 334861 333862 332863 332864 331865 332866
      333866 335867 337866 339865 341865 341864 342864 344862
      344861 345860
 2.00 325868 320868 315867 309863 310858 307856 301853 298855
      299859 299866 299870 297875 297880 298885 303885 311881
      318876 321873 323870 325868
 3.00 316875 316872 313871 310870 307869 304869 302869 300872
      299874 299878 300881 303882 307881 309880 312878 314876
      316875
 4.00 305873 306871 305871 303871 302872 303873 305873 305874
      305873

$$





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