QUANTITATIVE PRECIPITATION FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 421 AM EDT FRI AUG 12 2016 PRELIM DAY 1 QPF DISCUSSION VALID AUG 12/1200 UTC THRU AUG 13/1200 UTC REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR Day 1... Central Gulf Coast ~~~~~~~~~~~~~~~~~~ ...High Risk of Excessive Rainfall Continues Across Portions of the Central Gulf Coast... Abundant moisture remains in place across the Southeast, with the exceptionally anomalous 2.5-2.75+ inch PW values along the central Gulf Coast, including an observed 2.71" per the KLIX 00Z 08/12 RAOB. These values are between 3-4 standard deviations above the norm (approaching record values) per the SREF and GEFS. The best description of this system is that of a sheared inland tropical depression, as the upper high over the system has moseyed off to the TX/LA border, advecting north-northeast flow over the top of the system. The best analog is Tropical Depression Five (2010) during its second trip into the Gulf Coast. Given the deep high theta-e/moist profile for optimal warm rain processes (wet bulb zero heights a whopping 16KFT per the 00Z KLIX sounding), the threat for heavy tropical banding rains across this area will continue given the slow westward drift of the TUTT. WPC maintained a fairly large swath of areal-average QPF between 3-6" across eastern LA and southern MS. However, all of the higher-resolution CAMs indicate pockets of much higher amounts, 7-10+ inches between 12Z Fri-12Z Sat. Given the additional heavy rains over already saturated soils (low FFG values), WPC will maintain a fairly broad MODERATE and HIGH risk area in the day 1 Excessive Rainfall Outlook (ERO) over the central Gulf region -- similar to the day 2 ERO on Thursday. Central and Upper Mississippi Valley - Upper Great Lakes ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The anomalous rich moist profile with adequate deep-layer instability will pose a continued risk of excessive short-term rainfall rates during the new day 1 period (12Z Fri-12Z Sat). PW anomalies continue to be quite high on the western periphery of the broad SE ridge and ahead of the approaching trough currently across the northern High Plains -- as values of 2-2.3 inches is around 3 standard deviations above normal for mid August. As was noted yesterday, despite the rich moist profile and more than sufficient dynamical support ahead of the trough (broad-scale upper diffluence along with increasing right-entrance region upper jet forcing with time), the one limiting factor for widespread areal-average totals over 2 inches across portions of the central-upper MS Valley and into the upper Great Lakes will be the increasing forward propagation of convection with time later today. This as the upper trough and stronger westerly flow pushes across the area tonight, with the strengthening deep-layer shear and negative PW advection (tightening PW gradient along and west of the surface front) favoring a more progressive front and pre-frontal convection with time. Therefore, the main concern with this pattern during day 1 will be the potential for excessive short-term rainfall rates (to the tune of 2-4" per hour, as was observed on Thursday). WPC QPF featured a multi-model blend, weighted heavily toward some of the preferred high-res guidance (NSSL-WRF and WRF-ARW) in later periods as felt given the evolving pattern (height falls), the global guidance was too slow with the progression of the heavier rainfall overnight. However, again given the optimal PW environment, it should again be noted that the bulk of the high-res CAM guidance indicate isolated higher totals between 4-7+ inches. Central and Southern Rockies and High Plains ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Have maintained modest areal-average deterministic QPF over this region along the tail end of the cold front, on the back edge of the moisture gradient where the dynamical forcing is not expected to be as robust (weaker flow pattern aloft). Still, with the anomalous PW values in play (2-2.5 standard deviations above normal) along with generally modest instability (mixed layer capes 1000-2000 J/KG) and 850-700 mb frontogenesis and moisture flux, a marginal or more isolated threat for excessive rainfall will continue ahead of the cold front over these areas. Hurley/Roth Graphics available on the web at www.wpc.ncep.noaa.gov 24HR QP VT 13/12Z 0.01 459624 465632 470641 479663 480676 482682 483690 482696 483705 485722 487747 487773 487780 486786 488791 489797 491803 494807 503813 508818 514825 520834 522840 524847 527856 529861 530868 537896 541920 543932 544937 545944 546950 549955 550958 551966 547980 544990 540993 536995 532995 529992 520989 517986 513981 499967 494962 490958 486956 479953 469953 461956 456961 445976 443981 440985 433992 426997 421997 418995 416990 414985 416974 420965 426956 429953 430951 430948 419952 403959 398964 394971 390979 385988 383991 382999 380004 380010 385014 389016 392019 394024 400025 412026 416027 419031 429032 435032 440031 442032 445037 447041 445045 440050 427056 418060 414064 409065 394071 387075 381076 378076 369071 364070 362068 358067 345066 342067 335067 330067 324068 319068 316071 317074 321077 324079 330080 338080 341083 343088 342094 340096 335097 329097 327097 325099 323104 322115 316119 311120 308118 308123 311128 309130 304129 297123 293120 289118 280120 276118 274114 252093 241078 233062 229055 229044 229031 231019 232013 231008 231003 233997 240993 249998 281015 283017 288018 294013 300008 306001 315985 323966 325961 324955 321952 318950 315951 298958 289958 279958 272952 266945 261939 259931 258907 253859 254847 253840 249838 245836 241833 238830 237824 235816 237806 247792 251790 255789 258789 260793 265798 263801 266801 270802 287807 0.01 287807 300811 314813 322814 327807 334797 338791 341789 343785 345783 348782 354782 352788 352793 350798 350800 353801 361800 364801 366798 371793 379783 384778 387771 390764 393758 398744 399739 397736 392739 387735 381730 381723 380714 381695 380686 379680 380677 379672 380668 382665 385663 387661 390659 395654 404647 412640 0.01 560073 561061 560050 559045 557041 552037 541033 528031 521030 519032 515032 507032 503026 494018 488017 484017 483020 481022 480028 478037 474056 472064 469070 466075 460079 456078 454075 448070 442067 437068 422088 425102 421107 424112 430113 437113 444114 446116 448121 449128 452131 454132 458135 464132 469130 472129 476129 480130 483133 486134 487137 496149 499155 503161 513170 523178 526178 529176 531172 531166 530162 527154 524148 521143 515129 503101 499087 498084 499081 501078 505073 507071 511072 513074 517076 523081 529083 541085 548085 553083 560073 0.01 450090 450087 450085 449083 448082 447081 446081 444080 444079 443078 441078 439077 437078 437081 437083 439085 439086 440088 441089 442089 443090 445091 446092 447093 448092 448091 450090 0.01 377855 376849 374846 368842 366840 363841 355842 351843 349846 348850 349855 351864 354870 359876 362878 366877 372873 374864 376857 377855 0.25 550061 549057 546055 543056 541057 538058 537059 533061 532064 535066 536067 539068 542068 544067 546066 549063 550061 0.25 537963 537958 537953 536946 533931 532924 530917 526907 521895 515887 512883 509877 505867 502861 500861 498863 498872 498878 498885 498889 497891 493901 489904 486910 485916 485924 499939 506947 512953 526966 534966 537963 0.25 475695 474682 470671 468667 467661 463649 462643 461640 457637 455638 447645 443654 439670 437678 433683 421695 418715 415733 414739 411744 408751 397784 392789 387793 381798 377805 376810 377813 382812 385811 389809 392810 395814 396821 397833 396844 390862 387870 383879 373893 364903 359908 357910 353911 349910 346906 341898 338892 334889 331888 325884 323880 322875 319866 315856 313849 309841 307836 306831 305823 302820 298819 290817 274813 261808 257809 255812 257816 259819 265822 272824 281827 290828 293830 296833 300842 293858 288872 280887 277894 276904 276913 277921 280929 284936 291940 300942 309941 320939 335932 342928 348926 347934 344941 338956 334963 329971 313002 307019 294029 292032 293036 296044 311050 325055 335056 341053 346054 349056 359057 365052 369051 375052 378053 383054 386053 391051 390045 386044 376043 368041 363036 360030 359021 360011 364001 369985 377969 387955 398940 403935 410931 415928 421924 426918 430911 438899 442889 445880 451863 455841 459818 463799 471784 473775 474765 474720 475695 0.25 464930 462929 460927 459928 455930 454931 452932 450935 448937 450940 452940 454938 455937 459935 460934 464932 464930 0.25 306096 308089 307081 304073 298065 293058 290055 285052 278048 269043 261039 252035 248033 243034 241038 241045 238051 239056 242061 249066 261078 275091 282097 290100 296102 301100 306096 0.50 527928 525920 521916 518912 513909 507909 503909 502912 502919 507924 512925 517926 523928 527928 0.50 472698 471690 468685 461676 455665 454659 454657 451659 444678 442683 441690 439697 437700 434704 435710 434717 432722 430728 430737 428742 425746 420747 417752 421764 424766 429765 434764 440765 439770 436775 429784 418804 413813 411824 408835 405848 401858 397871 395877 392883 387891 360919 354927 349938 345951 341960 336969 330978 326985 321997 317007 313019 311025 313031 318035 322036 330036 333040 337043 335045 334051 342046 343024 349013 351008 352000 353993 355988 357984 360981 364978 366973 371963 377954 384946 391937 398931 413919 420913 427905 432897 436891 438886 445859 446846 450836 450830 450822 449813 447809 444804 444798 447790 450785 456776 456769 456759 455746 456733 458721 461715 465710 467709 470705 472698 0.50 459652 459649 459647 458644 457644 455645 455646 454648 454651 453653 454656 455656 457656 458655 458653 459652 0.50 337915 336910 334904 331895 323890 318881 313860 310855 306852 302852 300855 293874 288883 284891 280901 280912 283924 286931 291934 295936 307937 313936 319935 326931 333924 337916 337915 0.50 299082 300078 298073 294069 283061 277057 274058 274063 268060 263056 261053 257052 250050 247051 246056 248062 253066 260069 272077 280088 286091 293091 298087 299082 0.50 266815 265813 264812 262811 260811 259813 260815 262816 264816 266815 1.00 444740 442739 440740 440741 442741 444740 1.00 439839 440834 439828 436820 433812 433807 433795 435792 433791 432793 430799 429807 430816 430819 427822 422834 416848 410859 409870 407878 401888 391898 382906 378911 374917 376920 378920 385920 395913 400910 407908 413905 418900 427890 430885 433877 436861 436854 437847 439839 1.00 337993 336989 333987 328991 324999 322006 319014 317022 317027 320026 325021 331016 333010 335001 337993 1.00 329919 329914 328910 325902 316892 314883 312873 310866 307864 302865 300872 296878 292884 289890 286898 285906 285917 288924 294929 299931 304932 309932 316930 323926 328921 329919 1.00 289083 289079 289076 287074 285072 282070 278070 274071 272071 274073 276075 277077 279080 281082 283084 286085 289083 1.50 433840 432831 430829 427831 423838 421844 417858 416864 417869 416874 409884 403896 406902 412900 417896 420891 426876 428869 427862 429854 431847 433840 1.50 325919 325914 324911 322904 314894 312886 311877 308870 305870 302877 298882 292893 289899 288906 287916 290922 295926 300928 308929 314928 320925 324920 325919 2.00 425850 426848 426845 425844 424846 424848 423849 423851 424852 425850 425850 2.00 418886 418885 416885 415885 413886 412887 411888 410889 409890 408891 408892 407894 407896 408898 410898 411897 413896 413895 415893 416891 417891 418889 418888 418886 2.00 323917 320905 315897 311893 310888 308882 305878 302886 296894 291902 289907 289914 291920 294923 298926 303927 309927 314926 318923 322919 323917 3.00 318915 318907 315901 311898 307897 304897 300901 295906 293906 292910 293914 295919 301922 306922 312921 317917 318915 4.00 316913 316907 315904 313903 309902 306904 303907 300910 298914 300918 303920 308920 312919 315915 316913 5.00 314911 313909 313908 313907 311906 310906 308906 306907 304909 302912 302914 302916 303917 304918 306918 308918 310918 312916 312915 313913 314911 6.00 309913 310911 308910 306910 305911 305914 306914 308914 309913