QUANTITATIVE PRECIPITATION FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 539 AM EDT SUN MAY 01 2011 FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION VALID MAY 01/1200 UTC THRU MAY 04/1200 UTC REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR ...DAY 1... 06Z UPDATE... WITH THE 00Z ECMWF SHOWING REASONABLY GOOD RUN TO RUN CONTINUITY AND THE 06Z NAM ADJUSTING ITS QPF MAX MUCH CLOSER TO CONSENSUS..HAVE MADE ONLY MINOR ADJUSTMENTS TO PRELIM GUIDANCE BASED MAINLY ON SHORT TERM RADAR/SATL TRENDS. ...SRN PLAINS NEWD INTO THE OH VALLEY/ERN GT LAKES... ANOTHER DANGEROUS HEAVY RAIN SCENARIO SETTING UP ACRS PORTIONS OF THE LOWER MS VALLEY/SRN PLAINS THIS PD. COLD FRONT PRESSING EWD ACRS THE MIDWEST AND INTO THE OH VALLEY WILL STALL ACRS THE SRN PLAINS THIS PD AS FLAT RIDGE HOLDS ACRS THE SE U.S. A SFC LOW IS EXPECTED TO DVLP ALONG THE FRONT IN E TX LATE SUN AND BEGIN TO LIFT NEWD ACRS THE ARKLATX REGION IN RESPONSE TO SRN STREAM UPR TROF MOVG EWD OUT OF THE 4 CORNERS REGION. EARLY SUN..SHOULD SEE STG CONVECTIVE RAIN BAND PUSH EWD FROM AR INTO PARTS OF THE OH VALLEY WITH DIMINISHING INTENSITY AS LOW LEVEL JET QUICKLY BACKS ACRS THE SRN PLAINS LATER THIS MRNG. THE STRENGTHENING OF THE LOW LEVEL JET ACRS NE TX IN COMBINATION WITH INCREASING INSTABILITY TO THE SOUTH OF THE FRONT AND INCREASING HEIGHT FALLS WITH APCHG UPR TROF SHOULD ONCE AGAIN RESULT IN A RAPIDLY EXPANDING AREA OF CONVECTIVE RAINS ALONG AND NORTH OF THE FRONT LATE SUN FROM NE TX/SE OK ENEWD INTO PARTS OF THE LOWER/MID MS VALLEY. WITH THE MID AND UPR FLOW MORE OR LESS BECOMING PARALLEL WITH THE SFC FRONT...THE THREAT OF TRAINING WILL BE QUITE HIGH ESPECIALLY FROM NE TX ACRS MOST OF SW/CNTL/NE AR AND INTO THE EXTREME LOWER OH VALLEY SUN HIGHT. COMBINATION OF STGR MSTR FLUX..AT LEAT 3 STDS ABOVE NORMAL..AND SLOW MOVEMENT OF THE FRONT..WILL LIKELY SUPPORT WIDESPREAD 2 TO 6 INCH RAINS FROM NE TX INTO SE MO WITH HEAVIEST AMOUNTS EXPECTED ACRS SW TO NE AR. THE GFS/UKMET/AND 12Z ECMWF ALL SHOW REMARKABLY AGREEMENT WITH THE LARGE SCALE SYNOPTIC PATRNS AND ONLY MINOR DETAIL DIFFERENCES WITH QPF AND WILL TEND TO LEAN TOWARD A BLEND OF THESE VERY CLOSE SOLNS. THE NAM ON THE OTHER HAND HAS BEEN DOING QUITE POORLY WITH QPF THE PAST 24 HRS AND FEEL ONCE AGAIN THAT IT IS UNDER DOING AMOUNTS ESPECIALLY FARTHER SW OVER THE SRN PLAINS. ...SRN ROCKIES... UPR TROF MOVING SLOWLY EWD FROM THE 4 CORNERS REGION WILL SUPPORT SOME MTN SNOWS ACRS PORTIONS OF SRN CO/NRN NM WITH LIGHTER AMOUNTS FARTHER N. ELY UPSLOPE CONDS SHOULD SUPPORT LOCAL MAXIMA ALONG AND EAST OF THE SANGRE DE CHRISTO MTNS. LEANED A LITTLE MORE TOWARD NAM QPF HERE FOR TOPO DETAILS..OTHERWISE..MODELS SHOW REASONABLY CLOSE AGREEMENT. DAYS 2 AND 3... ...SOUTHERN PLAINS/LOWER MS VLY NEWD TO THE NORTHEAST... ANTICIPATE ONE MORE DAY OF MDT/HVY...AND IN SOME LOCALES...EXCESSIVE RAINFALL AMTS ACROSS AR INTO THE LWR OH VLY. FRONTAL BNDRY WILL REMAIN STALLED ACROSS THE REGION INTO LATE MON...PROVIDING THE FOCUS FOR DEEP MOISTURE WHILE RIGHT ENTRANCE REGION JET DYNAMICS AND WEAK MID LVL ENERGY LIFTING OUT OF THE BASE OF THE UPSTREAM TROF BOLSTER LIFT ALONG THE BNDRY. MODELS SHOW THIS TROF IN THE SOUTHWEST...MOVING EWD INTO THE SRN PLAINS MON NIGHT INTO TUE MORNING ALLOWING THE FRONT TO PROGRESS EWD AS WELL AND DRIER AIR TO FINALLY MOVE INTO THE REGION. THIS ALONG WITH DRIER PWS FROM THE ONSET OF THE PERIOD SHOULD HELP LIMIT AMTS TO THOSE LESS THAN THOSE EXPECTED ON DAY 1. HOWEVER THE AFOREMENTIONED FAVORABLE MID/UPR LVL FORCING ALONG WITH DEEP SWLY FLOW...CONDUCIVE TO TRAINING ACTIVITY AHEAD OF THE BNDRY...COULD RESULT IN ADDITIONAL HVY AMTS ACROSS THE REGION...WHICH COULD PROVE EXCESSIVE GIVEN THE ALREADY SATURATED ANTECEDENT CONDITIONS AND THE FORECAST FOR HVY AMTS ACROSS THIS SAME REGION TODAY INTO TOMORROW. AS THE TROF MOVES EWD...MODELS SHOW SOME PHASING WITH THE NRN STREAM AND THE DEVELOPMENT OF A CLOSED LOW IN THE VCNTY OF THE OH VLY LATE TUE...MOVING EWD TWD THE LWR GREAT LAKES REGION/NRN MID ATL STATES. THIS SHOULD SHIFT THE FOCUS FOR HEAVIER AMTS FURTHER TO THE NE THRU THE OH VLY INTO PARTS OF THE NORTHEAST/NRN MID ATL STATES BY EARLY WED WHERE THE MODELS SHOW STRONG UPR DIVERGENCE AFFORDED BY AN UPR JET COUPLET. WHERE THE LOW WILL CLOSE OFF AND HOW FAR TO THE N AND E IT WILL TRACK IS NOT AGREED UPON VERY WELL BY THE MODELS AND THEREFORE DETAILS IN THE QPF BY DAY 3 ARE FAR FROM CERTAIN. ADDRESSED THIS UNCERTAINTY BY TAKING AN ENSEMBLE APPROACH WITH SOME HEAVIER WEIGHTING GIVEN TO THE UKMET WHICH OFFERED A REASONABLE COMPROMISE BETWEEN THE NAM/GFS/ECMWF. EXCESSIVE RAINFALL BECOMES A CONCERN ACROSS PARTS OF CNTRL/WRN PA/NY ON DAY 3 WHERE FFG VALUES ARE FAIRLY LOW. ...PACIFIC NORTHWEST TO THE NORTHERN ROCKIES... A PROGRESSIVE PAC SHORT WAVE TROUGH WILL ROLL THROUGH THE NW ON MON AND THIS FEATURE WILL CONTINUE DOWNSTREAM INTO THE NRN ROCKIES/PLAINS ON TUES. SOME OROGRAPHICALLY FOCUSED LGT QPF IS EXPECTED MON INTO EARLY TUE...TAPERING OFF ON DAY 3 AS A RIDGE QUICKLY BUILDS ALONG THE NORTHWEST COAST...SHUTTING OFF ANY FURTHER PAC INFLOW INTO THE REGION. SULLIVAN/PEREIRA GRAPHICS AVAILABLE ON THE WEB AT WWW.HPC.NCEP.NOAA.GOV 24HR QP VT 02/12Z 0.01 528802 521792 515786 512781 509778 502776 494773 496770 501762 504753 507750 506745 500738 493730 486735 460753 449760 442763 437764 432766 423767 416768 410766 407765 403765 398766 383772 378777 374781 374783 373800 371809 369814 366823 363833 361841 358849 356856 352865 347877 340890 336898 332903 327914 323921 321926 317937 314943 305955 301961 297964 286974 283977 282981 282984 284987 285988 296994 292005 291009 296014 303020 309023 316027 321027 325026 333025 339024 343030 343037 341045 334048 329052 326055 327058 339064 345075 352082 357082 365083 372088 375094 377099 381100 387097 392094 404084 415071 419065 421059 419053 416048 413046 409045 404046 398049 393048 389046 383041 380033 377024 376013 376996 377985 379976 385959 387952 387946 390938 393930 396922 397916 398912 399906 401901 405895 419867 427852 433850 442850 448850 454852 467855 474858 481865 488870 491874 490879 483895 476911 472922 470930 468939 468952 469966 470970 472973 474975 482985 485988 491990 498991 504992 510991 518987 526981 528972 531965 533955 537943 537932 535902 534892 533879 531871 531862 530851 529842 527837 524829 522821 523815 526809 528802 0.01 524256 520246 514238 509231 501224 492226 486230 478234 470234 462236 454239 448242 443248 438258 437267 441273 444275 453281 472289 482294 492297 498297 500297 508293 513290 0.01 515091 514083 514080 510072 507072 503068 497066 494063 490061 484056 479052 473049 466045 461041 450033 442030 434031 433034 433040 437048 439052 439056 436064 435066 434073 437075 438080 436084 431086 427093 429100 426104 424104 422106 420109 418111 414112 408114 408119 411120 420123 426123 431123 437120 445115 449110 450107 453105 461105 466105 470106 476109 479107 482103 485097 488094 492093 500095 506097 510097 513096 515091 0.01 448084 447084 444081 444080 441078 439080 440084 441085 444086 447088 448084 0.01 275798 268795 262793 259793 256794 249797 244801 241805 241810 242817 243820 246823 250823 254826 257832 260834 267833 273829 271822 269818 265813 263809 268805 272803 275798 0.25 515276 516272 517268 514262 511260 506256 500256 499256 495254 491254 487257 485259 484263 485270 488274 493278 498282 504284 509283 512280 515276 0.25 495815 493807 487805 482805 478807 472810 464812 457817 456821 455827 458831 462832 468833 474832 483830 491826 495822 495816 495815 0.25 449800 449796 447794 444792 439787 430780 419781 405781 397787 393788 389791 387796 385803 383810 382817 381824 379829 367855 362860 358864 353875 342900 337911 331921 325933 320944 314954 308965 304970 301976 299981 300984 304984 309987 310992 311001 313005 316006 321005 325003 330998 340993 346989 349985 353974 357966 359959 365949 379928 386915 389909 389902 394888 399876 406863 413852 428830 435820 441813 446805 449800 0.25 379072 379066 378064 372059 369057 375053 375049 373047 367043 365041 360042 355047 355053 361057 361062 359067 361071 367073 375075 379072 0.50 430809 429803 428799 425795 424795 418795 413793 408795 402798 396805 393812 391818 387829 382840 378848 372861 365868 361873 357875 353881 351885 345896 341906 332924 326936 323945 318954 312964 307973 308979 312980 314984 314987 314995 316000 320999 328991 337986 343978 350969 360949 371931 381908 389887 394875 399864 404855 410844 422826 427816 430809 0.50 367050 366050 364050 363051 364051 366051 367050 1.00 401839 397838 394842 391849 384861 362885 351895 347898 345901 343907 330934 325949 318963 317966 317972 320978 322983 325985 328982 334977 338973 347961 354947 360934 376908 379898 381892 387876 389872 389868 392859 398846 401839 1.50 376890 374886 368886 363889 361892 346905 338922 334930 331937 325955 322966 324972 327974 331974 333972 336969 342962 351947 359928 366911 371902 375894 376890 2.00 369896 361896 357900 350905 346909 339921 334934 329948 327955 326963 328968 331969 333967 338962 342955 349944 354932 357924 359916 366904 369896 3.00 354918 354914 353912 350912 347913 345917 340925 336933 333944 331947 331954 330958 332962 337955 341949 346940 350931 354921 354918 4.00 351918 348918 346920 343924 340928 338932 337936 335942 334947 336948 338946 341944 343940 345935 347931 350926 351922 351918 5.00 345931 344928 342931 341931 339935 339939 340940 341938 342936 343934 345931 345931 24HR QP VT 03/12Z 0.01 505673 500667 496658 491640 489635 483635 481642 479645 478649 475661 471677 457699 450706 444710 431718 423723 418730 411740 405753 400763 394774 389785 379808 376815 372820 369825 364828 354836 350841 347846 343857 341862 337865 333868 326871 320874 314876 296892 287913 279930 265947 255953 246959 237975 237981 238984 239985 243987 245992 243998 243005 242016 243020 245022 249021 251017 253011 255006 257002 262999 265998 268998 272007 275010 281011 286013 293014 303015 312016 318014 323012 330010 334008 338004 343996 356975 361964 367954 377930 386908 395887 403875 409865 421841 426829 429825 434820 440816 445811 455804 470794 476790 479786 488772 492766 495758 499745 502738 505732 509717 511710 509705 505695 507688 505673 0.01 521270 522262 521255 520248 513232 510224 510219 512217 517219 522223 531228 534225 537214 538199 538192 538190 533180 526169 516158 506146 497136 492131 489126 478116 485104 488094 488086 488081 486081 481081 475085 471090 466095 462097 457097 452097 445101 441104 437108 433116 433121 435124 437127 438131 437136 435138 426146 420149 418151 417153 418161 417171 418177 423177 431177 437182 438185 439190 440197 442205 446206 450206 455204 458202 461202 459207 458209 452212 448213 442215 437219 432228 429234 425240 423246 425254 429260 434262 438263 452264 461264 466264 474265 481270 489280 501293 506294 508294 513290 0.01 479195 478193 476191 473190 470191 468192 467193 465195 463198 462199 462202 466200 469199 472198 475198 478196 479195 0.01 408053 405049 400047 397044 395040 394035 396030 395027 397023 396016 393011 390009 384007 379009 375011 371015 368018 365020 358026 351030 349034 350038 352041 352044 347048 345052 345055 347057 350058 358056 364055 369057 376062 375065 369068 369072 372075 376077 379075 381071 387069 392063 395061 401060 406057 408053 0.01 275805 274800 272799 265796 260796 252799 248804 245811 244817 247820 250819 255815 259811 266809 272807 275805 0.25 498721 497716 495714 490713 487711 487707 486703 484702 480704 471712 466717 462723 461728 458732 452740 448747 448751 444754 440750 434746 430746 427748 422752 414762 406777 400787 395798 386815 380825 374833 361847 355855 351862 345871 339878 334886 330896 309922 300939 294948 288954 261975 261980 263983 266985 271985 280985 290982 298978 303976 308976 311979 312984 312991 314994 317995 322994 330989 337984 344976 348967 352960 362944 379907 388887 396872 401861 405852 414832 417823 419819 420813 423808 427803 431795 435782 437778 441778 445780 449783 453784 459783 465780 470777 477769 484759 489747 495732 498721 0.25 516277 518270 518263 517253 509236 502219 498213 492207 488206 480206 477207 473211 470214 466217 466220 475221 479223 482227 482233 479235 478239 480245 485255 488260 492269 496277 501282 508283 513280 516277 0.25 524188 521181 516176 511174 507170 502164 499159 495157 493158 490166 489173 489176 491185 493189 496191 504192 511193 520195 523192 524188 0.25 473163 474158 473155 470152 465149 459149 453150 450152 447154 446158 447162 449164 452164 453168 453176 456181 459177 463172 466167 469166 473163 0.25 493689 493688 491690 493689 493689 0.50 490727 486724 477728 470735 464741 458748 455756 454765 455770 458772 462773 470768 478761 482754 486746 489737 490728 490727 0.50 516267 515259 513252 507240 501228 499223 497219 494215 490213 486211 481213 481217 483220 486224 492230 495235 496240 496243 494249 492254 493258 495264 499271 502276 507276 512274 516267 0.50 422784 422780 420778 417779 415782 413784 413785 411789 411790 409795 409799 411801 412802 415803 417800 418798 419797 421793 422788 422786 422784 0.50 409823 406820 403816 399815 393818 386825 380832 368847 358863 353869 348878 343886 341894 320923 316931 311939 310945 310949 311952 314957 319963 322973 325978 329980 334978 336975 342969 348961 358945 366928 373912 381892 389874 398856 403838 405831 405824 408825 409823 0.50 289974 289971 289968 287966 285967 282967 279968 277970 274971 272973 269974 268974 267976 266977 267980 268980 270980 273980 275980 278979 280978 283978 286976 288975 289974 1.00 476751 475751 474753 475752 476751 1.00 390855 390850 389845 387841 384839 381841 377844 375848 368858 362869 351887 341907 335919 330930 329936 329942 331957 333962 338964 345957 353947 358938 363926 368915 376892 380880 385868 388861 390855 1.50 381858 379854 374857 370864 365872 360880 354889 350896 343914 339922 337932 335942 336950 339954 345952 350946 355938 359929 364911 372891 378874 381863 381858 2.00 367889 367884 365882 362884 355894 351904 351913 348919 343927 340934 339939 341946 344945 348939 351934 355922 356916 359911 363901 366894 367889 24HR QP VT 04/12Z 0.01 493663 489660 488654 486649 484645 481644 478642 475639 472636 468635 465637 460645 455651 445661 435676 431685 428692 406734 402739 396744 389748 381751 355770 345773 341776 339783 336792 332801 316819 313821 310821 305821 291822 271822 266822 264819 262814 262810 261803 260799 257797 253799 250802 249808 251816 254822 257826 259827 259829 257833 258838 262843 264848 268853 269855 267858 264867 261876 259882 264888 267887 272889 278891 278895 273904 269914 263929 260935 255939 246946 239952 237958 238964 246969 255974 258976 263975 272972 293959 303953 308951 314947 325943 330941 337938 345934 350932 353929 363921 371913 382904 388898 391893 399883 402877 406873 418856 429834 435819 439813 444806 449801 452796 459784 464773 468761 478731 484718 488710 488703 489682 489671 493663 0.01 540202 538196 535190 530182 524168 522161 520157 517153 509147 508142 513142 520140 524138 530140 533140 539138 543134 545131 548123 549111 547100 544092 543087 541082 537070 532058 529051 526042 525034 522028 515019 513016 507012 503022 498024 490024 487026 486029 488035 489042 489050 486055 482061 477066 474072 470075 468081 467085 468090 478096 484099 485102 485108 457140 454147 454152 455156 459165 462170 467173 475176 477177 480180 486191 489193 490195 492193 501196 508201 513205 519214 524216 528217 534216 537211 540202 0.01 520274 521266 520259 519254 516248 507230 504224 503215 500210 487199 474207 467209 458211 452217 451221 451226 451239 454243 459245 468248 476252 482258 486263 491266 495273 499278 504280 511284 516284 0.01 491234 488233 485232 482231 485232 488233 491234 491234 0.01 470232 468231 470232 470232 0.01 475012 473007 469003 461998 451992 447992 446995 445000 446007 448011 447015 445017 441017 433015 430016 429021 432028 432037 429042 426046 422049 411051 406054 403060 398073 396076 396080 399083 403083 407080 408080 412080 419077 424075 432076 436080 436084 426087 424095 421100 416104 412102 409101 408103 409110 414118 416126 415135 409150 407157 406166 409169 413167 420158 424152 427146 431129 436122 437120 441121 449120 458114 461106 463099 465094 463092 459091 458089 459080 468068 468063 466057 463053 457055 455052 456047 457042 461034 465030 472021 475012 0.25 479666 453682 448687 442696 437705 430714 422727 415739 410746 404753 399759 392767 380778 369786 362791 356798 353804 351813 349819 345826 339836 331850 327856 321861 310885 305890 304896 305900 309901 311904 312908 311914 311922 314925 320926 333921 349912 361904 371896 384884 395872 404861 411850 420835 428819 434805 440792 448774 455759 466729 469720 472711 475689 478676 479666 0.25 532102 532095 529089 526086 520082 514083 508084 503086 500090 499095 500100 502106 505110 511111 516110 520108 525106 528105 532102 0.25 444109 444108 443105 441103 439104 438106 437108 438109 441110 444109 444109 0.50 468690 464688 461691 455701 441713 431726 425736 419745 401768 392778 385787 377797 366805 361809 359814 356823 350829 347834 342846 338856 337862 337866 341871 346874 345879 342884 335892 332896 331899 331903 335905 339904 345900 358892 368886 376880 386871 396860 403852 408844 416831 422819 428808 432798 438784 443771 454747 458734 460725 463717 466705 468690 1.00 449737 444735 438737 426750 417760 408771 402782 395797 395805 397813 395820 390826 384835 370836 366838 364842 366847 366849 370850 381850 387849 394845 398840 401835 403828 407821 412817 417812 421805 424800 429787 432779 436772 442760 448746 449737 1.50 435755 431753 426757 421762 419765 414770 412774 410778 411785 415787 420789 423783 425778 428773 430769 431765 434760 435755 $$