QUANTITATIVE PRECIPITATION FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 557 AM EDT WED APR 27 2011 FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION VALID APR 27/1200 UTC THRU APR 30/1200 UTC REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR DAY 1... UPDATED..CHANGES MADE ARE ALMOST TOO NUMEROUS TO MENTION. THE MOST IMPORTANT BASED ON CURRENT OBSERVATIONAL DATA INCLUDED ADDING TO AMTS INVOF THE LWR MS VLY DUE TO CNVCTN REFIRING THERE AS WELL AS ADJUSTING TIMING OF OF PCPN ACROSS THE CNTRL LAKES AREA ASOCTD WITH IMPULSE NOW LIFTING NWD FM THE MIDWEST. FOR TNGT... ADJUSTED TWDS A FASTER AND FARTHER EAST QPF SOLUTION ASOCTD WITH THE SRN PLAINS SHRTWV TROF AS IT LIFTS RAPIDLY NWD TO A PSN OVR THE LWR OH VLY BY THIS EVNG. SORRY ABOUT ALL THE CHANGES IN THIS DYNAMIC PATTERN. ...ERN HALF OF THE NATION... MODEL QPFS ALL INDC THAT THE MAJOR RNFL EVENT OVR THE CNTRL U.S. WILL CONTINUE TDA AND WORK EWD WITH TIME AS AN AMPLIFYING SHRTWV OVR THE SRN PLAINS BY THIS MRNG LIFTS RAPIDLY NEWD TO FIRE SGFNT PCPN TOTALS. HEAVIEST ACTVTY WILL BE CONCENTRATED FM THE TN VLY NEWD THRU THE MID/LWR OH VLY TO THE LOWER LAKES WHERE AN AXIS OF DEEP-LAYERED MSTR WILL BE AVBL FOR SUPPORTING HVY CNVCTV RAINS. THE DAY1 QPF IS PREDICATED ON THE ASSUMPTION THAT THE ONGOING CNVCTN INVOF THE LWR MS VLY WILL WEAKEN GRADUALLY ALLOWING THE BEST ACTVTY TO SHIFT OR REFORM NEWD OVR THE SRN PORTION OF TN VLY. ALL MODEL QPFS ARE ARGUING FOR THAT SCENARIO. HOWEVER..THE MANUAL QPF WILL BE SLIGHTLY FARTHER SOUTH THAN THE NAM/GFS/ECMWF WITH THE MAX QPF THREAT AREA BASED ON THE POTENTIAL OF STRONG MESOSCALE FORCING. THE GEM REGIONAL MODEL SUPPORTS THIS IDEA AND BASED ON WHAT HAS HAPPENED TDA SO FAR..IT SEEMS A GOOD POSSIBILITY. NEEDLESS TO SAY..MSTR..LIFT..AND INSTABILITY WILL BE AVBL IN LARGE QUANTITIES TO SUPPORT THIS EVENT PER MODEL GUIDANCE..WITH AN EXTREMELY FVBL COUPLED JET STRUCTURE AVBL INTO WED NIGHT TO ENHANCE THE LIFTING PROCESSES. THE GFS AND 26/12Z ECMWF AXIS OF PCPN THRU THE UPPER OH VLY TO THE LOWER LAKES WAS IN PRETTY GOOD AGREEMENT. MEANWHILE...ANOTHER SWATH OF SGFNT PCPN WILL OCCUR FM THE SRN PLAINS NEWD THRU THE CNTRL LAKES AREA WHERE STG DYNAMIC COOLING ASOCTD WITH THE AFOREMENTIONED LIFTING OUT PLAINS SHRTWV TROF AND ITS ASOCTD SFC LO WILL FIRE SHWRS. THE GFS AND ECMWF MODEL QPFS ARE IN VERY GOOD AGREEMENT ON THIS AXIS OF PCPN AND TOTALS AND BASICALLY BLENDED THOSE SOLUTIONS FOR THE QPF DETAIL THERE. FINALLY..PCPN WILL CONTINUE ACROSS THE UPPER LKS/UPPER MS VLY REGION ALONG A DEFORMATION ZONE ASOCTD WITH THE CLOSED OFF UPPER LO CNTR IN PLACE THERE. ...PAC NW... THE GFS AND ECMWF MODEL QPFS ARE IN VRY GOOD AGREEMENT HANDLING THE PCPN ASOCTD WITH THE NEXT FRONTAL BAND/CLOSED UPPER LO APCHG VRISL BY WED EVNG. DAYS 2 AND 3... .....PACIFIC NORTHWEST/NRN/CNTRL ROCKIES...NRN PLAINS... A MID-UPPER TROUGH IS AGAIN EXPECTED TO SWEEP DOWNSTREAM INTO THE NRN INTER-MOUNTAIN WEST BY LATE THURS AND NORTHERN PLAINS FRI. THE GUIDANCE GENERALLY SHOWS COMPARABLE HANDLING OF THE HT FALLS THROUGH THE PD...ALTHOUGH THE NAM IS A HIGHER AMPLITUDE OUTLIER FRI NIGHT AS THE ENERGY TRAVERSES THE NRN/CNTRL ROCKIES EN ROUTE TO THE NRN HIGH PLAINS. EXPECTING THE HT FALLS AND AN ASSOCD FRONTAL ZONE TO ADVANCE ACRS THE PACIFIC NORTHWEST AND THEN THE INTERMOUNTAIN WEST. THIS COUPLED WITH AN INFLUX OF PAC MSTR...STEEPENING MID LVL LAPSE RATES AND FAVORABLE OROGRAPHICS SHOULD ALLOW FOR WIDESPREAD SHWRS. THE INITIAL MAXIMUM STARTS OVER THE OR CASCADES IN THE LEFT EXIT REGION OF THE UPPER JET AND THEN PROGRESSES INLAND WITH THE DIFLUENT AREA IN THE LEFT JET EXIT REGION ACROSS THE RANGES OF SOUTHERN ID/NORTHWEST WY BY 12Z FRI/NORTHERN CO DURING FRI. WARM ADVECTION PCPN SHOULD BEGIN TO SPREAD OUT INTO THE NRN PLAINS BY LATE FRI AS A NEW AREA OF SFC LOW PRESSURE BEGINS TO DEEPEN IN THE LEE OF THE ROCKIES AND A STG FRONTAL ZONE DEVELOPS. THE MODELS DEVELOP TIMING DIFFERENCES WITH THE 00Z GFS/12Z ECMWF BOOKENDS ON THE FASTER/SLOWER ENDS/RESPECTIVELY. THE 00Z ECMWF SPED UP ITS FORWARD TIMING AND CLUSTERS WELL WITH THE 00Z UKMET. A CONSENSUS SOLUTION CLOSEST TO THE 00Z ECMWF/00Z UKMET WAS USED TO HANDLE THE QPF/TIMING ISSUES. ...EASTERN U.S... A COLD FRONT IS FCST TO MOVE THROUGH THE ERN U.S. BY LATE THU NIGHT/EARLY FRI. STRONGEST UPR SUPPORT SHOULD LIFT WELL NEWD ACRS THE LWR GRT LAKES REGION AND INTO SERN CANADA BY THURS AND THIS SHOULD ALLOW THE CONVECTIVE THREAT TO THE MID-ATLANTIC AND NORTHEAST TO BE SOMEWHAT MORE MODEST. THERE SHOULD BE AT LEAST BKN COVERAGE OF SHWRS/TSTMS GIVEN STG FRONTAL CONVERGENCE AND AN OTHERWISE MOIST AND GENERALLY UNSTABLE AIRMASS EXPECTED TO BE IN PLACE. A STG LOW LVL JET REACHING UP TO 60 KTS ALONG WITH PWATS AOA 1.5 INCHES ALONG THE ERN SEABOARD SUPPORT CONVECTIVE ACTIVITY CAPABLE OF PRODUCING BRIEFLY HVY RAINFALL RATES. THE GFS AMOUNTS FOR PRE-FRONTAL CONVECTION WERE HIGHER THAN THE THE OTHER MODELS/ENSMEBLE MEANS. THE NAM FRONTAL TIMING LAGGED THE OTHER SOLUTIONS SO NO ADJUSTMENTS WERE MADE FOR THE NAM OUTPUT. ECMWF PW VALUES OF 1.5 INCHES ARE WELL ABV NORMAL...SO ITS QPF AMOUNTS MAY BE LIGHT. HPC QPF LEANED TWD A NON-NAM CONSENSUS WITH AMTS MORE CLOSELY ALIGNED TWD THE 21Z SREF MEAN/00Z GEFS MEAN SOLNS. KORTY/PETERSEN GRAPHICS AVAILABLE ON THE WEB AT WWW.HPC.NCEP.NOAA.GOV 24HR QP VT 28/12Z 0.01 499694 495681 489667 484656 479651 476649 472646 468645 463643 459638 458634 456635 453641 447653 439672 421692 415699 408707 402716 399722 398727 399735 400742 398744 390741 383737 375733 370732 366733 360737 357740 349749 338765 328781 323789 322794 325798 330798 332801 325808 320813 316818 310826 304833 297840 293848 288857 285865 282875 278884 278886 279889 285888 288888 292891 295892 296896 294903 292913 293920 295922 299923 304922 311918 316916 319913 322912 325915 327928 328937 330941 334943 338942 338946 338951 338962 339968 341974 345986 349996 354006 359016 363022 370029 376032 383036 403039 412044 414050 411055 397070 397078 399083 401083 404081 417063 423061 428062 436060 438057 441057 446057 456061 473065 485067 496066 502064 503061 499055 496052 488045 479038 461026 458020 457014 457005 460001 462001 472004 477005 482004 488001 492998 496990 497986 495982 491981 485981 474983 463983 456982 452981 441978 430977 422976 413971 406968 403967 401969 402976 404981 407985 415992 422997 428001 428006 426009 417010 414010 409008 402004 394996 390991 388988 385984 382975 381965 382953 383948 384943 386934 388925 389911 392905 395902 399898 402895 408893 414891 423888 433884 445882 447882 447885 448893 452897 454902 454907 452913 450918 440940 438943 433947 432952 433955 437959 439959 447961 454963 461962 474959 482952 488943 493937 498927 502916 503908 503903 503871 502835 502820 502807 503774 503722 501706 499694 0.01 538211 538207 537202 535195 532189 529181 527174 523166 517157 508148 498140 491130 481121 478118 477115 479112 482107 484102 484097 484090 482087 474088 470089 467098 464100 458101 454101 453097 452094 449093 442095 438096 432097 429100 423103 420107 421110 423111 428115 431120 434118 440120 443123 449125 448129 447140 438146 436150 435155 437161 444171 446173 445177 441181 438189 438193 439198 441204 441207 438210 432212 426214 423220 421226 417231 413235 411242 411246 414252 421256 429256 439259 447262 450262 452260 458259 465261 472265 477270 481276 488287 493291 496294 501296 508296 513290 521270 522265 522260 521255 520250 519245 519244 519239 518236 517234 516229 515228 514223 517220 519222 522225 525226 528227 531228 534227 0.01 480195 481191 479188 476185 471181 467183 463186 459190 457194 455197 455201 454206 456209 459205 465207 468204 472200 475198 480195 0.01 301804 296800 291798 284798 278800 270801 265802 260806 260809 262813 266816 273818 278817 286816 291811 299808 301804 0.25 486685 484679 481673 475668 472666 467669 459668 450706 447725 446730 444735 441738 435742 415756 401767 393774 387779 377785 370791 364798 355804 350807 345809 335811 331813 329817 326824 318840 321852 319859 317868 316877 316895 330905 332907 334912 335924 335926 337927 340926 345920 347919 348923 350935 348957 348963 350968 353975 356978 360980 366986 374948 373926 378907 382899 387894 395887 405883 425877 443872 462866 470867 476865 480860 483849 486840 488828 490818 491795 492767 492744 492720 489700 486685 0.25 516272 517265 516260 513249 511238 507228 500209 498206 496204 491204 482204 474207 467211 454218 448233 447236 447240 449244 452247 455250 463251 470254 478261 485268 491275 493278 498283 502284 507283 512274 516272 0.25 520191 520186 519181 516175 511170 505166 501165 497166 493168 486166 481164 478162 477157 474150 472144 469142 465144 462148 463152 467158 469160 473162 477165 481169 485175 489179 493186 496192 499195 503194 511195 516195 520191 0.25 491901 487894 484891 480895 476902 471908 468913 464923 462931 461935 461938 463941 465942 469941 474937 481932 485926 489916 490906 491901 0.25 490139 489138 486135 486134 483133 482134 481138 483139 486141 489143 490139 0.25 312854 311851 310848 311844 309843 306846 303851 300855 299859 297862 297866 301867 306865 310862 312858 312854 0.50 486705 484694 482688 480684 475685 472690 468700 466708 464717 461725 457731 449743 443750 437754 429757 420761 412766 405772 396781 381793 372803 367809 359812 352815 347815 340815 336815 333819 330826 331835 330842 329848 325860 322866 321875 320889 320891 324894 327894 330896 332901 336907 338912 338917 341919 342917 347909 350904 352904 353909 353915 354923 358925 362918 368913 372906 375901 379895 384890 396882 403877 408876 417874 426872 432871 439869 447866 453863 460858 469852 474846 478839 481831 483822 485814 486805 486794 486783 487764 488743 488733 487721 486705 0.50 500275 502272 503267 503263 502258 500254 496250 490240 485238 482234 481231 482227 486228 491235 498243 501245 503243 504239 503234 500223 498218 494213 485209 481208 476210 460219 460221 462225 465228 466226 468225 471226 471229 467231 465230 461232 458234 455235 454239 456242 459244 471248 479253 487260 500275 0.50 364965 365962 365958 365955 364951 362948 361948 359948 358949 356952 356953 355956 355960 355963 356967 358970 361971 363969 364967 364965 1.00 481719 477717 473724 471731 468739 464747 460756 462761 467761 471758 475751 478742 480734 482723 481719 1.00 476817 475811 473805 471805 469809 464816 458815 455813 454812 452814 449817 444810 440811 436814 431820 426824 422832 420839 418843 418848 420852 424852 424857 426862 428864 435862 444859 452856 457852 465845 467839 475822 476817 1.00 445775 443771 440769 431768 422770 413776 400789 389805 382811 376818 368824 358828 349831 344834 341838 333854 326869 326877 326884 328887 331889 334893 339902 341905 344904 345902 348895 352888 358881 362878 367877 370877 373881 376885 379886 384885 387882 401869 400857 400852 402846 403836 405832 408828 406822 408818 412809 418801 425795 431790 440787 443783 444780 445775 1.50 416787 413787 410788 409790 410794 412794 414792 414791 416787 1.50 404805 402803 399804 395810 385819 376828 369837 360847 357848 353848 348847 342849 338853 335858 332864 331869 330876 332884 335888 342900 343899 346893 348887 352883 360875 366872 374870 377870 380872 384876 390870 393864 392858 392854 393850 395845 395840 393836 393831 394827 396822 399816 402811 404805 2.00 388852 389846 388844 385842 382835 379835 377837 370842 366848 361852 353854 347852 341854 336859 335866 334874 335881 337887 341895 345894 346890 349884 354879 365868 373865 378861 382860 386856 388852 3.00 358863 354861 351861 346862 343862 340864 339869 338873 341878 342882 342886 343890 345886 347882 349878 352875 354871 356867 358863 24HR QP VT 29/12Z 0.01 525719 522708 519697 515687 512682 510681 505675 501672 490665 485656 480654 471652 462647 453644 448643 442644 431648 417655 412660 409665 404677 401682 396686 385695 380699 374705 296772 288780 276787 270791 268795 265800 258803 255808 256813 255819 252823 248831 247836 247841 253849 259851 261852 260855 259860 258864 259867 261876 266878 275881 285875 294868 302861 316845 320841 326836 331831 335828 353813 359808 365806 372805 378802 381804 384805 388804 397800 400798 404797 408798 411802 411808 407813 395806 389813 387817 388819 389822 382831 379834 378837 376843 374850 374856 373861 374866 378871 381876 383883 384888 387891 391896 414893 424897 428901 430910 433921 437927 442927 450924 454921 456915 461903 463898 467895 475890 479887 485882 489876 496863 498860 500854 500845 502829 503821 505815 507809 511803 514796 515789 514778 515770 519758 523742 525730 525724 525719 0.01 532195 534163 533154 531149 528144 524140 522134 520131 513124 508116 506112 504110 502111 497110 494108 485103 481099 483094 488085 490073 495066 502060 505057 506054 506050 508047 513045 521043 527040 529036 532031 531024 527015 525012 523011 518011 501013 493015 485020 469031 461035 457037 453037 445034 438030 430027 420029 418034 416039 418049 417053 414055 410057 406057 404055 398054 392058 385063 384068 382074 385077 388081 392083 397090 404094 404098 402101 395105 390112 389115 389118 391123 394127 393131 391136 388139 385143 386149 386153 389156 394161 393172 392211 397217 404221 403246 409253 417257 437261 441260 444261 448261 453260 471264 476267 481271 488278 497285 502287 505286 512280 515277 516271 517263 518254 518250 518244 518235 519225 521216 524212 527207 530201 532195 0.01 487192 486188 482185 480181 477176 472175 468177 465179 466183 462186 460190 459198 463202 468204 472202 474203 478203 482200 485196 487192 0.25 495693 493687 490682 481675 477672 472671 469673 466677 459687 451693 444701 439704 436705 431705 428702 424699 422697 421694 421689 418685 413683 410684 400690 391698 376710 342739 330751 316764 289792 267815 270820 273821 284818 287817 285821 283829 281838 284844 287848 290849 293849 298847 305841 312834 324820 335808 349797 359790 369784 381779 390777 398776 409773 423767 431764 435765 438767 440770 439773 437778 435789 432798 429806 430815 435828 438832 441836 450838 460840 467844 472850 475852 478851 481851 484849 488845 492836 495825 499813 504801 506795 505788 504780 502773 499765 496762 493760 493755 494743 497731 498715 497709 496701 495693 0.25 528169 528164 526155 521148 512140 506137 501140 492140 489139 487144 488152 487161 484169 488175 492176 500184 508192 514193 518191 524179 528169 0.25 478243 479238 477234 471228 473221 476218 479217 479215 470214 464214 449214 435217 428219 426221 424226 423231 420232 414235 412241 414244 416248 423250 428251 443251 458250 471249 477245 478243 0.25 465153 464149 462143 461138 461131 462123 464119 467116 468111 467105 464101 459094 456091 451092 444095 439095 436096 432099 432104 429108 429112 434119 439120 442124 446130 449134 451138 451141 448145 445147 439146 437150 436156 448171 450175 453176 453172 454166 457162 464157 465153 0.25 417161 419158 419154 418152 417153 416157 417161 417162 417161 0.25 409110 409106 409105 408106 408110 409110 409110 0.50 490707 488700 486695 480688 477686 472688 465696 460702 456709 453713 452717 451726 451730 449733 442734 439730 436728 429728 401739 392744 384748 381746 378743 383736 388731 392724 393717 390711 386709 382710 374717 367722 361728 348738 338748 314770 304781 300785 296791 294798 294804 297807 299812 296819 290830 289836 293840 298839 305834 310828 313822 316815 317812 315807 315801 318796 322794 325794 328795 332797 349786 362778 377770 385766 393762 399763 407763 415760 419758 422754 424749 427745 430742 437742 442748 446752 450753 457754 462756 469759 471761 474760 479753 483740 487728 490717 490707 0.50 526164 524159 521153 517151 512147 509145 506144 503145 502150 503155 508159 511162 516165 519169 522171 525168 526164 0.50 494793 493787 491781 488777 478769 472770 469775 460788 460798 462807 463814 468834 472839 476841 480840 484838 487834 491826 493818 494810 494802 494793 0.50 504173 501171 499172 501174 504176 504173 0.50 463242 465240 465236 464231 463227 464221 462219 458218 452218 447220 443219 436221 433225 429235 424240 424243 426245 435246 441246 449246 456245 463242 463242 0.50 456110 455109 454105 453103 451101 450100 447101 444101 441102 438104 438105 437108 438110 440112 441113 443115 445117 446118 449118 450117 452116 454114 455110 456110 1.00 361737 356739 351742 346746 344748 339752 336755 335760 339759 344755 346753 350749 353746 357741 361737 24HR QP VT 30/12Z 0.01 516737 514726 512720 509717 505714 500712 496711 493711 490713 484718 480724 470688 466687 460691 459697 454702 443710 440712 438716 436723 433726 427726 422738 416741 412747 411750 409752 406753 404756 400768 398781 395786 390789 385792 382796 370819 371824 376824 383823 387824 390822 392819 396813 402802 405800 410800 419806 458815 462818 467823 471827 476830 481829 486826 493817 496809 497800 499793 503787 506781 511777 514764 516755 516748 516737 0.01 554970 554955 554948 553940 550925 546916 543912 536909 528911 521910 514908 509906 500900 489894 479889 467885 455879 449877 445879 444890 444892 439896 435897 433899 431905 428912 424918 420921 413924 409927 406931 403939 402947 402971 402977 401988 400995 398004 390033 386046 381057 379064 378072 376077 377083 382087 386091 392094 395098 392105 390109 387111 383114 381116 381120 382129 384134 387134 390135 387142 386148 386152 388154 393161 394169 394174 397176 401178 407174 410175 411179 414184 418187 424198 427199 430198 431195 433189 432185 430178 432172 432167 432163 427155 427148 431132 435129 438132 436143 435150 435156 438164 442169 442174 440181 439185 441189 443194 441207 436213 432214 430211 427205 422199 413199 412205 413208 416209 420209 423213 421225 418245 419249 421253 430256 434256 437255 444252 457249 463247 469242 473237 473233 475227 480223 491230 495236 500237 504230 505224 505220 502210 501203 504197 512195 514195 516189 517186 517182 517176 519168 521163 521158 520150 520144 518139 516133 513128 512122 513119 523107 522102 520092 518085 515082 508077 505073 509068 514063 519055 531029 544998 547989 550981 554970 0.01 488193 487188 483191 482191 476186 471181 466182 465185 461193 460199 459202 456204 453209 456210 464208 471207 477205 483204 487196 488193 0.01 306785 305777 302772 298771 295772 284776 278781 271777 267778 264780 259788 256794 251803 249809 248820 249828 251834 251841 256848 261849 264848 268842 272834 275827 283821 286817 288813 288809 290805 296799 300795 303791 306785 0.01 316967 312965 307966 301966 296969 294973 293977 294983 295986 298990 304988 306986 309982 311978 313974 315970 316967 0.25 527000 529992 528983 527975 525971 519965 512961 504959 495959 491956 490945 489936 486929 484926 478921 472919 467920 462922 454926 441935 435941 429949 426954 422962 417979 416984 417990 421997 424998 429998 439996 445999 454999 459000 462002 464005 465013 462021 461025 461030 461034 464039 470045 477047 485047 493045 502041 508037 514030 518023 522015 527000 0.25 498149 500141 499136 498132 495127 492124 490121 487117 481111 477107 472104 467103 461106 459107 457105 454101 452097 447093 446088 453080 454077 453071 450061 447058 444056 441057 435059 430056 424052 418056 412056 405057 399058 392063 389064 390069 390076 392078 395077 410084 412085 415084 418086 419088 423100 423104 428104 435108 444113 452119 457120 461118 465123 466127 463131 460132 457135 454139 452144 450151 451159 467163 471166 476165 481165 484160 484154 485151 492153 496151 498149 0.25 446752 444749 442747 439749 437753 437754 436758 439760 442759 445756 446752 446752 0.25 439226 439224 436225 435225 435227 438226 439226 0.25 442084 442080 441080 440080 438082 436083 434080 433079 430076 429076 428080 430084 432088 433089 435089 438089 441088 442084 0.25 420111 418109 415106 410103 409102 406106 403111 400110 397113 400118 404121 408123 413122 417119 420115 420111 0.25 277804 277798 273796 270798 267800 264803 261808 260811 259815 258819 260824 263825 268821 270819 273816 275811 277808 277804 0.50 517006 518996 514988 512984 508980 499978 490978 487981 486984 487988 486002 484011 484015 484020 487026 491028 496029 505024 511016 517006 0.50 491139 489136 486134 486135 486139 489141 491139 0.50 466962 466952 466949 464947 454944 447945 443947 439951 435955 433960 427966 425970 425978 427981 432982 440979 449977 458976 463966 466962 0.50 413072 413068 413064 412064 410064 408064 407066 404068 407070 410071 411072 412073 413072 $$