QUANTITATIVE PRECIPITATION FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 609 PM EDT TUE APR 27 2010 FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION VALID APR 28/0000 UTC THRU MAY 01/0000 UTC REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR UPDATE... NO SIGNIFICANT CHANGES MADE TO THE PRELIM DAY 1 QPF FOR THE FINAL ISSUANCE. MINOR CHANGES TO PCPN OVR NRN NEW ENGLAND FROM LATEST 18Z NAM AND LATEST HIRES HWRF RUNS. MINOR CHANGES FOR RADAR TRENDS OVR THE SOUTHEAST. ORAVEC ...DAY 1... ...NERN U.S.... MID LEVEL VORTEX IS FCST TO DROP SEWD ACRS NY STATE OVERNIGHT INDUCING A COLD AIR LOW NEAR THE NEW ENGLAND COAST THAT WILL LIFT NEWD ALONG THE COAST ON WED. MODELS ARE IN VERY GOOD AGREEMENT WITH THIS SCENARIO AND ALL SUGGEST A DECENT DEFORMATION AXIS WILL DVLP ALONG AND NORTH OF THE MID LEVEL LOW TRACK AS IT TRACKS EWD. THE MAIN QPF DIFFERENCE IS THAT THE ECMWF SHOWS ITS MAIN PCPN AXIS TO THE SOUTH OF THE NAM..GFS..AND CMC AND PREFER THE MORE NRN AXIS GIVEN THE EXPECTED TRACK OF THE MID LEVEL CENTER. COMBINATION OF SLOW MOVING DEFORMATION BAND AND INCREASING LOW LEVEL ELY/NELY SFC/85H FLOW SHOULD SUPPORT THE GENL CONSENSUS OF THE MODELS .50 TO 1 INCH LIQUID EQUIVS FROM NE NY EWD INTO WRN ME WHERE SIGNIFICANT SNOWS WILL BE PSBL..ESPECIALLY OVER THE FAVORED HIER TERRAIN. SEE QPFHSD DISCUSSION FOR SNOW DETAILS. ...NC/SC... REMAINS OF MID/UPR LEVEL S/WV WILL QUICKLY EXIT ACRS THE SE THIS EVENING WITH ASSOCD DEFORMATION RAIN BAND DIMINISHING RAPIDLY ACRS THE CAROLINAS. ADDITIONAL RAINS OF .10 INCH OR SO WILL BE PSBL IN LINE WITH MODEL MEANS. ...WRN U.S... DEEP NEG TILTED UPR TROF AXIS WILL CONTINUE TO PUSH INLAND ACRS THE WEST THIS PD WITH INITIAL FRONTAL BAND MSTR OUT RUNNING THE BETTER UPR SUPPORT AS IT GETS SQUASHED SEWD ACRS THE CA EARLY IN THE PD. MAIN HEIGHT FALLS ..JET DYNAMICS..AND POST FRONTAL ONSHORE FLOW WILL FOCUS HEAVIER PCPN AMOUNTS ACRS THE CNTL PAC COAST MTNS AS WELL AS THE NRN SIERRAS OVERNIGHT INTO WED..WHILE DIFFLUENT LEFT EXIT REGION OF JET AND FRONTAL CONVERGENCE WILL SUPPORT MODEST PCPN AMOUNTS OVER THE FAVORED OROGRAPHIC AREAS OF THE NRN INTERMOUNTAIN REGION OVERNIGHT..WITH SNOW LEVELS LOWERING RAPIDLY BEHIND THE FRONT. GIVEN THE RELATIVELY GOOD AGREEMENT BETWEEN THE MODEL MASS FIELDS...DID NOT SEE A COMPELLING REASON TO DEVIATE TOO MUCH FROM A MODEL BLEND HERE. SPECIFICALLY..LEANED CLOSE TO A NAM/ECMWF BLEND MOST AREAS THOUGH THE GFS ADMITTEDLY IS NOT TOO DIFFERENT. DAYS 2 AND 3... ...GREAT BASIN/INTER-MOUNTAIN WEST THRU NRN/CNTRL PLAINS INTO THE ENTIRE MS VLY... AN ANOMALOUSLY DEEP AMPLIFIED LONG WAVE UPPER TROUGH WILL COMPLETELY ESTABLISH ITSELF OVER THE WRN CONUS ON D2/THURS AND 3/FRI. A CLOSED LOW OVER NERN MT EXTENDING INTO CENTRAL CANADA WILL BE THE MAIN SYNOPTIC SCALE FEATURE ALONG WITH AN IMPRESSIVE UPPER JET CARVING THROUGH THE BASE OF THE UPPER TROUGH ACROSS THE DESERT SOUTHWEST AND ADVANCING INTO THE CENTRAL PLAINS/UPPER MIDWEST. IT IS THIS UPPER LOW AND POWERFUL JET THAT WILL STEER A NUMBER OF SHORT WAVE IMPULSES... ONE INTO THE DAKOTAS/MN ON THURS AND THEN A MUCH MORE DYNAMIC FEATURE ARRIVING ON FRI INTO THE CENTRAL PLAINS/MID TO UPPER MS VLY. OVERALL HPC CONTINUED TO FOLLOW THE CONSISTENT ECMWF WITH THE 12Z NAM FOR MOST OF THE FCST PERIOD ON ALL FACETS INCLUDING QPF. EXPECT SEVERAL POCKETS OF HEAVY QPF OVER THE TWO DAY FCST PERIOD. ACROSS THE WEST ENOUGH OF AN ONSHORE COMPONENT SPREADING INTO THE NW AND INTER-MOUNTAIN WEST SHOULD CONTINUE TO PRODUCE OROGRAPHIC AND INSTABILITY RAIN/SNOW. ON THE BACKSIDE OF THE LARGE CLOSED UPPER LOW FROM THE NRN ROCKIES DOWN THROUGH CENTRAL MT/WRN WY... EXPECT A COMBO OF NRLY/NERLY UPSLOPE COMPONENT AND DYNAMIC COOLING ALOFT QPF. AN IMPULSE ARRIVING INTO INTO THE DAKOTAS/MN ON THURS WILL IN THE VERY DIFLUENT UPPER-LEVEL FLOW ALOFT AND INTERACT WITH AN ACTIVE LL JET BUT LL MOISTURE CONTENT WILL STILL BE MINIMAL... LIKELY RESULTING IN A BURST OF ACTIVE CONVECTION/HEAVY RAIN ACROSS ERN ND/SD INTO NWRN MN. FINALLY THE STRONGEST SHORT WAVE IMPULSE WILL LEAVE THE CO ROCKIES AND ARRIVE INTO THE CENTRAL PLAINS INDUCING A SURFACE WAVE WHICH WILL DEEPEN RAPIDLY AS IT LIFTS NORTH INTO THE UPPER MIDWEST... THUS EXPECT POSSIBLE HEAVY RAIN/CONVECTION FROM NERN CO SPREADING ACROSS NE INTO IA AND SPREADING NORTH INTO THE ERN DAKOTAS/MN. TO THE SOUTH OF THIS AREA ON FRI... THE ASSOCIATED SURFACE COLD FRONT WILL BEGIN TO INTERACT WITH A RETURNING NORTH WARM FRONTAL BOUNDARY... DELINEATING A TREMENDOUS POOLING OF DEEP TROPICAL MOISTURE NEAR THE TEXARKANA FOR A POSSIBLE BLOW UP OF CONVECTION/HEAVY RAIN. SULLIVAN/MUSHER GRAPHICS AVAILABLE ON THE WEB AT WWW.HPC.NCEP.NOAA.GOV 24HR QP VT 29/00Z 0.01 557124 554118 552113 550112 546111 543107 540102 535097 531090 526073 517035 511019 506008 501003 495000 488000 484999 481000 475003 469006 456011 444018 441020 437026 436031 436035 437041 441044 453044 466042 473042 477045 480053 482059 482065 481077 480087 478095 475095 473094 471091 468089 465090 464088 464082 462078 456077 450072 444069 440070 437069 431067 427066 425068 420068 415064 412060 400062 392063 387065 381068 378074 378080 381083 387086 390087 392090 395095 398097 402096 403099 399105 394107 389112 385117 382123 379131 379139 378144 380149 380153 382156 387157 391154 398145 403141 409137 413137 412140 402149 396160 392165 390171 388175 388179 391183 396192 389191 385188 379185 373180 368178 361177 356178 352179 348177 346171 343166 332160 328159 325161 322166 321171 325175 334182 337186 340193 345204 348210 352215 362222 365226 370230 379237 383241 388247 392253 397257 402260 410262 422262 428263 435262 446260 472264 477265 481269 489274 496276 499275 502272 504266 505258 507256 510256 512255 513250 512240 508224 495201 500196 506194 516202 518205 521207 527215 534230 0.01 484672 476662 467661 463659 458660 453661 447666 437671 431674 429679 427685 425692 424705 423711 423717 424723 422728 421734 424737 426739 425752 429758 433761 437764 441764 445765 448764 452763 461757 467752 471745 474738 479727 483715 485702 486695 486686 484672 0.01 490193 489186 488183 480180 471180 467183 463191 457197 454201 450203 450207 457206 459203 462203 471204 477202 485201 490193 0.01 448088 447085 444086 442088 444089 447089 448088 0.01 438084 436081 435080 433078 430078 427077 424078 423080 424081 427084 430084 433088 436086 438084 0.01 424096 424095 421091 421088 418084 416087 416091 415094 415095 415099 418101 421101 422099 424096 424096 0.01 366746 364741 362738 355737 347740 341741 333746 328750 320756 315761 310766 305773 301779 298785 296792 296799 294807 294814 296824 300833 303832 305829 309822 315809 318804 322798 324794 327792 329792 333793 337799 340808 344810 345814 348819 348825 351836 353840 357838 360832 363824 361817 357808 355802 355798 355790 360774 364759 366750 366746 0.01 367204 366200 363199 361198 359195 358195 355194 352197 351200 351201 354202 357202 360203 363205 365205 367204 0.25 469689 467683 465677 462675 458674 445684 436689 431695 431700 431704 435715 436724 433726 430731 433734 436735 438740 437744 437749 444753 449751 454746 459739 462732 464727 465721 464712 465702 467695 469689 0.25 527150 528136 528123 526114 523106 518101 517100 512100 508097 504097 496098 493103 490112 488122 487125 484125 478124 475123 473125 465136 457136 451139 448139 445138 443136 439135 434139 431146 430151 431156 434164 444173 445174 446180 445186 446188 450191 454190 458184 460181 460176 457172 457167 460166 468169 476170 481169 482162 482159 479155 478152 480149 483150 491151 499153 506155 512160 516160 520159 525154 527150 0.25 488220 486215 484214 479212 477212 470214 466214 461214 431217 424219 419220 414216 406205 397201 391197 376188 370184 366183 361184 360186 360189 364192 369197 379207 385213 392217 397223 391228 389233 390236 391240 394244 400249 409252 419253 425253 440249 453247 460245 468241 474238 467232 468228 469225 472222 476220 483221 488220 0.25 476146 474144 471144 470145 471146 474149 476146 0.25 473111 472107 468104 461100 456099 453097 449095 444095 434095 429094 428096 429100 417112 412112 409109 406109 403111 397117 394120 391124 390131 393132 396130 403125 411122 413121 418122 425125 436127 446128 451128 454125 460118 468116 473111 0.50 519139 519129 516124 513122 510119 505115 499115 496118 496122 498128 501135 503141 506146 509149 512150 515147 518143 519139 0.50 458717 457710 455705 450697 445694 440694 436697 436705 438717 441722 441726 440729 440731 441737 441740 442746 448748 454743 455738 456733 458726 458717 0.50 482138 482134 481132 478130 475130 472132 472136 471137 474140 477140 480139 482138 0.50 469166 471162 471158 467153 465148 462147 458148 455151 450152 446150 439142 436144 434152 435156 437161 443166 446167 451171 453176 456181 452171 452167 455164 458160 464163 469166 0.50 460220 454218 448219 443219 437222 435223 431223 428223 427227 424231 420232 417231 405229 398230 394233 394237 395240 400245 407247 414248 420249 426248 430245 432241 431237 436230 440226 447224 452223 457221 460220 0.50 468111 464106 455104 450100 441099 432099 432104 428108 426112 430115 434116 438116 443119 446121 451120 454118 461115 467112 468111 0.50 453239 452236 449234 446234 443235 440235 437238 439242 442242 445242 448242 451241 453239 0.50 406217 405213 402211 397205 392201 385197 379193 373188 368185 366188 367191 372197 377202 383206 388211 393215 401219 406217 1.00 444708 441709 441711 440716 444717 445712 444709 444708 1.00 423242 421239 419238 418236 416235 413235 410235 407235 404235 403236 401237 399238 401240 403241 406241 408241 409241 412241 415241 418241 421242 423242 1.00 397211 397210 394207 393206 392205 389205 388205 389205 391209 391210 394211 396212 397211 24HR QP VT 30/00Z 0.01 535220 537203 538194 536187 536181 534174 531165 525154 520143 513129 512121 512110 512093 511086 508081 502072 495065 489064 485067 477071 470074 466074 462073 459072 454069 448063 443060 440060 437062 435066 434071 437076 444080 447084 446085 440085 434086 424084 422088 422096 417099 417091 415086 415083 417079 420078 423075 426066 428062 428055 428048 431044 435044 437046 444053 449052 450049 450045 448040 446035 444032 446027 449028 454031 459034 465033 472030 476028 484020 492017 503013 511011 515009 517006 519993 521981 521971 519963 517946 515932 510923 504912 492891 484881 476872 455839 453837 448835 441834 438834 434837 430841 429847 429858 431865 431870 433874 438881 441884 438889 436898 436903 437906 441910 445915 445920 441930 440939 439944 434953 430957 427957 421959 411971 408974 406979 404989 402999 404014 396031 393036 391042 390050 389055 386057 380061 377061 366061 363071 362082 354084 353092 356101 358108 357112 353111 349109 347106 344104 342108 344119 355131 360138 368145 372154 377159 380159 383160 385165 384171 386182 389184 392189 402193 403196 400197 392195 389191 385190 383187 379185 375181 369179 360179 352181 348183 346182 344169 340166 333164 328162 325164 325165 329168 335171 341174 342177 342189 344192 348194 356194 364196 369203 375209 384214 390219 394222 395225 391228 387230 379222 361217 363221 367225 374230 381236 389242 395249 399252 403254 412258 421260 430260 434260 439259 456257 466259 472260 476261 478264 483268 489274 492279 498283 502285 506285 509282 511279 515277 518273 519268 518254 514241 506220 506216 509214 513218 519221 525226 528228 530227 535220 0.01 472681 472677 469675 465672 463660 460658 454659 446663 439672 434683 428693 428698 431699 451693 453696 453702 449704 446705 443706 441709 439714 438717 433722 428726 427729 430732 437734 447731 455729 458726 460724 459719 458712 460707 466696 470688 472681 0.01 502252 501249 499246 498245 495244 495245 497250 500255 502252 0.01 491234 488231 487228 486227 483226 480224 477224 476225 477225 480227 482231 485233 488234 491235 491234 0.01 486201 489197 489193 488187 482183 477182 471181 466183 464187 461190 457196 455202 456207 460207 465205 471206 474204 480204 483203 486201 0.01 422702 420699 418696 416695 413697 412700 414703 416706 418707 421707 422702 0.01 464093 462089 459089 457089 458093 459093 462094 464093 464093 0.01 433140 434136 434133 433132 431131 430132 428135 427139 427141 430141 433140 433140 0.01 417138 419134 416133 414134 413134 410136 409137 410139 413140 416138 417138 0.01 392109 392108 389107 386108 386109 389109 392109 392109 0.01 264806 264800 260797 255799 250802 248804 246808 245813 244817 244821 246824 250825 254823 256822 259818 262814 264810 264806 0.25 512171 513165 513161 511152 508137 505120 503104 502099 499091 495086 491083 485084 480088 473095 465104 463106 464110 467115 470117 475114 479116 480120 478124 475125 469129 466135 465141 460144 456147 454150 453154 455158 458160 466161 473159 476155 481160 487162 493163 499167 501172 506175 510175 512171 0.25 507989 506979 504972 497960 499948 501935 501930 500929 492929 486932 480936 472943 464952 461955 454959 448966 445971 443978 442986 441991 434002 428012 428017 428021 430021 437013 440010 448008 454008 458009 464012 471009 480002 483001 491000 497000 503997 507989 0.25 486246 476234 471233 466231 467225 469219 470217 465214 458215 448216 440216 431217 428219 425222 420229 413231 405235 404236 405240 410248 416252 424253 431252 447249 464247 473247 480247 486246 0.25 482213 479211 476211 473213 471214 473216 475217 478217 480217 482213 482213 0.25 478150 477149 474149 472150 473152 476154 478150 0.25 416064 412053 406053 400055 397057 389064 387068 384071 373072 373079 374086 378095 384097 389096 395095 398091 405087 410079 413075 415068 416064 0.25 398124 399120 399117 394114 388114 385116 381119 378123 376126 375130 376133 379136 382137 387141 390141 393139 395135 396128 398124 0.25 385204 384200 381196 379193 377192 376190 373188 372187 371186 368185 365185 364189 365189 367193 370196 372198 375200 377202 379203 380203 383205 385204 0.50 503146 502132 501122 499109 496103 492101 489103 486112 484125 478129 473132 474137 477141 483146 488152 491153 500150 503146 0.50 501990 500985 497982 491978 489976 487973 488970 492961 494954 496946 496941 492939 488940 484943 473954 462964 459967 457970 455977 451986 451992 454997 460000 465001 470001 474999 476996 480994 491992 499991 501990 0.50 471111 473107 470104 468106 468111 470112 471111 0.50 455240 454239 451238 450238 451240 454240 455240 0.50 447241 445239 442239 440238 437238 436238 434238 431240 430241 427242 425242 427245 429246 432246 435246 436246 438244 441244 442243 445242 447241 0.50 446224 445223 442222 439222 438222 436225 435225 435227 438226 439226 441226 445224 446224 0.50 410072 411068 410065 407061 404060 401061 395063 392065 389068 387073 384077 382083 384086 389089 395087 398084 401081 404078 407075 410072 0.50 394124 394120 394119 391117 388119 387120 385121 384123 383127 385130 385131 387134 390134 392131 393128 394125 394124 0.50 376195 373193 370190 372194 373195 375195 376195 1.00 496131 497127 496122 496121 493120 492121 492126 492130 489134 489135 486137 485138 486140 488143 489143 492144 494140 494135 495133 496131 1.00 465988 469982 468980 464984 461986 460988 462991 465988 24HR QP VT 01/00Z 0.01 547012 547002 546991 545972 542960 541954 536937 531921 526903 522892 518883 517877 512873 500862 491851 482838 473827 465819 456811 437794 429788 425787 423788 419788 417790 417798 417803 420809 423817 426823 432827 438829 443831 447835 449839 453843 457848 463850 466852 469851 472860 457883 453886 451889 447894 437904 429908 421909 417909 414911 409915 405919 403919 397918 392919 387920 380918 374912 366904 357897 352894 348893 341893 338895 335897 328904 322903 319903 319900 314883 309869 308857 306842 303834 301828 297820 293814 282801 274798 268795 264795 258793 252792 248792 246798 244808 244817 244824 245828 247832 251834 257834 262837 267841 272845 276851 282862 285872 285886 283899 283905 285912 287924 289937 285947 283950 281956 278960 274964 268967 262968 253973 260980 271986 280991 288997 293000 298002 309004 316005 323003 327001 336001 338000 342003 345003 351002 355999 362994 368990 373989 380985 388985 391987 390993 387999 383008 377018 374022 369026 364030 361037 357050 352054 347056 344068 340071 336071 330072 324075 321078 322083 326098 329106 332115 336129 337133 341137 349143 354141 360137 363131 363126 362122 362118 363113 368108 371107 372103 372101 375098 376096 380096 384097 388097 392098 396096 399094 401092 403093 404095 402098 397102 394109 388112 384114 378115 375121 373126 373131 373136 374148 377148 380145 385134 388129 391129 391133 386142 387149 390156 392169 394173 402175 410166 421162 425155 426143 428134 431132 433136 433138 433148 433157 437162 441167 445174 445177 444180 441186 440193 443196 449196 452194 453192 454186 455181 454176 455171 458170 464173 474180 478183 485184 496191 500193 504192 509190 514190 517191 524193 528194 529193 533186 534180 533177 528169 526161 526154 525151 524144 522140 519133 516125 513118 511105 512091 511081 509074 505069 499063 499052 499047 497042 496037 493033 489033 482033 477031 466026 440026 436020 439015 448006 457002 465001 468000 471996 475990 480987 484986 487987 497993 509001 519010 524013 531014 540014 546013 547012 0.01 469222 470218 470214 465214 455214 449213 442212 435213 422219 419221 420227 423230 415227 415220 416215 415210 411205 405204 401201 396196 383190 377188 369183 365182 363186 363191 365193 370196 375199 386208 392212 399216 405220 406225 407226 409231 407235 406239 406244 409249 415252 422253 430252 436251 442251 456248 462246 465242 466237 464231 465228 469222 0.25 501930 501921 498915 494910 490900 483889 474887 458898 450912 437919 431921 424923 420925 418927 415932 408946 408951 406958 400985 396016 388023 385028 383034 379040 378046 379050 385061 381065 378065 373063 366063 362063 358065 357070 358073 361075 367078 373084 378087 384088 390084 394079 396073 397064 399061 403057 407053 409045 416034 423025 437006 445998 456989 473971 478968 483964 489958 493951 498940 500935 501930 0.25 505146 505137 503131 503126 504121 505109 505100 504095 503090 497080 491070 488065 485058 482056 479057 474059 465065 456072 450077 456085 462089 465093 464097 458101 447103 444105 443109 444112 446118 450121 454126 455131 455140 458147 459152 461160 465164 472166 478165 482161 491153 497149 505146 0.25 379965 377955 371949 372938 371936 364930 353914 350912 345912 336915 329921 324930 316947 314956 314967 318975 325979 333983 340990 343991 348991 351988 354981 358976 367970 373967 379965 0.25 299898 299892 298885 295882 293887 292890 292894 291900 291903 292910 294915 297917 299912 299908 299901 299898 0.50 497113 499108 497104 491103 487103 482101 475098 467100 463103 461110 467120 475129 478135 480138 483140 489140 489134 480125 478120 481113 491117 495115 497113 0.50 489929 489923 487918 481912 474904 470904 462909 457917 451918 443922 434927 428929 423933 421936 416944 410961 406969 403981 402989 404993 407996 411998 411004 407011 403019 399024 392030 388039 388044 389047 394047 399047 405041 410034 421022 431007 436001 442995 448990 455981 464968 468961 472956 476951 481940 486935 489929 0.50 384079 384078 382075 381075 379075 378076 377079 378080 381082 384080 384079 0.50 375960 372955 366951 363945 358941 352937 348933 344925 337922 332926 328933 321946 319951 319960 321966 326972 336977 342980 348977 358970 366966 372964 375960 1.00 472925 469924 466927 464929 459932 444933 438934 435937 430938 426944 420950 413964 410968 407977 407982 408987 412986 417981 423975 427970 430963 444958 452954 458949 465936 472925 1.00 473111 473110 470106 467107 466110 467112 470115 473112 473111 1.00 346958 347955 345953 343952 343948 342942 340936 336934 334936 333944 335950 339953 336957 334961 335964 341966 344966 345962 346958 1.50 425962 426958 423955 421959 418963 417967 416971 419971 421970 422969 423966 424963 425962 $$