QUANTITATIVE PRECIPITATION FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 608 AM EDT THU MAY 05 2011 FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION VALID MAY 05/1200 UTC THRU MAY 08/1200 UTC REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR UPDATE... ONLY SOME SLIGHT CHANGES MADE TO THE PRELIM DAY 1 QPF FOR THE FINAL ISSUANCE. THESE CHANGES BASED MOSTLY ON LATEST EXPERIMENTAL HI RES ENSEMBLE MEAN. DAY 1... UPPER TO MID MS VALLEY/LOWER OH VALLEY... NO MAJOR DISAGRMNTS IN THE LATEST MODEL RUNS WITH THE EWD PUSH OF THE LONGWAVE TROF THRU THE MS VALLEY AND TOWARD THE LOWER OH VALLEY DAY 1. PW VALUES EXPECTED TO REMAIN MODEST ASSOC WITH THESE HT FALLS...GENERALLY .50-.75". THIS AND THE PROGRESSIVE NATURE OF THESE HT FALLS SHOULD REDUCE POTENTIAL FOR WIDESPREAD HVY PCPN AMTS THRU THE UPR AND MID MS VALLEY/LOWER OH VALLEY REGION. LARGE SCALE LIFT AHEAD OF THESE HT FALLS...WL HOWEVER...STILL PRODUCE POTENTIAL FOR SOME ORGANIZATION TO PCPN DAY 1....WITH MODEL CONSENSUS FOR TWO PCPN MAXIMA. A NRN MAX INVOF NERN MN/NWRN WI ASSOC WITH THE CURRENT SHRTWV PUSHING INTO THE UPR MS VALLEY...AND A MORE SRN MAX ACRS MO/FAR NRN AR/SRN IL INTO FAR WRN KY ASSOC WITH UPSTREAM SHRTWV ENERGY FCST TO DIVE SEWD OUT OF THE CNTRL PLAINS THU EVENING AND INTO THE MID MS VALLEY/LOWER OH VALLEY REGION THU NIGHT/EARLY FRI. THE HI RES NMM AND SPCWRF ARE SHOWING MORE WIDESPREAD .50"+ PCPN AMTS OVR PORTIONS OF SRN MO INTO FAR NRN AR THAN THE REMAINDER OF THE GUIDANCE. DAY 1 QPF LEANED TOWARD THE CONSENSUS OF .25"+ AREAL AVG AMTS WITH BOTH THE NRN AND SRN QPF MAXIMA. FAR NRN NY INTO NRN NEW ENGLAND... THE AMPLIFYING MID TO UPR LEVEL CLOSED LOW AND ASSOC SFC LOW WL MOVE VERY SLOWLY DAY 1 ACRS NRN NEW ENGLAND. ORGANIZED PCPN ALONG THE ASSOC FRONTAL BNDRY SHOULD BE MOSTLY EAST OF NRN NEW ENGLAND DURG THU...POSSIBLY AFFECTING FAR ERN MAINE THRU THU MORNING. WRAP ARND/DEFORMATION PCPN WL LINGER FROM FAR NRN NY INTO FAR NRN NEW ENGLAND THRU THU INTO EARLY FRI...WITH LOWER ELEVATION RAINS AND HIGHER ELEVATION SNOWS POSSIBLE. LIGHT TO MDT AREAL AVG PCPN AMTS EXPECTED. PAC NW INTO THE NRN ROCKIES... FAST MOVG NERN PAC HT FALLS WL MOVE THRU THE PAC NW/NRN ROCKIES THU AND INTO THE NRN HIGH PLAINS BY EARLY FRI. RELATIVELY WEAK ONSHORE FLOW...MODEST PW VALUES AND THE FAST MOVEMENT OF THIS SYSTEM SHOULD KEEP PCPN AMTS ON THE LIGHT SIDE. S FL... PW VALUES WL REMAIN ABOVE AVG ALONG AND TO THE SOUTH OF THE WEAKENING FRONTAL BNDRY OVR SRN FL THIS PERIOD. SCT CONVECTION LIKELY IN THIS MOIST AIRMASS DAY 1...WITH MAX PCPN AMTS DEPICTED ALONG THE SW COAST WHERE PCPN MAY MAXIMIZE IN THE LOW LEVEL ELY FLOW REGIME ACRS THE SRN PORTION OF THE PENINSULA. DAYS 2/3... ...NORTHWEST/INTERMOUNTAIN WEST... DEEP LAYER ONSHORE FLOW WITH WINDS NEARLY ORTHOGONAL TO THE TERRAIN WILL INCREASE THROUGH THE PERIOD AS A DEEP UPPER LOW SLOWLY DIGS OVER WASHINGTON BY THE END OF DAY 3. DIGGING OF THE LOW SHOULD ALLOW THE ACCOMPANYING MOISTURE PLUME WITH PRECIPITABLE WATER VALUES OF 0.5 TO 0.75 INCHES TO DRIFT SOUTHWARD ALONG THE COAST IN ASSOCIATION WITH THE MID/UPPER LEVEL JET AXIS. DESPITE VIGOROUS LARGER SCALE ASCENT TOTAL QPF AMOUNTS FROM THE MODELS ARE NOT PARTICULARLY IMPRESSIVE. HOWEVER...OROGRAPHIC ENHANCEMENT ALONG WITH COLD MID LEVEL TEMPERATURES (-25 TO -27 C AT 500 MB) BENEATH THE CENTER OF THE LOW SHOULD FAVOR LOCALLY HIGHER TOTALS. ASIDE FROM THE ECMWF WHICH HAS TRENDED TOWARD THE PREFERRED CLUSTER OF LARGER-SCALE SOLUTIONS WITH ITS LATEST CYCLE BUT IS STILL SLIGHTLY LESS PREFERRED...MODELS WERE FAIRLY CLOSE WITH A BLEND OF THE NAM/GFS/UKMET MOSTLY USED TO DERIVE THE INITIAL VALUES. 48 HOUR LIQUID EQUIVALENT TOTALS ENDING 12Z SUN SHOULD BE HIGHEST ALONG THE WESTWARD-FACING SLOPES OF THE COASTAL RANGES OF WASHINGTON/OREGON ALONG WITH DIMINISHING AMOUNTS INLAND ACROSS THE BITTERROOTS/TETONS AND INTERMOUNTAIN WEST. ...MISSISSIPPI/OHIO/TENNESSEE RIVER VALLEYS... THE DURATION OF RAINFALL WILL BE SHORT-LIVED DAYS 2/3 DUE TO THE RAPID PROGRESSION OF THE NEXT SHORTWAVE TROUGH TO INFLUENCE THE REGION. HOWEVER...ASCENT WILL BE QUITE VIGOROUS WHICH WILL HELP TO COMPENSATE FOR THE MEAGER MOISTURE VALUES DEPICTED BY THE GUIDANCE. MODEL FORECAST SOUNDINGS INDICATE THE MAJORITY OF PRECIPITATION WILL ORIGINATE IN THE 800-600 MB LAYER WITH PRECIPITABLE WATER VALUES RISING TO NEAR 1.0 TO 1.25 DURING ITS PEAK...WITH ALMOST NO CONTRIBUTION FROM THE SURFACE. PREFERRED THE LARGER SCALE DEPICTIONS OF THE NAM ALONG WITH ITS DETAILS FOR DERIVING THE INITIAL QPF VALUES...WITH SOME CONTRIBUTIONS AS WELL FROM THE GFS/ECMWF/UKMET/SREF MEAN. HOWEVER...THE GFS QPF BECOMES A BIT CONCERNING NEAR THE APPALACHIANS BY 72 HRS AS ITS ACCOMPANYING SURFACE LOW BEGINS TO DEVIATE FROM THE OTHER CLUSTER OF SOLUTIONS WHICH ARE MUCH SLOWER. THE MAIN MANUAL ADJUSTMENT FROM THE MODEL QPF WAS TO TRIM AMOUNTS ALONG THE NORTHERN PERIPHERY OF THE MOISTURE AXIS AND INSTEAD FOCUS THE HIGHER AMOUNTS FARTHER SOUTH TO HELP ACCOUNT FOR THE POSSIBILITY OF ONE OR MORE COMPLEXES OF THUNDERSTORMS TO DEVELOP A MORE SIGNIFICANT PROPAGATION COMPONENT INTO THE SOUTHWARD-ORIENTED MOISTURE/INSTABILITY AXIS WHICH MAY BE ENHANCED BY THE DOWNDRAFT POTENTIAL. ...FLORIDA... THE MOISTURE PLUME DRAPED ALONG A STALLED FRONTAL BOUNDARY ACROSS SOUTHERN FLORIDA WILL BEGIN TO ASCEND AND FLOW NORTHWARD BY EARLY DAY 2 IN RESPONSE TO AN APPROACHING SHORTWAVE TROUGH WITH INCREASING PROBABILITIES THROUGHOUT THE DAY AS SEA BREEZES DEVELOP. OTHER THAN THE NAM WHICH DEVELOPS A QUESTIONABLE BULLSEYE OF PRECIPITATION NORTH OF JACKSONVILLE AND WELL OUTSIDE THE MAIN MOISTURE CHANNEL...THE MODELS WERE FAIRLY CONSISTENT WITH THE GFS/ECMWF/UKMET/SREF MEAN MOST PREFERRED. ASIDE FROM THE BASIN AVERAGE AMOUNTS...WEAK TO MODEST FLOW ALOFT ALONG WITH PRECIPITABLE WATER VALUES AVERAGING 1.5 TO 1.75 INCHES FAVORS LOCALLY HEAVY DOWNPOURS AS WELL. ...NEW ENGLAND... SCATTERED TO NUMEROUS SHOWERS EXTENDING FROM NORTHERN NEW YORK INTO NORTHERN MAINE SHOULD DECREASE BY THE END OF DAY 2 AS THE MOISTURE PLUME WRAPPING AROUND THE DEPARTING AND WEAKENING CYCLONE DIMINISHES. HOWEVER...A SECONDARY MAXIMA OF QPF ALBEIT LIGHT SHOULD DEVELOP ON DAY 3 FROM RHODE ISLAND INTO MAINE AS A NEW MOISTURE PLUME ORIGINATING FROM THE WESTERN ATLANTIC ROTATES AROUND A SURFACE LOW DEVELOPING NEAR THE GULF OF MAINE. THE GRAZING NATURE OF THE MAXIMUM ASCENT AND MOISTURE FIELDS SUGGESTS AMOUNTS WILL REMAIN LIGHT. HOWEVER...ONLY A SLIGHT NORTHWARD JOG OR SLOWER EXIT IN FUTURE MODEL CYCLES COULD RESULT IN MUCH HIGHER AMOUNTS THAN CURRENTLY ANTICIPATED. FOR NOW RELIED UPON A CONSENSUS OF THE GFS/ECMWF/UKMET...WITH THE NAM CONSIDERED TOO SLOW WITH THE LOW TRACK. ORAVEC/JAMES GRAPHICS AVAILABLE ON THE WEB AT WWW.HPC.NCEP.NOAA.GOV 24HR QP VT 06/12Z 0.01 520675 517665 513655 509646 505642 501634 497630 493624 488620 479611 469606 459601 451599 440605 435610 433613 434616 438624 436628 433631 426635 405648 389661 385665 379669 373675 370680 368685 367690 370693 375696 381697 386696 396694 407689 412687 419685 423685 428685 431686 433688 435692 434708 435714 434716 431718 426723 422728 422733 424737 427741 435752 439756 442759 455759 465758 471757 478754 483749 489745 494744 500741 507736 511731 515724 516719 519703 520687 519679 520675 0.01 532215 534210 535204 534196 530182 527174 525169 521164 517159 509150 500143 492135 484127 479124 473123 469126 467132 468137 469139 471141 459141 455143 452145 451149 450153 452157 455160 461164 465167 469171 475172 481176 486179 494186 492199 488205 483205 464213 460216 454218 459225 448239 449243 450246 457248 470253 476256 480259 486264 490266 494272 496277 496285 499293 502297 506294 510289 513281 516275 518271 519264 517258 513243 509230 503216 503214 506209 522217 526218 528217 532215 0.01 512903 510893 508886 504879 503877 501871 501861 497851 494846 490842 485840 483840 479838 476839 470835 454823 448821 441821 432825 422831 418836 412840 402847 396850 390851 387847 382847 376846 369848 363852 359856 354867 352877 350883 348888 342897 339901 338906 339910 340914 342917 345919 348925 349929 351933 353937 358938 364948 367952 371956 380962 384962 389961 395957 399953 405946 409941 415936 423930 426930 432934 442938 449944 454948 458950 461953 465953 469954 476953 481949 490942 498932 505924 510913 512903 0.01 511054 509049 507047 504044 494041 482037 473038 468043 465047 459060 456064 452067 449072 451076 452085 454091 452097 447101 443102 439107 442112 444117 447122 450123 452122 457118 461117 465114 471112 475107 476102 473090 474086 477081 484070 487065 491063 498062 504059 511054 0.01 302841 299831 296826 292825 284828 278827 277824 275818 273812 276809 277804 274799 268794 258793 253795 249798 243805 241812 242818 245823 250828 257831 266834 276849 279852 283854 289852 298847 302844 302841 0.25 508665 504652 500646 493642 488637 477623 471618 466616 462618 459623 456626 453628 450631 444637 439647 436649 427654 425657 426663 428666 435669 447674 451675 455677 458679 460683 461689 462694 461700 457708 453715 446730 448731 449735 448738 446742 448746 454745 462741 469741 475739 483733 490727 501713 505705 509696 510689 510679 508665 0.25 523192 521187 521186 518181 515178 512179 512180 512183 512185 514188 515190 517192 520194 523192 0.25 489907 487900 484897 480896 474894 465895 457901 452904 450909 449915 451919 455922 459925 467930 474934 480933 482930 485926 486921 486917 489907 0.25 414893 414888 411886 404886 396889 388894 377901 361908 359910 357914 357921 360927 365931 369936 371940 375942 379940 383936 385931 390924 395919 405908 410903 413897 414893 0.25 264800 261800 259802 258803 259802 262802 264800 264800 0.25 268821 267820 266818 264816 263815 262814 261811 260808 257806 255808 254811 254814 254817 255820 256821 257822 259824 260825 263826 264826 266826 268824 268823 268821 0.50 503669 496650 490644 483638 476635 469634 462634 458635 455637 453645 447654 446660 449665 456671 469680 472686 473693 471702 470715 472721 476722 480720 486715 495707 501698 505687 506682 506677 504674 503669 0.50 399898 399894 397894 394896 392900 395900 398899 399898 0.50 385906 384905 381906 380907 379910 377912 376912 374915 373917 371918 370921 369923 369925 370926 371928 373931 376928 377927 378924 379922 380919 381918 381914 382912 383910 384907 385906 1.00 486659 485655 483652 482652 479652 477652 476652 475654 477658 478659 480660 483662 487662 486659 24HR QP VT 07/12Z 0.01 501672 499664 497657 494649 490643 484632 478625 476622 471619 469616 464615 458616 454620 450627 448635 448640 451644 454652 456662 451672 449682 444692 443700 442705 440710 438715 438719 430732 433736 433742 431747 430752 431757 436763 440763 444759 446757 449756 454756 458759 459761 463765 467767 484760 490764 496768 499770 504769 508770 513768 516764 517760 518756 516748 514744 511741 503737 500734 497730 494726 494719 496717 498710 500705 501700 501690 501683 500677 501672 0.01 546103 545096 542090 538083 536077 534069 531062 529053 526047 526043 523034 522029 529029 537022 538013 537004 535997 532990 525980 516969 511966 505963 485961 481958 477953 471943 465932 459920 452907 448901 444896 437890 428884 419881 409880 398881 391882 385884 379887 375891 365900 359908 354918 352927 350933 349940 349945 350949 354953 360955 365958 369961 372964 374968 376970 379972 382973 387969 395961 407958 412958 417959 425965 431969 434969 440971 446973 456980 463986 467991 469996 463008 462014 461022 455031 452036 449037 448035 445033 442033 438035 437037 436042 437047 439051 442052 444059 441064 438068 437071 438075 450089 446088 440085 429090 426105 425109 426113 427116 427122 428125 430124 433122 436118 440117 443120 466123 461114 467115 470114 473111 473106 470102 470097 471092 468091 464098 463093 461087 459081 459075 459071 456065 454059 456052 459050 466047 470046 476046 479050 482053 486054 491055 496060 501064 504070 509082 514093 520102 526108 529108 531109 534111 537110 544108 546103 0.01 517278 519273 519268 518260 513246 511238 509232 505227 503219 501213 498207 495204 494201 495195 496194 499192 502193 508197 516205 522207 526204 530197 532191 532184 531174 528168 526162 522158 519152 516149 513147 508143 503140 500141 496139 486130 483128 477128 471132 468137 463136 457136 448146 444149 442152 443156 446162 447165 448171 448177 451183 454187 458188 461187 468179 475179 482182 483188 485195 483202 480205 473206 469208 457210 452211 447213 443215 441218 440223 444228 445231 444235 442240 444247 447251 453253 458253 464255 468257 474261 477268 480275 485286 489290 495295 500296 504296 508295 511291 515283 517278 0.01 477861 475852 470841 460829 455822 450812 445805 439801 417782 410779 403775 397776 389780 384784 375791 363801 355816 354824 355830 372858 378863 382865 387863 399864 405861 413858 422856 430854 437853 445855 455853 459856 463862 466864 470864 477861 0.01 419686 415678 409673 403671 398670 391672 384677 370687 362692 357698 347708 336721 333727 333735 332740 327746 318758 316762 315768 315771 318779 323782 330780 337781 340781 344779 350774 355771 360768 362764 368760 373754 388744 391739 393734 394730 397727 404728 411727 414724 418717 421707 421699 420690 419686 0.01 412739 410736 409736 408738 407739 405742 404744 403746 401749 398751 399755 401758 404757 405756 406754 407750 409746 411744 412743 412739 0.01 304820 292808 295805 296803 294800 288796 279793 277791 276785 274779 269776 262775 258776 256779 253786 251796 248804 246811 247820 248822 252825 258828 264829 268830 274831 283832 292835 295835 300832 302828 303824 304820 0.01 315032 315029 312023 309020 305020 298016 292012 289010 286009 283009 280010 276013 273020 273024 276028 279031 285031 290031 293033 299038 305039 310039 315032 0.01 264996 265991 264987 259982 255982 251984 246989 243992 239999 240004 243010 248012 251012 256008 260002 263998 264996 0.25 468695 465694 463696 460698 458700 455703 454705 454707 453711 454715 457717 459716 460715 462712 464708 465707 466704 467700 467699 468695 0.25 509283 510278 511272 512261 511252 509245 506237 503232 496218 491216 486214 490229 489234 486236 485237 482237 477234 473237 474242 475246 479252 482258 485264 491275 495282 500286 506286 509283 0.25 494171 494167 493165 490164 487164 484164 482164 484168 484169 486172 489175 492174 494171 0.25 394692 391688 388688 381690 373695 366701 359707 356713 357720 360720 364718 371713 379708 385707 389705 391702 393696 394692 0.25 366727 360724 352728 345733 341740 337745 333750 330754 330758 336760 341756 348751 356746 361742 364738 366735 366727 0.25 378937 378934 378930 377926 375924 375923 372922 369924 368925 367926 365929 364930 363934 363937 364940 366943 367943 370945 372944 375942 376941 377938 378937 0.25 276811 275808 272803 269798 266798 261799 256803 254806 253810 253814 256819 259821 262822 268820 273819 275817 277814 276811 0.25 258994 257991 256991 255991 253991 252992 249993 248995 247996 246998 246001 247002 250001 251000 253998 254997 255996 258994 258994 0.50 505277 504272 501266 498263 495258 492253 489247 487246 485250 487255 489261 492266 494271 496275 501280 502280 505277 0.50 500237 498232 497231 496231 497233 499237 500237 0.50 266812 264809 261810 260811 262814 263814 265813 266812 24HR QP VT 08/12Z 0.01 485649 483646 480643 471644 464653 458659 451664 446667 442672 437679 434678 430673 428667 425665 418659 412656 405655 397656 390656 382656 378658 375662 371670 367679 366686 370696 375701 383703 395708 397713 398716 397728 399734 403737 406738 409737 419732 427729 432728 435724 438717 439707 442706 446708 445712 447716 450719 453720 462716 471707 476699 480690 482681 485669 486659 486653 485649 0.01 537201 537191 537177 534166 533156 532150 530145 527140 519134 515132 511133 503132 496130 490126 484120 478085 481064 484042 485018 485010 484003 481993 480987 480984 482982 488987 499993 504995 509997 513997 517995 521992 526988 533985 538979 537969 533958 525942 519934 512928 502921 495919 488917 475946 472950 470954 468962 465964 462961 453961 449962 444964 437971 435980 434988 434000 437010 438018 441026 444035 445046 444057 442064 412098 408095 403097 401105 401114 400120 401126 399136 395141 389138 387136 385137 383138 381141 386148 389153 391159 390164 389171 387176 383183 379191 378196 381204 387209 395214 399218 398221 394221 391220 387220 383222 382225 382229 384234 390239 397242 406244 409245 412242 414241 416235 416228 418222 421213 427196 431189 432184 431178 432174 434171 438172 442174 442175 442179 439181 439188 439193 439198 442200 445203 451201 457193 463187 466179 470177 474178 480183 483185 484189 485193 484196 479200 466206 460208 453209 447209 443209 441210 437212 434215 431215 428217 422222 423227 425230 422234 420236 420240 426246 436249 444249 449250 458250 462251 468255 475260 480264 485271 489279 490281 494282 499286 503286 510284 516279 518276 520269 521266 521262 520259 518253 518250 517243 517239 514229 511222 506216 504213 502209 504205 508203 511205 515208 521213 526213 529211 535206 537201 0.01 447907 445899 443895 440888 437882 435878 431871 434858 433853 432846 427832 424827 421822 415816 411813 409810 409807 410800 409795 408791 404785 398780 390776 380774 375774 369777 363784 359793 356804 355816 354820 355827 355852 352872 349881 344892 342900 340911 340918 342925 348935 351938 354939 360941 366940 372938 378935 387928 390926 393923 395921 398918 400916 406912 412913 421918 428923 431924 437924 440924 443922 445917 447907 0.25 509264 511257 510249 508238 504229 502224 499219 497215 494212 488211 483210 477211 470213 463216 467222 469226 466229 460233 452235 448237 446241 453241 463243 471242 478243 483241 486246 490256 494264 500270 502271 506268 509264 0.25 491148 492143 491140 486135 482132 475130 472132 470135 468139 465139 461140 455143 446150 443152 442153 442156 446160 451164 455161 461160 465161 471166 478165 484165 485161 485156 484149 486147 491148 0.25 456114 457109 455105 455101 453096 450095 447095 444096 441096 438096 435097 433096 430094 428096 429099 431104 430108 432111 435113 441114 445117 449119 453118 456114 0.25 385853 384846 382843 379838 377833 374824 372819 367819 366824 366829 366838 366849 366859 363867 361876 359895 357904 357913 359919 361923 365924 369922 374916 379909 383901 385894 387884 387875 387868 385862 385855 385853 0.50 500232 498227 497222 496220 494217 493216 490216 488214 485213 482213 482214 479215 477216 478218 481219 484221 487222 489223 492224 493226 495229 496231 497234 500232 0.50 376879 375877 373876 372876 371880 373883 374884 376883 376881 376879 0.50 372910 372906 371902 368899 368900 366902 365904 364908 363912 365915 365916 368916 370914 371913 372910 $$