QUANTITATIVE PRECIPITATION FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 542 AM EDT FRI APR 29 2011 FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION VALID APR 29/1200 UTC THRU MAY 02/1200 UTC REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR DAY 1... 06Z UPDATE... ONLY MINOR ADJUSTMENTS WERE MADE TO PRELIM GUIDANCE GIVEN REASONABLY GOOD CONTINUITY. ...NORTHEAST... UPR TROF THRU THE GT LAKES REGION WILL LIFT NEWD ACRS NEW ENGLAND THIS PD WITH SFC LOW OVER QUEBEC PROV DROPPING SEWD AND MERGING WITH LOW PRES DVLPG NEAR THE SRN NEW ENGLAND COAST FRI NIGHT. END RESULT WILL BE SCTD SWHRS ACRS PARTS OF THE NE AND WRN UPSLOPE AREAS OF THE CNTL/NRN APLCNS MOST OF WHICH WILL BE LIGHT AS VERY DEEP MSTR FLOW AND FRONTAL BNDRY CONTINUE TO PUSH WELL OFF THE EAST COAST. GFS AMOUNTS LOOK HIGH ACRS ERN MAINE COMPARED TO OTHER GUIDANCE AND OWN CONTINUITY..A RESULT OF STGR UPR VORT DEPICTED DROPPING SWD INTO MAINE LATE IN THE PD THAT OTHER MODELS KEEP RATHER WEAK. LEANED TOWARD NAM/12Z ECMWF GUIDANCE. ...PAC NW INTO THE NCNTL PLAINS/UPR MS VALLEY... WITH THE EXCEPTION OF MINOR TIMING DIFFERENCES..MODELS GENLY SHOW REASONABLY SIMILAR HANDLING OF PROGRESSIVE UPR TROF EXPECTED TO MOVE FROM THE NRN INTERMOUNTAIN REGION INTO THE NRN PLAINS BY SAT MRNG. ASSOCD SFC LOW IS EXPECTED TO DEEPEN TOWARD THE NRN ND/MN BORDER REGION BY SAT MRNG WITH COLD FRONT SWEEPING EWD INTO THE UPR MS VALLEY. MODEST UPSLOPE PCPN BAND IS EXPECTED TO DVLP ACRS WRN MT AS COLD FRONT SLIPS SWD BEHIND MAIN DVLPG LOW AND MODELS ALL SHOW A DECENT COMMA HEAD PCPN BAND FORMING ACRS ND WITH DVLPG MID/UPR CIRC FRI NIGHT. LEAD COLD FRONT SHOULD GRADUALLY BECOME MORE ACTIVE FRI NIGHT AS AREA OF WEAK INSTABILITY DVLPS AHEAD OF IT AND MSTR SLOWLY INCREASES UNDER STRENGTHENING LOW LEVEL JET. DECENT LEFT EXIT REGION PUNCHING EWD INTO THE CNTL PLAINS SHOULD PROVIDE ADDED LIFT ALONG THE FRONT. MODELS SHOW VERY LITTLE SPREAD QPFWISE..WITH .50 TO 1 INCH AMOUNTS DVLPG IN COMMA HEAD ACRS ND..HALF TO .75 INCH AMOUNTS ALONG COLD FRONT OVER PARTS OF THE UPR MS VALLEY AND GREAT THAN .50 INCH AMOUNTS IN UPSLOPE AREAS OVER WRN MT AND BIG HORNS. GFS APPEARED TO BE ON THE FASTER END OF GUIDANCE WITH QPF..AND THUS ENDED UP BLENDING THE 00Z NAM..UKMET..AND 12Z ECMWF MOST AREAS. ...SRN FL... HIGH MSTR AND MODEST INSTABILITY REMAINING ALONG TAIL END OF COLD FRONT WORKING SEWD ACRS SRN FL WILL SUPPORT SCTD TSTMS ACRS THE REGION TDA. STAYED FAIRLY CONSERVATIVE WITH AREAL AVG AMOUNTS GIVEN RATHER SCTD NATURE OF CONVECTION..BUT LOCALIZED GREATER THAN 1 INCH AMOUNTS ARE PSBL GIVEN MDTLY HIGH PWS ALONG THE FRONT. DAYS 2 AND 3... ...NRN ROCKIES/HIGH PLAINS EAST INTO THE UPR MIDWEST/GRT LAKES/NORTHEAST... A DEEP LYR CLSD LOW AND ASSOCD TROF AXIS IS FORECAST TO MOVE ACROSS THE NRN PLAINS INTO THE UPR MIDWEST LATE SAT INTO SUN...WITH ITS ASSOCIATED SFC REFLECTION LIFTING N OF THE MN BORDER SAT AFTERNOON. STRONG MSTR TRANSPORT AFFORDED BY A 50 KT LOW LVL JET IS EXPECTED TO HELP SUPPORT A BKN AXIS OF LOCALLY HVY SHWRS/TSTMS ALONG AND JUST AHEAD OF AN ADVANCING COLD FRONT. THE MAIN FOCUS SHOULD BE ACRS THE UPR MIDWEST BY LATE SAT...ADVANCING INTO THE UPR GRT LAKES REGION SAT NIGHT WHERE ROBUST UPR JET DYNAMICS/DIV WILL BE IN PLACE AS WELL. MEANWHILE...LGT/MDT DEFORMATION PCPN SHOULD BE LIFTING OUT OF THE DAKOTAS AT THIS TIME. ON SUN...THE COLD FRONT SHOULD REACH THE LWR GRT LAKES REGION WITH THE FRONT TAILING BACK TO THE SOUTHWEST OVER THE OH VLY...BUT ALL OF THE STRONGEST UPR JET SUPPORT/DYNAMICS WILL HAVE LIFTED WELL NEWD INTO ONTARIO. THEREFORE EXPECTING MORE SCT SHWR ACTIVITY AND LIGHTER PCPN AMTS ASSOC WITH THE FRONTAL PASSAGE BY THEN. HPC PREFERRED THE SLOWER SOLNS OF THE ECMWF/UKMET/NAM. GFS IS ON ITS OWN LATE IN THE PERIOD...MOVING THIS TROF MORE PROGRESSIVELY EWD INTO THE DOWNSTREAM RIDGE. ...CNTRL/SRN ROCKIES...SRN PLAINS INTO THE LWR MS/OH VLYS... THE AFOREMENTIONED HT FALLS MOVING ACRS THE NRN TIER STATES WILL ALLOW A COLD FRONT TO MOVE DOWN ACRS THE SRN PLAINS/LWR MS VLY AND NEWD INTO THE OH VLY. HOWEVER...THE MID/UPR LVL FLOW IS EXPECTED TO BECOME PARALLEL TO THE BNDRY AND IN TURN THE FRONT SHOULD SLOW DOWN...AND WILL LIKELY STALL OUT BY LATE SAT OVER PORTIONS OF THE LWR MS VLY/SRN PLAINS AS IT AWAITS THE SRN STREAM TROF TO MOVE OUT OF THE SOUTHWEST. DEVELOPING SPLIT FLOW UPSTREAM WILL ALLOW THIS SRN STREAM UPR TROF TO EVOLVE OVER THE FOUR CORNERS REGION. THESE HT FALLS WILL BEGIN TO HELP INVIGORATE A NEW AREA OF LOW PRESSURE IN THE LEE OF THE SRN ROCKIES WHICH WILL THEN BEGIN DEVELOPING EWD ALONG THIS BNDRY TWD THE WRN GULF COAST BY LATE SUN. A RENEWED HVY RAINFALL THREAT IS EXPECTED TO EVOLVE SUN AND SUN NIGHT INVOF THIS FRONT AS VORT ENERGY EJECTING OUT OF THE BASE OF THE FOUR CORNERS AREA TROF INTERACTS WITH THE FRONT ALONG WITH INCREASING LOW LVL WARM ADVECTION/GULF OF MEXICO MSTR TRANSPORT INTO THE BNDRY. SRLY H85 FLOW OF 40 TO 50 KTS...PWATS RISING TO AOA 1.5 INCHES AND INCREASINGLY DIV FLOW ALOFT WILL BE CONDUCIVE IN ALLOWING AN ELONGATED SW/NE AXIS OF STG CONVECTION AND HVY RAINFALL. THE PATTERN FURTHERMORE IS CONDUCIVE FOR TRAINING/BACK-BUILDING CONVECTION WHICH WILL ALLOW FOR LOCALLY EXCESSIVE TOTALS. AFTER PERHAPS A BRIEF LULL DURING THE LATE MORNING HRS ON SUN...EXPECT A REPEAT SUN AFTERNOON/EVENING...WITH CONVECTION DEVELOPING A BIT FURTHER TO THE W AS STRENGTHENING NELY FLOW N OF THE BNDRY BEGINS TO PULL DEEPER MOISTURE ACROSS ERN INTO CNTRL TX. WILL CONTINUE TO MONITOR...BUT THE THINKING REMAINS 3 TO 5 INCHES OF RAIN COULD FALL ALONG AN AXIS FROM NEAR THE RED RIVER VLY NEWD THROUGH CNTRL AR AND POSSIBLY INTO FAR SERN MO THROUGH LATE SUN INTO EARLY WITH ISOLATED HEAVIER AMTS POSSIBLE. AMTS OF 1 TO 3 INCHES WILL BE POSSIBLE FARTHER NORTHEAST INTO THE LWR OH VLY AS FORCING AND MSTR TRANSPORT WILL BE INCREASING BY SUN EVE. ECMWF HAS TRENDED SLOWER OVERNIGHT...PUTTING IT IN GOOD AGREEMENT WITH A THE GROWING MODEL CONSENSUS TWD A SLOWER SOLN. SULLIVAN/PEREIRA GRAPHICS AVAILABLE ON THE WEB AT WWW.HPC.NCEP.NOAA.GOV 24HR QP VT 30/12Z 0.01 560932 557923 552916 547914 543915 541917 529927 526921 520915 502898 497895 491895 477896 446904 434899 430902 426904 422904 411902 403901 400908 397914 397921 403935 408953 407962 405969 400984 394997 387009 383022 381030 379035 375040 373042 372047 372050 378056 383060 384064 384075 385080 387083 391087 395087 398087 401090 402092 402097 400102 394109 393111 393116 394120 396121 399123 401126 405130 408129 411129 411133 410143 402151 401157 404159 408159 410161 413165 415172 417174 420174 424169 431168 430163 427157 428152 428147 429143 431143 433148 435156 440164 444169 446174 442193 446195 451196 455191 455187 459181 461178 460173 457169 459166 461165 466165 471169 479172 483177 485184 486190 486196 484200 482202 477207 471210 464213 458213 452213 444212 438214 435213 431215 426218 422224 420229 422235 423238 422241 423246 426248 432249 439248 444248 452247 459245 464241 466239 467235 466233 465230 467227 469225 472227 485233 494241 498245 502243 502237 501232 499228 494221 494216 496211 499205 503196 508198 514195 517195 520192 523188 527181 528176 528170 527160 527149 525142 523133 522127 523120 524113 525107 526097 526084 524077 516063 522044 524035 528028 532023 535017 553992 556986 559983 561979 561975 560964 558943 560932 0.01 490660 487653 483651 477652 472655 466660 461665 459668 456671 455676 453688 451694 447701 440712 437715 432718 425723 422728 418740 415753 415764 415767 413769 408773 398782 381797 373805 370810 367816 367822 368829 371836 373838 376839 379837 382834 390824 396816 399812 404808 418827 422829 428828 434826 436823 442812 440805 436801 435797 438792 443784 451772 460762 464758 469755 475750 480745 486740 488736 490727 489721 487711 482704 479702 476698 473696 474692 477687 481682 483678 488667 490660 0.01 479239 478238 476234 473237 475241 478240 479239 0.01 427100 427099 424096 421093 420091 420088 418084 415085 413087 412088 411091 412093 413095 415099 418101 421101 424100 427100 427100 0.01 297795 296785 293782 290782 284782 278781 265780 254789 246800 243806 242811 242819 245822 248820 251818 257822 266825 271826 275824 281819 290810 297799 297795 0.25 544952 543947 539942 528943 519943 511947 508952 505958 501968 492975 486977 483980 483985 484989 484994 483998 478007 475010 472016 471021 471029 473033 478037 482038 488038 497034 505027 511020 518011 523000 527991 532979 538969 541964 543959 544952 0.25 505146 505140 503137 499131 490121 487116 485107 483101 479098 475096 472095 467098 463100 459098 456093 455088 457085 458080 458069 458064 456060 452056 449056 442056 437060 434065 432068 433071 435073 438075 441076 447081 451085 452088 451090 449092 444095 440097 437100 438104 449108 454110 458110 460116 463122 471132 475137 480140 486143 492147 499148 505146 0.25 484944 483940 480935 473930 465928 458928 448932 441935 437938 435942 431948 427957 421965 417973 414981 413986 413994 416999 419000 424999 427997 433990 440984 446979 462971 468964 474957 480950 484944 0.25 417115 414113 412113 409112 406114 406118 408119 411119 414118 414117 417115 0.25 417064 415061 412061 410061 407061 404061 401062 398063 397064 396068 397072 398075 401074 404073 407075 410075 412073 414072 415068 415067 417064 0.25 272800 268795 264793 262794 257796 254798 252802 252807 252808 256812 259815 263816 264816 264811 266807 269804 272800 0.50 529971 530963 528956 523952 519953 517955 512961 503976 494987 490997 486005 478020 480026 482029 486031 490031 495029 497027 502022 508016 513009 521995 525986 528976 529971 0.50 476120 476116 476113 475111 474107 473105 470104 468106 467110 469115 470117 472118 474120 475121 476120 0.50 462954 461949 457947 451945 446947 438953 432960 425969 422973 421978 422986 424989 426986 433980 438978 442974 450969 460964 461958 462954 0.50 452076 451072 450071 449068 447066 444064 441066 440068 441070 442072 444074 447076 450077 452076 1.00 520982 520977 516975 512977 510979 506986 501995 498002 494009 489014 489019 493020 498016 504010 509003 512998 517988 520982 24HR QP VT 01/12Z 0.01 554908 554898 552890 551883 548877 547869 545865 542858 539852 535840 533835 530831 518822 503811 497808 488807 475807 468807 465807 460810 450813 440819 432818 424816 418813 412809 405806 402806 398808 392812 387818 378833 361862 341886 335893 334896 334901 331917 329924 324928 320930 316930 313923 309921 305922 298926 295928 293932 291939 291945 293948 297954 296957 297962 295972 295980 294983 295989 299993 304991 306988 311981 314980 315982 316001 317003 321005 325001 330995 338993 343993 346990 352983 356977 359968 363959 368955 372948 377942 391934 399930 403931 405936 404943 407947 411949 426951 431952 433953 439959 446957 455956 459957 462959 463963 461967 456973 451981 450986 450990 448994 446998 443001 438002 435004 428009 424017 424023 426027 429028 429031 426037 419041 415044 412048 409051 404051 400050 398046 396042 392040 382039 377036 372030 369026 369019 369012 368006 366004 363006 360014 351044 350050 350056 352062 355065 357068 360071 367068 372075 374084 387087 386083 389083 392083 395087 400086 404086 407091 405097 402103 400109 398110 396114 397117 404116 410117 415118 422113 431109 438108 442107 446109 448110 452109 455105 456102 459089 462082 462078 463049 465046 468046 472052 477059 481061 485060 485058 483054 479044 476038 476034 481028 496022 506018 513015 520010 525004 533996 537988 542979 547969 550959 553950 556939 555925 554910 554908 0.01 480639 476627 474621 471617 464619 461624 457627 445637 440643 439652 441660 446664 444682 443685 445688 447689 454690 459687 464684 475685 479681 480679 479673 476668 468659 474656 479650 480639 0.01 538206 539201 539195 537188 532177 531167 532158 532150 530146 530140 526128 525113 524107 523101 523096 526092 526087 524082 518072 514068 510066 505064 502060 499058 494061 491065 488072 483075 478074 476075 475079 477085 479094 477098 475098 471098 467098 464102 464107 467111 467117 468122 466124 463121 458122 451130 436124 431128 428132 422140 417148 416151 416156 417158 419158 431157 434161 436166 444171 447176 450178 453179 456176 457171 457168 459168 463169 467174 473175 477178 479182 482185 485185 522204 525209 528212 531212 538206 0.01 487219 486214 485213 482212 479212 478212 476213 473215 475219 478219 481221 483222 484223 487219 487219 0.01 463221 463220 461217 458217 454218 454219 457220 458224 459225 461224 463221 463221 0.01 267792 265790 260789 255791 247798 242804 240813 242821 244824 249824 253821 257824 260825 266824 268821 267815 265809 265803 268795 267792 0.25 540918 539911 537903 536898 535893 533888 526880 523878 519874 511865 508862 506858 505845 503841 500836 496831 492828 485826 476824 466824 463824 461827 459834 458844 458856 456870 455875 450879 442884 438889 437893 436898 435907 434912 436917 442925 448931 456936 466939 473943 476948 478956 479972 476984 474997 472005 476010 478012 484013 490013 496011 504007 512001 520992 526982 531972 535959 537944 540930 540918 0.25 473158 472154 470152 469149 468147 465145 462145 459147 459148 459150 459152 461156 464157 467158 470160 473158 473158 0.25 402846 401842 397841 391843 387845 380851 363873 359880 354886 349891 344894 340901 338908 335922 327948 326959 328968 334973 337973 341971 350961 356949 363936 369924 378911 386899 392886 396872 400857 402846 0.25 378050 375047 375046 373043 372041 370040 369038 366037 365040 365043 365047 366049 367050 369053 372053 375053 378050 0.50 531936 532928 531920 530913 527907 523901 519896 509885 504878 499870 497864 496857 494853 492850 486848 483847 478850 477860 475867 469884 465887 460886 455887 450890 445896 443902 445909 448917 453922 458925 465929 471931 480932 484935 489944 490950 488957 488965 489970 491974 492981 491986 488995 490000 493002 495003 498002 509993 513990 515988 520981 523977 523971 527964 530956 531941 531936 0.50 390874 390865 387859 384859 381860 376864 369870 361879 355887 350895 343904 339915 336924 334935 332946 331953 333960 337964 341963 348955 353947 358938 368918 379900 384891 388882 390874 1.00 520939 518930 517925 514919 510916 507919 504925 503930 502939 502944 503948 507952 512954 515953 517950 519944 520939 1.00 488884 487883 485885 485886 488885 488884 1.00 382873 380870 378872 376876 372877 367881 362886 358892 348905 343912 340920 336936 335946 336949 339953 342953 344951 349944 356931 363915 372902 375893 377885 379878 382873 1.50 368896 363894 357901 353904 349908 345916 342924 339935 339939 343941 350933 355925 359916 364909 368900 368896 2.00 359909 358909 355910 354911 353913 350914 350915 348918 348919 349921 351919 352918 354918 356914 358910 359909 24HR QP VT 02/12Z 0.01 537853 535840 534826 529818 524811 516800 512796 507794 494788 492788 489786 485775 482768 480763 481758 483754 484746 485742 486737 486734 484732 482731 477733 471735 449754 434761 428764 422762 416759 410759 405760 401762 395774 389781 385787 376809 362832 360837 356843 350855 327897 322906 315917 308927 301937 288957 276974 258986 252990 250995 248997 250000 256002 266006 271009 275014 279017 284019 289021 293022 302023 310022 322019 332011 335999 339994 344990 352980 357976 364973 377972 379970 378965 378959 380955 387945 398921 407893 411882 413875 416870 422858 430844 436831 440830 446830 452831 458833 469839 477852 484860 488866 487873 487883 486894 483912 482928 481933 481939 482949 482954 483957 489961 492964 495964 499963 506962 510959 516953 522947 525939 527931 526923 527916 532903 535899 536894 537890 538884 538881 537872 537862 537853 0.01 510284 513276 514266 515257 514252 508241 506235 503231 500232 497236 496240 495245 491243 487241 483245 482253 484259 483264 485268 487274 489279 495282 503287 506287 510284 0.01 524092 525087 523084 521081 517078 514074 512071 509065 508061 508055 509050 506048 502046 499043 491023 489019 485015 478014 471018 464023 459022 456019 449017 439019 431015 428012 425013 426022 431030 435036 438043 436051 432056 433063 435066 439075 440079 440083 439086 433089 427091 425094 425098 426100 428104 428111 431113 440114 443117 447117 452118 455118 458114 464115 466118 469118 473115 476113 479107 482099 485089 488085 491086 500088 507092 512096 517099 521097 524092 0.01 409064 408059 407057 403053 395044 390040 386038 379036 374033 369030 368026 367017 367009 372997 371995 370993 366993 362996 358999 355004 353009 351017 348023 346027 344034 346043 344050 343056 343061 342065 345071 349074 354076 357077 361077 366081 369085 375094 379097 383095 386094 395086 399080 404076 409064 0.01 392120 391119 388117 386116 386115 385116 383119 382121 382123 381126 382128 385129 388127 390124 391122 392120 0.01 265809 262804 260802 257799 255798 252799 248803 246805 244808 242812 241817 242822 244824 247823 249819 250815 253811 259812 262811 265809 0.25 472809 469807 468806 465805 462806 459808 458812 459816 462819 465820 468818 470815 472809 0.25 442795 440791 437790 431789 419792 412793 406793 402790 396791 391796 387802 385815 382821 379827 372836 364848 359858 354869 349880 342892 336901 323921 312941 307951 301961 293970 291974 291981 294987 298990 309987 317985 323986 328985 332983 342976 350968 365948 372939 374933 377927 378919 381912 384901 389888 396877 403865 407854 418828 424819 431811 438803 442795 0.25 381065 381058 381050 375047 371047 366048 360051 358054 358057 362061 363066 367068 372071 375079 379079 380074 380068 381065 0.50 418811 417807 415805 413805 410806 404808 400808 397807 394809 391814 387823 363859 354878 350888 344896 337905 332913 322931 317940 313948 309958 304968 300977 300981 303983 310982 314980 319978 324979 327978 333975 341970 348963 354954 364937 369928 374917 378906 380896 384886 390874 396865 401856 409835 415822 417815 418811 1.00 391839 387842 382845 378849 373854 369860 363873 357887 350898 341910 327931 323939 321944 317958 315964 313969 316971 324970 329967 340959 345954 350947 357937 360931 363923 372895 377882 383869 386860 387854 391839 1.50 377867 378863 375862 373864 372865 371868 370869 369872 368876 368880 370880 372877 375873 375871 377868 377867 1.50 363905 364900 362897 356898 349905 342915 335925 331934 329940 328948 329952 330954 336953 340951 344947 348942 351936 354925 359915 363905 2.00 349919 348919 346919 345920 343921 341924 340925 338927 337929 336932 336933 335936 335940 338942 340940 342938 343937 344934 345933 346930 347927 348923 349920 349919 $$