QUANTITATIVE PRECIPITATION FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 549 AM EDT SAT APR 30 2011 FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION VALID APR 30/1200 UTC THRU MAY 03/1200 UTC REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR DAY 1... 06Z UPDATE... BASED ON TRENDS OF 00Z ECMWF AND SATL..HAVE ADJUSTED COMMA HEAD BAND WWD ACRS WRN ND AND SLOWED COLD FRONTAL PCPN BAND PROGRESSSION ACRS MN FROM PRELIM GUIDANCE. ACRS THE SOUTH...MADE A SLIGHT SWD ADJUSTMENT TO HEAVIER QPF AXIS BASED ON 06Z ECMWF AND 06Z GFS..WITH MANUAL QPF A COMPROMISE BETWEEN THESE AND THE MORE NRN 00Z UKMET/CAN GLOBAL. ...CNTL/SRN ROCKIES INTO THE SRN PLAINS/LOWER MS AND OH VALLEYS... NRN PORTION OF SPLIT TROF WILL HELP PUSH A COLD FRONT ACRS THE MIDWEST INTO THE SRN PLAINS WHERE IT WILL STALL IN RESPONSE TO PRES FALLS IN ADVANCE OF SRN PORTION OF TROF LEFT BEHIND THAT WILL MOVE SLOWLY TOWARD THE 4 CORNERS REGION BY SUN MRNG. THIS WILL ONCE AGAIN ALLOW FOR THE SET UP OF A FAIRLY SIGNIFICANT HEAVY RAINFALL EVENT THAT SHOULD EVOLVE FAIRLY QUICKLY SAT NIGHT OVER SOME OF THE SAME AREAS THAT RECEIVED EXCESSIVE RAINS EARLIER IN THE WEEK. MODELS ALL SHOW RAPID RETURN OF GULF MSTR WITH PWS INCREASING TO OVER 1.5 INCHES SAT NIGHT ALONG THE BNDRY FROM THE RED RIVER ENEWD INTO WRN KY/WRN TN. UPR LEVEL WINDS ARE FCST TO BECOME INCREASINGLY DIFFLUENT OVER THE FRONTAL BNDRY..WHILE SUFFICIENT DAYTIME HEATING WILL SUPPORT INCREASINGLY UNSTABLE CONDS TO SUPPORT CONVECTIVE DVLPMENT LATER SAT INTO SAT NIGHT. WITH UPR LEVEL WINDS FCST TO BECOME PARALLEL TO THE SFC BNDRY..THE THREAT OF TRAINING WILL BE FAIRLY HIGH ESPECIALLY THROUGH PORTIONS OF SE OK..AR INTO WRN TN/WRN KY. WITH THE EXCEPTION OF THE UNUSUALLY DRY NAM WHICH APPEARS PARTICULARLY DRY ABOVE 7H BY 30 HRS COMPARED TO MODEL CONSENSUS ACRS THE REGION..THE REMAINING DETERMINISTIC MODEL RUNS ALL PAINT FAIRLY HEAVY RAINFALL AMOUNTS OF 1 TO 3 INCHES ON AVG ALONG THE BNDRY. THERE ARE ONLY SLIGHT DIFFERENCES IN THEIR AXES OF HEAVIER RAIN WITH THE 4KM WRF ARW THE MOST SRN OF ALL MODEL SOLNS WITH LOCAL AMOUNTS UP TO 8 INCHES. LEANED CLOSE TO IN HOUSE BIAS CORRECTED ENSEMBLE MEAN FOR THE AXIS OF HEAVIER RAINS THOUGH INCREASED MAGNITUDE OF HEAVIER RAINS SLIGHTLY. THIS SOLN APPEARED TO BE A GOOD COMPROMISE GIVEN ONLY MINOR SYNOPTIC SCALE DIFFERENCES. FARTHER W..MAINLY LIGHT PCPN AMOUNTS EXPECTED THRU THE ROCKIES..WITH BACKING MID LEVEL FLOW SUPPORTING SOME ORGANIZED OVERRUNNING PCPN DVLPG THRU SRN CO INTO NE NM SAT NIGHT..SOME OF WHICH WILL FALL IN THE FORM OF ACCUMULATING SNOW. GFS/UKMET/NAM AMOUNTS APPEARED VERY SIMILAR HERE AND LOOKED REASONABLE. ...NRN PLAINS/UPR MS VALLEY... DEEPENING STORM SYSTEM ACRS THE NRN PLAINS WILL MOVE SLOWLY NEWD INTO SRN CANADA BY SUN MORNING. MODELS SHOW FAIRLY GOOD AGREEMENT HERE IN DEPICTING SOME .50 INCH RAINS WITH ASSOCD COLD FRONT AS IT PUSHES INTO THE WRN GT LAKES REGION..AS WELL AS DEPICTING SOME ADDITIONAL .50 INCH AMOUNTS WITH WRAP AROUND/COMMA HEAD BAND ACRS NRN ND. STAYED CLOSED TO MODEL CONSENSUS AMOUNTS. DAYS 2 AND 3... ...SOUTHERN PLAINS/LOWER MS VLY NEWD TO THE NORTHEAST... ADDITIONAL PERIODS OF MDT/HVY RAINS ARE EXPECTED ALONG A STALLED FRONTAL BNDRY EXTENDING FROM THE LWR OH VLY BACK INTO THE LWR MS VLY/SRN PLAINS. A COLD FRONT PUSHED EWD BY A DEEP NRN STREAM LOW/TROF LIFTING ACROSS THE NRN PLAINS/UPR MIDWEST WILL STALL ACROSS THE SRN PLAINS/LWR MS/OH VLYS AS THE FLOW ALOFT BECOMES PARALLEL TO THE BNDRY. THIS FRONT WILL BE THE FOCUS FOR MDT/HVY RAINS...PARTICULARLY FROM NERN TX/SERN OK ACROSS AR AND INTO SWRN MO AND THE LWR OH VLY SUN AFTERNOON/EVENING AS STRONG SLY INFLOW OUT OF THE WRN GOMEX HELPS TO MAINTAINS PWS AOA 1.5 INCHES ALONG THE BNDRY WHILE MID LVL ENERGY AND FAVORABLE UPR JET DYNAMICS WORK TO ACCENTUATE LIFT ALONG THE BNDRY. FLOW WILL BE CONDUCIVE TO TRAINING CELLS...FURTHER BOLSTERING THE POTENTIAL FOR HVY AMTS ACROSS THIS REGION. BNDRY SHOULD BEGIN TO ONCE AGAIN PROGRESS SEWD AS A SRN STREAM TROF OVER THE SOUTHWEST BEGINS TO MOVE ACROSS THE SRN ROCKIES INTO THE SRN PLAINS ON MON/EARLY TUE. THIS SHOULD BEGIN TO SHIFT THE FOCUS SLOWLY TO THE SE AS WELL...BUT NOT BEFORE ADDITIONAL MDT/HVY RAINS FALL ACROSS THIS SAME AREA LATE MON INTO EARLY TUE. OVERALL...AN ADDITIONAL 2-5 INCHES WITH LOCALLY HEAVIER AMTS IS EXPECTED FROM SUN MORNING INTO TUE MORNING FROM NERN TX/SERN OK TO THE LWR OH VLY. GIVEN THE ANTECEDENT CONDITIONS AND THE EXPECTATION FOR HVY RAINS ACROSS PORTIONS OF THIS REGION ON DAY 1 AS WELL...THERE IS A CONCERN FOR FLASH FLOODING FOR BOTH DAYS. FURTHER TO THE NE...UNDER THE INFLUENCE OF THE HEIGHT FALLS ASSOCIATED WITH THE AFOREMENTIONED LOW LIFTING INTO AND MOVING ACROSS CAN...FRONT SHOULD BE A BIT MORE PROGRESSIVE. WHILE AREAL AVGS ARE NOT EXPECTED TO REACH THOSE FORECAST TO THE S...ENERGY AND MOISTURE RIDING NEWD ALONG THE BNDRY SHOULD HELP PRODUCE WIDESPREAD LGT/MDT AMTS ACROSS THE UPR OH VLY INTO THE LWR GREAT LAKES/NORTHEAST AND NRN MID ATL STATES. THE NAM MOVES TO THE SLOW SIDE OF THE GUIDANCE WITH RESPECT TO THE TROF MOVING OUT OF THE SOUTHWEST. OTHERWISE...MODEL MASS FIELDS WERE IN GENERALLY GOOD AGREEMENT THROUGHOUT THE PERIOD. DIFFERENCES IN THE FINER DETAILS WERE ADDRESSED WITH AN ENS APPROACH. ...PACIFIC NORTHWEST TO THE NORTHERN ROCKIES... SOME OROGRAPHICALLY FOCUSED LGT AMTS ARE EXPECTED LATE MON INTO EARLY TUE AS A WELL DEFINED...BUT MOISTURE DEPRIVED SHRTWV TROF AND ITS ASSOCIATED FRONTAL BNDRY MOVE ACROSS THE REGION. SULLIVAN/PEREIRA GRAPHICS AVAILABLE ON THE WEB AT WWW.HPC.NCEP.NOAA.GOV 24HR QP VT 01/12Z 0.01 567940 565923 563907 559894 554881 546865 536848 531841 527837 514826 508821 505819 500818 491816 483816 469814 461814 451813 439812 432812 425809 412805 406803 402804 398806 391814 385821 379829 375838 373843 368850 365858 361866 354878 346891 339902 331916 326922 319929 312932 303933 296932 293935 292938 290947 288950 289953 289959 290967 291973 294980 298985 301986 306985 311982 317979 317984 314993 311003 314014 320012 328008 333005 344992 349988 353981 360969 364964 369959 379948 391937 399929 405930 406932 405937 405943 408947 411949 429953 440957 453964 457966 460971 458978 455987 453993 451994 448998 444000 440001 436003 430007 425013 423019 425026 429030 428034 425037 421040 418041 410048 406049 402047 391041 384036 380032 375024 372018 370015 366012 361013 357016 352024 350034 351039 352044 353052 355058 359061 364061 367065 374078 379082 384083 391083 396083 399084 415083 420083 422085 423091 422097 420099 417097 414094 409092 403097 399103 392109 389113 388116 391120 399121 418125 432116 441114 446113 450110 452106 453100 455088 462076 458070 456068 454062 457059 462055 471055 479054 487050 493049 502045 508039 513030 523015 529005 533997 539990 544982 549977 552972 557962 563950 567940 0.01 475674 472662 470657 466655 459654 457650 453639 447635 441636 439635 436631 431630 427636 421644 417652 416657 417662 420667 431677 433683 436687 440689 445687 448685 452682 456680 461682 467681 474679 475674 0.01 530189 531182 531174 529170 529164 527159 524156 521148 518143 515140 509133 496123 483115 478109 473099 469099 464101 462111 469128 470134 467139 462135 457132 452133 448138 449141 448146 443145 441141 437139 434142 433147 433154 436161 441168 448173 459164 461165 464168 467170 472172 480177 484177 489176 491174 496166 498162 503162 508165 503171 501175 502179 504183 510189 518194 522195 527194 530189 0.01 512086 511080 509074 506071 500068 497067 491068 488068 485072 482077 480081 479085 479090 482094 485097 491098 496098 502097 507095 511091 512086 0.01 487219 486214 485213 482212 479212 478212 476213 473215 475219 478219 481221 483222 484223 487219 487219 0.01 463221 463220 460219 457219 454218 454219 457220 458224 460225 461224 463221 463221 0.01 272800 271794 269791 261788 257789 255791 246798 243805 241809 241813 242821 244824 249824 257823 266819 265813 266809 267805 271803 272800 0.25 548935 547930 543923 536915 529905 520896 512886 507878 504873 500869 495864 494854 490846 486842 479837 474836 468836 465837 462841 460847 461853 462858 466861 464866 461869 456875 449885 446888 444891 444895 445898 446906 445912 442917 439922 439926 441930 447939 450943 454946 462950 467953 471956 478967 481971 483979 482986 480994 477001 476007 469017 466021 464027 464032 466039 472042 476042 482042 487040 496035 500031 505026 512016 518005 523994 529983 537971 542963 545955 548943 548935 0.25 388852 387848 384847 380851 372861 364872 356884 350894 343906 333928 328939 326945 326950 328955 330961 332969 331978 333981 337983 344979 348975 353964 359952 363940 370928 372922 373913 379903 385891 388883 389877 390870 389859 388852 0.25 395061 393057 389056 384051 381046 376039 372034 369032 366032 363039 364044 367051 371052 375053 381057 386061 392063 395061 0.25 255807 254805 251806 251808 252809 255808 255807 0.50 530956 531949 531941 529936 526934 521932 516926 511921 506918 493918 486916 481913 477911 469909 462909 455912 450915 452923 456930 460935 463942 469946 478955 489964 492973 493979 492984 490993 489002 487014 484019 481024 478029 478033 479037 482037 486035 492032 496027 505016 510010 514002 521988 527971 530956 0.50 384872 382865 380862 377862 374864 371868 365876 359884 353893 348902 338922 334930 332935 332942 336967 338974 343975 346971 349965 352955 355943 359934 364925 369915 372906 380885 383877 384872 1.00 516969 516967 515964 512962 510963 507966 505971 504972 504976 502981 501986 503990 506991 507989 509988 511984 511983 513979 514978 515974 516970 516969 1.00 376879 375874 371876 365882 361887 356895 351901 348909 340922 337930 336933 335940 335946 337950 338956 339962 340967 344966 345962 349945 352938 356929 363915 369899 375883 376879 1.50 366900 367893 365890 363890 361891 358895 352904 348912 343920 340928 337938 338942 341944 344946 346943 351933 355926 360918 364908 366900 2.00 364901 361894 358899 354904 350911 348916 343924 345931 350929 353925 357920 360913 363905 364901 3.00 355914 357911 356908 354909 353911 352915 354917 355914 24HR QP VT 02/12Z 0.01 535879 534868 532859 529853 526843 519827 511816 502804 500798 502794 506785 506777 506771 504767 499762 494758 492755 494749 500735 502733 502728 499719 496719 492721 486725 458744 443754 436758 431763 427769 423771 417774 411774 400771 394771 391773 389777 385783 380789 378802 375814 370827 365836 360847 354859 349869 338894 326914 315932 309942 302950 297960 289970 286975 284977 284982 284988 285996 287000 291002 296013 299017 301019 304019 320018 334017 345010 348006 351999 352995 346993 347988 350984 356975 361970 365967 374959 383950 389943 392937 397925 400919 403912 410890 421867 428854 431848 435844 441842 449842 455843 461846 469852 479857 483860 489865 490884 489893 485900 479914 475920 473929 471947 473957 474963 478969 482975 488979 492983 497986 502986 510984 515978 519972 521963 531931 535920 537914 537908 536889 535879 0.01 520274 520268 519264 518255 516248 514242 511239 507238 502238 498242 492244 485243 483244 480248 477253 476256 472258 468259 463264 460273 461279 464282 468286 475291 489296 496297 501296 506294 511289 515286 0.01 519091 505054 498034 493026 490023 484024 473032 468031 464029 458025 449022 441019 432019 428019 423021 418025 420030 422033 424036 424041 420037 417034 413033 409034 407040 404047 401049 398050 393046 386043 384042 381037 377030 375020 376011 376005 378000 378996 381992 380985 374986 370995 367002 364011 363023 355034 352041 348048 342054 339061 339068 341072 345080 347083 350082 358081 366081 369082 372086 378089 384089 387087 400075 414068 418064 424067 433068 434072 435079 434082 431082 427080 422083 418092 416096 415103 418111 423116 430121 432124 433131 459131 460140 463140 465136 468134 472133 476133 478129 478119 477106 479098 481094 482090 485085 490085 494087 497090 499093 503093 508095 512096 516095 519091 0.01 414118 414114 411110 409108 406107 402110 397112 393113 388114 385116 382121 382126 385126 388125 391122 396120 398121 402122 407121 411119 414118 0.01 275798 273795 268794 262794 257796 251799 247802 245806 243812 243823 244828 245830 248831 253829 257834 261836 267837 270837 271832 271829 272826 277822 277816 273810 273807 276802 275798 0.25 482804 478797 473793 471791 472787 469782 464778 461777 457778 448781 440783 432787 428789 420791 413790 407790 402793 399796 396802 392808 388816 383828 375840 367852 359866 347889 340901 333915 322937 316950 309962 303973 302975 303978 307983 309984 315986 323985 328986 333986 337984 353965 362955 371943 399890 410866 417852 426836 434826 444815 448812 452810 454811 456815 457821 461827 465831 469833 474831 477826 478820 478810 482804 0.25 386068 385064 381064 377063 372061 369054 369050 366049 361051 355054 352059 355065 358069 361070 369069 375072 379073 382072 386068 0.50 426807 424804 419803 411801 405802 400807 394816 390824 386834 381843 378848 373853 366859 362867 351886 342902 334919 325937 317957 314963 313968 313974 315977 321979 331979 336977 338975 344969 351961 358952 369937 379919 388901 397881 401872 405862 410853 414841 421825 425816 426807 1.00 403826 401824 399828 395834 387850 377861 369865 365871 357885 348898 341911 335924 329938 323952 321959 321966 322969 325970 331970 335968 340965 346959 356947 363935 370921 377908 385893 391878 393871 396861 398856 399846 401837 403827 403826 1.50 387871 385867 380870 373877 364884 357892 346909 340918 335926 331936 327948 326952 326959 328963 330964 333964 341959 349951 354942 359932 369914 374905 379894 386873 387871 2.00 371899 370897 367898 360900 352909 345917 337925 333937 330948 330956 331958 334958 342951 349943 356931 361923 366911 371899 371899 3.00 350926 349925 346925 344926 343928 341929 340932 339933 338936 337937 337939 337943 338943 341942 343940 345937 348934 348933 350929 350928 350926 24HR QP VT 03/12Z 0.01 505673 503668 499667 494665 492664 492661 491657 489654 486653 484654 478659 471665 465669 459678 456684 454692 454700 451708 446714 438719 433722 429723 418723 414716 411715 408718 404722 403728 400736 395740 393743 392747 392753 391758 389761 385767 383774 382780 375802 374808 370813 365817 360822 355825 349830 343843 339854 332865 327870 324874 319879 306884 302887 298892 294903 294907 296909 299909 303908 308909 311914 309919 306923 299929 296932 290935 271947 249961 241968 238969 237972 239978 242987 244999 247013 246019 246024 251024 255023 258016 261010 266008 273005 277009 279013 281016 287017 297020 310020 323021 331021 334021 337018 347009 356000 360995 362991 364980 362976 362972 364966 369955 375942 377936 379930 383923 385915 393892 399868 404857 410845 416832 422828 428823 434819 441813 453806 463799 472789 483777 488765 496751 499743 503733 505725 507717 508708 506698 504695 504691 505684 505673 0.01 536221 537212 538202 538191 536185 533180 528173 525167 522163 514156 511152 506146 501144 494141 486133 483129 478127 475127 472125 469122 465119 462119 457120 454121 446128 440135 433144 432151 435154 439158 441165 442171 445175 446179 444183 443187 444193 444199 446201 451201 454197 461188 464186 471187 476190 475198 472204 468208 460211 451214 446216 442219 442223 443225 450226 455230 456232 445235 441239 442244 445252 448256 451260 456262 466264 474265 479270 489279 497286 503290 509291 512290 514286 517279 518272 519264 518251 519241 521235 536221 0.01 416002 416994 413993 409994 404996 398001 394006 393013 391021 389029 385034 380037 366035 360037 356040 350043 342044 338048 335053 334057 335061 338068 337072 338075 341082 347084 351084 355082 359081 364077 369075 378074 381075 385073 390070 392068 395068 401069 404066 407060 411053 408052 404051 401045 400038 407026 412014 416002 0.25 498721 497714 494709 489707 484706 479707 472711 463718 453729 448737 445742 441744 434743 427744 421746 416751 411758 405768 400778 394797 389812 383819 377826 365841 360848 354857 348870 343877 339883 332892 330899 329906 328911 325918 317931 307944 298957 294965 290974 296976 295981 298986 303986 308990 313997 320999 326998 331995 338991 342987 346980 351973 355965 371932 377917 383899 389880 392870 394857 398841 400831 404823 414805 423798 429789 433782 436775 438772 441771 445771 452773 457774 463773 468770 474765 482756 489747 492741 495733 498721 0.25 524197 522192 520187 516181 513177 510174 504172 500173 495175 494180 497185 500188 505192 509193 513197 519201 520201 522201 524197 0.25 511270 512266 513262 512254 508240 507236 504229 500219 494210 489207 483208 476213 473219 474224 479229 485231 491233 493237 498246 499260 500268 503271 506273 511270 0.25 479239 479236 477238 478240 479239 0.50 486725 480724 473726 470728 466732 461738 456746 452753 458759 464759 470757 474754 478750 482744 484740 485735 486725 486725 0.50 507254 507249 505244 505242 502241 501242 501247 503251 504253 506255 507254 0.50 496222 493219 490217 488215 484216 483218 484219 487221 490222 492223 496222 496222 0.50 386856 385846 384841 381837 378837 376839 373842 368848 360860 357867 351874 347880 345885 338901 326928 323935 319939 315946 312954 309959 309962 312964 315964 317968 320976 322985 326989 332986 338980 347969 350964 354956 367929 374914 379896 383884 386875 386864 386856 1.00 369874 367873 362874 355879 351885 347895 341908 334923 330941 330948 331961 332964 336966 343961 348955 353947 356941 359933 365915 367909 369899 368888 370877 369874 1.50 362909 362902 360895 360892 358890 354893 350901 346909 342917 340921 339928 337936 338947 341950 344950 347948 350940 349934 351929 355925 357921 360913 362909 $$