Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 301929
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
327 PM EDT THU APR 30 2015


PRELIM DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION
VALID MAY 01/0000 UTC THRU MAY 04/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR

DAY 1

CENTRAL APPALACHIANS INTO THE MID ATLANTIC

MODELS ARE SIMILAR IN TRACKING A WELL DEFINED CLOSED LOW
SOUTHEASTWARD FROM THE LOWER LAKES THIS AFTERNOON---INTO THE UPPER
OH VALLEY THIS EVENING AND THEN EAST SOUTHEASTWARD ACROSS THE
SOUTHERN APPALACHIANS TONIGHT AND INTO THE SOUTHERN MID ATLANTIC
FRIDAY.  SHOWERY CONDITIONS WILL PERSIST AHEAD OF THIS CLOSED
LOW---INITIALLY FOCUSED INTO THE UPSLOPE AREAS OF THE CENTRAL
APPALACHIANS WHERE SLOW MOVING CELLS CURRENTLY ARE PRODUCING
LOCALLY HEAVY RAINFALL AMOUNTS.   SHOWER THREATS WILL EXPAND
SOUTHEASTWARD INTO THE SOUTHERN MID ATLANTIC FRIDAY--BUT ALSO
REDEVELOPING OVER THE CENTRAL APPALACHIANS IN AN AXIS OF RELATIVE
INSTABILITY.  MODERATE TO ISOLATED HEAVY RAINFALL AMOUNTS ARE
POSSIBLE ACROSS THESE AREAS--WITH ISOLATED RUNOFF ISSUES POSSIBLY
EXTENDING INTO THE EARLY PORTION OF THE DAY 1 PERIOD FROM SLOW
MOVING CELLS OVER AREAS OF RELATIVELY LOW FFG VALUES IN THE
VICINITY OF THE CENTRAL APPALACHIANS.

EASTERN PORTIONS OF THE NORTHERN PLAINS---UPPER MS
VALLEY---SOUTHWESTWARD INTO THE LEE OF THE CENTRAL ROCKIES

A WEAK AND WEAKENING FRONTAL BOUNDARY FORECAST TO PUSH EASTWARD
THROUGH THE NORTHERN TO CENTRAL PLAINS AND SOUTHWARD IN THE LEE OF
THE CENTRAL ROCKIES DAY 1.  THE FAST MOVEMENT AND WEAKENING NATURE
OF THE FRONT SHOULD KEEP PRECIPITATION TOTALS ON THE LIGHT TO
LOCALLY MODERATE SIDE ACROSS THE NORTHERN TO CENTRAL PLAINS.  POST
FRONTAL UPSLOPE FLOW MAY ENHANCE PRECIP POTENTIAL IN THE LEE OF
THE CENTRAL ROCKIES WHERE MODEL CONSENSUS IS FOR AREAL AVERAGE
MODERATE AMOUNTS.

DAYS 2/3...


...GREAT BASIN/ROCKIES...

SHORT WAVE ENERGY TRACKING ACROSS THE GREAT BASIN AND CENTRAL AND
SOUTHERN ROCKIES ON DAYS 2 AND 3 WILL MAKE THE MOST OF THE DRY
COLUMN TO PRODUCE QPF. FOR THE MOST PART...THERE WAS DECENT MODEL
AGREEMENT CONCERNING THE TRACK AND STRENGTH OF THE SHORT WAVE
(THOUGH THERE WERE SOME DIFFERENCES IN THE QPF PLACEMENT IN THE
TERRAIN). WITH THIS IN MIND...THE WPC QPF WAS BASED ON A BLEND OF
THE 12Z ECMWF/GFS...WITH SOME 12Z NAM USED TO BETTER DELINEATE
HIGHER TERRAIN QPF MAXIMA.

A SHORT WAVE IN THE NORTHERN STREAM CROSSES THE CENTRAL ROCKIES
DURING DAY 2. THE MOISTURE IN THE COLUMN IS PALTRY (WITH MODEL
SOUNDINGS SHOWING PRECIPITABLE WATER VALUES GENERALLY 0.25 OR
LESS...WHICH INCREASES TO CLOSE TO 0.50 INCHES LATE ACROSS EASTERN
CO). HOWEVER...SYNOPTIC SCALE ASCENT WITH THE SHORT WAVE...COUPLED
WITH MARGINAL INSTABILITY (DRIVEN BY STEEPENING MID LEVEL LAPSE
RATES) MAKES THE MOST OF THE MOISTURE IN THE COLUMN. SCATTERED
CONVECTION IS EXPECTED TO PRODUCE LOCAL 0.10 TO 0.25 INCH QPF
AMOUNTS ACROSS THE PLAINS OF EASTERN CO...AS WELL AS THE HIGHER
TERRAIN OF THE CO ROCKIES...AND THE UNITAS RANGE IN UT.

SYNOPTIC SCALE LIFT IS WEAK ON DAY 3...BUT MARGINAL INSTABILITY IS
FED BY INCREASING MOISTURE IN THE COLUMN ACROSS THE GREAT BASIN
AND CENTRAL ROCKIES. WHILE THE COVERAGE OF THE CONVECTION MAY BE A
TAD LARGER ON DAY 3...LOCAL 0.10 INCH QPF AMOUNTS SHOULD BE
LIMITED TO THE CO ROCKIES AND PORTIONS OF CENTRAL NV.


...UPPER MS VALLEY/MIDWEST/CENTRAL PLAINS/GREAT LAKES...

A SHORT WAVE CROSSING THE CENTRAL PLAINS INTO THE MIDWEST RESULTS
IN SCATTERED CONVECTION DURING DAY 2. A STRONG SHORT WAVE CROSSING
SOUTH CENTRAL CANADA DURING DAY 3 TAPS MOISTURE FROM CENTRAL
PLAINS AND FUELS CONVECTION ACROSS THE UPPER MS VALLEY...MIDWEST
AND GREAT LAKES DURING DAY 3. THERE WAS GOOD MODEL AGREEMENT
CONCERNING THE TRACKS OF THE SHORT WAVES...AS WELL AS THE
MAGNITUDE OF THE RETURNING MOISTURE DURING DAY 3. BASED ON
THIS...THE WPC QPF WAS BASED ON A BLEND OF 12Z ECMWF/GFS.

A SHORT WAVE CROSSES THE ROCKIES AND CENTRAL PLAINS INTO THE
MIDWEST DURING DAY 2. THE BEST MOISTURE AND LIFT CROSSES THE
CENTRAL PLAINS AND MIDWEST DURING THE SECOND HALF OF THE
PERIOD...AND PRECIPITABLE WATER VALUES TOP OUT NEAR AN INCH AHEAD
OF A SURFACE FRONT ASSOCIATED WITH THE SHORT WAVE. MODEL SOUNDINGS
SHOWED MARGINAL INSTABILITY WITH DRY AIR IN THE MID
LEVELS...SUGGESTING THAT THE CONVECTIVE MODE MAY BE LESS CONDUCIVE
FOR HEAVY RAINFALL. AN AREA OF 0.10 TO 0.25 INCHES OF QPF WAS
PLACED OVER SOUTHEAST NE...SOUTHWEST IA AND NORTHERN MO WITH THE
EXPECTED CONVECTION.

A STRONGER SHORT WAVE CROSSING SOUTH CENTRAL CANADA PUSHES A COLD
FRONT ACROSS THE UPPER MS VALLEY INTO THE GREAT LAKES AND MIDWEST.
AHEAD OF THE FRONT...A 25 TO 35 KNOT LOW LEVEL SOUTH SOUTHWEST
FLOW TRANSPORTS PRECIPITABLE WATER VALUES NEAR 1.25 INCHES AND
MARGINAL TO MODERATE INSTABILITY INTO MN/WI DURING THE SECOND HALF
OF THE PERIOD. AGAIN...MODEL SOUNDINGS SHOWED DRY AIR IN THE MID
LEVELS...SO THE CONVECTIVE MODE DOES NOT APPEAR TO SUPPORT VERY
HEAVY RAINFALL. BECAUSE OF THIS...A LARGE AREA OF 0.25 TO 0.50
INCHES OF QPF WAS PLACED ACROSS CENTRAL AND SOUTHERN MN INTO
WESTERN WI. THE 12Z ECMWF HAD HIGHER QPF AMOUNTS IN THIS AREA THAN
THE 12Z GFS/NAM..BUT BASED ON THE SOUNDINGS...THE 12Z ECMWF VALUES
APPEAR TO BE TOO HIGH.


ORAVEC/HAYES


GRAPHICS AVAILABLE ON THE WEB AT WWW.WPC.NCEP.NOAA.GOV

24HR QP VT 02/00Z
 0.01 534225 536214 538202 538196 537192 534185 531178 527172
      518164 513158 507156 501156 499159 498164 498170 500173
      501181 508193 515207 521220 525225 530230 534225
 0.01 520271 521264 522258 519248 513230 508224 504215 499210
      494210 492214 491219 491223 491234 485236 481244 480250
      481255 483264 487272 491279 497286 503292 505295 508295
      511293 513288 520271
 0.01 533973 534957 533953 530950 525945 521941 513941 511937
      512932 510922 507918 504918 494919 487921 471921 457926
      449929 447930 446927 449925 453918 454913 455908 455902
      453899 449896 443899 437904 431909 426914 416928 410941
      403956 398963 394965 389965 384970 380974 385979 393979
      398982 401982 402984 402987 400992 394009 393013 391020
      391029 389038 388043 384043 378040 375037 371036 365040
      358042 356046 354051 355058 363060 366066 370073 374080
      378082 383081 386079 392081 395082 397085 402081 408077
      411076 414078 418079 420081 423081 425077 427072 428067
      427056 426051 427044 431040 436034 441030 443027 446026
      451020 456013 460006 474999 487995 490993 494993 502993
      508991 517987 527981 533973
 0.01 432759 431751 429749 426750 422749 422745 420740 416738
      414743 412751 409756 404760 402762 399760 395749 391733
      386721 386714 384708 382701 380695 377689 373685 370681
      364678 360680 356684 351693 347705 345712 342715 341723
      343728 342733 339738 334748 333756 334760 336769 339775
      343786 346790 350794 354799 354803 356806 356810 355814
      356821 352826 349829 346833 343839 345843 347844 350844
      369834 384817 388816 390818 393822 397827 401830 410834
      416833 417830 417825 418823 418817 418809 417792 425783
      427779 430772 432759
 0.01 418156 419148 416146 410145 405141 402137 399138 394138
      392140 392144 391152 389157 387164 385170 384175 387178
      391178 395173 405175 411164 415162 418157 418156
 0.01 406114 407107 406104 400103 397101 393101 390102 387109
      384111 383115 387116 389114 394112 399113 405114 406114
 0.01 393200 394198 394195 393195 392194 391192 390192 389191
      387189 385188 384188 383188 382190 381190 381191 382193
      383194 384195 384196 386197 388197 389199 389200 391200
      393201 393200
 0.01 345103 346096 345092 344087 341083 338081 334083 332088
      334093 335097 337102 341104 343105 345103
 0.01 251014 251007 248002 244998 240995 237995 235997 233003
      231009 230011 232013 238015 241018 245019 248018 251014
 0.25 532211 534204 533198 528189 525185 522183 515177 509171
      505172 505177 510186 515193 519202 524210 527213 531213
      532211
 0.25 514274 516267 517259 514250 511240 506232 500227 498231
      499237 501246 502251 500256 497257 496265 498269 500274
      506280 513277 514274
 0.25 408051 408047 406044 404044 402044 399045 397046 395048
      393052 395055 398057 402057 405056 407054 408051
 0.25 402781 393777 388774 385769 384765 384761 384754 384745
      384738 382729 380724 374713 371706 369701 365696 362696
      360698 358705 356710 352723 349735 348743 347745 348749
      350758 352764 354768 357774 362787 365804 368810 371813
      378813 384809 392802 396798 399793 402781
 0.50 514266 514264 513259 512255 510252 509249 508246 507243
      505241 504244 505247 506251 507256 507259 509262 510265
      512267 514266
 0.50 391789 391786 388783 385780 379779 373781 369786 368793
      368800 371805 376806 382804 387802 390796 391789
 0.50 380739 379734 377728 372722 366716 363716 361717 359720
      355730 354733 353739 355746 358748 360754 360760 363764
      367765 368755 371752 376749 378746 380741 380739
 1.00 382793 381791 380791 378791 377792 375794 374796 375797
      377797 379797 381796 381795 382793 382793
 1.00 371734 370732 370731 369730 368729 367728 366727 364727
      362728 362729 361731 360734 361736 363736 365736 366737
      367737 369737 370736 370735 371734

24HR QP VT 03/00Z
 0.01 558095 561074 561053 560046 560038 557025 555011 559002
      562995 563987 562977 561971 556938 555928 554922 556909
      558901 558891 559882 557875 557866 556860 555852 553846
      542825 535816 533814 528814 520822 515833 513839 511843
      510849 510856 505888 504895 503901 501906 498911 497916
      497922 494932 491937 490942 489944 482952 474959 470964
      468970 465974 464979 462987 465992 465001 466006 468006
      470004 472999 475986 480974 486965 496960 501960 503956
      509955 514955 517958 517963 516973 517981 518986 520993
      522996 521999 518002 516007 512012 510018 505030 502042
      501050 503056 505070 507076 509079 516080 519079 522078
      523082 522088 521099 520108 518116 516122 514127 512134
      511137 509136 506132 501131 497135 494136 494142 497147
      500150 503151 505154 504163 503166 502170 502175 503178
      505182 509186 515197 518200 520204 522206 522211 522218
      517218 514215 511214 510216 509220 510223 513227 517227
      522224 525219 530216 532213 535208 537202 539185 540175
      542169 547157 550145 552134 554127 558095
 0.01 537126 538115 538105 539094 538086 537081 536085 535096
      533098 533104 532106 532109 534112 533117 532120 531125
      530132 531140 534139 535134 535128 537126
 0.01 514250 515244 514239 510230 507219 504209 499202 496199
      494199 493202 492209 493215 496226 500233 504242 508251
      510256 512255 513253 514250
 0.01 517682 516672 514667 508659 501650 498647 494645 491648
      489653 483662 472666 467675 461685 458689 456695 455700
      455707 454714 452720 449725 450731 453728 456727 458724
      469706 477697 481694 486692 506691 510692 513689 517682
 0.01 480236 480234 480232 479231 480229 480228 478227 477227
      476227 476230 475232 475235 475237 475238 477239 478238
      479237 480236
 0.01 443988 443981 442976 438971 430966 427959 423950 421942
      417933 416930 417927 418924 417917 416912 415909 412905
      410903 405903 402905 401908 399913 396915 393918 391917
      389913 387906 385897 382889 379880 375875 375887 376893
      377897 378902 380907 383916 384921 385924 386930 387936
      387940 389943 392947 392954 391963 389968 391971 394979
      401993 406000 409999 410996 412991 411987 411981 412977
      414973 417969 420971 422975 426995 428997 432997 436995
      443988
 0.01 428113 428108 427103 424100 418099 417094 414091 410093
      407096 404100 403104 402111 403114 405114 408112 410108
      413104 416104 416109 414113 410115 410117 413116 419116
      426115 428113
 0.01 423148 423138 420137 418140 403142 396144 387143 387145
      391147 393149 397151 397155 395156 390162 386168 387176
      394175 399170 403165 405160 407156 410155 411150 413146
      415149 414158 412161 414163 418159 420155 421150 423148
 0.01 422747 421739 419737 415736 410737 404737 400739 393743
      389747 387751 383754 380755 373760 368763 363764 354764
      347767 344772 344777 342781 344785 354784 361779 370776
      377778 383777 386775 391769 393766 396766 401765 406764
      408761 414753 417752 421749 422747
 0.01 425075 427061 426057 424053 417048 415045 413045 410048
      407045 405035 404023 404014 399014 397016 391020 387020
      387017 384017 381023 375029 369034 367043 366049 363051
      357055 362061 359062 355066 351072 347070 342069 338073
      331077 330083 332086 338091 338095 342096 344094 346088
      347085 352084 354082 352079 353077 356074 363069 366069
      369071 372073 373080 374082 377085 382088 386089 388087
      391085 393088 392091 394092 400085 404079 410073 414073
      415072 417069 420067 425075
 0.01 407128 407124 406123 402123 399122 397122 396126 394128
      394133 396131 400130 403130 405128 407128
 0.01 393676 391665 390658 385652 382653 380655 369663 357671
      353675 348679 336687 334694 331699 325710 322717 323721
      325723 326731 328740 325753 322760 321767 320769 323771
      329770 338762 340759 344757 349755 357752 361748 368744
      372740 381730 384724 385717 386708 388703 390695 391688
      393676
 0.01 398793 396791 393791 389792 386794 381799 377800 374803
      371808 369812 370816 373817 377817 382812 385806 392801
      397796 398793
 0.01 382193 381190 379187 377186 375184 372182 368182 366182
      366186 367188 371189 372191 376192 379193 382193
 0.01 388120 389116 389114 385113 383113 380115 379117 377121
      377123 375125 375127 376130 377128 379126 381122 383120
      386122 388120
 0.01 367135 366130 364128 361125 356122 354117 352119 351124
      353127 357130 357136 361137 365137 367135
 0.01 259832 258825 256822 254821 250826 249831 247837 245843
      243849 245852 249852 250849 252844 255839 258834 259832
 0.01 257805 252803 248804 247805 243810 241815 239821 236826
      238828 240827 247825 250821 252816 252812 254810 257805
 0.25 549922 548914 547909 545906 540905 536907 531911 529918
      528928 531934 536938 541936 545932 548925 549922
 0.25 540011 541006 540003 539999 536000 534003 533005 532008
      530011 529015 528018 529021 531024 533026 536024 537021
      538016 539014 540011
 0.25 525923 525920 525918 524915 523913 522910 522907 521905
      521903 520904 520905 520906 520907 520910 520913 520915
      521918 521921 522922 522923 523926 525925 525923
 0.25 404947 404945 404943 404940 403939 403938 403936 402933
      400932 399933 399936 399938 399940 400942 400943 400945
      401947 401949 402951 403949 404947
 0.25 391041 391038 391037 389036 387037 387038 387039 389040
      390041 391041
 0.25 377714 376706 373704 367704 361705 349708 345708 344711
      345714 346718 345721 343726 341731 341737 343743 348744
      360741 365738 367734 373726 375721 377715 377714
 0.50 374715 374710 372708 367707 362710 358714 356720 353725
      350731 349734 351736 356737 361735 366730 369725 372720
      374715
 1.00 369714 368714 366714 365715 364716 363717 363718 361720
      360722 360723 360725 360727 362727 362726 364725 365724
      365723 367721 368719 368718 369716 369714 369714


24HR QP VT 04/00Z
 0.01 565996 566990 565984 564969 563963 563956 563947 561943
      553923 551917 553913 556906 557900 559892 559886 559869
      559860 558852 557844 556839 555830 553822 550809 549800
      547794 544784 543757 541744 538742 533741 526747 519754
      509770 505779 503788 497811 495825 492837 491843 488848
      487853 483857 478863 472868 464872 461871 455871 452869
      446869 440870 436868 431869 429872 423880 418879 414877
      410875 405875 401874 395875 391874 386874 384878 384886
      385891 387897 383902 383910 387920 392926 394929 396933
      400941 400956 396956 391954 388951 384947 382943 380940
      377940 377942 373947 366951 370959 375964 380972 384977
      387975 392973 396975 395980 392984 387992 382998 376001
      367005 363005 360007 355017 352028 351034 352039 356049
      355056 357062 359067 363071 365074 369077 372080 374084
      378092 381098 382103 376109 373113 372118 371123 372128
      375130 378129 392121 397120 399126 399130 397133 395137
      387142 385145 387150 383177 380180 376180 372180 367181
      364182 364184 366188 377190 382192 386190 388185 390183
      394182 396179 397170 402163 407161 412162 416163 419160
      422150 424135 425125 425121 427118 431114 435112 442114
      446119 444127 442130 437138 436151 441157 447158 450154
      455150 460142 461128 464125 466120 469110 470103 467100
      465099 462097 460092 457088 456081 451074 447062 446054
      448048 448042 445039 440031 432049 429052 427051 420045
      416038 408034 402030 400024 402017 408010 411007 416005
      420002 423000 429992 434986 439986 441990 443995 446994
      448995 448999 447007 448015 454015 458013 459010 462009
      466011 470009 475004 478001 479996 480989 481984 481968
      482962 484959 488957 491952 493949 495943 497939 500937
      502939 499946 499953 500957 500964 499971 498978 495995
      495010 494019 496025 496031 499031 500035 500043 501049
      503052 505050 513051 521047
 0.01 521047 525043 529044 531047 533054 526055 517062 513067
      512071 511076 511082 513084 516090 522104 528116 533122
      535131 537148 537160 538169 542174 545175 547172 550163
      555138 556119 556110 555104 551092 547081 542070 540064
      546063 550062 554059 556055 558048 559040 560032 562016
      564999 565996
 0.01 536180 532170 525161 519153 511146 504137 501136 500142
      503148 507151 513159 519168 525178 528182 531182 534182
      536180
 0.01 497926 497921 497916 495911 494909 490911 490914 489919
      489922 487927 489932 491933 494934 496929 497926
 0.01 463685 463678 460674 458670 455667 451664 448665 445673
      443684 439692 435700 434705 436707 443701 449695 454694
      457695 460692 462688 463685
 0.01 338025 336021 332016 327012 322012 312018 301024 288021
      276017 265012 255004 246998 241995 235993 232997 235002
      239006 245009 250011 256014 265021 268027 271032 282037
      287040 293044 299044 303045 306047 311045 315041 324034
      332030 338025
 0.01 285989 283982 277977 272974 263973 255971 252978 247982
      253985 261987 265987 268989 273993 278994 281993 285989
 0.01 269800 266796 264795 260795 257799 252800 248804 245808
      243811 241809 239814 239821 241835 245838 248837 249835
      251831 251824 249820 249813 251809 256806 259803 265802
      269800
 0.25 553996 554990 554984 554971 554966 553960 551952 545937
      543930 539925 535919 532918 528918 524924 524930 525935
      527942 529952 530961 532971 534979 537987 539994 542001
      543004 547005 552001 553996
 0.25 527812 528803 527794 525788 520787 515795 513800 514806
      511817 508831 507837 508846 510849 514845 519837 523824
      527812 527812
 0.25 476920 465907 460906 457908 453901 450898 447897 445898
      442901 440906 435927 432937 430947 428954 431957 440959
      445960 448958 451955 454955 455958 459967 461969 463964
      464960 465952 464946 462945 462942 465933 467920 468916
      469917 470923 474926 476920
 0.25 423982 424980 423978 422976 421977 419977 419978 418980
      417982 418985 419985 421985 422985 422984 423982

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