Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 302207
QPFPFD

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


FINAL 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


MADE ONLY VERY MINOR CHANGES TO THE PRELIM DAY 1 QPF..BASED MOSTLY
ON RECENT RADAR IMAGERY/TRENDS.

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/TERRY/HAYES


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

24HR QP VT 02/00Z
 0.01 534225 536213 538202 538196 537192 534185 531178 527172
      518164 513158 507156 504155 501156 499159 498164 498170
      500174 501181 508193 515207 521220 525225 530230 534225
 0.01 520271 521265 522257 519248 513230 508224 504215 498210
      494210 492214 491218 491223 491234 485236 481244 480250
      481255 483264 487272 491279 497286 503292 505295 508295
      511293 513288 520271
 0.01 533968 533961 532957 528949 523944 520941 516941 512941
      510939 511935 512931 511925 507918 500918 492919 489921
      485921 477921 467922 459925 452928 449929 447930 446928
      451923 453919 454915 455911 455905 455900 452898 449896
      446898 439902 434906 424916 415929 408946 405954 400960
      395965 390965 387967 385969 382972 380974 382977 385979
      389979 393979 398982 401982 403987 399995 395003 393011
      391021 390032 388041 385043 381042 374037 370036 367038
      361041 356044 354049 354053 355057 358059 363060 365063
      369070 372077 374080 378082 386079 391080 395082 397085
      399083 404079 410076 419080 422081 424079 428071 428066
      428061 427051 428045 430042 435035 444023 449017 454013
      460006 465003 472999 479997 492992 499989 506987 514986
      518984 520982 524980 528976 533968
 0.01 432759 431752 429749 427750 424750 422747 421742 420740
      416738 414742 411748 408753 405757 402762 401764 397765
      396761 395756 394748 392740 390733 388728 381699 379693
      376688 372683 368680 364678 360680 356684 353690 350695
      349700 345711 342715 341720 341728 339735 337746 335758
      336765 338771 343784 345789 348793 352796 354804 356809
      355815 355819 354823 350828 347832 344836 343841 347844
      350844 354841 366836 385825 391824 398824 405832 409835
      414835 416829 417823 418821 418816 418808 419802 418792
      420788 422787 425782 428777 430772 432759
 0.01 418156 419148 416146 409145 405141 402137 399138 394138
      392140 392144 391152 389157 387164 385170 384175 387178
      392178 395173 405175 411164 415161 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 534203 533198 528189 525185 522183 515177 509171
      505172 505177 510186 515193 519202 524210 527213 531213
      532211
 0.25 514274 517267 517259 514250 511240 506232 500227 498232
      499237 501246 502252 500256 497257 496265 498269 500274
      506280 513277 514274
 0.25 404780 402779 399780 393778 385771 383764 384755 385747
      385740 383732 380725 375714 372709 369702 366696 363695
      360698 356710 353722 350734 347747 352761 355766 358772
      362785 364789 364794 365802 367808 371812 377813 382810
      391803 398795 402786 404780
 0.25 408051 408047 406044 404044 402044 399045 397046 395048
      393052 395055 398057 402057 405056 407054 408051
 0.50 514266 514264 513259 512255 510252 509249 508246 507243
      505241 504244 505247 506251 507256 507259 509262 510265
      512267 514266
 0.50 390797 390787 386782 381780 375779 373779 371774 369782
      368788 368796 369802 374805 380805 385803 388799 390797
 0.50 380736 379731 376726 368718 365716 360718 356728 354733
      353739 355746 359750 363762 367771 371772 372767 377756
      379745 380736
 1.00 383793 382792 380791 379791 378791 377793 376794 375796
      375797 377796 379797 381796 381795 382794 383793
 1.00 371736 371734 370732 369730 368729 367728 366727 364727
      362728 362729 361731 360734 361736 363736 365736 366737
      367737 369738 371736 371736

24HR QP VT 03/00Z
 0.01 558095 560078 561060 561051 560044 559036 557026 555011
      558007 560999 562994 563985 562977 561971 558957 557942
      556935 555926 554918 556910 558893 559886 558878 556862
      555852 553846 544828 537818 534814 529814 522820 519824
      517829 514835 512842 510849 510856 507869 506882 505888
      504897 502904 499910 497916 497922 492934 490938 489944
      482952 475959 469966 465975 463983 463988 465991 465000
      465005 466006 468006 470004 472999 475986 480974 485966
      488962 493962 502957 507955 513955 516956 517962 516972
      517981 518986 520993 522996 521999 518001 516007 511015
      506026 503038 502042 502046 501051 502054 504068 507075
      509079 515080 518080 519078 523078 523082 522088 520105
      517118 513129 511137 506133 503131 499133 495135 493140
      496146 500150 503151 505154 504163 502168 502176 504180
      507183 520204 522208 523213 520218 516216 513214 510214
      509218 510221 513227 517227 521225 524221 530216 533211
      535209 536204 538196 539186 540175 542167 547156 549147
      550145 551140 554127 558095
 0.01 537126 538115 538105 539094 538086 537081 536085 535096
      533098 533104 532106 532109 534112 533117 532119 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
      510255 512255 513253 514250
 0.01 517682 516674 514667 511662 508659 501651 498647 494645
      492646 489653 483662 473666 467675 461684 458689 456695
      455700 455707 454714 452720 450724 449726 450730 452728
      455727 458724 469706 476697 480694 486692 506691 509692
      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 443978 438971 430966 426956 423949 420940 416930
      417925 417919 417914 415910 410903 402904 399913 393918
      391917 389912 383891 381883 379879 375875 375885 375891
      377895 382914 385925 383930 384936 387943 387957 387963
      385969 383972 386975 392979 394984 396986 406000 409999
      410996 412991 411986 411980 413975 416971 419971 421972
      423976 425988 425994 428997 432997 436995 443988
 0.01 428113 428108 427103 424100 418099 417094 414091 410093
      407096 404100 403104 402111 403114 405114 408112 410108
      413104 416104 416108 414113 410115 410117 413116 419116
      426115 428113
 0.01 423148 423138 420137 418140 403142 396144 387143 387145
      390147 393149 397151 398155 395156 390162 386168 387176
      394175 399170 403165 405160 407156 409155 411150 413146
      415149 414157 412161 414163 418159 420156 421150 423148
 0.01 422747 421739 418736 414736 406737 401739 396742 393743
      391745 388749 385754 380755 377758 373760 372758 372756
      375744 379733 383724 385719 386712 387706 389700 391688
      393676 390660 388655 387652 383652 375659 367664 357671
      349678 339685 329702 324711 322716 323721 327732 328740
      326747 324757 320769 326771 331769 336765 339761 343759
      347767 344772 343777 343783 344785 347785 353784 358782
      368776 376778 383777 388775 390769 392767 395766 406764
      409759 414753 417752 420750 422747
 0.01 425075 427063 427058 424053 413045 410047 408047 406042
      405036 404025 404014 400013 397015 391020 387020 385017
      383019 381023 376028 373030 370033 367043 366048 365051
      363051 358053 359057 362060 356065 351072 344069 341071
      338073 331077 330082 332086 337089 338092 338095 341096
      344094 345089 347085 352084 354083 352080 352077 356074
      362070 365068 369071 372073 373077 373082 377085 384088
      388088 391085 392090 394092 400086 404079 410073 415073
      417069 419067 425075
 0.01 407128 407124 406123 402123 399122 397122 396126 394128
      394133 396131 400130 403130 405128 407128
 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 373760 372759 370760 369761 370762 372762 373760
 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 402943 402940 402938 402936 400933 398933 398936 398938
      398940 397943 398945 398947 398948 399947 400945 402943
      402943
 0.25 391041 391038 391037 389036 387037 387038 387039 389040
      390041 391041
 0.25 377714 376707 373704 367704 361705 349708 346708 344711
      345714 346718 345721 343726 341731 341737 343743 346746
      350749 354752 360751 366748 368743 368737 373727 377717
      377714
 0.50 374715 373709 370707 365708 358713 356720 352726 349734
      351738 353739 357740 360738 365732 369726 372720 374715
 1.00 369714 368714 366714 365715 364716 363717 363718 362720
      361720 360722 360724 360725 362726 364725 364724 365723
      367721 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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