Quantitative Precipitation Forecast
Issued by NWS

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445
FXUS04 KWBC 201840
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
239 PM EDT WED SEP 20 2017


PRELIM DAY 1 QPF DISCUSSION
VALID SEP 21/0000 UTC THRU SEP 22/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

FAR SOUTHEAST MA AND OFFSHORE ISLANDS


AS PER THE LATEST NHC OFFICIAL FORECAST FOR JOSE AND LATEST MODEL
GUIDANCE---JOSE IS EXPECTED TO SLOW AND MOVE LITTLE DURING THE
UPCOMING DAY 1 PERIOD---REMAINING APPROXIMATELY 150 NM SOUTH
SOUTHEAST OF CAPE COD/OFFSHORE ISLANDS.  MODELS ARE SHOWING GOOD
AGREEMENT THAT THE NORTHWESTERN EDGE OF THE ASSOCIATED PRECIP WITH
JOSE WILL AFFECT FAR SOUTHEAST MA FROM CAPE COD---TO THE OFFSHORE
ISLANDS.  HEAVIEST AMOUNTS LIKELY OFFSHORE WITH TOTALS IN THE 2-4
INCH RANGE FROM MVY TO ACK---WITH LIGHTER TOTALS NORTHWARD INTO
THE CAPE

LOWER MO---UPPER MS VALLEY

THE SURFACE COLD FRONT STRETCHING CURRENTLY FROM THE UPPER MS
VALLEY---SOUTHWESTWARD INTO THE CENTRAL TO SOUTHERN PLAINS IS
EXPECTED TO BECOME STATIONARY EARLY IN THE DAY 1 PERIOD AS THE
ASSOCIATED HEIGHT FALLS PUSH NORTHEASTWARD INTO SOUTH CENTRAL
CANADA AND LEAVE THE FRONT PARALLEL TO THE INCREASINGLY SOUTHWEST
FLOW ALOFT.  THE LATEST GUIDANCE IS SHOWING ORGANIZED CONVECTIVE
POTENTIAL IN THE 0000 TO 1200 UTC TIME FRAME TONIGHT INTO THURSDAY
MORNING IN THE VICINITY OF THIS FRONT FROM NORTHERN
MO---NORTHEASTWARD INTO FAR EASTERN IA---FAR NW IL AS MOIST SOUTH
SOUTHWESTERLY FLOW INTERSECTS THIS FRONT.  THE HI RES GUIDANCE OF
THE NSSL WRF---ARW AND NAM CONEST ARE THE MOST EMPHATIC WITH HEAVY
TO ISOLATED EXCESSIVE PRECIP TOTALS ACROSS THESE AREAS---DEPICTING
SOME 2"+ TOTALS.  THESE SOLUTIONS DO NOT LOOK UNREASONABLE GIVEN
THE OVERALL PATTERN EVOLUTION...ALTHOUGH AREAL AVERAGE AMOUNTS IN
THE NEW DAY 1 QPF WERE NOT AS HIGH...GENERALLY .50-1"+.

GREAT BASIN INTO THE NORTHERN ROCKIES

THE INITIALLY WEST TO EAST ELONGATED MEAN TROF ACROSS THE
NORTHWESTERN QUARTER OF THE U.S./SOUTHWEST CANADA WILL BECOME MORE
ORIENTED IN A SOUTHWEST TO NORTHEAST DIRECTION THROUGH DAY 1 AS
HEIGHT FALLS DIVE SOUTHEASTWARD FROM THE PAC NW INTO THE GREAT
BASIN.  THERE IS VERY GOOD MODEL AGREEMENT ON THE STRIPE OF
MODERATE TO HEAVY PRECIP POTENTIAL AHEAD OF THIS AMPLIFYING TROF
FROM IN THE VICINITY OF CENTRAL TO NORTHEASTERN NV---NORTHWEST UT
INTO FAR EASTERN ID AND NORTHWEST WY.  ACCUMULATING SNOW POTENTIAL
DAY 1 WILL BE CONFINED TO NORTHWEST WY---WITH MORE EXPANSIVE SNOWS
POSSIBLE DURING THE DAY 2 PERIOD OVER THE NORTHERN ROCKIES.

ELSEWHERE ACROSS THE PACIFIC NORTHWEST INTO THE FAR NORTHERN
ROCKIES AND SOUTH INTO THE SIERRA---PRECIP TOTALS EXPECTED TO BE
LIGHTER WITH GENERALLY .10-.25" AREAL AVERAGE AMOUNTS.

OH VALLEY---TN VALLEY---CENTRAL TO SOUTHERN
APPALACHIANS--SOUTHEAST AND GULF COAST

WEAK UPPER TROFFING WILL PERSIST DAY 1 BETWEEN THE BUILDING MS
VALLEY RIDGE AND JOSE OFF THE NEW ENGLAND COAST.  THIS WILL
SUPPORT SCATTERED CONVECTION FROM THE OH VALLEY INTO THE TN
VALLEY---CENTRAL TO SOUTHERN APPALACHIANS--SOUTHEAST AND ALONG THE
GULF COAST.  LOW CONFIDENCE ON QPF DETAILS---WITH ISOLATED HEAVY
RAINFALL AMOUNTS POSSIBLE WHERE CONVECTION MAXIMIZES.


ORAVEC

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

24HR QP VT 22/00Z
 0.01 431634 433636 434641 436652 436660 435669 431682 426696
      422702 420705 417707 405714 400717 394721 388720 381718
      377715 372709 369704 366696 361680 359672 360666
 0.01 555119 556108 555097 553088 550082 546077 544075 540075
      535077 531080 515103 510108 506115 500126 498128 494130
      490129 486127 475121 474116 476113 478107 477103 477097
      474091 470088 467094 466097 463099 457094 455091 456088
      456078 451073 445068 441067 439070 439082 438088 435089
      432087 428083 425082 424082 421086 422091 423094 422100
      419105 414109 410095 407097 407103 401106 391112 391115
      394116 396119 395124 390126 386132 383135 379143 377150
      373156 370164 369170 371174 375180 373183 368181 360181
      355182 352183 348181 346176 344169 339165 331163 325163
      324167 326170 325174 329177 334180 338185 341191 343194
      347194 354191 361192 367194 372198 375200 377203 383206
      388209 394214 397215 400214 404212 408206 411201 413198
      414193 416183 421178 427174 429172 430166 432163 437163
      442168 446173 442181 441183 440188 442190 444191 448193
      451196 453196 455194 460188 461187 464184 466174 470170
      473169 477171 484172 490176 492183 493189 493194 491198
      489201 483205 471207 459211 454213 448213 441213 434212
      429208 427209 426215 418227 412231 408236 408240 409243
      412248 418252 424251 439251 450249 461245 464244 466240
      467238 466235 465232 466227 471225 482223 488223 495221
      499223 501227 505234 513247 520240 523238 525235 528229
      535215 537207 540199 542198 543192 546181 549162 551150
      551140 555119
 0.01 550797 550790 549781 546773 543770 540768 537767 534768
      530770 528771 526769 526758 526751 524746 521744 518742
      518737 517730 516725 513722 509723 499735 489749 485758
      481769 475786 466801 457816 445828 441827 436827 427829
      421834 418841 420842 424841 427843 432843 433847 433850
      428852 423852 418855 415876 408891 404900 402905 398906
      392910 386918 378933 372937 367944 361952 357959 357969
      361972 364972 371968 374966 379966 388968 393968 396967
      402963 407954 411947 416940 423923 427915 432909 456886
      463880 469875 476871 479869 483868 492866 496866 499868
      507872 514877 522879 530878 533869 536859 536852 537845
      538838 542837 546829 548817 549807 550797
 0.01 530957 529953 526952 522952 518954 512957 505962 495972
      492981 488990 483010 482016 481020 481027 483027 495016
      505004 514991 518983 522976 530957 530957
 0.01 393193 394191 394188 393187 391188 391190 391192 392195
      393193
 0.01 401837 399834 396833 390836 384839 379839 373836 369832
      370825 372819 379809 380805 379801 375798 370800 365804
      357812 348820 345827 344835 343851 337860 330870 330880
      333887 338886 342887 344888 347890 351891 356892 368870
      377863 382859 387854 395846 401837
 0.01 376994 375992 369992 366992 362994 353998 348998 344000
      333012 327016 321022 308032 304036 302040 308041 317038
      326036 333032 339028 352018 356014 359012 365005 371001
      376994
 0.01 352775 351770 349767 343768 336780 333787 328792 323799
      318804 313807 307812 299823 295829 293836 294857 296891
      293897 291900 291905 293909 295910 298908 302908 305910
      308909 308899 307887 308878 310861 311856 315854 316847
      318839 321832 329820 337808 345796 349785 352775
 0.01 225054 228059 232063 241071 250079 259086 266087 274088
      279086 281080 283063 284045 284040 286039 290034 301027
      305024 309021 318016 318007 316003 313000 310000 304002
      298004 295008 288018 286025 282029 271035 265037 258036
      248030 238024 233023 228024
 0.01 316956 314949 307946 298946 290947 285949 282950 278949
      272950 267951 265953 255963 257970 252974 255978 260978
      264980 270983 279984 288984 292983 295981 305972 309967
      314960 316956
 0.01 284794 282790 278790 271794 264792 258792 255795 250801
      249806 250812 255820 257822 263822 267823 270821 275814
      279807 281803 282798 284794
 0.25 410640 416641 420647 426652 429661 430672 428680 422695
      418702 413706 406710 398712 391711 386708 382701 379692
      377682 378673 380667 385660 388654 393648 401643
 0.25 546155 547149 547142 546133 545123 544117 543112 541109
      537109 534111 532114 527118 522123 518128 514137 509154
      509158 510164 512171 516177 521184 526189 530191 534192
      537190 539186 542176 545166 546155
 0.25 518816 518814 517814 516813 514814 513815 511816 509816
      508818 506820 506821 505823 505824 507824 508824 510823
      512822 513821 515820 516819 516818 518816 518816
 0.25 462221 463218 461218 459218 457218 456219 455221 457222
      459222 460221 462221 462221
 0.25 457239 458237 457236 455236 453236 451236 450237 449238
      448239 449240 451240 452241 454241 456240 457239
 0.25 455221 452219 449218 447219 443219 440219 438220 436222
      434224 434226 435228 438229 441229 444228 446227 448226
      451225 453223 455221
 0.25 454108 455100 452095 439093 434092 430089 428086 425085
      425091 427097 427100 425102 421107 419112 415116 410118
      402126 398131 394135 391139 389146 386154 384159 382170
      385176 389178 393175 397170 402167 407166 415158 418153
      421147 427134 433124 437122 443120 448119 451116 454108
 0.25 442877 443870 439868 435869 431871 424878 418886 408903
      403910 398918 392925 389930 388936 387941 386948 388953
      393955 398948 403940 414923 426909 431900 436892 440884
      442877
 0.25 385200 384196 383194 381192 379190 376188 375186 373186
      369186 366186 366187 367190 370192 372193 375196 377197
      380199 382200 385200
 0.25 289966 289964 288964 286962 285962 283961 281961 279962
      278964 279964 281966 283968 285969 286969 288968 289966
 0.25 273805 273801 270800 267800 265800 261801 259801 257803
      256807 257811 259814 260815 264816 268815 269813 271810
      272808 273805
 0.25 267070 263062 257056 250051 245046 238041 233040 230043
      228047 229051 233057 240063 247067 256071 263072 267070
 0.50 543154 543149 543141 539132 535131 533133 526140 522147
      520151 519159 520165 522169 528177 531180 534182 537180
      539175 542162 543154
 0.50 451105 450100 446098 434095 431092 427091 429095 429101
      423106 421113 418116 415120 411122 405130 395147 391156
      389164 389171 394165 397161 400159 404161 407159 414153
      418144 424135 429126 436119 438117 443115 447114 449109
      451105
 0.50 427676 426665 425660 423655 415648 409647 402650 397654
      393659 390666 386671 383677 381684 381693 385701 389706
      394709 400709 406707 413704 418698 424686 427676
 0.50 431890 432885 429881 425882 423884 419889 415896 412901
      408906 400917 393929 391934 391944 393946 397945 400940
      407929 415917 423907 429895 431890
 0.50 244056 244054 243053 241052 241051 239050 238050 236051
      237053 237054 239055 240056 241056 243056 244056 244056
 1.00 423677 423668 422663 421659 412653 409653 406655 404661
      399672 395677 390680 386684 384692 385696 389702 393705
      399706 406704 411701 415697 418692 421687 423679 423677
 1.00 436109 435106 433104 431104 430106 426110 422117 419121
      416127 417130 422129 426125 429120 433114 436109
 1.00 411917 410912 407914 405917 401922 399924 396929 395933
      398937 400933 402929 405924 407922 410918 411917
 1.50 421675 421667 418662 414659 410659 407663 405668 403673
      400678 392684 388687 387693 390698 393702 398704 404703
      409700 413697 418688 421683 421675 421675
 2.00 420676 419670 418665 412663 408669 404675 400681 394687
      390693 392698 395701 402701 408697 414691 417686 420676
      420676
 3.00 417679 417672 415669 413669 410673 408676 406679 403683
      400688 399691 398694 399696 405695 408693 411690 414686
      416681 417679

$$





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