Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 130932
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
431 AM EST WED DEC 13 2017


FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION
VALID DEC 13/1200 UTC THRU DEC 16/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

06Z UPDATE...
NO SIGNIFICANT CHANGES WERE MADE TO PRELIM GUIDANCE.

...NORTHEAST...

LOW PRESSURE WILL CONTINUE TO LIFT NORTH OF MAINE THIS MORNING
INTO EASTERN CANADA WITH STG CYCLONIC FLOW ON THE BACK SIDE
SUPPORTING LINGERING MAINLY LIGHT SNOWS IN THE WRAP AROUND
BAND..WITH SNOWS GRADUALLY DIMINISHING WED NIGHT AS MAIN
CIRCULATION PULLS FARTHER AWAY FROM NEW ENGLAND.  MODELS WERE
GENLY IN AGREEMENT HERE ON QPF AMOUNTS AND A GENLY MODEL BLEND
ALONG WITH CONTINUITY WAS USED.  SEE QPFHSD FOR MORE DETAILS.

...UPPER MS VALLEY INTO THE SOUTHERN GREAT LAKES REGION AND THE
CNTL APLCNS...

A CLIPPER SYSTEM WILL BRING A SWATH OF SNOW TO PORTIONS OF THE
UPPER MS VALLEY INTO THE GREAT LAKES REGION AND CNTL APPALACHIANS
WED INTO THUR MORNING.  AMBIENT AIRMASS TO THE SOUTH OF THE SFC
LOW TRACK IS QUITE DRY WHICH WILL LIMIT THE AMOUNT OF MSTR THAT
WILL BE LIFTED AHEAD OF THE LOW AND ASSOCD WARM FRONT.  THAT
SAID...THE SFC WAVE IS EXPECTED TO AT LEAST MAINTAIN DECENT DEPTH
AS IT TRACKS ESEWD ACROSS SRN WI THEN EWD THROUGH CNTL OH BY EARLY
WED NIGHT.  THAT ALONG..AN ASSOCD JET STREAK AND AREA OF CHANNELED
LIFT IN THE 85H-5H LAYER SHOULD LEAD TO A DECENT SWATH OF .25 TO
.50 INCH LIQUID EQUIVS..IN THE FORM OF SNOW.. FROM ERN WI..CNTL
AND SRN MI...NE OH AND WRN PA/SW NY THIS PD DESPITE THE RATHER DRY
AIRMASS SOUTH OF THE WAVE.  SOME SMALL NORTH/SOUTH DIFFERENCES
STILL REMAIN REGARDING THE AXIS OF HEAVIER LIQUID EQUIVS BUT
PREDICTABILITY OF THIS NARROW BAND IS TOO SMALL TO FAVOR ONE SOLN
OVER ANOTHER AND THUS STAYED FAIRLY CLOSE TO A MIDDLE GROUND SOLN
ALONG WITH CONTINUITY.  SEE QPFHSD (HEAVY SNOW DISCUSSION) FOR
MORE DETAILS.

ELSEWHERE...
ACRS THE NRN AND CNTL ROCKIES...MODELS HAVE TRENDED FROM
ESSENTIALLY DRY TO PRODUCING LOCAL .10 TO .25 INCH AMOUNTS THE
PAST SEVERAL RUNS WITH SYSTEM MOVING THROUGH THE NORTHERN PORTIONS
OF WRN CANADIAN UPPER RIDGE.. THEN DIVING RAPIDLY SEWD THROUGH THE
NRN INTERMOUNTAIN REGION BY WED EVENING AND CNTL ROCKIES BY THUR
MRNG.  COMBINATION OF MID/UPPER FORCING AND SOME WEAK EASTERLY
UPSLOPE IS EXPECTED TO GENERATE A SWATH OF MAINLY LIGHT PCPN
AMOUNTS FROM WRN MT/ID SEWD INTO CO.  A SEPARATE MORE ERN IMPULSE
DROPPING SWD FROM MANITOBA WED NIGHT IS ALSO EXPECTED TO SPREAD
SOME LIGHT SNOWS OVER PORTIONS OF THE NRN PLAINS.  MODEL SPREAD
FOR BOTH SYSTEM WAS GENLY SMALL WHICH ARGUED FOR FOLLOWING AN
ENSEMBLE APCH.



DAYS 2/3...

WPC QPF WAS PRIMARILY BASED ON A BLEND OF THE ECMWF...GFS...AND
UKMET...WITH GREATER WEIGHT PLACED ON THE ECMWF AND GFS.

...GREAT LAKES TO THE MID ATLANTIC...

THE CLIPPER SYSTEM MENTIONED IN THE DAY 1 PERIOD WILL BE MOVING
OFF SHORE VERY EARLY IN THE NEW DAY 2 FORECAST PERIOD (12Z
THURSDAY TO 12Z FRIDAY).  WHILE THERE WILL STILL BE A LITTLE QPF
IN THE NORTHERN PORTION OF NEW ENGLAND AS MOISTURE WITHIN THE
BROAD CIRCULATION OF THE CYCLONE...ANY ADDITIONAL PRECIPITATION
AMOUNTS SHOULD BE LIGHT.

THE NEXT CLIPPER SYSTEM IS PROGGED TO DROP SOUTHEAST FROM ONTARIO
INTO THE GREAT LAKES REGION DURING THE DAY ON FRIDAY AND THEN MAKE
THE TURN EASTWARD.  THERE WAS GENERAL AGREEMENT ON ONE AREA OF
LIGHT PRECIPITATION BREAKING OUT IN THE REGION OF DIFLUENT FLOW
AHEAD OF THE SURFACE FEATURE...WHERE SOUTHERLY LOW LEVEL WINDS
FORCES LOW LEVEL ASCENT ISENTROPICALLY.  THE MAIN MID/UPPER LEVEL
DYNAMICS HEAD EAST/SOUTHEASTWARD...PULLED ALONG BY THE AXIS OF 110
KT TO 125 KT UPPER LEVEL JET DIGGING SOUTHEAST.

WPC MANUAL FORECASTS WENT ABOVE GUIDANCE TO THE IMMEDIATE LEE OF
LAKES ONTARIO AND ERIE EARLY ON DAY 2.  THE COLDEST H85 TEMPS ARE
CROSSING THE LAKES AT THAT POINT...RESULTING LARGE DEL T VALUES.
GIVEN WEAK BOUNDARY LAYER WINDS...WAS NOT INCLINED TO GO TOO MUCH
OVER THE GUIDANCE BUT FELT THE MODEL VALUES WERE UNDER DONE.

...GULF COAST REGION...

MODELS SHOW SOME VARIABILITY WITH THE PLACEMENT OF THE QPF AXIS
ACROSS THE NORTHERN GULF OF MEXICO AND ADJACENT PORTIONS OF SOUTH
TEXAS AND NORTHERN MEXICO. THIS WILL OCCUR IN A REGION OF
INCREASING ASCENT NORTH OF A SURFACE COLD FRONT AND IN THE RIGHT
ENTRANCE REGION OF A SUBTROPICAL JET STREAK. WPC QPF TRENDED
WETTER DURING THE DAY SHIFT AND THERE WAS LITTLE REASON TO BACK
OFF THOSE AMOUNTS BASED ON THE 00Z MODEL RUNS.  THE ECMWF REMAINED
MOST AGGRESSIVE BRINGING THE MOISTURE AND ASSOCIATED QPF WELL
NORTH INTO TX WHILE THE NAM/GFS AND...TO A LESSER EXTENT...THE
UKMET WERE MORE SUPPRESSED.  WE GAVE MORE WEIGHT TO THE MODEL
CONSENSUS BUT DID START TO ALLOW SOME MOISTURE TO BE DRAWN
NORTHWARD CONSIDERING THE MAGNITUDE OF THE TROUGH APPROACHING FROM
THE WEST.  IT IS ASSUMED THAT THERE WILL STILL NEED TO MAKE
ADJUSTMENTS IN UPCOMING FORECASTS.

...NORTHWEST...

A SHARP RIDGE THAT HAD BEEN LOCATED OVER THE PAC NW WILL BEGIN TO
BREAK DOWN AS A STRONG SHORTWAVE DROPS IN FROM THE GULF OF ALASKA.
 THE FIRST PRECIPITATION WILL APPROACH THE PAC NW COAST LATE DAY
2.  THE MAIN TROUGH THEN DROPS SOUTHEAST TOWARDS THE INTERMOUNTAIN
REGION. THE ECMWF TENDS TO SHOW MOST OF THE PRECIPITATION BEING
POST FRONTAL FRIDAY NIGHT AND EARLY SATURDAY MORNING.

SULLIVAN/BANN

GRAPHICS AVAILABLE ON THE WEB AT
WWW.WPC.NCEP.NOAA.GOV/QPF/QPF2.SHTML

24HR QP VT 14/12Z


24HR QP VT 15/12Z
 0.01 507304 501301 498299 495297 479293 466295 460298 456298
      452296 449293 448289 450284 446280 445277 445272 448269
      449265 448261 446255 455243 465234 466229 470225 472223
      474222 473219 473216 475214 478215 482214 495217 501221
      508223 515222 516215 514211 509197 505179 506169 509167
      516173 523173 530170 533165 534160 536155 540156 542160
      545166 547171 547175
 0.01 562082 557087 550086 546085 544082 539078 536074 533069
      527063 522057 515051 509045 500045 494042 489037 487033
      485028 486019 485012 481012 479014 473019 468020 468024
      469028 474033 476036 475040 473047 471055 470060 468065
      465068 462070 457069 450063 444058 441056 439057 435064
      433066 430065 424059 420053 418047 419042 423041 427044
      434049 436044 435038 432032 428025 427020 428016 430014
      429011 427008 425004 422000 415994 412994 408991 403984
      401982 401979 401972 402969 404964 403961 400961 393966
      385970 380970 377968 375965 375959 377956 380954 386952
      389945 391940 394937 395933 399933 403933 407936 412940
      416942 421949 423952 423956 423959 425961 428961 432961
      434963 435960 435953 436948 440947 444947 448951 452952
      457959 460959 465961 472962 476964 479964 484969 487979
      489982 492985 498995 501993 507993 511993 515996 520999
      531007 538012 545019 557031 561034 565040
 0.01 446629 450635 453641 454646 451649 448653 444654 433663
      426679 421692 420702 418712 416719 413725 408732 404739
      404748 403750 399751 389742 385736 384731 385728 385718
      381716 377717 369719 363722 353724 349725 345723 340722
      335718 334712 335708 339702 348692 352686 358680 367671
      377659 385652 394645
 0.01 528242 527239 527236 526233 525230 523230 522232 521232
      520234 519236 519239 519241 520244 521246 523245 525244
      525243 526244 528242
 0.01 530941 531930 529924 526919 522916 517915 510917 505918
      500922 497923 495921 491917 487916 484910 481903 481898
      483896 483892 483887 483882 485879 484869 482864 479859
      479851 478840 477830 474825 472823 468822 465827 464831
      462828 460822 459814 459802 456795 455786 448787 445792
      442791 442796 443799 441801 439803 435806 431808 430813
      428814 428819 430821 438827 438832 435837 427848 423853
      420860 419866 415870 406875 417876 423873 426872 428874
      450877 452879 454884 451893 450899 451903 455908 460910
      466918 470918 472920 475929 477936 480942 484945 490945
      495947 499950 502955 505958 508958 515958 520956 527952
      530941
 0.01 441762 441752 440749 436751 431753 428755 427757 427765
      428774 429783 433788 435785 435777 438770 440765 441762
 0.01 428791 428786 424782 421782 419787 417797 416802 416805
      414807 409815 406817 407820 411826 417821 421811 424810
      426805 428793 428791
 0.01 416064 416057 413054 406053 402051 402049 403043 405037
      401035 398034 396036 394041 392043 389041 385038 382031
      381026 377024 370023 368030 366032 363031 359033 355033
      353031 350033 346038 345043 350055 358060 360062 358065
      360069 365073 370074 373075 374080 377082 381081 384077
      388077 390080 392079 394075 399076 402072 408075 413074
      414071 413068 416064
 0.01 402792 401788 399790 396791 388796 381802 375812 371813
      370820 370823 369826 369831 374824 379813 383811 387806
      394801 402793 402792
 0.01 366816 364816 363818 361818 360823 358825 358828 356830
      355834 355837 357834 359832 360830 361825 363823 363820
      366818 366816
 0.01 328720 329713 327708 324708 318711 311716 307724 304733
      302745 297765 291784 290789 291795 292802 296805 300806
      303806 305806 306802 307797 310788 312783 316779 319772
      319759 320748 321742 323736 326729 328720
 0.01 316048 312032 307015 305012 303011 301016 298017 295014
      291014 287016 285020 285024 286029 290037 292043 291045
      289045 286043 282040 276039 273040 271036 270031 264030
      265027 268024 272023 276020 280015 286003 282000 279996
      278984 279974 280968 282964 287956 288954 289949 294935
      296924 292914 289907 286902 286895 284892 285887 286882
      287879 287869 287858 291849 292841 292834 289832 283833
      279835 270847 267853 265856 266860 270862 273865 276878
      273898 269906 267915 264921 261928 257936 252944 249948
      246949 243953 241957 239965 239975 240979 240984 240988
      238991 237004 237014 238039 237060 238077 238084 243085
      246086 251086 256081 259076 262076 264078 270083 276081
      280076 284069 287069 289070 291074 293079 296082 301083
      305082 309079 311075 313061 315052 316048
 0.25 522264 521263 519261 518260 516259 515258 513258 512258
      511258 510259 509261 509262 508264 508267 507269 507272
      507274 508277 509278 510278 511279 513280 514281 516282
 0.25 434766 435763 434762 432764 432766 431769 432771 433772
      434770 434768 434766 434766
 0.25 424796 424794 423793 422794 421795 420797 420799 421801
      422801 423799 423798 424796
 0.25 407672 406666 404661 402657 397656 389663 383669 378675
      372683 371687 372692 375692 381692 391689 399683 405677
      407672
 0.25 422869 421869 419870 421870 422869
 0.25 307055 307053 307052 307051 307049 306047 306045 306044
      304042 303042 302044 302046 302047 302048 302049 303051
      303053 304055 305056 307055 307055
 0.25 287933 286927 282925 277928 274933 270942 265951 259957
      255961 253966 252970 254974 257978 259984 259988 256991
      249998 245006 244015 247019 251018 255015 264011 266006
      267000 265994 267988 270985 271980 272965 275956 281946
      285940 287933

24HR QP VT 16/12Z
 0.01 557117 547102 543096 539089 537086 534080 532077 530075
      528076 526079 524082 524086 523102 525116 525121 527123
      529127 532133 533138 534144 534149 535152 534161 535170
      537183 536197 535205 533211 530215 529214 524214 522216
      521221 521226 520232 518235 517243 515247 516251 517255
      518261 517265 510268 505266 501263 496255 493251 489249
      481247 477248 471248 467248 462251 456256 448261 444260
      441256 442252 444247 452235 453232 451231 448232 445233
      441237 439241 438248 435252 431255 429258 425255 421247
      415240 414235 415227 423220 427218 430214 433211 438211
      444212 449210 456206 460207 466207 471203 477202 481202
      485203 493202 496199 496195 495194 491191 491187 489185
      486184 481181 479175 476173 473175 471178 464186 456193
      452195 448192 442190 441185 440180 438185 433193 430202
      428207 427211 421216 418211 416208 415203 415199 413198
      410195 407187 411173 406165 402155 402148 400143 397139
      397134 400129 404125 411108 414106 416102 415090 416084
      419081 426084 432085 436082 437075 436069 436064 438061
      446058 454054 458049 462043 467038 473038 475042 474047
      471051 469056 468063 468071 469078 473086 479094 482090
      484085 485072 485066 484062 485047 487041 487034 482012
      478004 475993 472987 468984 465981 463976 460971 458966
      456960 454952 450942 448930 450928 450923 450916 448911
      448906 450903 458903 461905 463903 462901 461891 462878
      460874 457869 454868 449869 445871 440872 422877 417881
      414881 411880 410877 409872 405859 404853 408849 416844
      414842 411843 407845 404848 401848 397844 396838 398834
      401825 405817 407811 407807 404807 401809 400814 397820
      394824 390824 387820 384816 383809 378807 377801 379796
      382793 388787 392784 397783 402776 404775 404771 406766
      407757 407754 410751 414743 423741 426735 422732 422730
      425729 428728 429725 431720 441713 451710 455710 460713
      462718 460717 461721 459724 457723 458727 454726 450729
      448734 450736 453735 459733 462728
 0.01 462728 466722 468719 471720 472725 473733 472746 471753
      466759 459765 463775 462779 464782 469788 471791 471796
      470799 472803 474808 476817 477821 476825 476840 476846
      477852 482869 483875 483883 483887 480892 474895 470901
      465907 472912 477916 480925 484933 489941 497954 504959
      510964 518965 526965 529967 534968 541973 542984 545991
      551998 553001 554007 556014 556024 562026 566030
 0.01 495151 494148 494145 494143 493142 492142 492143 490144
      490147 491149 493150 494152 495151
 0.01 447179 445177 444177 442176 440178 440180 441183 443183
      445181 447179
 0.01 427690 426685 425682 422680 419681 415681 411680 405675
      400676 393680 388686 384692 382699 381704 381709 380727
      384733 387735 388735 394729 400725 405720 411716 416710
      418706 418702 422695 427690
 0.01 435140 434138 432135 431131 428130 424131 422133 422138
      422143 423146 424146 428146 431145 433143 435140
 0.01 372690 369682 367679 364676 349684 337693 329699 324704
      319709 315716 310723 306731 298742 292749 289757 286764
      285772 284781 282790 284797 281805 282809 285811 290809
      293810 301808 304801 306797 308793 313786 321775 332761
      338749 343740 347734 357723 360720 363715 367708 370700
      372690
 0.01 299928 300911 299903 297895 297888 296877 296874 293871
      290868 286868 282868 282865 284858 287845 287833 286821
      285818 281818 276823 273829 272835 272852 271860 270865
      268867 259878 252906 250909 247911 240915 238923 240930
      241937 241944 233953 236968 238987 237997 236002 234009
      233018 233029 234039 236043 240050 245053 246059 249065
      251067 251071 249079 253085 260089 263091 266091 264085
      264077 266071 268068 272067 279065 276060 271046 270041
      272039 276039 278040 285041 291039 296025 292018 288017
      285014 292954 294938 299928
 0.01 277877 277875 274875 272880 270883 269887 267892 266896
      268901 269898 272894 273890 274885 276879 277877
 0.25 541043 541038 539033 535024 527017 521009 513003 509001
      506001 506003 508008 511013 517021 522032 525036 528040
      537046 539046 541043
 0.25 503996 500990 497982 492975 489969 484964 482962 479960
      478962 478968 479974 482982 485989 490994 497997 503998
      503996
 0.25 482138 481136 479136 477136 476137 475139 477141 478140
      480140 480139 482138
 0.25 469153 470150 469149 467148 466148 464148 462148 461148
      459149 457150 457151 456152 456155 458157 459158 460158
      461159 463160 465159 467157 468155 469154 469153
 0.25 458800 458796 456793 453795 450800 447806 443811 440815
      441818 442821 448822 452818 455813 457808 458800
 0.25 450855 450854 448855 448858 449858 450857 450855
 0.25 440760 439758 438760 439761 440760
 0.25 338718 337713 335711 327710 317720 310733 303746 298760
      296767 295775 295779 299781 303780 306778 315766 322754
      329740 331734 335727 338718
 0.25 286914 285908 284905 282907 272916 264924 259937 254937
      249940 246945 243954 243961 244970 246978 248984 243994
      241003 240012 240019 241026 245032 247034 251034 255033
      260029 267017 270011 271002 272995 273986 274978 275970
      277962 279955 281948 281941 281934 283926 286914
 0.50 327725 327722 324721 320724 314734 309742 305750 302762
      300766 301771 304770 310763 316755 321746 325738 327725
      327725
 0.50 272956 273950 273944 271940 270938 266939 262944 256945
      253947 249955 247960 246966 249975 252978 253983 253986
      251990 246998 244007 243014 244020 246023 249025 255025
      258023 263016 265012 266007 266986 266977 269968 272956
 1.00 257002 257000 255000 254000 253002 252004 251006 250008
      251009 253009 254008 254007 255006 256004 256003 257002

$$




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