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Quantitative Precipitation Forecast (QPF) Discussion
 
(Caution: Version displayed is not the latest version. - Issued 2051Z Dec 12, 2017)
 
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
351 PM EST TUE DEC 12 2017


PRELIM DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION
VALID DEC 13/0000 UTC THRU DEC 16/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR

DAY 1


...NORTHEAST...

A MID/UPPER LEVEL TROUGH WILL TAKE ON AN INCREASINGLY NEGATIVE
TILT AS IT MOVES INTO THE NORTHEAST THROUGH TONIGHT. WILL SEE
SURFACE LOW REDEVELOPMENT NEAR THE MAINE COAST...WITH AN
INTENSIFYING LOW MOVING NORTH INTO CANADA ON WEDNESDAY. WILL
CONTINUE TO SEE SNOW/SLEET WITH THIS SYSTEM ACROSS INTERIOR
CENTRAL/NORTHERN NEW ENGLAND...WITH MORE OF A SNOW TO RAIN
SCENARIO ACROSS EASTERN NEW ENGLAND. SOME WEAK ELEVATED
INSTABILITY WILL CLIP CAPE COD THIS AFTERNOON AND MOVE INTO
DOWNEAST MAINE THIS EVENING. THIS MAY ALLOW FOR A FEW EMBEDDED
HEAVIER CONVECTIVE CORES RESULTING IN SOME ISOLATED 0.5" IN AN
HOUR TOTALS. MODELS WERE IN CLOSE ENOUGH AGREEMENT THAT A MULTI
MODEL BLEND SEEMED TO SUFFICE FOR QPF. THIS RESULTS IN AN
ADDITIONAL 0.5"-1" OF QPF AFTER 0Z ACROSS PORTIONS OF CENTRAL AND
NORTHERN MAINE.

LAKE EFFECT SNOW WILL CONTINUE INTO TONIGHT OFF OF LAKE ERIE AND
ONTARIO. FOLLOWED CLOSE TO A HIGH RES MODEL BLEND FOR THIS
ACTIVITY.

SEE THE QPFHSD (HEAVY SNOW DISCUSSION) FOR MORE DETAILS.


...UPPER MS VALLEY INTO THE GREAT LAKES REGION...

A CLIPPER SYSTEM WILL BRING A SWATH OF SNOW TO PORTIONS OF THE
UPPER MS VALLEY INTO THE GREAT LAKES REGION TONIGHT INTO
WEDNESDAY. MODELS HAVE ALL COME INTO AGREEMENT ON A MORE INTENSE
SYSTEM WITH HIGHER QPF AMOUNTS. THIS TREND SEEMS TO BE RELATED TO
THE INTERACTION OF TWO SHORTWAVES...ONE THAT WILL MOVE ACROSS THE
DAKOTAS AND INTO THE MS VALLEY TONIGHT...AND THE OTHER PUSHING
INTO MN ON WEDNESDAY. THE SOUTHERN OF THESE TWO SHORTWAVES HAS
BEEN TRENDING STRONGER...RESULTING IN MORE INTERACTION WITH THE
NORTHERN WAVE. THIS RESULTS IN BROADER AREA OF MID/UPPER LEVEL
FORCING AND GREATER COVERAGE OF MORE SATURATED CONDITIONS. WILL
ALSO SEE GOOD FRONTOGENETIC FORCING AND OMEGA WITHIN THE DENDRITIC
SNOW GROWTH ZONE MOVE ACROSS THIS SYNOPTICALLY FAVORED LOCATION.
THUS ANTICIPATE WE WILL SEE A BROAD SWATH OF LIGHT TO MODERATE
SNOW...WITH A NARROWER CORRIDOR OF MODERATE TO HEAVY SNOW.

MODELS ARE GENERALLY IN GOOD AGREEMENT ON THIS EVOLUTION. SOME
DIFFERENCES IN THE EXACT QPF AXIS EXIST...AND WITH SYSTEMS SUCH AS
THIS WILL PROBABLY CONTINUE TO SEE SOME SLIGHT SHIFTS RUN TO RUN.
FOR NOW STAYED CLOSE TO A BLEND OF THE 12Z NAM/GFS/NAM NEST/ARW2
AND THE 0Z ECMWF. THIS RESULTS IN LIQUID EQUIVALENT AMOUNTS
BETWEEN 0.25"-0.5" FROM CENTRAL WI INTO SOUTHERN MI. STAYED AWAY
FROM THE HRW ARW AND NMMB...WHICH SEEM TO BE LAGGING TRENDS AND
APPEAR TOO DISORGANIZED INITIALLY WITH THE SYSTEM.

SEE THE QPFHSD (HEAVY SNOW DISCUSSION) FOR MORE DETAILS.



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 AND MID ATLANTIC...

THE CLIPPER SYSTEM MENTIONED IN THE DAY 1 PERIOD WILL CONTINUE TO
DIG FROM THE GREAT LAKES INTO THE MID ATLANTIC REGION DURING THE
DAY 2 PERIOD (WEDNESDAY NIGHT AND THURSDAY)...WITH A SOUTHEASTWARD
CONTINUATION OF THE SWATH OF SNOW. UPWARD TRENDS IN QPF FROM MANY
OF THE AVAILABLE MODELS IS REFLECTED IN A SIMILAR UPWARD TREND IN
THE LATEST WPC QPF. ALTHOUGH THE DURATION OF THE EVENT WILL NOT BE
LONG...STRONG FORCING SHOULD BE ABLE TO COMPENSATE TO PRODUCE SOME
LIQUID EQUIVALENT TOTALS OF AT LEAST 0.25 INCHES NEAR OR JUST
NORTH OF THE TRACK OF THE 850MB LOW IN PORTIONS OF OH/PA. THERE IS
SIGNAL IN ALL OF THE OPERATIONAL MODELS FOR A SMALL BAND OF PRECIP
APPROACHING 0.25 INCHES...AND A STRONGER SIGNAL IN WPC INTERNAL
BIAS-CORRECTED ENSEMBLE GUIDANCE. THE COMBINATION OF A STRONG
UPSTREAM +PV ANOMALY AND MODERATELY STRONG FRONTOGENETIC
CIRCULATION SHOULD YIELD SOME BANDED PRECIPITATION AND MAY LEAD TO
SHARPER GRADIENTS THAN ARE DEPICTED IN THE CURRENT FORECAST. SEE
THE QPFHSD (HEAVY SNOW DISCUSSION) FOR ADDITIONAL DETAIL ON
SPECIFIC WINTER WEATHER IMPACTS.

COLD AIR ADVECTION IN THE WAKE OF THE CLIPPER...AND STEADIER WNW
LOW-LEVEL FLOW...SHOULD REACTIVATE LAKE EFFECT SNOW ACROSS THE
GREAT LAKES REGION. THE COLDER TEMPERATURES WILL BE CONCENTRATED
OVER THE NORTHERN LAKES WHICH IS ALSO WHERE THE LARGEST
LAKE-INDUCED INSTABILITY WOULD BE LIKELY. MODELS HAVE MORE QPF IN
THE FAVORED REGIONS FURTHER NORTH...AND THIS PATTERN WAS FOLLOWED
WITH WPC QPF. LARGE SCALE SUPPORT SHOULD BE PROVIDED BY ANOTHER
DIGGING WAVE DURING THE DAY 3 PERIOD...WHICH MAY PRODUCE BROADER
LIGHT PRECIPITATION THAN WOULD BE EXPECTED IN A TYPICAL LAKE
EFFECT PATTERN.

...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 WAS TRENDED
WETTER BASED ON THE TRENDS IN MOST OF THE MODEL GUIDANCE. FOR
PLACEMENT...TRIED TO STRIKE A BALANCE BETWEEN THE ECMWF (FURTHER
NORTH) AND GFS (FURTHER SOUTH). GIVEN THE STRONG SURFACE HIGH
SETTLING INTO THE RIO GRANDE VALLEY...THE TREND MAY BE FOR THIS TO
END UP TOWARD THE SOUTH END OF MODEL SPREAD...BUT CONFIDENCE WAS
NOT HIGH ENOUGH TO PLACE GREATER WEIGHT ON A PARTICULAR SOLUTION.

CHENARD/LAMERS

GRAPHICS AVAILABLE ON THE WEB AT www.wpc.ncep.noaa.gov/qpf/qpf2.shtml

24HR QP VT 14/00Z
 0.01 492612 501627 510642 512652 513655 515661 520685 520694
      522708 521731 517738 514742 512747 509752 503758 499763
      496766 492765 481774 476780 471788 460798 452832 450833
      446833 446840 448845 457858 462863 464862 465859 466853
      468855 470859 472863 476862 479867 483873 483879 485883
      489890 498902 504910 509915 513920 518923 524928 527930
      530931 541944 544951 546955 546960 546968 546974 545979
      542984 539990 536992 532992 525992 520987 509978 503973
      499970 494968 492968 491972 493976 497979 508990 513996
      513999 510000 505998 501999 494996 489004 485003 483000
      480994 478990 476988 474989 472990 469994 463994 458988
      453981 447978 441973 438968 438964 435959 431952 426947
      421942 419938 419933 421931 425930 429928 431924 431918
      429914 427905 426902 425897 425892 423890 418896 415898
      411899 407897 404894 400887 393870 391867 391864 392858
      394856 394845 393842 394836 396832 393830 388824 385819
      378817 371817 366816 367814 372810 378804 383797 386795
      391793 396789 401786 403787 415778 422775 424773 423770
      422766 419757 419752 420746 423741 423736 420735 418733
      422731 428727 431725 432720 433714 432707 432701 428699
      421697 414702 412713 412718 411721 407727 401733 398735
      393737 378743 376751 371757 368757 364754 358748 354742
      352736 351731 348729 344735 342738 339737 332732 327729
      325726 326723 331708 332704 336701 339700 342697 368682
      373675 377669 389656 400643
 0.01 477147 476141 474135 470125 466116 466109 465104 458096
      450092 442086 435080 434075 431070 424065 420065 418070
      417076 417081 425098 431108 436115 440125 443130 446133
      457148 461151 466152 470153 474149 477147
 0.01 445152 445147 443142 441138 439134 437130 433130 434135
      435140 436145 437151 439155 443154 445152
 0.01 430125 431121 430118 428112 425107 422101 420099 417098
      410097 408101 412106 416109 420114 423119 426124 430125
 0.01 398818 398816 396814 395816 395819 397821 398818
 0.01 394807 394805 393803 392801 391803 391806 391808 393810
      394807
 0.01 251812 250808 249802 249796 248790 244791 242794 240797
      239802 238807 239813 240817 245817 247813 251812
 0.25 474619 481625 488633 493642 498652 500657 503664 505680
      507696 507709 505716 504722 499732 496736 491738 481739
      475739 472737 463733 456729 450721 446718 445714 446711
      446704 443699 436693 430686 426684 421683 416685 411688
      404696 402706 401713 399717 395719 389722 370731 367732
      364731 361728 353722 349720 348716 358712 364705 367701
      368694 370690 373687 381681 409652 415646 418642 420637
 0.25 478915 478912 478910 478907 477905 475905 474906 472906
      471907 470910 470912 470915 470917 470918 472919 474919
      475917 477916 478915
 0.25 461896 459889 457884 452875 447868 447863 445859 441856
      438852 434844 423827 420824 416827 417842 424862 432885
      441903 451920 455923 458922 458918 457910 457902 461896
 0.25 438763 438758 437754 435753 433754 430756 428758 428762
      429767 430769 431773 432777 433774 435771 436768 437765
      438763
 0.25 425791 424789 421788 417789 416791 414793 414798 415801
      417804 419805 422804 423801 424798 424794 425791
 0.50 461623 465626 468626 476628 479630 481633 484639 484646
      485653 487657 489662 492666 495668 497674 499688 499701
      497712 495716 492720 485723 477724 468724 462718 457712
      456709 456705 458700 459694 455695 447693 443692 441689
      441684 443680 443676 439674 435674 431673 424672 419672
      414674 407679 395691 391697 387700 383703 377709 374710
      373706 376697 377693 380690 387684 394680 397677 401675
      404673 409670 417666 424660 427654 428647 430640 431634
 0.50 445894 444889 443887 443882 442880 440877 438875 435873
      433877 433878 435881 437884 439887 440890 441893 443895
      445894
 1.00 490690 489688 486687 480687 479683 480681 480675 477674
      474677 473680 474690 472695 471703 471709 473711 477711
      482708 486702 488696 490690
 1.00 476656 477654 476651 475649 473649 472650 471650 470651
      469652 467654 466657 466660 466662 467664 467665 469666
      471665 472665 474664 475662 475661 476659 476658 476656 

24HR QP VT 15/00Z
 0.01 524259 516259 506260 499263 491271 488273 483275 480277
      475280 469286 465289 463294 460298 460305 461318 462324
      465328 470332
 0.01 477618 485625 487629 491633 497639 501642 504647 509658
      514670 519681 524693 526698 529705 533717 538729 542742
      544749 553800 540802 528799 524799 521796 516793 512789
      503782 501780 497779 494777 490777 485774 481769 479767
      477760 476750 474733 464725 459724 454725 447727 443725
      468671 470666 471658 463650 458651 454651 452654 449657
      446663 441668 435673 430676 428683 423699 419716 417722
      419729 422730 421733 420736 421741 424743 428746 439748
      444754 443762 442769 439775 436783 432790 433796 434801
      435804 440804 442803 443799 442792 445792 448793 450796
      455804 455811 454819 460834 463839 469838 474841 476844
      477848 480872 480882 478889 474906 469917 466920 462918
      460912 460902 462892 463881 463877 461874 459871 460867
      460864 458862 454862 448867 449872 446878 446882 443885
      438889 433890 430890 429888 425886 421882 411874 407868
      400864 396859 393852 392848 390843 388836 385831 380828
      376826 372826 365827 365820 366816 371813 374808 377801
      381795 390785 392783 393780 393776 391775 390762 388757
      385754 369735 366735 363736 359740 350745 345750 339755
      333759 330759 328757 317749 319733 321718 324714 330710
      333706 336701 343694 353685 359681 364676 371671 375666
      380661 386655 391651 397644
 0.01 555050 556040 555031 552020 543009 536000 518993 513991
      506990 500987 495984 486979 481979 477976 467967 459962
      452961 447963 440968 434969 428968 419961 414961 411963
      407963 403965 401968 399975 400979 401982 404988 408991
      413995 418998 424006 428010 430016 432018 435019 438019
      441017 451022 452025 452029 450034 441038 438039 438041
      438045 441046 445050 450051 456052 460050 463045 468043
      472039 477034 479032 482032 487037 492043 502049 507053
      514054 519052 525052 528052 532048 536048 537051 539059
      542065 549066 552058 553053 555050
 0.01 527949 527940 525931 522928 520926 517925 512923 510921
      507921 500929 496933 492939 489942 491949 492955 496960
      499965 504970 508970 514968 522962 525957 527949
 0.01 447099 446096 443094 439089 436087 434082 434073 427061
      426058 423055 417050 412045 407043 401037 396034 390030
      386030 383038 380037 378035 375033 372032 365031 362029
      359031 357033 356038 356043 357046 357050 355053 362067
      362070 365073 371073 372072 373074 374078 376080 379080
      382078 386077 389082 397085 401086 403089 405092 406096
      405101 405104 406106 409108 414104 418100 423096 437103
      447099
 0.01 309055 309049 308045 306040 306036 304032 301027 299027
      297031 297038 298042 298046 301051 303055 306057 308056
      309055
 0.01 292841 292835 291832 289832 280831 275836 272845 267853
      265856 266860 273865 275869 276874 279875 283873 283869
      286864 288856 291847 292841
 0.01 270058 271048 272036 270032 268030 265027 265021 263015
      256010 252010 250012 247016 245020 244028 240036 238057
      237067 237079 238086 241090 244088 249086 256081 259074
      266068 270058
 0.25 437632 437639 436642 433647 430651 424655 417662 414671
      410681 407688 403698 400705 396708 391711 383708 374708
      369707 366705 364699 363695 366687 372680 382665 394653
      404642
 0.25 516711 515709 515706 514704 513702 512701 512702 512704
      513707 513709 513712 513715 514717 514720 514722 515725
      515722 515719 515717 514714 515713 516711
 0.25 416821 417818 417816 417814 416811 415809 414808 412809
      412810 412812 411814 412817 412819 413820 414821 415822
      416821 416821
 0.25 407794 408787 404783 400786 398789 395792 391794 390797
      395798 399798 402802 406802 407796 407794
 0.25 257065 257061 256059 253058 250057 247058 246061 245064
      246066 247070 249072 252071 254069 256067 257065
 0.50 403663 400657 396657 393659 387664 383670 378676 376683
      376687 378689 383689 386687 392683 398678 403672 404667
      403663 

24HR QP VT 16/00Z
 0.01 503313 500309 495308 491308 485306 480304 476304 471305
      468304 464304 459303 450304 445302 442299 440293 441286
      442283 440281 435275 430268 427260 425254 424250 422240
      424236 427235 429234 431231 431224 459207 465208 469207
      475204 480202 483202 488202 492201 495200 496196 491191
      489185 486184 482181 480177 478175 475174 469180 457192
      450195 447192 444191 441189 441184 447179 447172 445167
      446153 460142 463142 466141 470133 471128 475126 478126
      481129 485131 486133 489134 493132 495130 496127 496122
      495116 493102 494099 497095 501083 505074 506065 507060
      507055 506052 506043 503032 501027 499023 494013 487998
      483990 480979 479975 478967 477956 472949 469940 472930
      472921 472917 471914 466915 463913 456908 453906 451902
      450899 452892 454887 454883 452879 444876 436876 429875
      424875 421878 415882 413882 412879 410874 409869 408863
      409857 409850 408845 405843 401835 403828 401823 399818
      395817 386819 376824 374822 373815 379795 381787 380775
      375768 370763 364760 359759 353761 347766 342775 324808
      316824 310833 307844 303858 303864 304867 305879 305888
      304899 302910 300922 297945 295969 296974 296980 295996
      296003 297006 299012 302012 304010 315039 316048 313057
      312070 311075 309079 305082 301083 296082 293078 289070
      286069 283069 281072 277080 274083 268083 261085 250083
      244078 240072 236065 236053 236044 236034 236009 238984
      235963 235956 234952 235947 235939 242921 246913 250906
      252903 253897 252883 252875 253866 256850 257846 257842
      259838 263827
 0.01 263827 271812 274803 273796 274790 274783 276774 279765
      282758 289742 291738 294735 302727 311718 318711 324706
      354684 367674 378663 393651 399646 405644 407651 406670
      404675 406682 408693 407703 405713 400723 400730 399735
      402739 403744 407753 407761 408766 411768 413767 421768
      424767 427765 427762 427760 429757 432757 435751 441747
      447742 448741 451745 452750 451755 449766 449773 448778
      453779 456776 456774 459775 462778 464782 466784 471791
      471801 474810 476817 477822 476828 476835 478851 478858
      481862 484867 484872 485879 483885 484890 487894 490899
      498904 502914 502927 499940 497947 495950 492952 491956
      493959 497962 502967 529989 553008 557010 562013 568022
 0.01 547178 547170 545166 542160 539156 534153 534144 532133
      529127 526123 524116 524107 526105 526100 527092 531088
      535093 537105 540111 543114 546120 549123 556130
 0.01 546790 546769 544752 535727 530714 526703 515682 508676
      503678 502682 500685 501689 502698 500711 499718 500721
      502724 502731 505736 509750 514762 519773 522775 525781
      531789 534792 537794 540796 544796 546790
 0.25 562083 556077 551069 546061 541054 535048 530039 528029
      528024 529022 533023 541026 549028 554030 557031 562038
      565042
 0.25 525258 522257 518257 514253 510243 505232 497225 494225
      494227 493233 492239 489244 487252 483255 483260 484266
      486271 490276 499280 510285 514286
 0.25 532203 532197 530192 528188 525185 521183 517182 515187
      515192 518197 520201 523204 528205 531205 532203
 0.25 471845 471843 469842 468842 467843 467846 468846 470847
      471846 471845
 0.25 457808 458800 456794 451796 449799 446804 443806 440810
      439815 441820 444823 448824 451821 453818 455813 457809
      457808
 0.25 456852 457847 456843 452844 451846 449848 447850 444853
      443856 441858 440861 441863 445863 448862 450861 452860
      454857 455855 456852
 0.25 387684 387678 385675 381675 376677 370679 365683 363683
      361686 356692 352696 343699 337703 332707 327712 324717
      316729 312735 310741 305755 300768 299775 298786 299790
      301793 305792 308790 316778 322767 331756 339744 347733
      356725 361719 366714 374704 387684
 0.25 288937 289925 288915 287904 286895 284884 282873 278872
      276875 276880 277886 268900 264915 261924 257932 250944
      246951 242959 242969 244977 246985 246990 244995 241001
      240004 239009 240019 242029 244036 248042 254047 258047
      262045 267041 271034 275027 277023 277016 278995 279985
      281975 285956 288945 288937
 0.50 522266 520266 518266 517268 516270 516273 517275 517276
 0.50 351709 350707 347707 341709 336709 334710 334715 332721
      330726 329733 334732 339728 343724 346719 349714 351709
 0.50 279949 280941 278935 278928 275925 270926 266930 261937
      258943 255948 250956 247961 245968 247973 250976 253982
      253986 248996 243006 242013 243020 244024 248030 252032
      259031 263029 266023 270013 271007 271999 270987 270982
      272976 276966 277955 279949
 1.00 268964 269960 269956 269952 268949 266951 265952 263955
      261956 259959 258962 257964 258966 261967 265967 267966
      268964
 1.00 262009 262004 262002 260000 257999 253000 251002 250004
      249006 248010 248014 249017 250018 253018 256017 258015
      260012 261011 262009