Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 112257
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
557 PM EST MON DEC 11 2017


FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION
VALID DEC 12/0000 UTC THRU DEC 15/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...GREAT LAKES / NORTHEAST...

WITH A DEEP COLD TROUGH ESTABLISHED OVER THE EASTERN U.S...A
CYCLONE IS FORECAST TO SPIN UP ALONG THE LEADING EDGE OF A FRESH
SURGE OF ARCTIC AIR TRACKING THROUGH THE NORTHEAST QUARTER OF THE
NATION. THE SYSTEM WILL PRODUCE AN INLAND SURFACE LOW TRACK
ROUNDING FROM THE NORTHERN OHIO VALLEY TO CENTRAL AND NORTHERN NEW
ENGLAND...THOUGH THE LOW MAY GET CLOSE TO COASTAL MAINE. A
PRONOUNCED LEAD SHORTWAVE TROUGH THAT WAS SEEN DIVING TOWARD LOWER
LAKE MICHIGAN THIS AFTERNOON WILL BE THE MAIN DRIVER OF THE
EVENT...ALTHOUGH A TRAILING LARGER SCALE TROUGH AXIS WILL
CONTRIBUTE TO FURTHER DEEPENING ON TUESDAY AS THE LARGER SCALE
SYSTEM TAKES ON A NEGATIVE TILT.

FROM A LIQUID TO LIQUID EQUIVALENT STAND POINT...THE SYSTEM
PROGRESSION...ALONG WITH LOW PRECIPITABLE WATER VALUES / BRIEFLY
PEAKING TO 0.50 INCHES OVER CENTRAL TO NORTHERN NEW ENGLAND / AND
THE DISJOINTED INTERACTION BETWEEN THE LEAD SHORTWAVE AND LARGER
SCALE TROUGH...ARE ALL REASONS TO HOLD THE PRECIPITATION TOTALS IN
CHECK. IN TERMS OF WINTER WEATHER IMPACTS...HOWEVER...CONDITIONS
ARE RIPE FOR SNOW WITH FAIRLY HIGH SNOW TO LIQUID RATIOS OF AT
LEAST 12:1 AND AS HIGH AS 16:1 IN SOME OF THE LAKE ENHANCED SNOWS.
SEE THE WPC HEAVY SNOW DISCUSSION...QPFHSD...FOR DETAILS.

LAKE EFFECT WILL BEGIN OFF LAKE SUPERIOR THIS AFTERNOON...LAKE
MICHIGAN THIS EVENING. SNOW BANDS WILL INITIATE OFF ERIE AND
ONTARIO TUESDAY...WHILE CONTINUING BACK WEST AS WELL...WITH SOME
STREAMERS FLYING ALL THE WAY THROUGH PARTS OF IN/OH TOWARD THE
CENTRAL APPALACHIANS...PER THE HI-RES GUIDANCE. FOR THE LAKE
EFFECT WPC QPF USED HI-RES MODELS WITH A CHECK VERSUS NDFD AS WELL.

THE SYNOPTIC PRECIP EVENT WILL KICK IN OVERNIGHT AS WARM ADVECTION
DEVELOPS FROM THE MID ATLANTIC TO NEW YORK / NEW ENGLAND...WITH
DEEP LAYER ASCENT ENHANCED BY THE LEAD SHORTWAVE. UPSLOPE
ENHANCEMENT LOOKS TO BE IN PLAY DURING MUCH OF THE EVENT FOR THE
MOUNTAIN AREAS IN NEW YORK AND NEW ENGLAND...THOUGH AGAIN THE LOW
PW VALUES WILL CAP THE PRECIP MAGNITUDES SOMEWHAT. THE 12Z 27KM
GFS SHOWED GOOD DETAIL IN THE TERRAIN ENHANCED AREAS AND COASTAL
MAINE...SO IT FORMED THE BASIS OF OUR FORECAST. THE BEST MATCHING
HI-RES MODEL WAS THE 12Z NMMB...SO WE STARTED WITH A 50/50 BLEND
AND THEN MADE SOME MANUAL ADJUSTMENTS.



DAYS 2/3...

WPC QPF WAS BASED ON A CONSENSUS VALUE FROM THE 12Z
GFS/ECMWF/NAM...WITH MINOR CONSIDERATION OF THE 12Z UKMET.

...EASTERN GREAT LAKES/NEW ENGLAND...

LOW PRESSURE WILL CONTINUE TO DEVELOP AS IT MOVES NORTH FROM NEW
HAMPSHIRE TUESDAY NIGHT. ATLANTIC MOISTURE STREAMING IN AHEAD OF
THE LOW ON 45 TO 55 KNOT 850MB FLOW WILL CONVERGE INTO THE COMMA
HEAD ACROSS MAINE WITH SNOW CHANGING TO RAIN BEFORE TAPERING OFF
IN THE DRY SLOT THROUGH THE NIGHT. 12Z GUIDANCE INCREASED PRECIP
ACROSS NORTHERN MAINE DUE TO TIMING AND INTENSITY CHANGES. PLEASE
REFER TO THE HEAVY SNOW DISCUSSION FOR SNOWFALL DETAILS...QPFHSD.
THE DEFORMATION ZONE ON THE NORTH/NORTHWEST SIDE OF THE LOW WILL
MAINLY BE OVER QUEBEC BY TUESDAY NIGHT THOUGH PERSISTENT FLOW WITH
UPSLOPE FORCING IS NOTED FOR THE ADIRONDACKS THROUGH TUESDAY NIGHT.

NORTHWEST FLOW BEHIND THE LOW AND STRONG LOW LEVEL ADVECTION WILL
SET UP FAVORABLE CONDITIONS FOR SOME INTENSE LAKE EFFECT SNOWS IN
THE EASTERN GREAT LAKES TUESDAY NIGHT...TAPERING OFF WEDNESDAY
MORNING FROM THIS LOW. THE NEXT CLIPPER IS FORECAST TO TRACK SOUTH
OF THIS AREA THURSDAY.


...UPPER MIDWEST/GREAT LAKES/MID-ATLANTIC...

A RELATIVELY WEAK SHORTWAVE TROUGH DROPS SOUTH-SOUTHEAST ACROSS
THE UPPER MIDWEST WEDNESDAY MORNING...CROSSES THE SOUTHERN PORTION
OF THE GREAT LAKES INTO WEDNESDAY NIGHT...THEN PUSHES OFF THE
CENTRAL MID-ATLANTIC COAST THURSDAY MORNING. A CONTINENTAL AIRMASS
WILL BE IN PLACE...SO GENERALLY LIGHT PRECIPITATION IS EXPECTED
OUTSIDE OF LOCALIZED MESOSCALE BANDING. OF NOTE IS THE INCREASE IN
PRECIP IN THE LEE OF THE CENTRAL APPALACHIANS THURSDAY
MORNING...PARTICULARLY IN THE 12Z GFS AND UKMET. SOUTHERN PA AND
CENTRAL MD DOES EXPERIENCE LESS DOWNSLOPING EFFECTS THAT AREAS
FARTHER SOUTH (LIKE VA)...SO IT IS REASONABLE TO HAVE MEASURABLE
PRECIPITATION ALONG THE PA/MD BORDER THURSDAY MORNING.

BURKE/JACKSON

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

24HR QP VT 13/00Z
 0.01 505281 506276 505271 502263 500256 496249 492247 490244
      482242 475242 469244 464248 458249 455251 451251 445255
      441261 444263 447262 453260 459263 467265 474266 482268
      486271 488275 492281 501283 505281
 0.01 489701 488692 487686 483675 478667 474662 471659 465653
      459643 456639 451638 445638 439640 434642 430645 425647
      419648 409648 400647 390650 382657 377661 375665 368675
      346706 339715 337718 335724 332735 334740 338742 343743
      345746 349747 354746 362739 365736 367732 374726 380723
      383720 399703 403705 404711 402722 402749 403758 402762
      404769 405773 404776 400780 396783 387788 362817 358821
      356826 354830 352836 354842 357841 359839 363836 368836
      377835 382838 384843 388852 390856 392857 394861 393885
      394894 396897 397901 400901 405903 409902 412899 416891
      418886 421882 423878 425875 429875 441874 447874 451875
      454875 456877 459882 458898 463905 466904 469900 480882
      471828 472822 472814 470799 469791 468786 468781 468771
      466755 467751 469749 472746 476741 479736 482731 485725
      488714 489701
 0.25 472713 472706 470700 468687 466682 463677 460672 457667
      456663 453659 449658 444659 439663 436666 433670 432675
      416711 415717 415723 414734 415747 418757 422765 425770
      425775 419783 416788 413791 411794 411800 411809 412816
      414821 418820 421817 426814 427822 428824 431825 437823
      442821 453820 457818 459815 460808 456803 448800 444799
      440801 439796 441791 445781 446775 448770 464733 472713
 0.25 473880 472875 471869 469865 465861 462860 459864 458869
      461874 463876 465881 468884 471882 473880
 0.25 450862 448858 445857 438856 431857 424855 418853 414852
      412853 412856 415865 418867 421868 425868 429867 438867
      447865 450862
 0.25 408676 407671 404668 401666 397666 392667 388670 382675
      371688 362700 354715 353719 353724 354730 353735 357736
      360733 366727 377715 381709 386701 390695 397691 403685
      407678 408676
 0.50 455693 453682 452674 449670 445669 442672 439676 437680
      434689 430697 427707 425717 423728 424732 427736 426747
      426760 429764 432765 436767 439763 441760 441753 439746
      439741 440737 439734 438731 441728 445725 446720 447715
      449710 453703 455698 455693
 0.50 455732 455731 453732 452733 453733 455733 455732
 0.50 428788 427786 424789 422794 420797 418802 417807 417811
      419809 421804 423799 425796 428791 428788
 0.50 396680 393678 390680 387682 385683 383685 382689 382691
      384692 387691 389690 391688 394685 395682 396680
 0.50 373711 372707 370705 368707 367710 368712 367714 365717
      363719 362722 361724 362727 364725 365722 367720 368717
      370715 371713 373711
 1.00 444698 444693 441693 440695 439698 437700 435703 434706
      435710 437711 439712 441711 442708 443705 444701 444698

24HR QP VT 14/00Z
 0.01 487614 497630 507653 511661 515671 518682 521700 522715
      522726 521731 519735 517740 514742 511750 506756 499761
      494767 479775 473784 471789 469791 467792 459798 456799
      455803 456810 456815 455821 452832 450833 447831 442828
      434826 427822 425820 423814 420815 421818 422823 430836
      439851 440854 442855 447853 451855 456856 461856 465851
      468857 475863 478866 480871 479875 476878 474881 470881
      459869 456867 451869 454874 456879 457882 460885 468885
      473883 475884 478882 481882 483884 491891 498897 510910
      517913 525912 530918 532923 534925 539932 545937 549944
      550953 552959 552968 552974 550977 547979 542980 540982
      536981 534979 531979 525978 514978 509978 506977 503974
      499972 494970 491970 487965 483963 475964 468964 466959
      466956 467949 466941 464937 461935 456931 445923 424889
      419882 416878 412880 409882 407880 402870 399861 399849
      398835 394826 401802 404802 401798 396799 393802 389813
      384814 379816 368818 365820 362824 358825 358822 363816
      375804 381798 387792 393788 398788 402785 408781 412774
      411761 409758 409753 414750 418745 417737 418732 417724
      421723 431720 433716 435710 435705 434697 427696 422697
      418698 413706 413711 411716 409719 407723 405727 404733
      402736 392737 386744 384745 380744 373746 370750 369755
      366756 361749 358746 353747 344752 339754 336756 331757
      328760 321757 311758 302762 299762 298758 297748 301742
      311740 314738 319737 329734 332733 332732 327729 325728
      325725 326720 329711 331706 334704 341697 345697 349693
      353692 356690 364687 367685 371684 380681 386674 391666
      397660 402654 406648 412647 417643 420637
 0.01 560065 561057 560050 558045 555043 550043 545043 543046
      544052 546055 549058 553061 557064 560066 560065
 0.01 520078 520072 519067 519064 516061 514058 513053 517048
      518045 517041 513036 505026 501019 497015 489005 487004
      486009 484010 482005 479999 477992 471977 467974 465974
      465979 468986 468992 468998 465000 463998 458995 452993
      448993 448995 451001 456005 475021 491043 493051 497058
      505068 508074 513079 516080 520078
 0.01 456108 455103 455097 453093 450092 445094 440092 438094
      439098 443101 446104 449107 452110 456108 456108
 0.01 431928 431926 429923 428919 426916 426914 424909 423907
      422905 420905 420910 421912 422917 424919 424921 426924
      428926 429929 431928
 0.01 430973 429973 428971 428970 428971 427973 428975 428976
      428975 429974 430973
 0.01 395865 394863 394862 393860 392860 391858 391856 390856
      390858 392860 392863 394865 395865
 0.01 257817 255812 251808 247805 247800 244796 240799 238805
      239810 242810 243808 246809 249813 253816 257817
 0.25 535960 534960 533959 531959 530959 528959 528960 530962
      531963 532963 533963 534961 535960
 0.25 509698 508690 507680 504667 500657 495648 489639 483634
      477629 470626 461626 450628 445635 435638 432642 430648
      429659 429671 431675 434679 438680 441684 444699 445708
      445715 443720 440723 436727 436730 440732 443736 443743
      438750 432757 429762 428768 427772 428779 427784 429788
      432788 434781 436770 440762 442757 444754 449751 453750
      461747 471746 477748 482748 487745 496739 501732 505723
      507716 508708 509698
 0.25 506939 505937 504936 503937 502938 501938 499937 497938
      497939 497940 499941 501941 502941 504940 505940 506939
 0.25 426789 424787 422787 421787 418790 417792 416795 415800
      416804 417808 420806 422804 424802 425798 425796 426791
      426789
 0.25 412680 409676 407674 403673 400675 397678 393681 389684
      387687 386690 391689 396687 401685 405683 410681 412680
 0.25 428867 428862 427860 425857 422856 420855 417855 415858
      417863 419865 421866 424867 426867 428867
 0.25 402701 400694 399692 385694 371699 361705 353714 354717
      356718 358723 362728 366732 372733 379732 385728 389724
      393720 396714 401704 402701
 0.50 503702 502692 501681 498667 495660 491656 484648 480645
      476643 465643 460643 455641 446641 441643 436647 434653
      434658 437665 441670 446680 449687 450697 454710 455720
      456727 460731 464732 476734 480734 486733 491731 495726
      501717 503708 503702
 0.50 422796 422794 421794 420794 419797 418799 418800 420801
      421799 422797 422796
 0.50 385706 383705 379706 376707 372708 370709 369712 369716
      370720 372721 376720 378719 380716 382713 383711 385708
      385706
 1.00 490693 489687 487684 485682 483677 481673 478672 476676
      478681 480685 479690 475696 470702 470708 471713 474715
      477715 483711 487704 490695 490693

24HR QP VT 15/00Z
 0.01 470620 491635 499645 508659 509662 510668 512682 515707
      516714 514717 512725 508740 505746 500752 495756 491762
      488765 484766 482766 479763 470753 467750 464748 461739
      460736 457735 451740 446744 443745 440743 446734 444727
      443722 445719 447712 453706 457700 460691 459679 461673
      463670 467667 471668 476666 478663 480660 479657 475649
      472641 469639 467642 463646 446670 438680 433687 430690
      427690 421687 415683 410697 411701 414698 416703 417707
      416711 417721 418741 417745 417751 420759 425776 426788
      428795 428806 429812 431812 438810 442810 444812 444817
      441820 440824 437825 435824 433824 431826 431831 432836
      433838 437846 441851 443854 448855 454857 458861 463867
      466860 468851 470851 471855 473875 481886 482895 482904
      480912 477915 474915 470915 466909 458908 456905 453903
      448901 445901 443899 439899 434895 429893 423886 419879
      418875 415873 412866 407862 401862 393849 388845 384841
      379824 374818 372815 371813 375806 377797 379795 383794
      388790 392784 390778 387776 384777 377778 370779 365780
      361783 357786 356783 357779 360765 360759 360754 362746
      365739 366736 361736 359739 354740 347736 343732 339726
      335721 334717 335714 349690 356680 359677 362673 366672
      371672 382674 385674 387671 391666 402653 405650 408649
      417646 430642 434638 437632
 0.01 498281 501269 502257 503251 501254 498263 495265 492264
      488258 485259 482263 478269 476273 476278 478281 482282
      489283 496283 498281
 0.01 516957 514952 513947 511942 510936 507931 504930 501933
      499939 499944 501947 505949 507952 510956 514958 516957
 0.01 508045 507031 503018 499013 495010 493009 493005 495000
      493996 489995 486997 483997 477996 472994 465993 459993
      455988 455981 452976 443971 440964 437960 432959 428956
      412940 403938 396938 393940 391943 391946 391955 391964
      393970 395975 398979 401984 405987 408991 412995 416999
      418005 421017 423024 426030 429042 431040 431033 432026
      436022 441025 440032 437037 437041 438044 440050 444053
      451055 453061 453065 452068 448072 447078 450078 451076
      453073 455072 460069 462067 464062 464053 467046 471045
      471054 472056 475056 478052 485053 486053 488048 489043
      488039 490038 494038 496036 501040 505045 508045
 0.01 504055 502052 500052 498054 496056 495057 491057 489059
      489063 490066 492067 496067 497065 499063 501060 502057
      504055
 0.01 504965 504964 503962 503960 502959 501957 501954 500954
      500957 500960 500962 500965 500967 501968 502968 503967
      504965 504965
 0.01 489932 489929 487927 487929 487932 489932 489932
 0.01 435770 435766 435761 434756 432754 431752 429750 427748
      425748 426753 426755 428760 428764 430766 431771 433773
      435770
 0.01 424063 420055 409049 401049 396047 394043 392047 386049
      389051 389055 388056 386061 389064 392068 396067 402068
      406070 412073 417074 423067 424063
 0.01 418024 418022 416020 416019 415017 414017 413015 411014
      409014 407016 407017 409017 411019 412022 413022 414024
      416025 418024 418024
 0.01 401012 401009 401007 399006 397005 395006 395007 395009
      397011 397012 399012 401012 401012
 0.01 372062 371061 371059 370058 368058 367059 366061 367063
      368064 369064 370064 371062 372062
 0.01 363796 363794 363791 362791 360791 360792 360794 360796
      361797 363797 363796
 0.01 361056 359056 357056 359056 361056 361056
 0.01 282935 281931 279929 277931 273935 270940 267945 265952
      262956 261960 265961 266959 270955 274950 277945 280941
      282935
 0.25 500703 500695 498688 497681 494677 491680 490685 489690
      489698 488704 488707 490711 495711 498707 500703
 0.25 406815 404808 404801 405792 404787 401787 396789 391793
      387797 386799 387803 392803 397807 400811 404818 406815

$$





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