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Quantitative Precipitation Forecast (QPF) Discussion
 
(Caution: Version displayed is not the latest version. - Issued 2004Z Dec 11, 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
304 PM EST MON DEC 11 2017


PRELIM 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 506275 505271 502263 500256 496249 492247 489244
      482242 475242 469244 463248 458249 454251 451251 445255
      441261 444263 447262 453260 459263 468265 474266 483269
      486271 488275 493281 501283 505281
 0.01 489701 488692 487686 482672 476665 470658 464651 459642
      455639 451638 447638 442639 436641 433644 427647 420648
      411648 402647 388650 382657 379659 376663 371670 360687
      349703 337718 334727 332737 335741 339743 342743 344744
      348747 353746 356745 364738 369731 375726 383720 391712
      393707 396704 400703 402704 404706 404711 402717 402723
      401728 402735 402760 404771 402778 399781 391786 386789
      382793 370808 359820 355829 353835 353841 357841 361839
      363836 367836 371835 376835 380837 384841 385846 389855
      396860 403864 408868 410873 412877 417877 422875 428875
      439874 450874 455877 459881 458896 461902 463905 467904
      478886 481874 479864 476859 474853 472848 471840 471831
      472823 472818 472811 470794 468788 469781 467765 467757
      466753 468750 475743 481734 484726 487715 489707 489701
 0.25 472713 472705 470699 467685 465680 462676 457667 455662
      452659 447659 442660 436666 433670 432675 427685 424694
      423699 420704 416711 415718 415724 414736 415748 418757
      423767 425772 423776 421780 419785 413791 411795 411800
      411812 413819 415821 418820 421817 424815 427817 427824
      430825 438823 446821 451821 457818 459815 460808 458804
      454802 446799 441800 438799 439796 443786 446778 449768
      453758 457749 461740 465730 469721 472713
 0.25 473880 472875 471869 469865 465861 462860 459864 458869
      461874 463876 465881 468884 471882 473880
 0.25 450862 447858 445857 438856 431857 424856 417853 414853
      412856 413861 415864 418867 421868 429867 438867 447865
      450862
 0.25 408676 406670 404668 401666 397666 391668 388670 382675
      371688 362700 354715 353735 358735 361733 366727 377715
      381709 386701 391695 397691 403685 407678 408676
 0.50 455693 455687 453680 452673 449670 445669 442672 437680
      434690 430697 427708 425717 423729 424732 427736 426749
      426760 429764 433765 436767 439763 441759 441752 439746
      439741 440736 439733 438731 441728 446725 446719 447714
      449710 453702 455698 455693
 0.50 455732 455731 453732 452733 453733 455733 455732
 0.50 451735 450735 450736 450737 451735
 0.50 428788 427786 424789 422794 420797 418802 417807 417812
      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 373707 371706 368709 365715 361721 361725 363725
      367718 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 498633 508655 513664 516673 519685 521698 522714
      521727 520732 518736 514744 511750 507756 501760 496766
      493769 487771 481772 477776 473785 470790 466792 460798
      457799 455804 456811 455816 453828 452833 450833 443830
      437827 434825 429824 427823 425819 423814 420814 419816
      420820 421827 424836 437851 439854 442855 444854 448852
      453855 461856 464852 466854 477864 479866 480870 479875
      476879 473882 469880 464875 458868 453867 451868 452871
      459885 471885 474883 477884 481882 486886 493893 500898
      503903 507906 511911 518914 523912 526912 528916 530920
      532924 536928 544936 549944 552966 552974 549977 541982
      536981 533979 522978 513978 507978 504975 498972 494970
      491970 488967 485970 481969 479967 476965 472965 469964
      466960 465957 467953 467946 464941 457935 452929 445923
      440912 429897 423892 415887 411887 409883 407880 407874
      406867 405863 401853 400848 398844 394835 394828 392823
      391819 393815 394812 397811 405810 407809 406806 404801
      400798 395800 392804 391810 388813 383814 379816 375817
      370818 367818 365820 363823 360826 358824 359821 371808
      377803 383796 387792 393788 398788 401786 408782 410780
      411777 412771 411762 409757 408749 411746 414747 417743
      417732 417726 419723 424722 427719 433712 435708 435701
      435698 432697 429697 425696 420697 416700 414704 412709
      412713 408720 405727 403731 401733 391738 383743 371746
      368748 366747 361746 339749 335754 328756 327764 320759
      317758 311758 302762 299762 298757 297748 301742 309740
      348695 354691 362688 365685 371684 380681 387673 391667
      400655 405651 407648 411647 417643 420637
 0.01 555056 554051 552047 548042 544037 539035 531033 524032
      518031 512033 503023 498010 488012 486013 484010 480006
      477003 475004 473009 470010 465011 463013 464016 473026
      477029 482033 487033 488038 490046 496059 501063 505068
      508074 513079 516080 518078 520076 520072 519068 520064
      524060 529053 533049 538047 544049 550055 553057 555056
 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 257817 256814 253810 251807 250802 250798 247796 242796
      240799 238803 239809 242812 247811 251814 253816 257818
      257817
 0.25 535960 534960 533959 531959 530959 528959 528960 530962
      531963 532963 533963 534961 535960
 0.25 509698 508688 506680 504667 500657 495648 489639 483634
      477629 470626 460626 450628 445635 435638 432643 429648
      429659 429672 430675 434679 438680 441685 444699 445708
      445715 443719 436727 436730 440732 442736 443743 442747
      440752 436755 433759 430763 428768 428778 427783 429788
      433787 434781 436770 444753 462745 471745 477748 480748
      483747 488745 495739 501733 505723 507716 508708 509698
 0.25 506939 505937 505936 504936 503937 502938 501938 499937
      497937 497939 497940 499941 501941 502941 504940 505940
      506939
 0.25 425796 426791 424787 422786 419787 418790 416792 416795
      415800 416804 417808 420806 422804 424802 425798 425796
 0.25 410678 407675 404673 401674 398677 394680 390682 387686
      385689 389690 395688 400686 403684 406682 410678
 0.25 425864 426862 424860 422859 420859 419859 417860 419863
      421864 421865 422865 424865 425864
 0.25 402701 400694 399692 385694 371699 361705 353714 358723
      362728 366731 372732 379731 384728 389724 393720 396714
      401704 402701
 0.50 503702 502692 502683 498668 496662 492657 486650 479644
      474642 471643 459643 451641 446641 442642 437646 435650
      434657 436662 442671 445676 447682 449688 450697 454711
      455719 456726 460731 464732 474732 485732 490731 494728
      500718 502712 503705 503702
 0.50 422796 422794 421794 420794 419797 418799 418800 420801
      421799 422797 422796
 0.50 385706 383706 379706 376706 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 470701 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