THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


QUANTITATIVE PRECIPITATION FORECAST DISCUSSION


[Abbreviations and acronyms used in this product]
Geographic boundaries:    Map 1- [Color] [B/W Print Version]      Map 2 - [Color] [B/W Print Version]



QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
529 PM EST SUN DEC 28 2014


FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION
VALID DEC 29/0000 UTC THRU JAN 01/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


WITH THE 18Z MODEL RUNS IN VERY GOOD AGREMENT WITH THE 12Z
RUNS..MADE NO CHANGES TO THE PRELIM DAY 1 QPF.

DAY 1...

...LOWER MS VALLEY INTO THE TN VALLEY...SOUTHEAST...SOUTHERN
APPALACHIANS...AND MID-ATLANTIC...

THE AXIS OF ABOVE-AVERAGE PW VALUES ALONG AND AHEAD OF THE SURFACE
FRONTAL BOUNDARY WILL SHIFT SLOWLY TO THE EAST ALONG WITH THE
FRONT DURING THE DAY 1 PERIOD (INTO THE SOUTHEASTERN U.S.).
PRECIPITATION RATES BE MOST ROBUST ALONG THIS PW AXIS WHERE BEST
LI'S ARE NEAR OR SLIGHTLY BELOW 0C (I.E. WEAKEST STATIC
STABILITY)...HOWEVER...DEEP-LAYER INSTABILITY IS FAR TOO LOW TO
SUPPORT AN EXCESSIVE RAINFALL THREAT DURING THIS PERIOD.
OTHERWISE...THERE WILL STILL BE A BROAD AREA OF FORCING BEHIND THE
SURFACE FRONT...WITHIN A FAIRLY EXPANSIVE WARM CONVEYOR BELT (WBC)
WHERE DUAL UPPER DYNAMICAL SUPPORT CONTINUES AHEAD OF THE SHEARING
OUT SOUTHERN STREAM SHORTWAVE (SUPPLYING THE DEEP LAYER MOISTURE
FLUX) AND WITHIN THE RIGHT ENTRANCE REGION OF THE NORTHERN STREAM
JET STREAK (SUPPLYING THE LOW-MID LEVEL FGEN...WITH A GOOD PORTION
OF THE PCPN SHIELD ANAFRONTAL OR BEHIND THE SFC COLD FRONTAL
BNDRY). OVERALL...WPC CONTINUED WITH A MULTI-MODEL BLEND WITH THE
QPF DETAILS...THOUGH UTILIZING THE MOST RECENT NSSL-WRF OUTPUT
EARLY IN THE PERIOD TO CAPTURE SOME OF THE CONVECTIVE DETAILS.
AREAL-AVERAGE AMOUNTS RANGE BETWEEN .25 AND .50+ INTO THE LOWER
APPALACHIANS AND LOWER MID ATLANTIC REGION (PTNS OF WRN/CEN NC
INTO SOUTHERN VA).
 

...PAC NW...NORTHERN GREAT BASIN...NORTHERN-CENTRAL
ROCKIES...PORTIONS OF THE CENTRAL/NORTHERN HIGH PLAINS...

MODELS REMAIN= IN GOOD AGREEMENT WITH THE LOWERING OF HEIGHTS
ACROSS THE NORTHWESTERN QUARTER OF THE NATION DAY 1 AS AN INITIAL
AREA OF SHORTWAVE ENERGY CONTINUES TO PUSH SOUTHEASTWARD EARLY
INTO THE CENTRAL GREAT BASIN...FOLLOWED BY A STRONGER AREA OF
HEIGHT FALLS DIVING SOUTHWARD ACROSS THE PACIFIC NORTHWEST TONIGHT
INTO MONDAY. PW VALUES WILL REMAIN LOW AHEAD OF THE LOWERING
HEIGHTS. HOWEVER...THE PERSISTENT CYCLONIC FLOW WILL SUPPORT
MODERATE TO ISOLATED HEAVY PRECIP TOTALS IN THE FAVORED UPSLOPE
AREAS OF THE OR/SOUTHERN WA CASCADES...BLUE MTS OF NORTHEAST
OREGON...INTO THE BITTEROOTS/SAWTOOTH OF ID AND FROM THE WASATCH
INTO THE TETONS AND INTO THE NW COLORADO ROCKIES. TO THE EAST OF
THE CONTINENTAL DIVIDE...ARCTIC AIR WILL BE SINKING SOUTHWARD INTO
THE NORTHERN HIGH PLAINS. POST-FRONTAL UPSLOPE FLOW WILL SUPPORT
GENERALLY LIGHT PRECIP TOTALS (SNOW). FOR QPF DETAILS...WPC
UTILIZED AN ENSEMBLE OF HIGH-RESOLUTION GUIDANCE ALONG WITH THE
HIGH-RES ECMWF. SEE THE LATEST QPFHSD FOR FURTHER WINTER WEATHER
DETAILS.


DAYS 2/3...

WEST
~~~~
LIGHT TO MODERATE PRECIPITATION IS EXPECTED ACROSS PORTIONS OF THE
INTERMOUNTAIN WEST, INCLUDING CA AND AZ, DURING THIS TWO-DAY
PERIOD AS A CLOSED CYCLONE DROPS TOWARDS THE SOUTHWEST, WITH SOME
UNUSUALLY LOW SNOW LEVELS DUE TO ITS STRONG NATURE ALOFT.  THE
HEIGHT FALLS SHOULD BE SUFFICIENT TO BRING SOUTHERN AZ INTO THE
PRECIPITATION PATTERN ON WEDNESDAY.  OVERALL, WENT WITH THE WETTER
GUIDANCE IN THIS REGION (NEAR THE 00Z GEFS-BASED REFORECAST/TO
SOME DEGREE THE 12Z ECMWF) AS THE MODEL GUIDANCE (MESOSCALE AND
OTHERWISE) TENDS TO HAVE A DRY BIAS IN THIS REGION.  THIS FORECAST
MAINTAINED REASONABLE CONTINUITY WITH THE 12Z WPC QPF.

TEXAS
~~~~~
A RETURN FLOW OF MOISTURE INVADES PORTIONS OF THE LONE STAR STATE
TUESDAY AND WEDNESDAY DUE TO THE UPPER LOW MOVING THROUGH THE
SOUTHWEST.  THE AVAILABLE GUIDANCE IS GENERALLY AGREEABLE WITH
MODERATE TO HEAVY RAINS NEAR THE INTERNATIONAL BORDER, WHICH WAS
CLOSE TO THE 12Z WPC QPF, SO STAYED THE COURSE HERE.

GREAT LAKES
~~~~~~~~~~~
LIGHT LAKE EFFECT SNOWS ARE EXPECTED THIS PERIOD AS COLD AIR
SWEEPS ACROSS THE LAKES ON THE HEELS OF LOW-LEVEL
WEST-NORTHWESTERLY FLOW.  THE FLOW ITSELF IS NOT STRONGLY CYCLONIC
IN THE LOW-LEVELS, SO BELIEVE AMOUNTS WILL BE RATHER LIGHT, WHICH
IS REFLECTED IN THE MOST RECENT MODEL GUIDANCE.  THIS IDEA IS ALSO
CLOSE TO THE 12Z WPC QPF, SO MAINTAINED GOOD CONTINUITY IN THIS
REGION.

SOUTHEAST/MID-ATLANTIC STATES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THE 12Z NAM/09Z SREF ARE MUCH WETTER THAN THE OTHER GUIDANCE WITH
THE PRECIPITATION PATTERN ACROSS PORTIONS OF THE MID-ATLANTIC
STATES.  CONSIDERING THE GENERAL TREND TOWARDS A DRIER FORECAST
WITHIN A REGION OF QUASI-ZONAL FLOW, WHICH SHOULD LIMIT THE
AMPLITUDE OF ANY EMBEDDED SHORTWAVES, WENT TOWARDS THE DRIER
GUIDANCE WHICH MAINTAINED REASONABLE CONTINUITY WITH THE 12Z WPC
QPF, 00Z GEFS-BASED REFORECAST, AND 12Z ECMWF/GFS RUNS.  OUR
AUTOMATED QPF PROBABILITIES (AND SNOWFALL AMOUNT-BASED
PROBABILITIES) ONLINE ARE LIKELY TOO HEAVILY SREF-BASED
CONSIDERING CURRENT MODEL PREFERENCES, AND SHOULD BE GIVEN MINIMAL
WEIGHT.

HURLEY/TERRY/ROTH

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

24HR QP VT 30/00Z
 0.01 528175 530169 529164 526155 528150 528143 529129 529124
      528121 523118 517121 512123 505124 499121 489114 485110
      482102 475086 472066 471061 471055 472040 473035 473029
      471025 471019 470015 466011 445993 438983 433968 431957
      432944 433940 433934 433930 429926 425927 418926 413929
      410934 396961 391976 382983 378989 374999 374009 375013
      375019 379024 384029 392040 390045 388047 385048 381046
      375043 370043 369048 368051 365052 365054 368055 375057
      377061 375063 371062 367061 366063 370069 372074 372078
      373083 375086 377094 378098 379099 382097 383099 387095
      392097 394099 395096 398087 399083 402086 405091 407093
      408096 406098 403104 401107 398106 396104 396107 394108
      390109 384113 380114 379118 378123 377125 377128 380131
      386133 390137 395136 397136 398139 397143 390145 389148
      391152 390153 394155 395163 397171 401172 403177 405180
      408178 410175 413172 414177 413179 416182 416184 420191
      421194 421199 416201 410202 414205 421206 420209 421211
      422216 420219 418221 418225 421228 420231 414233 409240
      402242 399244 401249 407253 413255 420255 427257 433254
      440254 446253 451250 458250 460250 463247 466242 470239
      473239 480241 484240 485238 488240 489237 487236 486235
      483234 482231 484226 486225 491219 493217 495216 501221
      506225 509229 511233 514231 515229 516224 520209 520199
      520193 519188 517180 513173 508167 503160 481144 478142
      480140 486143 497150 506152 511157 516162 521169 525176
      528175
 0.01 476192 476189 475187 475186 475184 474182 474181 474179
      473177 472178 471180 471183 470183 469183 467184 467185
      466187 465189 466191 468190 468189 470189 471190 473191
      474193 476192
 0.01 468692 467684 466676 462666 462660 462653 462649 460641
      456632 454629 451629 449634 448638 448643 449650 455675
      458683 459689 457693 454697 452702 449710 442713 441718
      442723 438721 439725 440727 439730 438733 439736 441742
      435743 432745 430747 427745 426752 427765 428771 426777
      423777 421777 422781 422787 420791 420801 422801 423796
      428787 431784 431779 433768 435773 435768 437763 439759
      440755 441751 443750 447749 448746 449741 449736 447733
      448730 451726 454723 459722 464718 467707 468692
 0.01 481874 481866 479862 476858 474853 473848 470843 468841
      463841 457832 454821 451810 453805 453799 453790 450786
      447783 445785 443800 439801 442805 441807 438808 435809
      430816 427821 429822 433824 436830 436835 439832 445827
      448827 448831 444835 444839 445845 443851 443855 441860
      439863 436864 433864 424862 418867 413874 413876 418877
      417874 417870 421870 429867 440866 447863 450858 455856
      458859 459864 463873 465877 464883 463889 462898 466907
      469908 471904 474892 477881 481874
 0.01 432730 430729 429730 428731 429732 431731 432730 432730
 0.01 428831 427829 427826 426829 426831 428831 428831
 0.01 408683 405682 402683 397685 395684 395680 395675 391676
      387677 385681 380689 375695 369700 363708 350720 334731
      328735 321744 314753 305764 290770 282770 274772 268776
      265784 265792 269795 278797 284800 290802 291803 303804
      316797 314806 310812 307819 304824 300827 292832 289834
      286839 278853 271868 270872 268876 266886 263895 259905
      253921 255930 255935 257937 265942 272947 281950 292950
      310946 322938 329933 335926 341919 346911 354895 367860
      381824 388808 390804 390800 392787 393776 393769 391763
      391752 394743 398737 400734 401729 404725 404719 406708
      408683
 0.01 422086 422084 421082 420081 419081 418080 416079 415079
      413080 414082 416083 418085 419085 419086 421088 422086
 0.01 413139 411137 410136 408133 406133 405131 403130 401131
      400132 399134 397136 399138 400139 401139 402140 404141
      405142 407142 409142 411141 413139
 0.01 267808 268806 268804 267803 265803 263804 261804 259804
      258805 257805 256807 255808 255810 256812 256813 257814
      258814 260814 262813 263813 264812 266811 266810 267808
      267808
 0.01 254820 254818 253817 252816 251815 249815 248815 246815
      244816 243817 243819 243821 244823 245824 247824 248824
      250824 252823 253822 254821 254820
 0.25 482204 482203 480202 479201 477202 476202 475203 474204
      473205 473206 474208 476209 478208 480206 482204 482204
 0.25 466212 465211 464210 462208 461208 460208 459210 460211
      462211 463212 465212 466212
 0.25 462223 461216 459213 456205 454201 455195 456189 458186
      463179 462175 460172 455164 452162 447162 445182 441185
      442191 443194 444200 446204 450207 452208 453212 451214
      444216 438214 433221 432229 436230 439230 446228 453225
      460224 462223
 0.25 457237 453235 450235 446237 441237 437237 432237 430240
      431242 436242 440242 444240 447240 451240 455238 457237
 0.25 447070 447068 447067 446068 446070 447070 447070
 0.25 416118 417116 415115 413114 412115 411115 410116 408115
      406115 405116 406117 408118 409119 411120 412120 413120
      415119 416118
 0.25 411068 410067 408066 408065 407065 405064 403065 401065
      400067 401068 402069 401072 403073 404072 405072 406073
      408073 408072 410070 411068
 0.25 394703 393697 390694 384696 381699 377706 371711 367713
      364717 360724 354729 349731 345732 343735 342740 336742
      333745 327751 324758 323762 323768 326770 331768 336763
      340755 349752 351749 354751 356756 356762 355770 349776
      342777 340782 340788 338795 334803 328810 326812 321813
      317815 315819 296845 269906 269912 270919 273919 277915
      286904 289898 292890 296883 302876 307869 312861 315852
      318845 327832 331826 334827 338830 339834 339841 339845
      336849 333852 332857 332869 333875 332879 332884 334886
      341880 346873 355857 358850 360839 362832 365825 373807
      382789 383782 382769 382757 383747 387728 394703
 0.25 391070 389070 388070 389072 390072 391070
 0.25 384086 384085 383083 382083 384086 384086
 0.50 379730 377726 372727 369725 366728 365731 364737 366741
      368748 371749 376749 377745 378739 378734 379730
 0.50 372779 371774 368770 366772 364776 359783 355792 352800
      349809 349816 350820 354823 358821 362812 365803 368795
      372786 372779
 0.50 303846 305844 303843 301844 300846 300847 298849 298850
      297851 298852 300851 301849 302848 303846 303846
 0.50 296872 297870 297868 295867 294868 292870 292871 291872
      290874 290877 291876 292876 294874 296872 296872 

24HR QP VT 31/00Z
 0.01 417638 420642 421649 418662 412681 392725 390777 395798
      390803 385807 377815 372822 369829 369833 367829 365827
      363829 358837 355842 353844 349844 346841 347836 350824
      354817 357814 364809 371799 374790 377779 378773 379771
      379766 376759 372757 365758 360761 355773 335806 322821
      305840 299845 293854 282868 269884 265887 261891 257897
      253900 245904 239902 236900 232892 230881 230874 232869
      236860 242851 245837 249828 253818 263804 268797 274787
      279777 282771 285766 296749 304733 316713 330696 337691
      343688 346683 351677 359671 363666 368663 374662 378663
      381663 383664 387667 391672 393669 394666 399656 402650
      404642
 0.01 507148 503144 497140 486132 482127 480124 479119 477102
      475096 474092 471089 466093 465098 466105 466112 467122
      469129 470133 473136 477139 484143 488148 494153 499156
      504152 507148
 0.01 488881 488873 486866 483858 480852 476845 473841 465831
      458821 456813 455807 453805 450806 448808 442809 438808
      433814 430816 430819 432824 438826 443832 447836 449842
      443856 429867 442865 444865 447866 452870 457874 460878
      464885 465893 468900 471899 476893 480887 483882 488881
 0.01 463178 459163 457154 454147 451143 449141 445140 438137
      436136 435139 431140 427141 423135 424112 427111 431114
      435114 439113 443112 446114 450117 453117 459116 459108
      457099 456095 456087 454080 450075 445070 441069 436069
      434071 432075 436076 438077 440081 443088 445093 443095
      440094 435092 430091 426089 424091 424093 427096 429102
      425102 422104 418107 420110 417109 411106 410093 409087
      409080 416073 417060 414052 410045 410036 411026 409022
      410017 410007 408004 408999 405979 402966 398958 396954
      393952 389952 385954 384959 380967 379976 378987 376992
      374996 368000 363005 360009 356016 355020 354024 352036
      353046 355052 355057 357059 361061 369068 371070 373076
      374081 376084 377094 375103 371108 367115 364117 360118
      348112 345103 341097 339091 335086 333086 334089 335096
      336103 334103 331101 328099 325096 319091 317091 316095
      319099 320103 312100 313103 313109 313113 314116 319119
      324113 331117 342125 346129 348130 348127 347122 350121
      351123 356127 363132 368136 371140 373145 374150 372154
      369160 370161 372165 376166 378164 381165 384164 386166
      392171 394175 396172 403159 407159 407166 409173 412176
      414179 415184 415188 414191 412194 408194 404195 392197
      389192 384185 373179 370176 366177 361179 355182 355185
      366192 373196 380202 385207 387210 390213 402222 401226
      397227 392226 389224 386222 384223 379228 380232 378234
      386239 392241 398244 411246 426246 432244 437239 439234
      440228 442222 444219 452216 457209 459201 459193 461183
      463178
 0.01 440762 439755 438748 436748 434754 435761 434766 434773
      434778 436782 438784 439780 439774 439767 440762
 0.01 424801 424798 424796 423794 421796 421797 420799 419801
      419803 418804 418806 419809 421807 421806 422804 423803
      424802 424801
 0.01 401144 402141 400139 399141 399143 400145 401144
 0.01 404095 403091 402088 400086 398088 396090 394092 392096
      390098 390102 390107 391110 393109 396108 398106 400104
      402102 402097 404095
 0.01 375223 374218 371216 368218 364214 363212 362209 366213
      369212 367208 363204 360203 359205 360208 358207 350199
      348194 347191 346189 343191 344202 345205 348206 353210
      361217 367220 373224 375223
 0.01 343182 344175 343171 341166 336167 330165 327163 327166
      330169 334169 337170 340173 341179 343182 343182
 0.01 293004 291997 288994 286989 281972 274958 272954 263957
      254958 250958 246960 237971 235975 235979 235984 237987
      240994 243997 247000 260007 265011 269013 274013 279014
      283014 289010 293004
 0.25 410068 410067 408066 407067 405067 403067 405068 407068
      408069 410069 410068
 0.25 368705 368700 367696 363695 362693 358692 354694 349700
      347703 343705 336708 322717 316727 309742 296768 290780
      287787 287792 288796 290798 294799 299798 303797 305800
      312805 313815 315815 317813 327801 335791 343777 349766
      356752 362740 369723 368715 368705
 0.25 283842 283840 280839 275842 263843 255850 252854 249861
      245871 244877 245883 250886 256884 260881 264876 270866
      275857 281847 283842
 0.50 353737 352733 350731 345733 335742 327752 320763 315776
      313781 313789 317789 322784 330774 335771 340766 347755
      350749 352742 353737
 0.50 312751 312748 310752 306758 303764 300771 297778 296782
      296785 298788 305787 307784 308780 309772 311764 312756
      312751
 0.50 268857 267855 263855 262856 260858 258860 257862 255865
      253868 252871 254874 257874 260872 261870 263868 264865
      266862 267859 268857


24HR QP VT 01/00Z
 0.01 493873 487831 480827 477827 473830 470831 467828 464824
      462819 461811 458799 455769 455764 453758 451745 449740
      446737 437739 432744 430749 430755 430768 430774 428779
      425782 423786 420794 420801 424801 427797 431797 433801
      435805 436812 433816 435820 441826 445835 446849 443860
      444863 448865 455869 463872 464886 463893 463898 465905
      467908 469911 473909 478900 483892 488881 493873
 0.01 440670 439665 438663 435662 433661 430662 428664 426667
      425669 426674 427676 429680 431681 434680 436678 438675
      439673 440670
 0.01 413073 412071 411068 412066 414064 412063 410065 407065
      403065 403067 405070 406072 408075 411073 413073
 0.01 398147 398143 397140 394140 390137 391131 393126 396121
      398117 399112 396105 393105 390107 384111 382110 382107
      383102 383097 385095 395085 400080 403073 399067 397058
      389059 387059 385056 381051 379049 376048 370051 366054
      368055 375053 380060 378063 375061 370059 363059 360062
      359066 359072 352075 341083 331076 328077 327083 328090
      321088 316084 313084 311088 310098 311113 312118 315120
      322122 329126 333132 337137 337141 333142 329142 327143
      322146 315148 306147 302146 299143 293138 283130 283135
      284138 287142 292147 296153 301158 307162 311169 316173
      323177 328181 333184 336190 340198 343205 345207 348206
      350203 354202 360200 363195 369193 374193 378195 381193
      382190 378187 377182 385168 386159 388157 391156 395150
      398147
 0.01 406058 405058 404056 402055 400055 402058 404058 405058
      406058
 0.01 323033 323022 320013 313998 309989 306979 300960 297952
      294943 289938 282935 275934 272934 271932 271920 270909
      270898 267880 266876 268869 269860 273840 277832 282829
      284827 288819 292813 296806 301800 307792 309788 311784
      305763 303759 302754 300750 301745 307730 308724 306718
      301724 295730 287730 282733 279736 277743 272759 270764
      270769 272773 273779 268787 266790 260792 255797 256800
      256802 254803 252806 256807 260815 262819 261823 257831
      254840 248848 243863 241873 241883 241896 241902 239906
      236928 236939 237950 239953 239959 238967 237976 240987
      244995 249002 253008 257014 259018 262019 266021 272022
      278026 285028 289030 296035 300037 304039 306041 309041
      315039 320036 323033
 0.25 452813 452811 452809 451806 450806 449807 448808 448809
      448812 447814 447815 447817 447819 448820 449821 451820
      452818 452816 452815 452813
 0.25 394115 394113 392113 391114 392115 394115 394115
 0.25 384124 385122 385120 383122 382122 381124 382125 384125
      384124
 0.25 377130 378128 377125 375125 373127 374129 374130 376130
      377130
 0.25 371131 373127 371124 367119 359118 353114 348110 345104
      342097 338092 334103 329105 325106 324109 334115 338120
      341127 349136 350140 354140 361141 364140 366137 371132
      371131
 0.25 375066 373065 371066 373067 375068 375066
 0.25 350179 350170 351165 349162 345161 340160 333160 325161
      322163 324167 330171 336174 339181 341185 344188 349183
      350179
 0.25 286793 287789 286785 285781 283781 281784 280786 279788
      278790 277794 276797 277800 279801 283801 285799 286796
      286793
 0.25 284010 284004 283001 280993 273978 268962 266959 262956
      252956 251947 251941 247941 246945 246950 248958 249962
      246965 245969 246976 247984 251992 255998 260003 266008
      273012 276014 278013 283012 284010
 0.25 263923 262911 261901 259891 259878 258873 255869 253873
      253879 252889 252901 253913 253925 255929 259930 261927
      263923
 0.50 330166 328166 330166 354122 354118 352116 351115
      347112 346111 343109 341109 342113 343116 345118 347120
      348121 352123 354122
 0.50 270999 269993 267986 265980 263974 261969 255970 252976
      253982 255988 259993 262997 267001 270999 





Last Updated: 529 PM EST SUN DEC 28 2014