Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 261854
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
154 PM EST MON JAN 26 2015


PRELIM DAY 1 QPF DISCUSSION
VALID JAN 27/0000 UTC THRU JAN 28/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1...

...EASTERN U.S. BLIZZARD...

INTENSE CYCLOGENESIS WILL YIELD A SMOOTHLY DEFINED SYNOPTIC
PRECIPITATION DISTRIBUTION OVER NEW ENGLAND AND PORTIONS OF THE
MID ATLANTIC. THE MODELS SHOW GOOD AGREEMENT ON A LARGE
SCALE...BUT DIFFER IN FORWARD SPEED AND IN THEIR MESOSCALE
DETAILS. FOR THE 18Z QPF ISSUANCE WE BLENDED OUR PREVIOUS FORECAST
TOWARD THE 12Z NAM AND 00Z ECMWF. THOSE MODELS WERE SLIGHTLY
SLOWER THAN THE ENSEMBLE CONSENSUS...BUT FORECASTS FROM THE RAP
LEND SUPPORT THROUGH 06Z TONIGHT. A STRONG NEGATIVE TILT TO THE
UPPER TROUGH AND PRONOUNCED DOWNSTREAM RIDGE ALSO CAUSED US TO
THROW A LITTLE MORE WEIGHT TOWARD THE SLOWER SOLUTIONS. THE MAIN
IMPACT OF THIS CHOICE WAS TO NUDGE THE CENTROID OF HEAVIEST DAY 1
QPF SOUTHWARD...DOWN THE COAST...CATCHING MORE OF EASTERN
NJ...LONG ISLAND...AND WESTERN CT IN 1.5 INCH AREAL AVERAGE LIQUID
AMOUNTS. THERE WAS A CORRESPONDING DECREASE TO AMOUNTS OVER MAINE
THROUGH 28/00Z...PUSHING MORE OF THE EVENT INTO DAY 2. THESE
CHANGES WERE COORDINATED WITH THE WPC WINTER WEATHER DESK...GIVEN
IMPLICATIONS FOR SNOWFALL TOTALS...INCLUDING IN AND AROUND NEW
YORK CITY. THE 12Z ECMWF THEN CAME IN WITH A FORECAST THAT WAS NOT
AS SLOW AS THE 00Z RUN...BUT WAS IN GOOD AGREEMENT WITH THE WPC
QPF...WHICH HAD RETAINED SOME INFLUENCE FROM THE PREVIOUS - MORE
ENSEMBLE MEAN DOMINATED - PACKAGE. BOTH THE NAM AND ECMWF...ALONG
WITH SOME OTHER HIGH RESOLUTION MODELS...PREDICT DISTINCT BANDS OF
MAXIMUM PRECIPITATION EMBEDDED WITHIN THE SYNOPTIC SHIELD. ONE
BAND SEEMS TO CORRESPOND TO THE MID LEVEL
FRONTOGENESIS/DEFORMATION BAND EXPECTED IN THE VICINITY OF WESTERN
LONG ISLAND UP THROUGH WESTERN CT/MA...WITH ANOTHER BAND FOLLOWING
THE TRACK OF STRONGEST HEIGHT FALLS ALONG THE IMMEDIATE LEFT SIDE
OF THE SURFACE LOW TRACK...AND AFFECTING EASTERN MA AND RI. WE
ATTEMPTED TO POINT TO THESE BANDS IN OUR QPF AND WINTER
PRODUCTS...BUT WITH ONLY MODERATE CONFIDENCE GIVEN THEIR
NARROWNESS. PLEASE REFER TO THE HEAVY SNOW
DISCUSSION...QPFHSD...FOR WINTER WEATHER DETAILS.


...SOUTHWEST...

A HIGHLY AMPLIFIED...NEGATIVELY TILTED MID/UPPER LEVEL TROUGH
PIVOTING TOWARD NORTHWEST BAJA AND SOUTHERN CA WILL PROVIDE
STRENGTHENING UPPER LEVEL DIVERGENCE/DIFFLUENCE AND ANOMALOUS
MOISTURE (PWATS INCREASING TO 3-4 STANDARD DEVIATIONS ABOVE
NORMAL) INTO FAR SOUTHERN PORTIONS OF THE SWRN U.S. (SOUTHERN
CA-AZ). THE TROUGH IS EXPECTED TO WEAKEN WITH TIME AS IT BEGINS TO
OPEN UP AND LIFT TOWARD THE NORTH BY TUESDAY MORNING. DESPITE THE
WEAKENING TREND...THE COMBINATION OF INCREASING MOISTURE AND LIFT
WILL PRODUCE GENEROUS COVERAGE OF LIGHT PRECIPITATION...AND SPOTTY
MODERATE PRECIPITATION ACROSS SRN CA/AZ. WE BLENDED OUR PREVIOUS
FORECAST TOWARD THE 00Z ECMWF AND 06Z NAM. RECENT GFS RUNS
APPEARED TOO WET GIVEN THE DEPTH OF DRY LOW LEVEL AIR PRESENT IN
THE 12Z SOUNDINGS ACROSS THIS REGION. MUCH OF THE PERIOD OF
GREATEST MID LEVEL ASCENT WILL GO INTO MOISTENING THE LOW
LEVELS...LEADING TO A LIMITED WINDOW FOR EFFICIENT PRECIPITATION
TO OCCUR BEFORE THE TROUGH WEAKENS.

BURKE

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

24HR QP VT 28/00Z
 0.01 538199 539192 537186 533178 529167 520159 518155 512155
      513162 511169 506169 505172 507175 508188 509195 507200
      505205 505210 505214 502214 497209 494206 490206 485204
      482205 475209 471212 467214 459217 452232 447233 443235
      436242 431250 426258 425266 429265 436260 443253 449248
      456249 460248 462251 461255 462258 464262 469265 472267
      477269 481268 486273 491282 495286 500288 504290 507288
      514279 520269 523259 521254 521250 522246 526244 528243
      530239 533225 536212 538199
 0.01 519236 521234 520231 520228 521223 520220 519216 515214
      513218 512220 511226 512228 513233 514237 516239 519239
      519236
 0.01 499633 498627 495623 493622 490622 485622 479625 472626
      465628 447636 440639 432641 418646 411651 406656 394666
      388672 384677 377687 369700 364707 360712 347720 336725
      321734 313746 309752 306758 300768 295774 295777 297781
      300787 302789 306791 312794 320793 326791 334789 338789
      341790 346792 349795 355798 361798 364796 369796 375798
      376808 375810 375815 382816 384814 388813 395812 405809
      422806 433800 438794 442786 444778 444771 441767 440765
      441762 445757 450754 455749 473723 480709 482703 484696
      487688 490680 495663 496655 497647 499633
 0.01 490234 491229 491226 488223 484224 481223 478222 475222
      474227 477229 479231 481233 484232 486233 488235 490234
 0.01 493878 492872 489868 483867 479865 475864 470865 461870
      455871 451873 444875 438875 416874 404875 404880 407885
      410887 416888 421888 424889 424893 422897 424900 430900
      432900 434897 445897 455903 458903 462901 470893 485882
      490882 493878
 0.01 422188 419179 422170 423164 422161 422152 422141 424137
      425131 427127 427120 425116 422114 410104 409100 406100
      405103 402105 398105 395107 389110 378109 369110 366108
      363104 362100 366099 372100 372097 370093 363089 358093
      347081 340074 336071 333068 329068 327070 322070 320070
      317067 313061 304047 296035 292033 289036 289041 289045
      291049 297056 301061 304068 310084 311092 310102 311107
      310112 312120 321134 322138 320142 315147 313155 314161
      317168 321175 333188 335191 336195 338203 343208 346213
      349221 351224 355225 358223 360219 363216 368217 365203
      368197 372202 389210 396215 400216 404219 403226 405229
      408228 410227 413224 414216 406216 403213 403209 404202
      406199 409195 413194 418191 422188
 0.01 386086 384081 381078 379076 375075 373080 373084 375089
      376096 376101 379099 382097 384092 386086 386086
 0.01 380868 380859 376853 370846 368840 364840 361843 357848
      356857 362859 367862 370865 371869 377871 380868
 0.01 363820 361821 358825 356829 354833 352837 351842 350844
      352848 354846 356841 358837 360832 362828 362823 363820
 0.25 530200 531194 528189 527184 526179 523175 521173 518175
      518180 518185 520189 522194 525198 529201 530200
 0.25 517267 518259 515253 510241 507235 502230 499227 497223
      494223 494228 496235 502246 504252 505260 504265 502265
      497261 495262 496265 500269 503274 509273 513271 517267
 0.25 482641 480637 477635 470635 465636 460637 450642 430647
      419651 412656 402669 394676 388682 380698 376708 369713
      366717 365720 364726 367728 375726 378730 378736 378741
      377742 376748 378753 383761 390765 394767 399766 406763
      416760 425756 449729 458714 468697 472689 475681 479670
      481660 482641
 0.25 481247 481246 481244 480242 479241 478240 477238 475237
      474237 473239 473241 473242 474243 476245 477245 478246
      479246 481247 481247
 0.25 381197 381195 380192 376189 374186 370183 369178 365176
      361177 358181 355184 360187 365189 369191 372193 376196
      381197 381197
 0.25 371163 371161 369159 368158 366158 365157 364157 363156
      361155 359156 358156 358158 359158 360160 362161 364162
      365163 367164 369164 371163 371163 397168 397168
 0.25 355131 355123 352119 349114 345109 341105 338106 338111
      342115 346118 341120 340124 340128 344131 349135 353133
      355131
 0.25 350738 348736 343735 341734 336736 331741 327746 325753
      323762 323765 325769 327771 331772 335771 339768 343762
      346756 349749 349739 350738
 0.25 345180 345178 344176 343177 342180 343181 345182 345180
 0.25 344171 343169 343168 341168 341170 342172 344171
 0.50 516264 516262 516261 514259 513258 512260 512263 514265
      515265 516264
 0.50 474652 474645 472643 467640 460641 453644 446647 438649
      423652 416655 412660 403671 393680 388687 385694 383701
      383706 385710 384726 384735 386743 390750 394755 401755
      407754 422748 428744 432740 441728 448717 456702 462691
      466682 468674 472663 474652
 0.50 343750 342748 341746 338745 335745 334746 332748 331752
      330755 330759 331763 334764 336762 338760 340757 341755
      343752 343750
 1.00 449682 449674 447668 442667 436668 422659 417661 414664
      406672 394686 392690 391695 393711 391721 392729 392734
      393741 395745 398748 404747 410746 415744 423739 429732
      435725 445705 447695 449682 449682
 1.50 438690 437685 435683 430685 425685 422687 419688 416686
      414678 411676 408676 399688 395694 396700 397703 399706
      400710 400721 399730 399736 402740 408740 415736 420732
      425726 428724 430721 432713 431710 432707 435704 436700
      438690
 2.00 421711 420704 414701 412698 411694 409688 407687 406690
      405694 407699 410703 410708 409714 409716 413716 418714
      421711

$$





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