Quantitative Precipitation Forecast
Issued by NWS

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341
FXUS04 KWBC 051858
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 PM EDT THU MAY 05 2016


PRELIM DAY 1 QPF DISCUSSION
VALID MAY 06/0000 UTC THRU MAY 07/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1...

...WESTERN U.S...

A LARGE CLOSED LOW HAD DUG TO A SOUTHERLY LATITUDE...WITH LARGE
NEGATIVE HEIGHT ANOMALIES IN PLACE OVER THE SOUTHWEST STATES.
GIVEN THE SEASON...HOWEVER...THE LOW WAS CUT OFF FROM ANY
APPRECIABLE SUB-TROPICAL MOISTURE FEED. TO THE WARM SIDE OF THE
SURFACE BOUNDARY LOWER LEVELS WERE QUITE DRY...WITH PRECIPITABLE
WATER VALUES ABOUT 0.3 TO 0.45 INCHES IN THE SOUTHWEST AND GREAT
BASIN. THUS...MORE ORGANIZED TYPE OF RAINFALL...AND SOME EMBEDDED
HEAVIER SHOWERS...WERE CONFINED TO THE POST FRONTAL ENVIRONMENT
FROM CENTRAL/NORTHERN CA INTO NORTHWEST NV AND UP THROUGH EASTERN
OREGON. THERE WAS STILL SOME CONNECTION TO THE NORTHERN
STREAM...WITH FLOW PASSING THROUGH THE PACIFIC NORTHWEST AND UP
THROUGH WESTERN MONTANA...AND THIS FLOW PATTERN WILL SUPPORT A
PERIOD OF 850-700 MB FRONTOGENESIS THIS AFTERNOON ACROSS EASTERN
OREGON AS A JET STREAK ROTATES UP FROM THE SIERRAS. MODELS ARE
JUST ABOUT EQUALLY HEAVY WITH SOME LOCAL CONVECTIVE PRECIPITATION
IN SOUTHEAST OREGON WITH THE DEEP SYNOPTIC FORCING...AS THEY ARE
OVER NORTHERN AND CENTRAL CALIFORNIA...WHERE INSTABILITY BENEATH
THE COLD CORE LOW AND SLOW CELL MOTIONS WILL BE RESPONSIBLE FOR
LOCALLY HEAVY DOWNPOURS. BY FRIDAY THE LOW BECOMES MORE STRONGLY
CLOSED OFF...WITH AN INCREASING EASTERLY COMPONENT TO MID LEVEL
FLOW OUT OF THE NORTHERN GREAT BASIN AND INTO CA/OR. DESPITE BEING
POST-FRONTAL...AND FED IN THE LAYER ABOVE 850 MB...THE MOISTURE
AND INSTABILITY PROFILES WILL CONTINUE TO SUPPORT OCCASIONAL
MODERATE OR HEAVY RAIN/THUNDERSTORMS ON FRIDAY...WITH SOME
EXPANSION OF MORE APPRECIABLE COVERAGE OF RAIN EASTWARD INTO
MT/ID/UT/WY/CO AS A BROADLY DIFLUENT PATTERN SETS UP NORTHEAST OF
THE MIGRATING LOW. THE PREVIOUS WPC FORECAST HAD THIS FAIRLY WELL
HANDLED. WE ATTEMPTED TO PRESERVE CONTINUITY WHILE TRENDING TOWARD
THE WRF-ARW...GEM REGIONAL...AND APPLYING THE LATEST GEFS AND
ECMWF ENSEMBLE PROBABILITIES FOR VARIOUS QPF THRESHOLDS. THE
CONVECTIVE AND SHOWERY NATURE OF THE REGIME LIMITS AREAL AVERAGE
PRECIPITATION...WITH MOST AREAS FORECAST TO RECEIVE 0.10 TO 0.75
INCHES THROUGH FRIDAY. ISOLATED HEAVIER TOTALS UP TO 1.50 OR 2.0
INCHES WILL BE POSSIBLE...THOUGH...ESPECIALLY ID/OR/NV INTO
NORTHERN AND CENTRAL CA.


...MID ATLANTIC AND NORTH CAROLINA...

A STRONGLY ANOMALOUS UPPER LOW...4 STANDARD DEVIATIONS BELOW
CLIMATOLOGY AT 500 MB...CONTINUED TO DIG INTO THE SOUTHERN
APPALACHIANS. THE DIFLUENT AREA EAST OF THE LOW HAD SUPPORTED
ROBUST DEEP CONVECTION OVER SOUTHERN VA AND NORTHERN NC THROUGH
MIDDAY. THE LARGER SCALE CONVEYOR BELT WAS WELL OFFSHORE WITH THE
LEADING COLD FRONT THAT HAD EARLIER ESTABLISHED DEEP
TROUGHING...SO NEAR-SURFACE INFLOW WILL BE LACKING. STRONG
LIFT...HOWEVER...WILL SHOULD ENSURE WIDESPREAD RAIN OVER
VA/NC...PIVOTING NORTHWARD UP THROUGH THE MID ATLANTIC TONIGHT AND
FRIDAY AS THE UPPER LOW TURNS THE CORNER AND PRODUCES A NEW
SURFACE REFLECTION NEAR THE COAST. THE GLOBAL MODELS ARE CLUSTERED
CLOSELY ENOUGH...THAT A CONSENSUS APPROACH COULD BE USED. THE 00Z
ECMWF QPF HAD APPEARED TO BE TOO LIGHT OVER MD/DC GIVEN THE
DEEPENING SURFACE LOW AND DIFLUENT MID/UPPER LEVEL PATTERN. THE
GFS HAS PRODUCED SOME SPURIOUS HEAVY RAIN SIGNALS OVER THE PAST
FEW CYCLES...BUT THESE ARE SMOOTHED OUT BY THE ENSEMBLE AND BIAS
CORRECTION TOOLS AVAILABLE FOR QPF. WE TRENDED TOWARD A WETTER
FORECAST IN THE AREA OF 850-600 MB FORCING WEST OF THE SURFACE LOW
AND ALONG THE TRACK OF THE PIVOTING MID LEVEL LOW...WITH OTHERWISE
LITTLE CHANGE ELSEWHERE FROM PA TO NC.


...NEW ENGLAND...

OUT AHEAD OF THE CLOSED MID LEVEL CENTER...ALONG THE PRIMARY
FRONTAL ZONE IN THE WESTERN ATLANTIC...LOW PRESSURE IS FORECAST TO
STRENGTHEN AND MOVE QUICKLY UP TOWARD THE CANADIAN
MARITIMES...BRUSHING NORTHERN NEW ENGLAND AND ESPECIALLY DOWNEAST
MAINE WITH LIGHT TO MODERATE PRECIPITATION TONIGHT. THE OVERALL
GUIDANCE TREND HAS BEEN TOWARD SOME OF THE DRIER GUIDANCE...AND
AWAY FROM THE WETTER 00Z ECMWF. GIVEN THE LIKELY TRACK OF THE
SURFACE LOW...THIS TREND SEEMS TO HAVE A GOOD CHANCE OF
VERIFYING...ALTHOUGH THE WPC FORECAST HAD ALREADY BEEN ADJUSTED
TOWARD THE DRIER SIDE...SO LITTLE ADDITIONAL CHANGE WAS NECESSARY
ON THIS CYCLE. AREAL-AVERAGE FORECAST AMOUNTS ALONG THE COAST
RANGE BETWEEN 0.25-0.50"...WITH POTENTIALLY HIGHER AMOUNTS
(0.50"+) OVER DOWNEAST MAINE.

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

BURKE/HURLEY

24HR QP VT 07/00Z
 0.01 480616 487624 493629 497637 496643 494648 491657 491662
      489666 486676 483682 475701 464718 453730 442741 440742
      439746 440753 439763 436774 431783 426789 419794 413798
      406802 398808 393814 379826 370840 364843 362840 357841
      350844 348841 348837 349832 349825 347820 345816 342809
      341799 339782 341778 340773 343765 340764 337768 333777
      329783 320785 314781 313775 314772 314766 317763 322756
      328749 334743 346732 357721 370709 377703 385697 392695
      397702 406715 415717 420723 426723 430725 438719 439714
      440712 438710 431711 422711 416707 409702 403697 402692
      406688 409685 414683 421679 423676 426671 428663 430653
      434640 440631
 0.01 525179 526160 521149 515136 513129 511124 502118 499115
      497109 501096 502088 502080 501072 498065 496061 491058
      486056 485052 485047 485042 487038 488030 486030 486033
      484036 482035 477041 473050 466060 464062 461061 457060
      455058 453054 451048 449040 447036 443031 441028 437028
      433028 429032 420038 418041 413044 404046 397045 394045
      391047 382051 368050 363052 361054 361057 362063 358065
      360074 356075 352079 352082 355084 366091 373098 383106
      380112 377116 374116 373119 368121 360116 356116 351114
      342111 338113 336116 335120 335126 338131 341135 344138
      344142 342146 345151 353157 356161 362163 364171 367175
      365177 362176 351169 342164 337160 330157 325155 318154
      311160 310165 311171 326184 340201 342207 346211 349216
      352221 355225 361227 366227 370224 373222 377226 381234
      391242 395242 401244 407246 412246 421241 429238 433236
      438232 445226 451220 456205 462195 465189 468182 471176
      475172 478169 483169 489170 493174 502179 513182 521183
      525179
 0.01 517863 515853 510853 505854 500857 494862 485878 476890
      473893 471897 470900 472905 474908 474913 473918 470921
      461922 454927 452930 448932 445933 443935 443943 442947
      441961 442966 445966 448965 450964 452966 452974 450978
      448990 446994 446998 449000 453001 459996 464989 467981
      471972 479955 483948 487952 492952 494950 494944 491940
      490937 491932 496925 500917 504909 508901 511893 514886
      516877 517863
 0.01 468888 468883 468880 466876 464875 461875 457876 454876
      452879 452882 453884 456886 458886 461888 463891 465891
      466890 468888
 0.01 426874 425874 423872 421872 419872 418874 416874 416875
      416877 418877 419877 421877 423876 425874 426874 426874
 0.01 407173 407170 407168 407166 406164 405165 404167 404170
      404172 405174 407173
 0.01 406161 407149 407145 407140 408128 408122 406120 401118
      397120 392123 390127 387129 385133 387136 392142 396147
      400154 404160 406161
 0.01 347072 346070 344069 342067 340067 337068 333068 331070
      331073 332075 334075 336074 338072 342072 345072 347072
 0.01 268835 268827 265823 260815 254806 248800 244796 240794
      238799 239805 241817 247826 253833 257836 260838 263835
      268835 268835
 0.25 508154 508151 508150 506148 504148 503149 502150 502152
      502153 504154 505155 507155 508154
 0.25 483644 482638 479635 474631 468628 461629 454628 449630
      446633 443636 440643 437651 436659 437664 440667 441671
      441675 436682 434686 436689 443689 451688 460684 465680
      470674 474668 478660 481653 483644
 0.25 481127 481125 480122 479119 475117 472117 470120 470125
      471129 471132 470135 470140 473138 475136 477135 479132
      480130 481127
 0.25 459185 459180 458178 453180 450183 445184 438182 433178
      431166 427157 426151 427148 430149 433151 437151 440147
      440144 437138 434133 430124 429118 428110 429106 430103
      433104 436106 441108 445109 447104 450100 449098 442092
      437090 432090 423086 418077 415077 413079 414085 407089
      403093 402099 400102 396100 395103 397106 398108 401110
      404110 408112 415116 422125 424131 422139 421145 418148
      419154 421159 423168 424174 423181 416190 412192 408192
      403193 397192 399182 397176 394173 388166 383164 381163
      381159 380156 378151 369136 362129 359129 357131 357135
      358137 365143 367146 369152 375159 379165 384177 385181
      383184 378185 371184 364183 359183 351185 346182 344176
      340168 336167 332164 328162 324161 321162 318165 318168
      320170 328176 332179 335184 338188 342190 344195 347199
      350198 352192 357196 359203 363207 371211 391215 394218
      393221 390222 387226 386231 390235 401238 413238 419234
      427226 424216 426213 429214 431213 431210 433206 446196
      452195 455191 459185
 0.25 459131 459127 458123 457120 456118 453116 450115 448114
      447114 446118 446121 447124 449128 450130 453132 455132
      457132 459131
 0.25 441220 440218 438218 436218 434220 435223 436223 437223
      439221 441220
 0.25 441053 441052 439052 439053 441054 441053
 0.25 426753 426744 423737 415733 404731 393730 388733 385739
      381748 376752 371755 365757 361759 356762 353768 352775
      350779 348784 348789 349794 351799 354802 360801 366798
      371796 375797 379797 380800 383807 387806 392803 400797
      405793 408789 414779 420771 425760 426753
 0.25 387714 386710 384708 382708 380711 378714 377716 376719
      375722 374724 375727 376726 380723 381721 383720 385717
      387714
 0.25 393066 393065 391064 389064 388066 389068 391068 392067
      393066
 0.25 379080 379078 378076 377076 376074 374075 374077 374078
      374080 375082 377082 379080
 0.25 368822 367820 366819 365819 363820 362821 361821 360822
      359823 359825 358828 360828 361827 362826 363825 363824
      365823 367823 368822
 0.25 342748 339745 336748 333752 331755 329759 327763 325766
      328766 330763 334760 337756 339753 341750 342748
 0.25 416095 415093 415094 415095 416095
 0.50 477127 476125 475126 476128 477127
 0.50 479648 478643 476641 473639 468636 464635 456633 450634
      447637 441646 440652 442659 446671 449675 454674 461672
      464670 474662 477653 479648
 0.50 452190 452188 451187 450187 449187 448187 446188 444189
      443191 443193 445194 447195 447194 449194 450193 450192
      452190
 0.50 427206 428201 427196 426190 417196 413201 410206 407203
      403204 402210 403214 405216 411215 414217 406228 402233
      403236 409235 413232 416226 417220 414212 417210 420211
      427206
 0.50 430173 430172 430171 430168 429166 428164 426163 425165
      425167 425168 426170 427172 428175 430174 430173
 0.50 420756 420748 416743 409740 403738 398740 390744 381752
      373758 364762 356768 353780 351785 351789 354794 355797
      358797 366791 369781 372780 375781 378784 392798 396795
      401792 404790 405788 400786 412770 418763 420756
 0.50 420114 421109 419107 416104 415101 413099 413096 412092
      410091 408092 407096 406100 406105 407107 409110 412112
      414113 417114 420114
 0.50 396231 395231 396231
 0.50 379210 376206 373204 376204 377201 376198 372193 367190
      362187 357187 356191 358192 361197 365201 370206 375209
      379210
 0.50 341184 342182 342179 341178 340178 339179 339181 340183
      341184 341184
 0.50 333173 332171 333169 332167 331166 330166 329165 327165
      327166 326167 326168 328170 329172 331173 333174 333173
 1.00 462653 461651 460651 458649 456650 455652 454653 453655
      453656 453658 454659 456659 457658 459657 461656 462653
 1.00 411751 410748 406749 401751 389756 382759 377762 367767
      360769 357774 358780 362780 364778 368773 375774 387773
      392776 396775 405766 408760 410754 411751
 1.50 389765 388764 387763 386763 385763 384763 383764 381765
      380766 380767 379769 380769 382770 383769 385768 386767
      387767 388765 389765
 1.50 363773 362772 360773 360774 360776 361776 362775 363773

$$





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