Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 210701
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
301 AM EDT SAT MAY 21 2016


PRELIM DAY 1 QPF DISCUSSION
VALID MAY 21/1200 UTC THRU MAY 22/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...WESTERN U.S...

A RATHER SLOW MOVING UPPER AIR PATTERN REMAINS IN PLACE...WITH A
DEEP TROUGH PRODUCING MORE WIDESPREAD PRECIPITATION TODAY NORTH OF
A LINE FROM CENTRAL CALIFORNIA TO CENTRAL UTAH TO EASTERN WYOMING.
AREAL AVERAGE AMOUNTS GENERALLY INCREASE WITH NORTHERN AND
NORTHWESTWARD EXTENT...AS A NOTEWORTHY SHORTWAVE WILL ROTATE UP
THROUGH THE EAST SIDE OF THE TROUGH...OPENING UP DIFLUENT FLOW
OVER NORTHERN ID/MT...AND SLIGING AN INVERTED TROUGH FEATURE BACK
INTO THE WASHINGTON CASCADES. OUT ALONG THE LEADING FRONTAL
ZONE...LOW PRESSURE IS FORECAST TO DEEPEN OVER EASTERN MONTANA AND
LIFT OUT OF THE U.S. THIS EVENING. A FEW HEAVIER THUNDERSTORMS
WITH LOCAL DOWNPOURS ARE LIKELY AHEAD OF THE FRONT IN EASTERN
MT/WY...BUT LOCALLY HEAVY RAIN MAY ALSO OCCUR BACK UNDERNEATH THE
COLD CORE ALOFT OVER THE MOUNTAIN AREAS OF ID/MT AND EASTERN
OREGON. AREAL AVERAGE AMOUNTS ARE FORECAST AT VALUES MAINLY UNDER
ONE INCH. WPC USED A BLEND OF OUR IN-HOUSE ENSEMBLE WITH THE 12Z
ECMWF AND 00Z NAM CONUS NEST...BEFORE MAKING MANUAL ADJUSTMENTS.


...CENTRAL U.S...

DIFFICULT FORECAST SCENARIO THROUGHOUT THE CENTRAL AND SOUTHERN
PLAINS THROUGH SUNDAY NIGHT...AS POCKETS OF CONVECTION ARE
LIKELY...BOTH ELEVATED AND SURFACE-BASED...BUT THE INGREDIENTS FOR
LARGE SCALE ORGANIZATION ARE NOT NECESSARILY IN THE SAME PLACE AT
THE SAME TIME. EVOLUTION WILL LIKELY DEPEND ON STORM SCALE
PROCESSES...MORE-SO THAN USUAL...WHICH TENDS TO LOWER QPF
CONFIDENCE. ON TOP OF THIS...THE CAP WILL BE BUILDING AT THE SAME
TIME THAT MOISTURE DEPTH IS TRYING TO INCREASE ACROSS CENTRAL
TEXAS TODAY. INSTABILITY WILL BE STRONG...AND COULD BE A PRIMARY
DRIVER BEHIND LARGER SCALE ORGANIZATION AND LONGEVITY...BUT THERE
COULD BE AREAS IN WHICH THE CAP PREVENTS CONVECTION OR LIMITS ITS
EFFECTIVENESS. FOR THESE REASONS THE HI-RESOLUTION MODEL FORECASTS
ARE DISPLAYING A LOT OF SENSITIVITY. SOME...LIKE THE THE NAM CONUS
NEST AND CANADIAN GEM REGIONAL INDICATE ONLY ISOLATED STRONG
CONVECTION...WHILE OTHERS LIKE THE WRF-ARW AND NSSL WRF PREDICT
FAIRLY WIDESPREAD MODERATE TO HEAVY RAINFALL. THE WRF-ARW MAY BE
OVER-FORECASTING CONVECTION IN THE TEXAS HILL COUNTRY GIVEN THAT
AREA IS DIRECTLY WITHIN SHORTWAVE RIDGING AT 700-500 MB. WARM
ADVECTION BENEATH THIS LAYER SHOULD SUPPORT SCATTERED STORMS...BUT
ODDS FOR UPSCALE GROWTH SEEM MORE LIKELY WITHIN THE DEEPER AND
STRONGER LOW LEVEL MOISTURE TRANSPORT AHEAD OF THE DRYLINE FROM
SOUTHWEST KS TO NEAR LUBBOCK TX. THESE THOUGHTS LINE UP BETTER
WITH THE NSSL WRF...ALTHOUGH WPC TOOK A CONSERVATIVE APPROACH TO
FORECAST AMOUNTS GIVEN FAIRLY LOW CONFIDENCE. THE QPF HERE WAS
DERIVED NOT ONLY FROM THE 00Z NSSL WRF...BUT ALSO THE MOST RECENT
RUNS OF THE WRF-NMM AND THE ECMWF.


...EASTERN U.S...

A WELL DEFINED UPPER TROUGH AND DEVELOPMENT OF A COASTAL
LOW...ALONG WITH ONLY WEAK TO MODERATE INSTABILITY...MAKE THIS A
RELATIVELY STRAIGHTFORWARD FORECAST IN THE EAST. THE INHERITED
FORECAST WAS MORE BROAD WITH HEAVY AMOUNTS ACROSS THE CENTRAL
APPALACHIANS AND MID ATLANTIC...SO WE ATTEMPTED TO REFINE
EXPECTATIONS USING SOME OF THE DETAIL OF THE ECMWF AND PROBABILITY
FIELDS FROM THE ECMWF ENSEMBLE WHICH ARGUED FOR HEAVIER AMOUNTS
NEAR THE COASTAL LOW...AND SOMEWHAT LIGHTER AMOUNTS TOWARD THE
MOUNTAINS. STILL...EXPECT WIDESPREAD 0.50 TO 2.0 INCH AMOUNTS
THROUGHOUT THE MID ATLANTIC.

BURKE

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

24HR QP VT 22/12Z
 0.01 546169 547156 548139 549129 550123 552106 552098 552092
      548082 545076 542072 537072 533073 529073 524071 517066
      500055 497053 495048 494041 492037 488032 484031 476026
      466025 458029 451035 447037 444035 441033 436032 428036
      424039 420043 418048 417055 418060 420063 430067 439072
      444073 448075 450076 450079 446081 442085 437084 435080
      428079 424077 422074 418073 414075 408082 400089 398092
      396097 393100 391105 389111 390116 397122 398125 397129
      395133 385150 383153 381159 379165 374167 373171 373175
      373179 372180 366179 362182 363188 366193 369196 372204
      369213 376232 381242 387250 394255 403261 409262 414260
      415255 413243 413240 415239 418237 427237 431235 432232
      434231 439233 442234 440236 436243 440245 446246 452248
      455247 465247 473244 476242 481241 482239 483234 484232
      487232 492235 495239 500246 505253 509254 509248 511242
      514237 516224 514219 516213 521201 522198 524198 525191
      528187 532187 546169
 0.01 515869 512851 509841 506831 504778 501755 501733 501727
      502722 502715 502709 502698 501684 498667 497659 496655
      494649 492646 489639 486636 483636 477643 474644 473649
      469656 466663 462667 459669 453678 450685 448692 443708
      439713 436710 434705 433702 434697 436688 438679 438670
      437663 435658 434654 431651 423651 414652 407655 401662
      399665 395667 390672 385677 381683 374695 368702 365704
      361706 333722 324731 314742 303754 286762 276769 264779
      262778 257780 255782 253786 252794 250802 246809 245813
      248815 252815 254814 260817 266821 274823 278830 281836
      285840 292842 308844 317842 320839 321834 321824 322816
      324806 322797 326790 327795 326799 347800 349805 348811
      351819 352825 351830 349833 350836 351841 354844 358846
      360845 361851 361856 363860 368869 375869 380869 383867
      386865 386860 387857 389854 391854 394853 396850 396844
      398840 403836 406834 410834 416840 419839 422837 427832
      431825 436817 438810 438804 436801 434799 432793 434784
      436775 441757 446739 451723 453714 455706 458704 459710
      458716 459723 458742 457767 457772 456779 457788 456793
      453797 449799 448802 445810 444819 444824 446827 447833
      449834 450836 454833 458825 461828 462832 464836 467838
      469841 473841 475838 477837 478840 480850 483860 486869
      489878 493886 498891 501893 505893 510890 514881 514873
      515869
 0.01 491253 491250 491248 491247 489246 488244 486245 485246
      485248 486249 487251 488253 490253 491253
 0.01 428245 428242 428241 426240 424240 423239 421239 420240
      419241 418242 418243 420244 422245 423245 425245 427246
      428245
 0.01 433971 379931 375931 371934 368936 366940 362949 362956
      363961 364972 369981 360980 348979 338980 335980 333978
      330975 319962 314956 310948 308944 305941 300942 296941
      290945 284951 278958 274966 271974 276981 280983 286985
      292990 294992 299992 311992 317994 318999 321008 316015
      313018 309015 300013 295014 291015 286010 279005 264996
      257995 252993 249991 243991 240998 241002 245004 251007
      255009 261009 264007 268007 271009 273014 279018 284020
      289021 290027 293029 299037 316037 337037 348036 353035
      357034 359031 359027 358025 360023 363021 370016 373014
      377015 381018 387018 390016 390011 391008 394008 396010
      400012 406013 410015 416015 418015 418012 418006 415998
      411990 405984 401981 398977 395970 391967 390966 392964
      403964 408966 414966 417966 421968 425972 428973 431973
      433971
 0.01 417149 417144 416141 412134 408134 406136 405142 399157
      396163 392168 390169 385168 383172 382174 380179 382181
      386183 390188 392191 396193 401197 403198 405196 406186
      406177 409172 410164 411159 412156 415151 417149
 0.01 299863 299859 297855 294852 291850 286851 283852 276857
      270862 265868 261875 261878 263882 267887 270890 272894
      272899 271903 271909 272913 276920 277923 281925 285920
      288916 289912 289901 288889 291881 294874 299863
 0.25 540113 540108 537105 533102 529103 517090 512086 507078
      501070 493064 483050 476045 472043 467042 458043 454044
      455049 448053 445054 443053 441050 437048 432049 428051
      427054 444061 453061 463063 472068 480073 486079 487084
      484087 475091 469095 463098 460102 462107 466111 469115
      470121 468125 464131 457137 451143 451148 450150 448149
      445147 442145 440146 437149 435155 437166 444171 440176
      437178 432177 430171 429174 425184 424189 424195 426206
      443212 446213 445218 446222 451224 459228 464230 468229
      476228 483224 492223 498231 502231 504225 501213 500200
      499195 496191 493187 491186 489188 486191 483197 480200
      477202 470205 464207 458206 455202 455196 457192 463185
      464179 466174 470172 475173 479172 482173 488180 490183
      493183 500178 514170 521165 527160 530158 533152 535147
      536139 537128 540113
 0.25 453098 452096 450096 448096 447097 446099 448101 449101
      451100 452100 453098 453098
 0.25 448109 446104 443102 439099 436096 433094 428093 425096
      425101 428105 431109 435111 439112 441116 445116 447111
      448109
 0.25 426681 426676 424671 422667 418664 415664 410665 401670
      395675 389681 384689 380697 376703 374707 371709 365711
      362715 356720 339729 333733 329740 324745 318751 316755
      315761 310761 308764 304772 300774 295773 287772 282777
      275792 272795 269796 263797 258799 254804 254808 257811
      261813 265813 273816 278817 283816 288815 291813 292808
      289804 287801 286796 287785 290784 293785 297786 301785
      308781 316781 320780 323777 329770 333763 338758 341756
      346754 354753 356755 356758 358764 362771 364773 364777
      366782 369785 376789 381795 380799 377803 374803 370802
      366801 363804 362806 362810 363816 362820 363826 365829
      371835 375837 378833 381824 384820 388818 395814 400809
      404806 408804 413804 417801 419792 425772 428764 428762
      423762 415762 413760 412754 417735 422716 424694 426681
 0.25 407236 408232 408228 406227 403226 401226 398227 396229
      394230 392232 392236 394238 397240 399242 402244 405243
      406239 407236
 0.25 413106 413103 411101 409101 408101 406102 406103 405105
      404107 405109 405110 407111 408111 410110 410109 411108
      412106 413106
 0.25 389986 388984 387981 385980 385979 384978 382977 381979
      380981 381983 382984 383986 384986 385987 387988 388988
      389987 389986 373972 373972
 0.25 298830 298828 296827 294826 293826 292828 293830 295831
      297831 298830
 0.25 292866 293863 292860 289857 286858 282861 279865 277869
      276873 278878 281880 285878 287875 290870 292866 292866
 0.50 532136 532126 530117 526110 521106 516102 510099 503094
      499092 496094 494096 490101 483100 478102 475104 473106
      473109 475113 489119 493123 496125 497129 498134 501136
      501140 498141 495142 492140 490137 487134 481131 477131
      474132 470136 466144 464147 463152 463161 465164 468166
      472166 475166 477164 481164 484163 487159 487157 490154
      493150 494150 499155 505159 510156 512153 515151 522150
      525145 532136
 0.50 491214 492206 491203 488203 481206 476208 470211 463213
      461215 460220 462223 465225 472224 478221 483219 487218
      490216 491214
 0.50 480064 478060 475056 471054 468053 464053 459053 457057
      461059 464060 469062 473064 477066 480064
 0.50 451188 451186 450185 449185 448186 447187 447189 447190
      449190 451188 451188 453186 453185 452186 453186 453186
 0.50 420690 420683 418676 415672 410671 406672 402673 395680
      389688 383696 379705 376710 373713 366714 359720 355724
      350726 342731 336738 335741 334745 336748 340750 345749
      357747 366766 371774 379779 385785 391784 394788 395795
      392798 385804 381812 386812 392810 397802 406798 415781
      417777 415772 411770 407772 404774 400773 398769 399764
      406745 414726 416716 418704 420690
 0.50 294778 293777 292776 291776 291778 292779 294779 294778
 0.50 290862 288860 287860 285862 283865 282867 281870 280873
      282875 284875 286873 287870 288868 290864 290862
 0.50 277809 278807 277805 276804 274803 273803 272803 271806
      271808 272810 273810 275810 276809 277809
 1.00 412706 412701 410697 407689 405680 402678 400681 398688
      395694 388705 385712 383718 379720 375720 369723 366719
      363719 360722 355726 350730 344733 340738 340743 342744
      346745 350744 360736 364731 367728 371729 377725 380728
      377734 374740 373748 370754 370760 371765 376768 382770
      387769 391763 394757 398752 401746 407733 409726 410719
      412706
 1.50 402734 400730 397729 391730 386735 381741 378748 375756
      375758 377761 384762 389756 394750 398744 401737 402734
 1.50 360729 358727 357728 353730 352731 348733 347734 344737
      342739 342740 344742 348741 349739 352737 354736 356734
      358732 360729
 2.00 396735 394733 390735 387739 385742 383745 380750 379755
      384756 387753 390748 393745 395741 396737 396735

$$





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