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Quantitative Precipitation Forecast (QPF) Discussion
 
(Latest Discussion - Issued 0637Z Apr 28, 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
237 AM EDT FRI APR 28 2017


PRELIM DAY 1 QPF DISCUSSION
VALID APR 28/1200 UTC THRU APR 29/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...ONSET OF PRONOUNCED HEAVY RAIN EVENT EXPECTED THIS EVENING
PLAINS / MISSISSIPPI VALLEY...

A 2.5 TO 3.0 STANDARD DEVIATION TROUGH IS PRETTY STRONG BY LATE
APRIL STANDARDS. WE ALSO NOTED NEARLY 100 KNOT WINDS AT 500 MB
THIS EVENING AT RENO NEVADA. ANOTHER VERY ENERGETIC JET WILL FORM
DOWNSTREAM OVER THE MIDWEST STATES AS THE FLOW PATTERN BUCKLES TO
PRODUCE A DEEPER TROUGH OVER THE SOUTHERN ROCKIES. THE SURFACE
GRADIENT BETWEEN DEVELOPING LOW PRESSURE IN THE SOUTHERN PLAINS
AND A 1032 MB HIGH OVER THE NORTHERN ATLANTIC WILL PRODUCE A DEEP
FETCH OF TROPICAL MOISTURE FROM THE CARIBBEAN THROUGH THE WESTERN
GULF AND INTO THE SOON-TO-BE CONSOLIDATED FRONTAL ZONE OVER THE
PLAINS AND MID MISSISSIPPI VALLEY. DETAILS OF CONVECTIVE EVOLUTION
COMES WITH THE USUAL SMALL SCALE UNCERTAINTIES...BUT ON THE LARGE
SCALE THIS INFLUX OF RICH MOISTURE INTO A STRONG SYNOPTIC SYSTEM
WITH LATE APRIL SUN ANGLE WILL LEAD TO A BROAD ZONE OF HEAVY
CONVECTIVE RAINFALL AND EMBEDDED SWATHS OF VERY INTENSE RAINFALL.
FLOODING AND FLASH FLOODING IMPACTS ARE LIKELY...BEGINNING FRIDAY
NIGHT FROM OKLAHOMA TO SOUTHERN ILLINOIS.

EARLY THIS MORNING WARM ADVECTION IN THE MID LEVELS WITHIN
GENERALLY CYCLONIC AND DIFLUENT FLOW ALOFT WAS CONTRIBUTING TO
LIGHT CONVECTIVE SHOWERS OVER OKLAHOMA. THIS ACTIVITY WILL PUSH
EASTWARD DURING THE DAY...WITH LOWER LEVEL MOISTURE BEGINNING TO
ARRIVE...AND UPGLIDE ON THE 300 TO 305 K SURFACES CONTRIBUTING TO
AN EXPANSION OF PRECIPITATION THIS AFTERNOON AND EVENING FROM
EASTERN ARKANSAS NORTH AND EASTWARD INTO MO/IL/IN/KY. THIS WILL
ALL OCCUR AS SURFACE BASED CAPE GROWS WITH BREEZY SOUTHERLY WINDS
AND DEWPOINTS RISING TO THE 60S / LOW 70S PER THE NAM...AS FAR
NORTH AS THE OHIO RIVER. THIS SURFACE BASED INSTABILITY MAY BE
UNCAPPED WITH NORTHWARD / EASTWARD EXTENT.

BACK WEST THERE ARE QUESTIONS OVER WARM SECTOR INITIATION...GIVEN
STRONGER CAPPING OVER THE SOUTHERN PLAINS ALONG WITH BROAD SCALE
HEIGHT RISES AS THE TROUGH DIGS INTO THE FOUR CORNERS REGION...
ALL NOTED IN THE SPC DAY ONE OUTLOOK AS WELL. VERY DIFFICULT TO
GAUGE WHERE AND WHEN INITIATION WILL OCCUR...WITH FORECAST
SOUNDINGS INDICATING A SIZEABLE CAP...AND WITH DEEPEST MOISTURE
LOCATED SOUTH OF THE BETTER UPPER DIFLUENCE SIGNATURE TO THE REAR
OF THE MIDWESTERN JET STREAK. OUR HUNCH IS THAT THE DEEP MOISTURE
WILL ENCOUNTER AN ENVIRONMENT JUST FAVORABLE ENOUGH FOR SCATTERED
INITIATION WHEN IT REACHES SOUTHERN OK AND PARTS OF NORTH TX LATE
TODAY. WITH QPF WE TRIED TO GIVE SOME INDICATION OF THE RESULTING
CONVECTION PRODUCING A FEW PERSISTENT OUTFLOWS TO YIELD FURTHER
INITIATION THROUGHOUT THE NIGHT AS LOW LEVEL FLOW
STRENGTHENS...ALTHOUGH SYNOPTICALLY FORCED PRECIPITATION WILL ALSO
BREAK OUT TO THE NORTH AND WEST.

WE STARTED WITH AN EVEN BLEND OF GFS/ECWMF/WPC CONTINUITY...AND
INCORPORATED SOME OF THE 00Z WRF-ARW FOR THE WARM SECTOR
CONVECTION IN OK/TX/AR. THE 00Z RUN WAS MORE REASONABLY PLACED
THAN THE PRIOR 12Z RUN.


...ELSEWHERE...

A SIMILAR QPF BLEND TO THAT MENTIONED ABOVE WAS USED FOR OTHER
PARTS OF THE COUNTRY. THE MOST NOTEWORTHY IMPACT WILL BE THE
CONTINUED ACCUMULATING SNOWFALL THREAT OVER THE ROCKIES AND HIGH
PLAINS NEAR THE FRONT RANGE. REFER TO THE WPC HEAVY SNOW
DISCUSSION FOR DETAILS. GENERALLY...THERE WAS GOOD MODEL QPF
AGREEMENT ON DAY 1. WHERE THERE WERE DIFFERENCES WE USED THE
ENSEMBLE QPF PROBABILITY MAPS TO CENTER OUR EXPECTATIONS WITH
RESPECT TO PLACEMENT AND COVERAGE. THE CANADIAN GEM REGIONAL WAS
ALSO USEFUL...ESPECIALLY OVER THE SOUTHWEST STATES...WHERE WE USED
ITS WETTER SOLUTION GIVEN THE TROUGH STRENGTH AND HEIGHT FALLS
SWINGING THROUGH AZ/NM/WEST TX.

BURKE

GRAPHICS AVAILABLE ON THE WEB AT www.wpc.ncep.noaa.gov/qpf/qpf2.shtml

24HR QP VT 29/12Z
 0.01 543173 542169 540164 536161 533156 528150 524147 520145
      503133 486126 477122 469121 469117 472116 476114 477108
      478102 480097 479092 476081 464070 459064 455060 453054
      450046 448042 447036 444026 440017 435991 434978 436965
      439953 440947 439942 444934 445929 445923 443911 440902
      436892 435875 434847 433834 434831 437831 440837 442843
      445843 447832 447826 448821 450809 451802 452796 454784
      454774 451759 446752 441743 436734 434732 428730 422727
      413725 409724 409720 412718 416715 421713 437704 442702
      446702 450704 453707 460709 468706 478700 480696 481692
      482686 480680 487671 488668 487660 481652 475649 467649
      463648 457649 449647 440646 436645 430647 422648 416650
      413652 409655 406658 401665 392683 387691 385696 384701
      382704 383708 379712 376717 371723 367731 362738 359747
      355758 350766 346774 345778 347780 353778 357775 363768
      375753 381748 387741 394735 398732 399740 398763 399769
      398774 395784 384801 381812 375818 367836 364845 358852
      356856 356863 354874 352885 350897 347905 345916 342925
      341930 338933 335938 335945 333956 327973 323988 316006
      315007 312015 312021 314025 321021 331018 334019 337022
      338026 336031 330036 326038 323041 312058 308065 303072
      298083 295086 294091 296095 299097 304097 307098 310102
      316102 322095 326095 327100 333110 338115 342116 346114
      350107 359103 364102 367099 371087 373083 375085 380087
      385089 392090 393095 395095 398092 401094 402097 400102
      396105 381115 379117 379123 384127
 0.01 384127 390129 389131 386131 382132 380133 379135 379140
      381145 388150 391161 393165 398169 405175 409175 413172
      411163 412160 414161 417163 423143 422138 419138 412145
      407144 404141 399138 395140 391140 391134 395131 398131
      402132 406131 409128 416128 424132 430125 434122 438119
      446117 452119 455122 457126 452129 450131 448135 443147
      446156 454163 457165 462167 467167 472166 478168 483170
      490177 500178 505180 509184 515191 518196 521200 526207
      530205 533201 536196 540190 541180 543173
 0.01 530074 531062 529053 526046 522041 516038 510037 504038
      499041 494044 490050 484062 484068 485070 488071 491069
      495065 499060 505059 511062 515067 518072 523078 526079
      528077 530074
 0.01 491216 488213 484211 480211 476211 472212 469215 468218
      470219 473219 476219 481221 483221 486219 490217 491216
 0.01 504916 504911 502908 502903 500903 497903 495906 492911
      490917 489919 489924 489929 490932 492937 496937 497935
      500929 502924 504916
 0.01 464224 464221 463218 461219 457218 455219 452219 449218
      447220 446222 448225 450225 453224 455222 458224 460226
      462226 464224
 0.01 274822 273820 271818 269816 267814 265813 262811 260810
      257811 258815 260817 262819 265820 266821 270822 272823
      274822
 0.25 509149 508148 506148 505148 506149 508150 509149
 0.25 456108 457106 457103 457101 456100 456098 455096 454093
      453093 452091 450092 449095 449097 449099 450100 450102
      451103 453105 454107 455108 456109 456108
 0.25 454110 454109 452109 452110 454110 454110
 0.25 445096 444091 442087 440083 439079 441076 446075 447070
      444059 434043 434036 433029 431018 428993 426982 425967
      424954 424944 424932 423923 420919 415917 413914 406917
      405912 405904 406888 409866 410854 412840 414829 413815
      413809 411803 408800 405799 402801 394806 389813 384821
      380832 377841 372848 368856 365860 364866 362877 359886
      352908 347929 344938 340948 338958 336969 337976 336983
      331993 326003 325006 326010 330010 334006 341001 344999
      350999 354001 356003 356007 353018 350029 346040 342049
      340052 335052 329052 325055 323060 326064 337066 340070
      339073 335082 334088 335094 336098 339103 342105 345103
      349092 351086 351079 352073 353068 366055 372055 378057
      382058 384063 390069 396071 402070 408071 413073 416075
      418078 418085 419088 421090 427098 432102 436101 442100
      445096
 0.25 417106 416102 415100 413098 412096 408094 406096 405100
      405105 405109 407112 410112 412110 415108 417106
 0.25 407035 408026 407019 406012 405003 405993 405986 403979
      401972 398966 395963 390961 390965 392972 395977 397984
      396992 394009 394018 397024 403035 405037 407035
 0.50 433090 433087 432085 432084 430082 429080 427079 426079
      425079 423081 423082 422084 422086 423087 423089 424090
      425091 426092 428093 429094 431094 433092 433091 433090
 0.50 436066 435061 432057 425052 422048 421043 419034 423020
      424008 423996 422985 421978 421973 420966 417962 414964
      412968 410975 411982 412994 413007 415017 414022 414029
      415038 416048 418052 421054 426061 434066 436066
 0.50 409105 409103 408100 407103 407105 407106 409106 409105
 0.50 415935 415940 417945 417946 417942 417937 416935 415935
 0.50 410056 406051 402047 394037 382034 382025 384015 386008
      388000 389993 389989 387986 384981 382974 381965 382955
      388944 390937 391926 393912 397895 401881 403865 405858
      405849 405841 405829 402823 398819 396818 394820 389825
      386830 384836 377849 367875 362889 358901 353914 350929
      345942 343949 341958 340966 341973 343980 340986 337990
      335993 337996 344994 351993 358995 362998 362005 359013
      357018 355025 352044 355046 359045 363042 368039 371038
      373039 372042 372047 377051 382055 388057 393061 401061
      406060 410056
 0.50 411959 411956 411954 410953 410952 409950 408949 407948
      406949 406952 406954 407956 407957 408959 409960 410960
      411959
 0.50 338088 339090 340094 340096 341096 344094 347086 348083
      348081 347079 347078 345077 343077 341078 340080 339081
      339082 339084 338087 338088
 1.00 399055 399053 399052 397051 396050 395049 394049 392048
      390049 389050 390051 392052 393053 395054 397055 398055
      399055 399055
 1.00 398858 397848 395840 389840 386839 384844 383853 381859
      376873 369885 363896 361904 359912 355926 350941 345954
      343961 344971 347976 349985 350987 354988 360986 364983
      370977 372971 373961 377947 380939 381931 381922 383913
      391883 395870 397862 398858
 1.00 378010 379004 376001 372002 370005 367009 365012 362016
      361020 361025 364028 368027 372023 374020 376017 378012
      378010
 1.50 393865 393856 392853 389854 387858 385865 384872 381879
      374889 367896 364903 362909 361916 359923 355934 350946
      346958 345967 348972 351977 353984 359982 362977 366965
      370949 371942 371935 380909 383897 387884 391873 393865
 2.00 378902 377899 374896 367899 365907 364916 363921 361925
      357932 352947 348954 346962 346965 348968 351970 353974
      355976 357976 361969 364961 366952 366941 366932 368923
      372916 376909 378902