Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 171842
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
241 PM EDT WED AUG 17 2016


PRELIM DAY 1 QPF DISCUSSION
VALID AUG 18/0000 UTC THRU AUG 19/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


...EASTERN U.S...

WITH A PERSISTENT TROUGH IN THE CENTRAL U.S. AND STAUNCH EAST TO
WEST RIDGING POKING IN OFF THE ATLANTIC...EACH SHORTWAVE THAT
SKIPS THROUGH THE OHIO VALLEY / MID ATLANTIC / NORTHEAST IS
FINDING RICH MOISTURE AND SUFFICIENT HEATING / INSTABILITY TO
YIELD SCATTERED AND LOCALLY GREATER ORGANIZED CLUSTERS OF
THUNDERSTORMS. ANOMALOUS PRECIPITABLE WATER VALUES AVERAGING
AROUND 2.0 INCHES ENSURE A RISK OF HEAVY SHORT TERM RAIN RATES AND
ASSOCIATED FLOODING WITH ANY OF THE STRONGER OR MORE PERSISTENT
INDIVIDUAL THUNDERSTORM CLUSTERS. IN THE 18Z QPF RELEASE WE NUDGED
ONE AXIS OF HEAVIER RAIN NORTHWARD WHERE THE MAJORITY OF HI-RES
GUIDANCE HAS IT FROM NORTHERN VIRGINIA THROUGH THE DC AREA AND
ANAPOLIS TO THE EASTERN SHORE OF MARYLAND. A SECONDARY
MAXIMUM...HOWEVER...IS EXPECTED DOWN TOWARD RICHMOND...WHILE A
THIRD LOCAL MAXIMUM IS EXPECTED OVER WEST VIRGINIA. THE STRONG
WAVE EXITING NEW ENGLAND HAD VEERED WINDS SUCH THAT A SURFACE
FRONT AND CAPE AXIS WAS ORIENTED FROM CENTRAL VA UP THROUGH
CENTRAL AND EASTERN MD. DESPITE DEEP WESTERLY FLOW...SUFFICIENT
MOISTURE AND INSTABILITY EXISTS BACK WEST INTO THE TERRAIN...SUCH
THAT THUNDERSTORMS ARE FORECAST TO ROLL OUT OF THE MOUNTAIN AREAS
AND MERGE WITH ANY ACTIVITY OCCURRING DOWN IN THE COASTAL PLAIN.
WPC TRENDED TOWARD THE 12Z GEM REGIONAL ESPECIALLY...BUT ALSO THE
12Z GFS AND UKMET...WITH SUPPORT FROM THE GLOBAL ENSEMBLES.

MEANWHILE...A FAIRLY WELL DEFINED SHORTWAVE TROUGH WILL SLIDE INTO
THE LOWER GREAT LAKES STATES...STRETCHING BACK TO NORTHERN
MISSOURI. DEEP LAYER MOISTURE IS LESS ANOMALOUS BACK IN THIS
VICINITY...BUT PLENTY SUFFICIENT TO SUPPORT DIURNALLY ENHANCED
RAINFALL IN AN AXIS FROM MO/IA TOWARD FAR WESTERN NY AND NORTHWEST
PA. MODEL QPF SIGNAL IS A BIT MORE VARIABLE HERE...AND WPC RELIED
MOST HEAVILY ON THE GFS AND GEM REGIONAL.


...SOUTHERN U.S / NORTHERN MEXICO...

ANOMALOUSLY LARGE AMOUNTS OF DEEP LAYER MOISTURE REMAIN IN PLACE
ACROSS TEXAS AND THE LOWER MISSISSIPPI VALLEY. THE MOISTURE
APPEARS ENHANCED BY A VAGUELY DEFINED EASTERLY WAVE PUSHING INTO
SOUTHWEST TEXAS AND EASTERN MEXICO...WHICH HAD LED TO SOME
NON-DIURNAL THUNDERSTORM TRENDS THIS MORNING IN MEXICO.
OVERALL...LARGE SCALE FORCING IN THIS REGION IS SUBTLE...BUT
MOISTURE IS SO PLENTIFUL THAT VERY LITTLE ORGANIZED ASCENT IS
NEEDED TO YIELD LOCALLY MODERATE AND HEAVY RAIN. THIS ASCENT WILL
AGAIN TEND TO OCCUR FROM SOUTHWEST TX TOWARD THE ARKLATEX
REGION...CUTTING ACROSS THE AREA NEAR OR JUST EAST OF DALLAS/FORT
WORTH TONIGHT AND THURSDAY. MODEL QPFS WERE SIMILAR ENOUGH THAT A
CONSENSUS APPROACH COULD BE APPLIED...BUT WPC SHOWED SOME
PREFERENCE FOR THE GFS/UKMET/NSSL WRF WITH RESPECT TO PLACEMENT OF
HEAVIER RAIN IN THE ARKLATEX. FARTHER EAST...HOWEVER...THE GFS
APPEARED TOO WET ACROSS MS/AL/GA...DIRECTLY BENEATH THE WESTERN
EXTENSION OF THE ATLANTIC RIDGE AXIS...WHERE SEA BREEZES AND
CONVECTIVE OUTFLOWS MAY NOT BE TERRIBLY PRODUCTIVE IN TERMS OF
AREAL COVERAGE GIVEN LIGHT WINDS / RELATIVE INFLOW.


...WESTERN U.S...

WPC MAINTAINED CONTINUITY WITH THE PREVIOUS FORECAST AND GENERALLY
TOOK A CONSENSUS APPROACH. UPPER AIR TROUGHING OVER THE ROCKIES
AND SIERRAS WAS NOT SHOWING MUCH DEPTH...BEING BEST DEFINED ABOVE
500 MB. MOISTURE THROUGHOUT THE REGION WAS ALSO NEAR OR BELOW
CLIMATOLOGY...EXCEPT WHERE CONVERGENCE AND LIFT WAS RESULTING IN
SOME BETTER POCKETS OF MOISTURE ACROSS THE NORTHERN GREAT BASIN
AND INTO THE NORTHERN ROCKIES. AREAL AVERAGE FORECAST RAINFALL
AMOUNTS REMAIN MODEST HOWEVER...WITH MOST GUIDANCE AND THE GEFS
REFORECAST ANALOG CASES POINTING TOWARD NO MORE THAN A HALF INCH
IN THE 00Z-00Z PERIOD.


...NORTHERN PLAINS / NORTHERN ROCKIES...

RAIN SHOULD BREAK OUT AHEAD OF A FRONTAL SYSTEM MARKED BY
SUBSTANTIAL HEIGHT FALLS THROUGH THURSDAY AFTERNOON OVER MONTANA
AND THE DAKOTAS INTO MINNESOTA. MOISTURE WAS INITIALLY SOMEWHAT
SCARCE...BUT STEEP LAPSE RATES HAD ALREADY DEVELOPED PER THE
BISMARCK SOUNDING. ARRIVAL OF THE FRONTAL SYSTEM SHOULD SET UP A
SOUTHWEST TO NORTHEAST ORIENTED AXIS OF RAIN/THUNDERSTORMS ACROSS
WESTERN NORTH DAKOTA...BUT EXPECT A SOUTHEASTWARD EXTENSION AS
WARM ADVECTION DEVELOPS ACROSS GRADIENTS AT 850-700 MB...AND WHAT
COULD BE TERMED A WEAK WARM FRONT. INITIALLY THIS MORNING THE
ENSEMBLE QPF PROBABILITIES SHOWED WHAT LOOKED LIKE THE MOST
REASONABLE COVERAGE AND MAGNITUDE OF RAINFALL...BUT THE
OPERATIONAL MODELS ARE CONVERGING TOWARD A SIMILAR LOOK AND
FEEL...ALLOWING WPC TO AIM TOWARD THE CONSENSUS. AMOUNTS WERE
INCREASED SOMEWHAT OVER EASTERN ND COMPARED TO THE PREVIOUS
FORECAST...AND MAY CONTINUE TO TREND UPWARD A LITTLE BIT...WITH
THE WPC IN-HOUSE ENSEMBLE STILL LOOKING A LITTLE HEAVIER...WITH
MORE HALF TO ONE INCH AREAS EASTERN ND / WESTERN MN.

BURKE

GRAPHICS AVAILABLE ON THE WEB AT
WWW.WPC.NCEP.NOAA.GOV/QPF/QPF2.SHTML

24HR QP VT 19/00Z
 0.01 553892 553879 552867 544858 539851 534851 533853 530854
      526854 519859 507864 498875 492880 489883 484884 478886
      470887 461888 458886 456884 451879 449872 447844 443841
      440838 440835 442835 446834 447830 450824 454810 455806
      456800 455793 455786 458783 460778 461770 467693 470684
      474680 479674 486669 488666 491664 492661 492657 489648
      487637 484634 481634 478634 475633 471630 467629 465631
      463631 454646 451654 448663 445671 444676 445681 447691
      450692 452689 453684 454681 455683 456688 455691 453699
      450705 443716 438731 436734 434736 433735 428731 425729
      421730 414736 410741 409735 407733 403727 401716 398709
      391705 389702 388697 387686 386676 385673 382671 377668
      374668 371670 364674 361677 360680 358701 357717 355733
      352742 349751 343765 341772 336776 327785 316795 313798
      309801 299801 285800 282797 279793 274789 267787 257788
      249790 243792 239796 237799 236802 242815 245822 246828
      248832 249837 252838 260840 273844 286846 291845 294844
      296840 301839 302843 301846 298851 302857 306864 303878
      303884 305887 305898 304903 302905 296912 293912 287917
      283920 279927 270960 270978 279985 281987 277986 270984
      265983 260984 263991 266997 266001 261002 258996 256994
      252993 244994 240999 239004 240007 242016 244020 242023
      241021 234021 230022 226048 229063 236072 242084 244086
      247087 252087 262094 272102 292117 306122 312124 319123
      325122 330127 333133 331140 337142 343140 347140 349141
      355140 365137 363129 367128 369127 370131 369133 371134
      373131 384127 394119 399115 403114 406116 410117 414116
      418116 418120
 0.01 418120 417128 417133 415137 405146 397157 395166 393172
      397170 401171 402173 405175 406180 411186 414186 416185
      415180 411174 410171 410167 413173 418175 420173 418170
      417162 420156 422147 427129 430123 434119 439121 440133
      441137 442137 446136 450138 455141 459146 477167 492172
      496177 498180 501181 512179 519179 523180 526178 527175
      527168 525160 523153 520146 516141 516132 513124 510116
      506109 504101 496091 493084 492080 496080 500075 505069
      511056 513049 516038 517020 517014 517007 516001 515997
      514988 514983 512980 512975 510972 509967 512963 532947
      535940 537930 537925 539921 542914 553892
 0.01 487075 484068 483060 476059 471058 468052 465051 462052
      464060 465063 467065 469067 472068 475071 480076 483077
      487075
 0.01 460920 460909 459904 457901 451896 448894 443894 439894
      438893 429893 425894 424899 423909 421917 417922 413928
      407934 405936 400936 395933 392926 391921 389918 391879
      379855 378850 376852 373857 370864 365871 363874 365877
      367884 368890 369893 369898 368903 368920 369942 369952
      368965 365981 364985 362988 359993 349005 331025 327029
      323035 321038 322043 325045 330046 344048 353048 360046
      365043 371041 378039 385036 392033 398030 409021 413018
      417013 421006 425997 428990 431981 431973 433968 435966
      439960 440952 435948 431941 431935 434933 440930 446931
      450932 453930 460920
 0.01 409213 404203 391197 388194 386187 386183 384181 381181
      379182 373183 370182 368180 361179 362184 368186 371190
      375196 380199 385201 390205 400212 405215 409213
 0.01 420095 419091 416086 413080 409080 406082 400086 384088
      381091 381096 381100 377101 374103 372105 373107 373112
      371113 368112 366111 364112 360115 363118 367119 370122
      371124 373122 376120 377115 378109 380108 384110 390110
      396108 406094 409096 411101 413104 415104 416102 420095
 0.01 376091 376089 375088 373089 373091 374093 376091
 0.01 368079 367078 366077 365076 364076 363079 365081 366081
      368079
 0.25 540885 540882 538884 538885 537887 536888 535890 535891
      535893 537891 538889 539888 540886 540885
 0.25 506153 507149 507145 505140 500129 495118 493113 490109
      487109 484113 481118 477122 474121 471123 471130 473136
      480142 488151 491155 495157 501157 505156 506153
 0.25 503003 503995 502991 499988 495987 489986 487984 486979
      484972 480971 476971 471973 465975 466967 469953 471947
      473943 474939 475934 474928 471928 469930 460940 455945
      452949 450957 449969 449980 450984 453986 457985 462981
      464982 465987 468994 470001 473009 475011 475016 475021
      475026 472034 473041 476042 478041 482037 487032 491025
      496021 499016 502009 503003
 0.25 473111 470098 467091 466089 462089 460092 460101 453094
      450092 444094 441098 444103 447104 448107 447116 447125
      452129 457130 459129 459126 458120 459113 461111 464111
      469114 472113 473111
 0.25 450075 449073 448071 447070 447069 445068 443068 441069
      441070 441072 443073 444075 446077 447077 448078 449078
      450076 450075
 0.25 446819 446810 445800 442795 438790 435787 429785 426786
      424788 421792 415804 413810 411817 409831 406845 404851
      405862 405873 404890 403897 402901 402906 404912 406914
      409912 413907 416903 419888 420872 422866 422855 423848
      425843 437821 439818 442818 445821 446819
 0.25 405771 406762 403756 402748 401743 400740 394730 392722
      388721 386727 382731 377728 370728 368734 367741 361750
      355759 352764 350770 346782 341792 338802 340809 340818
      339824 337831 331839 326848 328856 326862 324867 323876
      322887 321895 322901 324904 328904 332903 333900 334893
      333885 333876 334869 335865 334862 331859 331854 332852
      335846 337841 339836 342834 346834 352836 358828 360826
      360833 360851 362859 365860 365852 367848 369842 372836
      375831 379827 382822 384817 389808 396796 395793 397793
      397789 398776 402771 405771
 0.25 380793 381789 380786 376786 375788 371790 370792 369795
      368799 368802 369805 371803 372801 374799 376796 379794
      380793
 0.25 378076 378074 378072 377071 376070 375071 376073 376074
      377076 378077 378076
 0.25 359812 359810 358810 357809 355808 354808 353810 353811
      354813 355815 357815 357814 359813 359812
 0.25 346110 346109 345107 344106 343107 343109 344110 346110
      346110
 0.25 354952 354943 353936 352926 353916 353907 351899 346896
      340899 336903 333908 330913 326913 324910 319909 313910
      308915 308918 312920 317922 318924 317928 306937 299946
      295950 294958 292962 293966 300968 308967 312971 310979
      306982 299985 295990 291994 286997 281997 274993 274997
      275001 273005 270011 269017 269024 268031 258039 252041
      243041 238043 234047 233051 233055 235061 238067 242072
      246077 251080 264086 270089 274089 280087 282084 281078
      279073 278066 277062 279058 285053 288049 289043 290038
      293037 301035 309027 318018 326008 332995 336990 343987
      346982 348974 352962 354952
 0.25 342100 343096 342093 340090 339088 339085 339084 336082
      334082 330081 332085 333088 335090 335093 336096 338099
      340100 342100
 0.25 291828 291824 288822 281820 275817 269814 263811 259809
      257813 261819 267824 272828 278831 287831 291828
 0.25 255018 256016 255014 254013 254012 253010 253008 252006
      252004 251003 249003 248004 247006 247008 248010 248012
      249014 249016 250018 251018 252020 254020 255018
 0.50 498146 499140 497136 494131 492127 490124 487121 485123
      482128 481132 482138 484141 487144 490147 494148 498147
      498146
 0.50 497005 498000 497996 495995 494995 490997 488999 487001
      483002 482004 482009 483013 485016 488016 490015 491012
      494010 496008 497005
 0.50 474989 474987 474986 472986 472987 471989 472990 474991
      474989
 0.50 438806 437802 434799 427800 422805 421813 418823 417832
      417836 419839 426834 429828 433821 436813 438806
 0.50 415893 415889 414886 412887 410889 409891 408894 406899
      406901 406905 408907 411905 412903 413899 414896 415893
 0.50 401765 402760 401754 400749 399745 395740 393738 391739
      388746 383752 380749 378741 375742 373744 369750 365764
      364772 368779 367787 372783 382777 392780 393772 394767
      395763 401765
 0.50 380807 379802 375803 373807 371810 369815 367820 365825
      365829 367832 370829 372824 374821 377818 379814 380808
      380807
 0.50 349954 349943 347932 345921 343918 341917 335920 330920
      326924 322941 321944 317945 312939 308941 305945 301951
      297957 296962 301963 308959 316957 318959 319964 320975
      319981 318985 313990 308996 300999 292001 284001 281001
      278003 274011 273015 276019 283021 290024 299026 306022
      311017 317013 322007 324999 323993 324989 337982 341979
      343975 345966 349954
 0.50 340096 340095 340096 340096
 0.50 283825 280823 278823 275822 272821 270820 268818 264819
      267821 270822 272824 274825 276826 280827 283825
 0.50 272079 271072 271067 267056 267052 270048 270044 265043
      256047 245047 241049 238053 238060 240064 245072 249075
      254077 260079 266080 270080 272079
 1.00 395752 395750 395747 393747 392748 390750 391753 392753
      394753 395752
 1.00 392762 392761 390760 389759 388759 387760 387763 386763
      386765 385767 386770 387770 389771 389772 390771 391770
      391769 391766 392764 392763 392762
 1.00 381766 380764 380761 380759 379757 378756 377755 375758
      375759 375760 375762 374765 374767 374769 374772 375774
      377773 377771 378769 379769 380767 381766
 1.00 341954 342943 343937 342932 340929 335929 332930 330929
      328931 327937 326945 324954 325958 327961 329969 329974
      331975 335969 338962 341955 341954
 1.00 301015 300012 297010 295009 291009 289008 285007 284008
      284010 285012 287015 289017 292018 294016 296017 299017
      301015
 1.00 255069 255065 255063 253060 252058 249056 246055 244056
      243060 244063 246066 247068 249069 252070 255069
 1.50 338941 339939 337936 336937 334937 332939 331941 331943
      331945 332946 334946 334945 336945 337943 337942 338941

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