Quantitative Precipitation Forecast
Issued by NWS

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480
FXUS04 KWBC 170715
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
314 AM EDT THU AUG 17 2017


PRELIM DAY 1 QPF DISCUSSION
VALID AUG 17/1200 UTC THRU AUG 18/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1...

...GREAT LAKES/OHIO VALLEY...

AN AREA OF LOW PRESSURE WILL TRACK ACROSS THE GREAT LAKES
TODAY...WITH A COLD FRONT EXTENDING SOUTH FROM THE LOW. THE MID
AND UPPER LEVELS WILL BE QUITE FAVORABLE FOR ASCENT...WITH A
STRONG MID LEVEL SHORTWAVE MOVING EAST AND A VERY DIFFLUENT UPPER
PATTERN. ALSO WILL HAVE STRONG 850 MB MOISTURE TRANSPORT AND LOW
LEVEL CONVERGENCE...WITH PWATS ALSO ABOVE THE CLIMATOLOGICAL 90TH
PERCENTILE. THUS WE WILL CONTINUE TO SEE A BROAD AREA OF SHOWERS
AND THUNDERSTORMS MOVE EAST ACROSS THE GREAT LAKES AND OHIO VALLEY
THROUGH TODAY. THE ACTIVITY MOVING THROUGH THIS MORNING IS MORE
ASSOCIATED WITH WARM FRONTAL ADVECTION AND CONVERGENCE...WITH THE
COLD FRONT MOVING ACROSS THIS AFTERNOON/EVENING. DEPENDING ON THE
AMOUNT OF DESTABILIZATION...SHOULD AT LEAST SEE SOME CONVECTION
LATER IN THE DAY ASSOCIATED WITH THE COLD FRONT. THE PROGRESSIVE
NATURE OF THE CONVECTION SHOULD HELP KEEP RAINFALL AMOUNTS IN
CHECK. HOWEVER GIVEN THE STRONG FORCING AND ANOMALOUS PWATS IN
PLACE...WOULD STILL EXPECT TO SEE POCKETS OF LOCALIZED 1-3"
AMOUNTS ACROSS NORTHERN AND EASTERN MI. FURTHER SOUTH ACROSS
IN/OH/KY WE ARE MORE REMOVED FROM THE BETTER FORCING...WHICH MAY
TEND TO KEEP CONVECTION MORE SCATTERED IN NATURE. THIS SHOULD KEEP
AREAL AVERAGED AMOUNTS LOWER...ALTHOUGH STILL COULD SEE ISOLATED
AMOUNTS UPWARDS OF 1.5". WPC QPF WAS PRIMARILY BASED ON A BLEND OF
THE 0Z HRW ARW/NSSL WRF/NAM NEST AND RECENT HRRR RUNS.

...VA/NC/SC...

MODELS CONTINUE TO BREAK OUT SCATTERED CONVECTION TODAY ACROSS
PORTIONS OF VA/NC/SC. ACROSS VA MODELS SHOW A SLIGHT UPTICK IN
850MB MOISTURE TRANSPORT AS A WARM FRONT SLOWLY LIFTS TO THE
NORTH. THIS MAY BE ENOUGH TO RESULT IN ISOLATED TO SCATTERED
ACTIVITY THIS MORNING INTO THE AFTERNOON HOURS. THE APPROACH OF A
PRE FRONTAL TROUGH FROM THE WEST SHOULD ALSO PRODUCE ISOLATED TO
SCATTERED CONVECTION MOVING FROM WV INTO VA THIS
AFTERNOON/EVENING. ACROSS NC/SC A COASTAL CONVERGENCE BOUNDARY
SHOULD ACT AS A FOCUS FOR CONVECTIVE DEVELOPMENT BY EARLY
AFTERNOON WITH ADDITIONAL DIURNALLY DRIVEN CONVECTION POSSIBLE
OVER CENTRAL NC AS WELL. SC/NC WILL FEEL THE ADDED INFLUENCE OF
ENHANCED DIFFLUENCE ALOFT...IN BETWEEN THE NORTHERN STREAM JET TO
THE NORTH AND THE UPPER LEVEL HIGH CENTERED OVER THE FAR
SOUTHEAST. THIS MAY ALLOW FOR A BIT BETTER COVERAGE OF ACTIVITY
OVER THESE AREAS. PWAT VALUES WILL BE INCREASING THOUGH THE DAY AS
WELL...GENERALLY TO 2"+ BY THIS AFTERNOON. THUS WHILE THE COVERAGE
OF HIGHER TOTALS MAY NOT BE WIDESPREAD GIVEN A LACK OF A FORCING
MECHANISM...ANTICIPATE LOCALIZED 2-4" AMOUNTS WILL BE POSSIBLE
FROM VA INTO PORTIONS OF NC/SC...WITH THE BEST CHANCE OF THESE
HIGHER TOTALS FROM NORTHEAST SC INTO SOUTHEAST NC.

...PLAINS TO THE LOWER MS VALLEY...

AS OF 06Z THURSDAY A CONVECTIVE LINE WAS MOVING SOUTHEAST ACROSS
OK INTO AR AND NORTH TX. WOULD APPEAR THAT THE NSSL WRF WAS DOING
THE BEST JOB CAPTURING THE SOUTHWESTWARD EXTENT OF THIS ACTIVITY.
THUS WPC TRENDED OUR FORECAST CLOSER TO THE NSSL SOLUTION THROUGH
THE DAY TODAY FROM CENTRAL TX INTO THE LOWER MS VALLEY. THIS
CONVECTION SHOULD CONTINUE PROGRESSING SOUTHEASTWARD INTO
NORTHEAST TX AND WESTERN AR THROUGH THE MORNING HOURS. THINK THE
LINE SHOULD GENERALLY BE PROGRESSIVE...ALTHOUGH THE SOUTHWEST
FLANK MAY HANG UP FOR A BIT AND RESULT IN LOCALLY HIGHER TOTALS
THROUGH THE MORNING HOURS FROM NEAR THE RED RIVER INTO NORTHEAST
TX. IN GENERAL SHOULD SEE A WEAKENING TREND WITH THIS ACTIVITY BY
MID TO LATE MORNING. HOWEVER ANTICIPATE WE SHOULD SEE AFTERNOON
REDEVELOPMENT ALONG THE LINGERING BOUNDARY. SOME MODEL DIFFERENCES
EXIST WITH EXACTLY WHERE THIS REDEVELOPMENT OCCURS...BUT GIVEN ITS
HANDLING OF THE CURRENT ACTIVITY...AGAIN PREFER SOMETHING CLOSER
TO THE NSSL WRF. THIS POINTS TOWARDS CENTRAL TX AS THE MOST
PROBABLE LOCATION. WITH SOME LOW LEVEL SOUTHERLY FLOW INTO THE
BOUNDARY THINK THIS AFTERNOON CONVECTION MAY TEND TO BACKBUILD
ALONG THE BOUNDARY FOR A PERIOD. ALTHOUGH GIVEN THE GENERAL LACK
OF SYNOPTIC SUPPORT AND WEAK FLOW OVERALL WOULD NOT ANTICIPATE ANY
ORGANIZATION TO BE LONG LIVED. THUS AGAIN THINKING JUST LOCALIZED
HEAVIER AMOUNTS WITH THIS ACTIVITY.

ALSO LIKELY TO HAVE AFTERNOON/OVERNIGHT CONVECTION ACROSS THE
WESTERN PLAINS WITH THE APPROACH OF A MID LEVEL SHORTWAVE TROUGH
AXIS AND INCREASING SOUTHERLY RETURN FLOW. IT REMAINS UNCLEAR HOW
ORGANIZED ANY OF THIS CONVECTION WILL BECOME. WOULD STILL APPEAR
THAT THE BEST CHANCE FOR A MORE ORGANIZED COMPLEX IS ACROSS
PORTIONS OF THE TX/OK PANHANDLES. IT IS HERE WHERE WE SHOULD END
UP WITH MODERATE INSTABILITY ALONG WITH SOME RIGHT ENTRANCE REGION
JET DYNAMICS. 850 MB MOISTURE TRANSPORT IS ALSO FORECAST TO
INCREASE OVERNIGHT...ALTHOUGH THE LATEST GUIDANCE DOES NOT SHOW
MUCH IN THE WAY OF 850 MB MOISTURE CONVERGENCE OVER THIS AREA.
THIS CONVERGENCE IS USUALLY A PRECURSOR TO ORGANIZED
CONVECTION...AND MAY BE THE REASON WHY THE LATEST GUIDANCE IS
OVERALL NOT THAT ROBUST WITH QPF AMOUNTS. ALSO ADD IN THAT PWAT
VALUES ARE ONLY NEAR AVERAGE...AND CORFIDI VECTORS SUGGEST ANY
CONVECTION SHOULD GENERALLY STAY MOVING. THUS DO HAVE MANY FACTORS
POINTING TOWARDS MORE SMALLER SCALE PROGRESSIVE DISCRETE
CONVECTION. ALTHOUGH CONFIDENCE REMAINS LOW...AND THE PERSISTENT
850MB MOISTURE TRANSPORT THAT IS FORECAST INTO THE WEAK LOW LEVEL
BOUNDARY..COMBINED WITH THE UPPER JET DYNAMICS...DOES SUGGEST THAT
ORGANIZED CONVECTION AND HEAVY RAINFALL IS STILL A POSSIBILITY.
THUS WILL HAVE TO CONTINUE TO MONITOR TRENDS.



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

CHENARD

24HR QP VT 18/12Z
 0.01 521010 521001 518998 510991 498976 493969 488966 483966
      468956 460961 456962 451963 447961 445961 444957 440949
      437946 433947 426952 421959 419961 416961 412961 409965
      405977 405983 407988 412995 412997 409997 403996 400994
      398990 395988 390988 387984 383981 375977 366974 361973
      358975 355983 353989 351991 344995 331004 328005 327002
      329997 333985 336977 337969 339964 342953 347946 352937
      357930 363925 366923 371921 373923 376920 380914 382905
      385894 388884 395875 399878 400880 413878 417875 419873
      420875 419880 420887 420896 421901 423906 424909 426910
      431914 434913 434917 433923 433929 434933 438940 443945
      450950 458954 466952 476949 484948 491942 499934 502924
      505912 507906 508899 509892 511886 510873 511860 511847
      511842 511833 511827 509821 506809 493764 487757 483752
      480747 466737 459733 450730 433726 425724 416723 412722
      408724 400730 394735 389740 383746 378753 379761 376765
      372770 370772 367772 356771 346772 338776 332781 325789
      320796 316802 310808 303806 296804 276800 267798 262790
      256783 252781 249785 243792 241795 239800 239804 240809
      245816 248816 251814 254818 258821 264824 267825 266828
      262829 260832 262835 268840 275843 279845 285844 288844
      290846 292851 293862 295864 298864 301864 302867 304873
      303879 303886 301891 297893 294897 292906 297914 300927
      301940 301943 311993 321011 320030 321032 324032 329031
      334037 346037 350038 353042 357043 360041 363038 368037
      373037 375035 378030 379024 379020 381016 390016 398013
      400016 400020 396021 393025 387034 385038 386043 389045
      391043
 0.01 391043 395032 397027 400025 410026 414024 415019 421018
      426019 432018 435016 438013 442011 447013 446017 440026
      440033 441036 446039 451040 462041 472039 474036 474031
      472026 468023 465021 466019 471020 479025 488028 499029
      507027 514022 519015 521010
 0.01 473989 470985 468981 465977 463974 459972 454974 452976
      450980 451983 452988 455992 458995 463996 468996 472991
      473989
 0.01 399772 399770 399767 397767 396766 395768 395770 396772
      397772 398773 399772
 0.01 357848 347849 344845 343840 348832 349827 349820 348817
      345817 341820 334826 333828 333832 336835 334839 331844
      330846 327846 323846 320849 320855 324864 317869 314873
      312880 311886 312892 314897 317897 320896 323887 327874
      330871 334873 347871 348868 347864 349861 357848
 0.01 322048 320044 316041 312037 311032 310029 307028 304028
      297033 295036 293035 295031 297026 299024 298021 294018
      288016 283015 278015 268011 262010 259012 256018 254023
      255033 263051 269059 275065 284070 294075 298074 300074
      301071 305061 308056 311053 320048 322048
 0.25 502860 502844 500833 497825 494820 492818 489815 488811
      487802 485788 483779 481774 478770 473765 462755 457749
      452744 448737 442737 435742 434746 434752 435759 434763
      436768 433776 432781 427783 415788 412791 408791 405789
      404784 402780 401778 399779 398783 399789 396803 394807
      390806 385806 383818 381821 378821 372826 369831 371840
      370844 371849 371856 369860 368863 366865 363869 363876
      363879 366881 371876 373869 375872 377874 383873 386871
      394860 397858 399853 401845 404847 405853 408862 408868
      414868 420865 424862 427859 433857 436860 438864 443868
      450867 453875 457884 458887 458892 455897 455901 458900
      463906 465911 464918 461925 458933 462934 463940 465944
      468943 474941 484928 493914 497906 500897 501886 500875
      500869 501865 502860
 0.25 472900 472898 470899 469900 468901 468903 468904 470904
      471902 472902 472900
 0.25 433971 432968 431967 430966 429966 428967 428968 428969
      428971 429972 431972 433971
 0.25 410749 410747 409746 408745 406746 405748 406750 406751
      408751 410750 410749
 0.25 418980 417978 417977 416975 416974 414973 412975 411977
      411980 412981 412982 414984 415984 417982 417981 418980
 0.25 402741 402740 400740 398741 397742 397745 399747 399746
      400746 402744 402743 402741
 0.25 387785 387779 386776 381784 381777 377775 373776 370779
      363782 364790 361791 360790 357786 352780 345778 340779
      338781 333787 330794 330799 334801 339801 343799 353806
      357808 360807 367807 372801 376799 378798 381800 383801
      384799 387790 387785
 0.25 390000 390997 389995 389994 387994 386995 385997 386999
      387001 389001 390000
 0.25 374012 371998 367992 362989 358989 357991 353997 349002
      344005 337006 332010 325020 325024 328026 334025 337031
      341030 342028 345028 347030 352029 361025 368025 371019
      374012
 0.25 366892 365889 366887 366885 366883 365881 363882 362883
      361884 360885 360886 359887 359890 360891 360892 362894
      363894 364894 365892 366892
 0.25 358830 358828 358827 357826 357823 358821 356820 354821
      354822 352823 352824 353826 353828 354830 355831 355832
      357833 357832 358830 358830
 0.25 360916 360914 360912 359911 357910 355911 354912 353914
      352916 352919 350921 350922 349923 350924 352924 353924
      355924 356923 357921 358918 359918 360916
 0.25 350910 349902 344899 341900 337904 333908 328906 325902
      322904 322909 323911 321917 319922 316926 313930 311937
      311945 312949 316962 316977 315984 313992 314996 316998
      320999 324996 327990 330979 337954 338947 341941 346932
      346925 346922 344921 340922 338921 338917 348915 350910
 0.25 316911 315909 315911 315913 316911
 0.25 307827 307819 304814 299810 295809 282807 271805 265807
      262807 260805 253808 257813 260817 264819 274824 279828
      283831 288833 293832 294826 299828 304830 307827
 0.25 304038 304036 304035 304034 303033 302034 301035 300036
      299038 298040 297042 297044 298045 300046 302045 302044
      303042 304040 304038 304038
 0.50 497860 497854 495847 490839 484834 479826 477816 475807
      476794 475780 473773 471771 468771 462773 460777 460784
      459791 458796 457801 454804 451803 447804 444802 443797
      443783 450782 453779 452776 451772 453767 455763 455758
      454752 452748 447742 444741 441744 439747 439753 438766
      437770 437775 439781 438784 436787 432793 428798 424796
      422797 416802 410805 406803 402803 400813 389823 385830
      379836 375842 374851 373858 376858 378857 385856 392851
      393840 394835 397832 403827 408826 410829 412831 415831
      418835 417841 416847 414851 411860 411864 413865 417863
      420860 422855 422851 425846 431844 437847 441850 442853
      441857 439861 441863 446863 449861 454862 456865 457872
      458877 461887 463896 467896 469893 468885 469878 471875
      475877 477880 478886 475896 476905 475911 474914 469922
      465927 465931 465935 468938 471939 473938 476934 480927
      484918 489909 493902 496894 497883 496868 497860
 0.50 422820 422815 421813 420808 417808 416810 414814 413816
      414821 415825 417828 419825 420823 422820
 0.50 394828 394826 394824 393826 392828 392829 394829 394828
 0.50 384791 383788 380788 378785 377782 376778 374778 372779
      369781 370786 371790 371792 375794 377795 379793 380790
      383791 384791
 0.50 369012 370005 369001 366996 362994 358997 355000 354005
      354010 356016 359016 362016 365016 369014 369012
 0.50 355786 353782 350780 345780 340781 337784 335787 332791
      332796 335798 339797 343795 348794 351793 355793 355788
      355786
 0.50 356025 356022 356020 356018 354019 353020 352021 352022
      352023 354024 356025 356025
 0.50 344013 342011 338011 334011 333013 331014 329018 328021
      330022 334022 337021 340020 341017 343015 344013
 0.50 341934 341930 338929 332926 329924 326925 325934 322939
      316939 317949 319956 319962 318971 317981 315988 315994
      319996 322995 325989 327982 329974 332967 335952 337943
      339939 341934
 0.50 301823 298813 295811 291812 288810 284808 276809 273812
      271810 267808 265810 262814 263817 271820 279822 288820
      296824 299825 301823
 0.50 260811 261809 260807 259807 258809 258810 259811 260812
      260811
 1.00 491871 492866 491861 488856 484852 480853 475855 470860
      471867 474872 478875 481880 483883 486883 489877 491871
 1.00 479919 480917 479915 478917 477918 476920 475921 475922
      474924 474925 472927 472930 472931 473932 474932 475930
      476929 476927 477925 477924 478922 479921 479919
 1.00 473845 474840 473835 470831 467823 466818 466808 465805
      463803 459808 456813 454818 448819 444820 439823 438831
      438838 442844 446846 451845 455847 460861 467859 469853
      473845
 1.00 463878 463876 462875 462876 462878 463879 463878
 1.00 436816 436813 435812 434811 433811 431811 431812 430814
      430817 429819 429820 427822 425824 427826 429825 431824
      432823 433821 434819 434818 435817 436816
 1.00 408815 407813 405815 404818 406818 406817 407816 408815
 1.00 389840 389838 389836 388833 387833 385833 385834 384835
      383836 382838 382839 381841 381842 380843 379846 381847
      383846 384846 386845 388842 389840
 1.00 375790 375787 374786 374787 374790 375790 375790
 1.00 351789 350787 349786 348785 347784 345783 343784 342784
      340786 340787 340788 340790 342789 344789 345790 346790
      348790 349790 351789
 1.00 340795 340792 340790 339790 337790 335790 334791 333793
      334794 334795 336796 337796 339795 340795
 1.00 336939 335936 331939 329943 327947 324949 323954 323958
      324964 328967 329960 330955 332950 334945 335941 336939
 1.00 325977 325973 324971 323967 322967 321969 320973 319977
      319981 318984 317988 318992 321993 322990 322986 323984
      324980 325977
 1.00 295815 293814 292815 290814 289814 288812 287812 286810
      284812 284813 286814 288816 289818 290819 292819 294818
      295817 295816 295815
 1.00 278815 278813 277811 275812 274814 274816 275816 277816
      278815
 1.00 269816 268814 266817 268817 269816
 1.50 481869 482867 482864 481862 480861 480859 479858 477858
      475860 474862 474865 475867 476868 477869 479870 481870
      481869
 1.50 466841 465839 464838 464839 463841 462841 462844 462846
      463847 463846 464845 466844 466842 466841
 1.50 463854 463851 462851 461852 461854 461856 462857 462856
      463854 463854
 1.50 444841 445839 445836 444834 444831 443831 441831 441832
      441834 441837 442839 442840 443841 444842 444841
 1.50 387840 387838 386836 385836 385838 384840 384841 386841
      387840
 1.50 321979 322977 322975 321974 320975 320977 321979 321981
      321979

$$





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