Quantitative Precipitation Forecast
Issued by NWS

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000 FXUS04 KWBC 040647 QPFPFD QUANTITATIVE PRECIPITATION FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 246 AM EDT WED MAY 04 2016 PRELIM DAY 1 QPF DISCUSSION VALID MAY 04/1200 UTC THRU MAY 05/1200 UTC REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR DAY 1 CENTRAL TO SOUTH FLORIDA CONVECTION EXPECTED TO ENHANCE ACROSS CENTRAL TO SOUTH FLORIDA WEDNESDAY ALONG AND AHEAD OF THE SURFACE COLD FRONT FORECAST TO SINK SOUTHEASTWARD ACROSS THE PENINSULA. STRENGTHENING WEST SOUTHWESTERLY LOW LEVEL FLOW OFF OF THE GULF OF MEXICO WILL RAISE PW VALUES TO 2 TO 3 STANDARD DEVIATIONS ABOVE THE MEAN ALONG AND AHEAD OF THE FRONTAL BOUNDARY. THIS ALONG WITH ENHANCED UPPER DIFFLUENCE MOVING ALONG THE FRONTAL BOUNDARY DURING THE FIRST HALF OF THE DAY 1 TIME PERIOD WILL SUPPORT POTENTIAL FOR WIDESPREAD HEAVY RAINFALL AMOUNTS ACROSS THE CENTRAL TO SOUTHERN PORTION OF THE PENINSULA. THERE MAY BE TRAINING OF CELLS IN THE DEEP LAYERED WEST SOUTHWESTERLY FLOW ALONG AND AHEAD OF THE FRONTAL BOUNDARY. WHILE FFG VALUES ARE HIGH ACROSS CENTRAL TO SOUTH FLORIDA---ISOLATED RUNOFF ISSUES ARE POSSIBLE IN URBANIZED AREAS ALONG THE WEST CENTRAL TO SOUTHWEST COAST AND THE EAST CENTRAL TO SOUTHEAST COAST WHERE TRAINING OCCURS. COASTAL NORTHERN MID ATLANTIC INTO SOUTHEAST AND COASTAL NEW ENGLAND AN AREA OF PRECIPITATION ALREADY BREAKING OUT THIS MORNING OVER THE MID ATLANTIC AHEAD OF SHORTWAVE ENERGY PUSHING ACDROSS THE CENTRAL APPALACHIANS. THIS PRECIP SHOULD CONTINUE TO PRESS NORTHEASTWARD WEDNESDAY FROM THE COASTAL NORTHERN MID ATLANTIC INTO SOUTHEAST AND COASTAL NEW ENGLAND AS THIS SHORTWAVE ALSO PRESSES NORTHEASTWARD. RUN TO RUN MODEL CONTINUITY HAS BEEN POOR AHEAD OF THIS FEATURE AND THERE IS A LARGER THAN NORMAL MODEL SPREAD IN QPF DETAILS ON DAY 1 ACROSS THESE AREAS---LEADING TO LOWER THAN NORMAL CONFIDENCE. DAY 1 QPF LEANED TOWARD THE ECMWF AND HI RES ARW WHICH WERE SHOWING BETTER RUN TO RUN CONTINUITY. .25-.50"+ AREAL AVERAGE AMOUNTS DEPICTED---WITH LOCALLY HEAVIER TOTALS POSSIBLE. GREAT LAKES---OH VALLEY INTO THE CENTRAL TO SOUTHERN APPALACHIANS SHORTWAVE ENERGY OVER THE UPPER LAKES/UPPER MS VALLEY REGION EXPECTED TO DROP SOUTHEASTWARD DAY 1---AMPLIFYING INTO A CLOSED LOW MOVING ACROSS THE OH VALLEY AND TOWARD THE CENTRAL TO SOUTHERN APPALACHIANS. WHILE THERE ARE A LOT OF DETAIL DIFFERENCES AT THE SHORTER TIME SCALES---GENERAL MODEL AGREEMENT ON AREAL AVERAGE MODERATE PRECIP TOTALS FROM MI---SOUTHWARD INTO THE OH VALLEY AND CENTRAL TO SOUTHERN APPALACHIAN REGION. THE COMMA HEAD DEFORMATION PRECIP BAND MAY PIVOT EARLY DAY 1 IN THE VICINITY OF THE L.P. OF MI--SUPPORTING A POTENTIAL MAX PRECIP AREA HERE. THE PRECIP ALONG THE ASSOCIATED FRONT PRESSING THROUGH THE OH VALLEY SHOULD BE MORE PROGRESSIVE--BUT STILL SUPPORT A PERIOD OF MODERATE TO HEAVY PRECIPITATION. TOWARD THE END OF THE FORECAST PERIOD EARLY THURSDAY MORNING---ANOTHER COMMA HEAD DEFORMATION PRECIP BAND MAY DEVELOP ACROSS THE CENTRAL APPALACHIANS INTO THE EASTERN UPSLOPE AREAS OF THE APPALACHIANS FROM WV INTO NW VA...FAR WESTERN MD. ANOTHER MAX PRECIP AREA WITH LOCALLY HEAVY AMOUNTS POSSIBLE WHERE THIS PRECIP AREA PIVOTS EARLY THURSDAY. WITH FFG VALUES LOW ACROSS THESE AREAS----ISOLATED RUNOFF ISSUES POSSIBLE. NORTHERN CALIFORNIA INTO THE PACIFIC NORTHWEST THE FORMERLY FULL LATITUDE EASTERN PACIFIC UPPER TROF CONTINUES TO SPLIT INTO TWO PIECES DAY 1. THE PRIMARY CENTER WILL BE THE SOUTHERN PORTION CLOSING OFF ALONG THE NORTHERN TO CENTRAL CALIFORNIA COAST---WHILE THE NORTHERN PORTION REMAINS MORE PROGRESSIVE INTO B.C. CANADA. AN AXIS OF ABOVE AVERAGE PW VALUES TO THE NORTHEAST OF THE CLOSING OFF LOW OFF THE CALIFORNIA COAST AND TRAILING FROM THE INLAND MOVING NORTHERN STREAM HEIGHT FALLS---WILL REMAIN ACROSS NORTHERN CALIFORNIA INTO THE PACIFIC NORTHWEST. BROADLY DIFLUENT UPPER FLOW IN THIS HIGH PW AXIS WILL SUPPORT A WIDESPREAD REGION OF LIGHT TO MODERATE PRECIP TOTALS FROM NORTHERN CALIFORNIA INTO THE PACIFIC NORTHWEST---WITH ISOLATED HEAVY TOTALS POSSIBLE. GRAPHICS AVAILABLE ON THE WEB AT WWW.WPC.NCEP.NOAA.GOV ORAVEC 24HR QP VT 05/12Z 0.01 461623 464624 468627 471635 474642 474647 474652 476666 475670 476676 471691 461720 458727 455730 452730 448732 447735 447738 448742 450746 435773 428786 424801 421806 421811 423815 427816 429814 433814 441812 469803 486800 494799 498798 499801 493818 490825 486831 475840 469845 464850 457860 450862 443864 435866 427868 419867 415867 412868 406871 401875 392888 388893 382895 375897 367896 364895 362890 360887 356886 350886 343882 341880 340874 340863 333853 336847 337843 341840 349829 353825 356819 356813 360809 356804 352797 350793 349790 347787 349786 357782 357779 355777 352776 341785 322804 302823 298828 293834 291840 289847 285864 283871 280877 271888 267894 266897 262897 246896 244893 244887 240886 236886 232881 228874 224865 223859 221855 220846 219836 217829 214823 212815 213807 215800 219788 224775 231763 234756 238751 242745 248741 255738 263736 272734 279736 284741 287743 289740 308724 330704 354686 367677 379670 392662 399658 407654 413650 420647 432640 435637 440634 447628 0.01 536212 535199 536188 536180 535175 533166 531163 529161 523157 517153 509151 494155 490155 488158 483158 480155 475154 474167 479185 474195 472197 469195 460192 458190 460188 462186 462181 462176 460166 458163 456161 453159 449158 444162 443169 442175 440180 437184 437188 436191 434193 429192 427194 423193 419192 415193 409196 406198 401197 394193 391190 386189 377186 370183 366182 363183 361186 363190 368195 381206 393215 380227 382232 384235 388241 396245 404249 410252 419255 427255 433252 446248 460245 467245 473240 475238 477233 476229 472227 467227 463228 458230 458226 461225 468223 474221 481220 485221 487224 492230 499247 503255 508256 517244 525231 528226 531222 536212 0.01 489934 489929 486926 482922 479921 475919 470919 462917 457915 453915 448916 445918 443921 445925 450932 454935 457935 462936 466937 476938 484937 489934 0.25 528202 527191 526187 522184 519178 515171 509170 503173 502180 501186 501191 503195 511198 517202 521203 525203 528202 0.25 512236 512234 512231 512230 511228 510228 509225 508225 508224 506223 505224 504225 503226 502226 501227 501230 502231 502233 503234 504236 505236 506238 507239 509240 511239 512236 0.25 498208 497204 492202 488203 485204 480206 476207 473209 471213 475215 479214 482211 486210 489211 494211 498210 498208 0.25 461671 461664 460658 456648 454646 450645 442648 433652 426657 415667 409673 405679 400684 393688 385693 380698 369709 364714 359720 357728 357734 358737 360737 363735 368730 375726 382727 387731 389735 390741 393750 396756 400759 404758 409752 413746 416738 419730 423727 425725 433711 437704 440702 444700 451696 455690 460680 461671 0.25 458219 458217 457215 454213 451212 448213 442215 435216 428218 425220 424224 423232 416230 410225 405229 399230 398234 400237 407241 415244 423246 429245 434239 429234 433230 438229 451224 458219 0.25 460842 461838 459835 455833 448834 439834 431832 424828 419820 409805 406794 406786 404780 401777 398776 388778 381782 378786 377792 372799 371804 371810 373818 372823 369826 365828 358833 355835 353839 356843 359843 363841 366840 370842 374843 375845 372848 367856 367860 369864 373867 377866 383861 384845 389838 394832 400830 405831 409833 412835 415839 414844 413847 411854 416857 420858 430857 446852 455847 459844 460842 0.25 419223 418221 418220 417219 416220 415221 414222 416224 418224 419223 0.25 296815 290801 286798 285795 283786 276772 276765 275755 272753 270751 260752 253755 247758 241763 237768 229780 226786 224794 221808 220816 221824 225831 229836 234840 237846 245859 247867 249875 253881 257882 261880 265875 269869 276857 283844 288831 296815 0.50 453673 453668 451664 447661 442661 437664 433669 435679 435687 436690 438692 444688 447684 451679 453673 0.50 445221 447219 445218 443219 442219 441219 441220 443221 445221 445221 0.50 449845 447843 444842 442841 439840 437839 433838 430839 428841 426843 427846 429848 431850 434851 437851 441850 444848 446847 449845 0.50 427700 424695 419693 413693 406695 399696 393699 388703 387708 388714 391720 394726 395731 395741 396745 398747 404746 409743 411737 412730 410721 413718 417717 418715 421711 425705 427700 0.50 394800 395797 393795 389793 384793 381796 377800 376805 376807 379812 384812 387810 390806 393803 394800 0.50 291818 291813 289810 284807 279796 276790 274786 272785 266784 265776 267761 264760 260762 255763 249767 245771 238779 231790 228795 226801 223813 224820 227825 236832 240836 243841 249853 253865 257870 263870 267866 270861 276851 281840 286827 291818 1.00 289818 278811 276803 270798 266794 262791 260791 255790 251792 248797 244803 241809 244817 250820 252828 252838 254847 257849 261848 267845 274842 278841 280838 282831 285824 289818 1.50 284823 276817 274812 273807 269803 265800 262796 260795 257797 252805 251809 256808 258808 257813 257826 257833 259839 265838 269836 276835 280832 280829 282825 284823 2.00 272824 272822 272821 272820 270818 268817 266817 264818 264819 263821 263822 263823 262825 262827 262829 262831 264832 266832 267831 268831 269830 271828 272826 272825 272824 $$

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