Quantitative Precipitation Forecast
Issued by NWS

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609
FXUS04 KWBC 280710
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
309 AM EDT WED SEP 28 2016


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


DAY 1


...MID ATLANTIC INTO THE NORTHEAST...

THE SOUTHWARD MOVING CLOSED LOW OVER THE OH VALLEY WILL BE BACKING
THE LOW TO MID LEVEL FLOW DOWNSTREAM OF IT ACROSS THE MID
ATLANTIC---BEGINNING A MULTI DAY PRECIPITATION EVENT THAT WILL
BRING QUITE A BIT OF RAIN OVER NORTHERN PORTIONS OF THE MID
ATLANTIC REGION. AS THE DEEP-LAYER FLOW BACKS S-SE...THE INJECTION
OF MOISTURE OFF THE ATLANTIC GULF STREAM WILL BRING HIGHER PWS
W-NW INTO THE MID ATLANTIC REGION. TAKING A LOOK AT THE LATEST 00Z
GFS-BASED ESRL FORECAST OF INTEGRATED WATER VAPOR TRANSPORT (IVT)
SHOWS A WELL-DEFINED ATMOSPHERIC RIVER SET UP FROM OFF THE
ATLANTIC COAST NORTHWEST THROUGH THE NORTHERN MID ATLANTIC
REGION...THEN WESTWARD INTO THE OH VALLEY AND SOUTHERN LOWER MI.
MEANWHILE...THE NEGATIVE U (EASTERLY) WIND MOISTURE FLUX ANOMALIES
CLIMB TO AROUND 3 STANDARD DEVIATIONS ABOVE NORMAL ALONG THE
MASON-DIXON LINE PER THE GEFS/ECENS. ADDING TO WHAT WILL BECOME A
VERY FAVORABLE THERMODYNAMIC ENVIRONMENT IS SOME ELEVATED
INSTABILITY TO WORK WITH -- WITH MUCAPES AVERAGING 400-800 J/KG
PER THE MODELS.

IN TERMS OF THE DAY 1 QPF...WPC FOLLOWED A BLEND OF CONTINUITY
(PREVIOUS FORECAST) ALONG WITH THE 00Z GFS...UKMET...AND RGEM. THE
00Z ECMWF IS SOMEWHAT OF A WET OUTLIER WITH THE HEAVY RAIN AXIS
REACHING FARTHER NORTHEAST INTO SOUTHEAST PA...NORTHERN DE...AND
SOUTHERN NJ...THUS FOR NOW HAVE NOT INCORPORATED THE ECMWF IN THE
QPF BLEND OVER THIS AREA. MEANWHILE...THE 00Z NAM IS A NOTABLE
WESTERN OUTLIER WITH THE HEAVIEST RAINFALL (2-3+ INCHES) ACROSS
THE BLUE RIDGE AND EASTERN SLOPES OF THE APPALACHIANS. GIVEN THAT
THE MEAN LOW-LEVEL INFLOW WILL HAVE MORE OF A SOUTHERLY VS.
EASTERLY COMPONENT (I.E. MINIMAL UPSLOPE) THROUGH MUCH OF THE
PERIOD...ALONG WITH THE INSTABILITY GRADIENT EAST OF THE BLUE
RIDGE...HAVE DISMISSED THE 00Z NAM QPF.

HEAVIEST QPF -- 2 TO 3+ INCHES -- WAS NOTED ALONG AND WEST OF THE
I-95 CORRIDOR TO INCLUDE RIC...DCA...BWI...AND MDT. DESPITE THE
DRY ANTECEDENT CONDITIONS (RELATIVELY HIGH FFG)...WILL MAINTAIN
THE LARGE SLIGHT AND SMALL MODERATE RISK AREAS (WITH SOME MINOR
TWEAKS) IN THE NEW DAY 1 EXCESSIVE RAINFALL OUTLOOK THAT WERE
INHERITED FROM YESTERDAY`S DAY 2 ERO.


...SOUTHERN LOWER MICHIGAN INTO THE OHIO VALLEY...

THE STRONG CLOSED LOW INITIALLY OVER THE UPPER LAKES WILL BE
DROPPING SOUTHWARD INTO THE LOWER LAKES AND TOWARD THE OH VALLEY
THIS PERIOD.  SHOWERY CONDITIONS WILL DROP SOUTHWARD THROUGH THE
WESTERN LAKES AS THE ASSOCIATED COMMA HEAD DEFORMATION PRECIP BAND
ALSO PUSHES SOUTHWARD. AS NOTED ABOVE... THE WESTWARD EXTENSION OF
THE ATMOSPHERIC RIVER WILL REACH THESE AREAS...AS THE APPROACHING
UPPER LOW ALLOWS THE WARM CONVEYOR BELT (WCB) AND ANOMALOUS PW AND
850-700 MB MOISTURE FLUX TO BACK MORE WESTERLY INTO A DEEPENING
TROWAL ZONE. HAVE BOOSTED MAX AREAL-AVERAGE QPF TO 0.50-1.00
ACROSS SOUTHEAST LOWER MI SOUTH INTO OH A RESULT OF GOOD
MULTI-MODEL CONSENSUS...SOME OF WHICH MAY BE ENHANCED WITH THE
STRENGTHENING EASTERLY FLOW OFF LAKE ERIE.


...SOUTHWEST/SOUTHERN GREAT BASIN/SOUTHERN CALIFORNIA...

THE CLOSED HIGH OVER THE GREAT BASIN WILL BE WEAKENING THIS
PERIOD---ALLOWING CONTINUED SLOW NORTHWARD PUSH TO THE CLOSED LOW
INITIALLY OVER THE NORTHERN BAJA INTO THE SOUTHWEST AND SOUTHERN
GREAT BASIN THIS PERIOD.  WIDESPREAD SCATTERED SHOWERS LIKELY TO
CONTINUE IN THE ABOVE AVERAGE PW AXIS AHEAD OF THIS CLOSED
LOW---SUPPORTING LIGHT TO MODERATE AREAL AVERAGE PRECIP TOTALS
ACROSS THESE REGIONS.

HURLEY

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

24HR QP VT 29/12Z
 0.01 494333 486328 477323 470320 464314 462309 462306 467298
      473293 481290 486290 489288 492286 495285 505289 510291
      513290
 0.01 544041 544032 542023 539008 536003 532998 528994 526997
      522002 519009 517017 516025 512041 512056 512066 511071
      509075 508081 504088 499100 494112 492120 491129 494133
      501136 504135 507129 515124 519117 521111 523104 525094
      531083 534076 535069 537061 540053 544041
 0.01 497151 498149 498146 498144 497143 495145 495146 493148
      494151 496151 497151
 0.01 473900 472888 471882 470877 467869 466861 465849 465844
      466839 466829 464819 463817 461819 459824 457830 459838
      459842 461844 461855 458862 454864 450865 448867 444868
      439868 435866 432865 433861 436856 439849 441840 442837
      441832 439824 436816 439810 443806 445802 444797 447795
      447790 444782 443774 441762 440752 437745 433737 429731
      424731 415732 416726 421716 426711 429705 426700 424698
      420698 415702 412708 409715 406722 399735 397736 394735
      387733 376728 372726 367723 360731 351740 347754 346763
      345767 343770 334778 330780 325780 319779 312777 313772
      311766 308765 305764 295763 287763 280762 264764 255766
      248768 240779 241784 242786 246786 251789 253791 254796
      256797 254800 252806 257814 260830 258835 253838 250841
      248844 247851 254860 262860 264862 265866 272880 272887
      274893 276898 280904 283905 287904 291900 295897 299891
      302884 305876 307871 313867 317862 320856 322849 327842
      334835 339831 344828 351824 359824 362824 360827 356830
      352837 350846 351859 350866 352870 355870 361868 364876
      379884 381886 384887 389885 395881 404880 415889 421892
      425895 431893 437887 438883 446882 451882 455877 459872
      461875 461880 460900 460911 460915 464916 468914 471910
      471903 473900
 0.01 426117 424117 422114 420116 420119 422119 424119 426117
      426117
 0.01 413103 413099 410098 405100 394094 385088 376080 362078
      349073 346070 340069 335070 328069 319069 317069 314071
      309074 307075 305074 292058 281053 273051 265051 262054
      260059 260066 264070 274077 284083 290085 295088 298092
      298095 302095 312092 315092 315096 317099 318101 319108
      324111 330112 336114 340119 342124 344131 346138 349141
      352147 350154 349159 354165 354172 352177 355184 358187
      363188 367184 365178 372171 373167 378164 379156 377153
      378146 382145 385145 387145 390148 393144 388139 388132
      391128 393121 396117 398113 401113 406113 409108 413103
 0.01 386808 385807 383808 382808 380809 382810 384810 385810
      386808
 0.01 375815 373813 371814 370815 372817 373816 375815
 0.01 331129 331127 332125 330127 329129 331129 331129
 0.01 318131 318129 317127 315125 312124 308123 306125 304125
      302127 302131 303133 305134 309134 312135 314133 316133
      318131
 0.01 311158 312154 310152 309147 306140 302142 295140 291140
      289142 288148 287152 289154 292159 298161 305162 309160
      311158
 0.01 231979 232987 232996 231000 232004 234007 240019 245022
      250020 256012 260007 262002 261999 259998 254993 255989
      257989 263986 269983 274979 279968 281962 281953 276941
      273926 272918 272915 270911 266895 265891 263890 262895
      262914 261922 258927 250937 244940 239943 236947 234953
      230963
 0.01 236810 232800 230786 227784 224787 221791 219796 220810
      225819 227824 226829 225834 225838 228839 230840 231836
      232831 232824 235814 236810
 0.25 505307 504307 503307 502308 500308 499308 498309 497310
      496310 494311 493313 492316 492318 493320 493321 494323
      495325 497325 499325
 0.25 429764 428755 426750 422746 416744 406744 397747 386745
      379744 375749 372753 369757 362765 354773 345781 339787
      335791 333796 328807 326812 324812 324817 329817 341813
      346811 353809 357808 362810 370804 379799 387798 393797
      398794 405793 408797 407803 405809 402813 391817 381823
      374830 372835 371842 372846 374847 379848 390847 393851
      397855 402855 406857 415864 420862 425858 428854 430850
      433844 433838 432830 431822 429815 426808 427800 428795
      427789 424784 429764
 0.25 319791 315787 307787 301785 298779 292776 287773 285772
      280772 275776 277780 279782 285783 287785 286787 282789
      281792 282807 284809 288808 292807 290804 291801 296802
      301804 309804 317795 319791
 0.25 307850 304833 300825 296820 290816 284814 277817 272820
      269823 268827 268837 267846 269853 273861 276867 280874
      283881 286882 291881 296876 298869 300862 306856 307850
 0.25 271970 271954 268940 265935 261936 257940 254944 250949
      246949 243950 242952 239956 234967 235976 237980 241984
      245985 248984 258980 263977 268974 271970
 0.50 426827 425820 422815 416814 413817 406819 400819 394821
      390823 382829 380833 383836 385837 389837 394836 398839
      400844 405846 408843 412839 416840 419841 422840 425836
      426827
 0.50 420771 419763 416760 413756 410753 406751 400751 392750
      386749 380752 374758 367765 362771 348785 342792 340797
      338801 341806 347805 356802 361803 366802 374798 384795
      392794 403790 412786 415784 418779 420771
 0.50 294843 293832 290828 287827 278825 273826 272830 274834
      279835 281835 281838 279842 275843 273847 274853 276857
      282861 286864 288864 288861 289858 291855 293851 294845
      294843
 0.50 267972 268965 266961 266955 267952 265943 261944 261949
      255956 252959 248961 241964 238968 239973 241976 246977
      252977 255975 264974 267972
 1.00 409775 409769 408766 404760 393755 390754 386755 382759
      373768 363777 357781 353785 351788 350793 352796 355796
      364795 370793 378790 382788 394784 398783 402782 407778
      409775
 1.00 404785 403784 401783 399784 397784 396786 398788 399787
      401786 403786 404785
 1.50 404771 403764 399760 395758 391757 386758 383762 375769
      368776 361783 356786 355790 360791 366789 372788 376786
      385781 391778 397778 402776 404771
 2.00 401769 401765 399762 396760 391760 384763 379768 375774
      368779 365784 368785 372783 379780 383779 386777 393775
      398774 401769
 3.00 396768 397765 395764 394764 394763 392764 390764 389767
      390769 391769 392769 394769 396768 396768

$$





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