Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 041854
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
254 PM EDT FRI SEP 04 2015


PRELIM DAY 1 QPF DISCUSSION
VALID SEP 05/0000 UTC THRU SEP 06/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1...

...NORTHERN ROCKIES AND NORTHERN PLAINS....

THIS AFTERNOON A LARGE SCALE AND DEEPLY ANOMALOUS TROUGH OCCUPIED
THE WEST COAST STATES AND IDAHO AND NEVADA. A FRONTAL ZONE WAS
LOCATED ALONG THE EASTERN EDGE OF THE INITIAL HEIGHT FALLS...OVER
THE NORTHERN PLAINS. A LEAD SHORTWAVE WHICH ORIGINATED IN THE
SUB-TROPICAL / MONSOON REGIME...HAD BEEN SWEPT INTO THE FLOW...AND
WAS DRIVING AN ORGANIZED PRECIPITATION EVENT OVER EASTERN ND
TODAY. THE INITIAL WAVE OF CONVECTION WILL MOVE QUICKLY UP INTO
CANADA THIS EVENING...AND STABILIZATION IN ITS WAKE WILL LIKELY
REDUCE THE EFFICIENCY OF ADDITIONAL SHOWERY / THUNDERY ACTIVITY
TRYING TO DEVELOP LATE THIS EVENING WHEN THE LARGER SCALE LOW
LEVEL FLOW ACCELERATES INTO THE BACK SIDE OF THE SHORTWAVE. THESE
REDUCED EXPECTATIONS ARE EVIDENCED BY A SHARP DECREASE IN THE
HI-RES MODEL QPFS BETWEEN THE 00Z AND 12Z CYCLES. WPC REDUCED QPF
THIS EVENING OVER MINNESOTA...BUT MAY NEED TO REDUCE IT FURTHER
BASED ON THE TRENDS.

MEANWHILE...ADDITIONAL MODERATE PRECIPITATION WILL GET GOING BACK
TO THE WEST...NEAR THE STRENGTHENING UPPER LOW IN EASTERN
OREGON...AND WITHIN THE BROADLY DIFLUENT UPPER FLOW OUT ACROSS
IDAHO/MONTANA. THE MODELS HAVE BEGUN TO BETTER RESOLVE THE
INTENSITY OF THIS SYSTEM...WITH A MARKED INCREASING TREND TO THE
QPF AS SEEN IN OUR IN-HOUSE ENSEMBLE OVER THE LAST FEW CYCLES. WE
TRENDED IN THAT DIRECTION...WITH FORECAST AREAL AVERAGES EXCEEDING
1 INCH IN THE FAVORED UPSLOPE AREAS OF NORTHEAST OR AND WESTERN
MT. ANOTHER RELATIVE MAXIMUM IS FORECAST WHERE DEEP LAYER ASCENT
BEGINS TO OVERLAP WITH THE LOWER LEVEL...850 MB...FRONTAL ZONE IN
EASTERN MT/WESTERN ND. PLACEMENT OF THIS AREA WAS WELL HANDLED BY
THE PREVIOUS FORECAST...ALTHOUGH WE DID FIND ROOM TO INCREASE
AMOUNTS BASED ON MODEL TRENDS.


...SOUTHWEST U.S...

THE MONSOON CONTINUES ALONG A SWATH FROM SOUTHERN AND EASTERN
ARIZONA THROUGH NORTHERN NEW MEXICO TO CENTRAL COLORADO.
PRECIPITABLE WATER VALUES WERE RUNNING A BIT ABOVE AVERAGE (1-2
STANDARD DEVIATIONS PER THE ENSEMBLES)...INCLUDING A CONNECTION TO
HIGH ALTITUDE MOISTURE STREAMING NORTH FROM TROPICAL STORM KEVIN
AS PER THE 700-500 AND 500-300 CIRA LAYER PW LOOPS. A DEEP TROUGH
ALONG THE WEST COAST WILL BEGIN TO SWING EASTWARD...WHICH SHOULD
FURTHER STRENGTHEN THE DRY SLOT OVER NEVADA AND WESTERN UTAH...BUT
WITH JET LEVEL FORCING PASSING WELL NORTH INTO THE NORTHERN
ROCKIES...THERE DOES NOT APPEAR TO BE ANY APPRECIABLE INCREASE TO
DEEP LAYER ASCENT OVER THE SOUTHWEST THROUGH SATURDAY. MODEL QPF
SIGNAL IS NOT PARTICULARLY HEAVY...BUT THE OVERALL CONSENSUS IS
GENEROUS WITH THE COVERAGE OF 0.10 TO 0.25 INCH AREAL AVERAGE
PRECIPITATION... ESPECIALLY ALONG THE S/SW FACING SLOPES IN
SOUTHEAST AZ...WESTERN NM...AND SOUTH-CENTRAL CO.


...EASTERN U.S...

A SORT OF BROAD...WEAK...AND UNUSUALLY ORIENTED COL WAS LOCATED
OVER THE EASTERN U.S...COMPRISED OF RIDGING IN NEW ENGLAND AND THE
WESTERN GULF STATES...AND LOWER HEIGHTS OVER THE GREAT LAKES AND
SOUTHERN ATLANTIC COAST. THROUGH SATURDAY THE SMALL CYCLONIC
CIRCULATION OVER THE GREAT LAKES IS FORECAST TO WEAKEN...AND
SHOULD CONTINUE TO DRIVE ONLY SMALL SCALE PRECIPITATION AREAS WITH
OCCASIONAL LOCAL DOWNPOURS BUT LIGHT AREAL AVERAGE QPF. THE LOWER
HEIGHTS OVER THE SOUTHERN ATLANTIC COAST ARE LARGE IN SCOPE AND
WILL RETROGRADE SLIGHTLY. WARM AND HUMID LOW LEVEL AIR SURROUNDING
THIS SYSTEM WILL SUPPORT WIDELY SCATTERED AFTERNOON
THUNDERSTORMS...WHILE A WEAK BACK DOOR COLD FRONT WILL RESTRICT
THE NORTHERN EXTENT OF THIS ACTIVITY...ESPECIALLY BY SATURDAY. THE
SOUTHERN APPALACHIANS WILL BE FAVORED FOR CONVECTIVE INITIATION
BOTH DAYS AND AREAL AVERAGE QPF GREATER THAN 0.25 INCHES. SOMEWHAT
HEAVIER AMOUNTS ARE EXPECTED OVER THE SOUTHERN FLORIDA
PENINSULA...WITHIN THE LIGHT BUT CONVERGENCE FLOW REGIME AHEAD OF
A WEST TO EAST TROUGH CURLING ITS WAY OUT FROM THE LARGER SCALE
LOW. WPC QPF TRENDED TOWARD THE 12Z WRF-ARW...ESPECIALLY OVER
FLORIDA...AND TRENDED TOWARD OUR IN-HOUSE ENSEMBLE AND SREF MEAN
IN OTHER SPOTS.

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

BURKE

24HR QP VT 06/00Z
 0.01 553898 546849 543841 540837 537836 533835 530837 527838
      524841 515853 511858 507864 498878 495886 490891 480901
      474907 467911 462912 459914 455916 452920 445935 438937
      433942 428947 424952 424956 424963 427971 438977 432979
      426984 413994 408000 404010 400018 396025 396034 396040
      397041 400041 401037 405030 413017 418011 424007 430005
      436001 440999 445998 453001 455002 455004 451007 446011
      440016 435023 432027 431031 429035 431037 433040 437041
      442041 445043 452045 458048 459053 457057 455064 455069
      456072 459075 461077 460079 455076 450075 445070 441071
      439075 438076 440080 446086 445089 442092 434094 428089
      426089 424093 427099 425103 419106 415105 415102 419095
      420087 417085 414085 409086 407088 403091 400095 395101
      393105 392110 378119 374126 374132 375134 384125 387122
      391121 398122 413123 416124 419126 422125 425122 431116
      438117 434157 437163 438167 438171 432176 427178 423178
      420180 414186 412191 413196 414198 418199 421203 423212
      422219 420225 418230 420234 434232 442230 448224 450220
      452214 455206 461205 468204 475202 481199 486197 491194
      501184 505178 510167 512162 516162 520162 523158 524147
      522138 519130 518118 517113 517106 519096 522087 522079
      522070 519062 518052 519038 519029 518024 517018 515014
      512006 519002 525997 530990 538975 544960 548940 551919
      551904 553898
 0.01 465849 464839 462832 457826 452822 449820 447817 449809
      450803 451796 449792 446791 440790 432791 426789 421787
      420780 413772 409769 406768 402768 394770 389771 387774
      381777 377777 374775 376767 377758 379742 379738 376733
      365730 352732 345734 341738 337744 336749 334752 329757
      328762 330765 333766 340769 340774 339777 336784 330793
      313809 306809 300807 305803 305800 303797 297796 291798
      288797 286795 281790 270783 268786 261787 256789 253794
      251800 251808 254813 259817 264822 266824 266826 277848
      284858 287859 291858 294857 296860 298866 299874 300878
      298882 296886 293885 291878 285875 281879 277885 275891
      274898 274904 275907 290927 291929 291934 291942 290948
      287953 284958 282965 283968 287969 290966 291963 292959
      293957 301956 307952 310945 311937 314930 315927 317926
      320924 323926 326926 328928 332926 330921 327917 322906
      317901 314893 315886 318878 321872 322869 325868 330863
      332861 335861 349860 353859 355857 359852 363848 368844
      377837 382832 384824 388818 389820 389824 388828 388837
      388845 392860 399860 401858 403862 404867 407873 411877
      414880 426885 432886 436885 437881 435871 433865 427850
      425844 428843 429844 432847 434848 440847 445846 449850
      457862 459861 462857 465849
 0.01 416793 412789 408788 403788 398789 393790 391796 392801
      392805 393809 394811 398808 401806 406803 408801 411797
      414795 416793
 0.01 416066 416058 416055 415052 402050 391049 379050 373049
      367047 361046 357045 356042 353039 348037 340039 332046
      329050 325056 326062 330065 331068 333069 335065 336068
      334071 330074 326078 319078 306074 298071 292069 284068
      277068 271068 266069 261068 254069 254075 256079 260083
      265085 272087 283088 295091 301092 307094 309097 307100
      308104 311109 315108 318107 324107 328110 331116 333122
      336126 343132 347134 351132 354127 356121 359111 368106
      370102 374098 378098 381095 385092 390089 398086 406081
      410078 412073 416066
 0.01 384797 383797 381797 380798 379799 377800 377801 378803
      379802 381801 382800 383799 384797
 0.01 268011 265005 259000 255996 248992 243994 240001 243006
      248010 254014 260017 266015 268011
 0.25 544906 543896 541886 537869 534868 532870 526875 514878
      509882 505888 498898 491913 482921 477924 472929 468933
      466942 464950 464954 465957 469962 474967 483976 490987
      495992 503992 508991 513988 519984 524979 531969 534962
      537953 538945 538933 542919 544906
 0.25 512147 513138 513128 511113 514085 513078 508073 507071
      506067 507058 509042 509034 509029 504016 499006 497003
      492001 487001 480000 468020 466024 465030 469042 470047
      472054 473061 475068 480077 482082 482086 481090 475098
      470100 465101 460101 458105 460116 458124 455129 453137
      454146 452154 451158 446169 439179 436183 433188 432196
      433201 439204 444205 460195 468190 475185 483178 486175
      490173 497165 502157 505155 509152 512147
 0.25 406102 406103 406102
 0.25 476994 476989 475985 474983 472982 469979 467978 464978
      462979 459981 459986 462988 464990 466991 469993 471994
      473996 476994
 0.25 473161 473160 472161 473162 473161
 0.25 394075 392068 388066 384066 377062 370059 365060 362063
      358067 359071 362073 366074 369076 372084 377088 380087
      382085 388080 392080 394076 394075
 0.25 360749 359743 356739 353739 350742 347745 345750 344754
      344759 348760 353757 357756 359752 360749
 0.25 363816 363810 362807 356804 351804 350807 352815 349822
      346829 345833 346836 348840 352839 355833 356829 358826
      361821 363816
 0.25 344118 345116 345114 344112 342112 340112 338113 338115
      339117 339119 340120 341120 342120 343119 344118
 0.25 343098 343096 344094 344092 344089 344087 343085 341085
      339086 338087 337087 336089 336091 336093 336094 337095
      337097 338100 340100 341100 343098
 0.25 332813 330812 328813 327814 328816 330815 332813 332813
 0.25 309865 309861 307858 306854 306850 305847 303846 299846
      298848 298851 299853 301855 304857 305859 306863 307865
      309865
 0.25 305831 304829 304827 304826 302825 300823 299823 298822
      296822 294822 292824 294826 295828 296829 297830 298831
      300832 302832 304832 305831
 0.25 299080 299078 298076 298075 296075 294074 292074 291075
      290075 289075 287075 285076 283076 282076 283077 283078
      285079 287080 288080 290081 292081 294081 296082 297081
      299080
 0.25 293851 294849 293847 293845 292843 292842 291841 290839
      288837 286836 284837 283840 283842 283844 284846 285848
      286850 287850 289851 291851 293851 293851
 0.25 285808 283803 281800 277795 275792 271792 262793 256797
      254801 255806 258812 264817 270820 276822 279824 282823
      283815 285808
 0.50 538917 539912 539906 538895 537887 535880 514888 504895
      501898 501903 503905 508908 509911 507914 504919 500921
      490927 482935 479942 476947 473952 473957 475959 491975
      495980 497981 501981 510978 516975 520971 527963 530955
      532947 534933 536923 538917
 0.50 508143 509135 509130 507119 505105 506096 507088 507085
      504084 499084 496086 491095 487101 481108 478112 474113
      470115 467118 463126 461131 462138 465141 469142 477148
      478152 478160 479165 481169 486169 489167 494158 499152
      506148 508143
 0.50 502044 504035 502027 500021 498017 495013 491010 485009
      481011 476022 474026 473034 474041 477046 481055 485060
      489061 494059 496056 500051 502046 502044
 0.50 475176 474171 471170 466171 463168 460164 457165 451171
      445179 440185 438192 439197 445200 448199 454192 457189
      461188 468185 471183 474179 475176
 0.50 380083 381078 381074 379071 378069 376067 373064 371063
      368062 365063 366065 368068 370070 371073 372077 373080
      374082 377085 380083
 0.50 280807 278803 274798 270795 266794 262795 258799 260805
      258807 260811 264815 266815 269814 267810 273811 278811
      280807
 1.00 530926 530913 525913 520916 517923 514929 511930 507929
      503930 501932 497937 495940 494946 494950 492952 485954
      484959 486962 491967 496970 502968 506965 512961 518960
      525947 528931 530926
 1.00 502137 500129 497122 490119 485121 478122 473127 472132
      472137 474139 477139 483142 492144 498142 501140 502137
 1.00 498036 497031 496026 493021 490019 486020 483025 481029
      480034 482039 484042 487047 490049 493047 496043 497038
      498036
 1.00 461183 462181 461178 457178 455179 452180 450182 448184
      446186 444189 445194 447192 449189 452188 454186 457185
      458184 461183
 1.00 270802 270801 269800 268798 267798 266798 265798 264799
      263800 265801 266800 268801 270802 270802
 1.50 523928 523926 522926 520927 520928 519931 520933 522932
      522931 523929 523928
 1.50 483135 484133 483131 481131 479132 481134 481135 482136
      483135
 1.50 491033 491030 489028 488026 486027 486030 487032 488033
      489034 491033

$$




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