Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 230629
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
228 AM EDT SAT SEP 23 2017


PRELIM DAY 1 QPF DISCUSSION
VALID SEP 23/1200 UTC THRU SEP 24/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...CENTRAL AND NORTHERN PLAINS...

A MULTI-DAY HEAVY RAIN EVENT COVERING PARTS OF MANY CENTRAL U.S.
STATES FROM TEXAS TO MINNESOTA...IS SET TO BEGIN TODAY. THE
PRECIPITATION...OCCURRING ALONG AND STRADDLING BOTH A DRYLINE AND
COLD FRONT...MAY SLIDE EASTWARD EACH DAY SO THAT THE EVENT TOTALS
OVER A GIVEN REGION WILL NOT BE TOO EXTRAORDINARY...BUT WE DO
FULLY EXPECT POCKETS OF VERY HEAVY LOCAL RAINFALL PERHAPS
EXCEEDING 5 INCHES...WHICH WILL CARRY A RISK OF FLASH
FLOODING...WHILE BEING EMBEDDED WITHIN LARGER SCALE 1 TO 4 INCH
RAINFALL ACCUMULATIONS THROUGH MONDAY. ON DAY 1 A LENGTHY SLIGHT
RISK OF EXCESSIVE RAINFALL WAS DRAWN. THE RISK MAY BECOME MORE
FOCUSED AND BETTER PRONOUNCED OVER PARTS OF EASTERN NEW MEXICO AND
CENTRAL/WESTERN NEBRASKA...BUT WITH THESE AREAS HAVING BEEN DRY
RECENTLY...WITH HIGH FFG VALUES...AND SOME OF THE HEAVIEST RAIN
PROGGED OVER THE SAND HILLS IN NEBRASKA...THE PROBABILITY OF FLASH
FLOODING AT A GIVEN POINT IS BEST DESCRIBED BY THE SLIGHT RISK
CATEGORY AT LEAST FOR THE INITIAL ISSUANCE TODAY.

THE DRIVER OF THIS EVENT IS A STOUT UPPER LEVEL TROUGH/RIDGE
PATTERN WITH NEGATIVE 3.5 DEVIATION HEIGHT ANOMALIES OVER THE
SOUTHWEST STATES COUNTERED BY PLUS-TWO DEVIATION ANOMALIES OVER
THE GREAT LAKES. THE RESULTING MERIDIONAL FLOW WILL TRANSPORT AIR
MARKED BY PRECIPITABLE WATER VALUES 1.25 TO ABOUT 1.60
INCHES...PLENTY ANOMALOUSLY HIGH FOR LATE SEPTEMBER...ESPECIALLY
AT HIGHER LATITUDES. A NARROW STREAM OF HIGH LEVEL MOISTURE
EMANATING FROM A TROPICAL WAVE OVER SOUTHWEST MEXICO...WILL ALSO
CONTRIBUTE TO DEEPER COLUMN MOISTURE AND MORE EFFICIENT RAINFALL
PROCESSES OVER AT LEAST THE SOUTHERN PLAINS/ROCKIES STATES THROUGH
SATURDAY NIGHT.

A SHORTWAVE TROUGH ROUNDING THROUGH THE EAST SIDE OF THE WESTERN
U.S. LONGWAVE WILL ENHANCE THE PATTERN INFLECTION AND ASSOCIATED
JET STREAK SUCH THAT SYNOPTIC DEEP LAYER FORCING WILL BECOME
EXTREMELY FAVORABLE FOR PRODUCING A RAINFALL MAXIMUM FROM EASTERN
COLORADO THROUGH WESTERN NEBRASKA INTO SOUTH DAKOTA. ON THE
SOUTHERN EDGE OF THE SHORTWAVE CLUSTERS OF EQUALLY PRODUCTIVE
THUNDERSTORMS SHOULD OCCUR OVER NM/TX/OK...THOUGH MESOSCALE
INFLUENCES / OUTFLOWS MAY PLAY A BIGGER ROLE HERE AT DETERMINING
WHERE THE RAINFALL MAXIMA OCCUR.

WITH STRONG FORCING AND THE MAJORITY OF PRECIPITATION OCCURRING
NEAR OR TO THE COOL SIDE OF THE SURFACE BOUNDARIES...THERE IS
UNUSUALLY STRONG MODEL AGREEMENT AS TO THE QPF. THE PREVIOUS WPC
FORECAST SEEMED TO BE IN VERY GOOD SHAPE...SO WE MADE MINOR EDITS
TO INCORPORATE THE LATEST TRENDS...EMPHASIZING THE 00Z GFS...NCEP
WRF-ARW...AND NAM CONUS NEST.


...WESTERN U.S...

THE CLOSED LOW MOVING INTO UTAH WILL HAVE A VERY LIMITED MOISTURE
SUPPLY...BUT SLOW MOVEMENT AND FAVORABLE LAPSE RATES AND SUSTAINED
MID LEVEL ASCENT SHOULD YIELD AREAL AVERAGE PRECIPITATION A TENTH
TO A QUARTER INCH OR MORE...IN LINE WITH THE LATEST MODEL
CONSENSUS. IN WYOMING SOME UPSLOPE ENHANCEMENT INTO THE TETONS AND
WIND RIVER RANGE COULD BOOST LIQUID EQUIVALENT AMOUNTS TO JUST
OVER A HALF INCH THROUGH SATURDAY NIGHT. FARTHER
EAST...FRONTOGENETICAL BANDS ASSOCIATED WITH THE LARGE UPPER JET
STREAK SHOULD PROVIDE SOME MODERATE TO HEAVY PRECIPITATION TO
EASTERN WYOMING AND WESTERN SOUTH DAKOTA WHERE WPC LEANED TOWARD
THE HEAVIER GUIDANCE SUCH AS THE GFS.


...FLORIDA...

MOIST 20 KNOT EASTERLY FLOW AT LOW LEVELS...DIURNAL HEATING...AND
A SLIGHTLY DIFLUENT UPPER PATTERN...SHOULD FAVOR AN ACTIVE DAY
WITH NUMEROUS SHOWERS / THUNDERSTORMS. THE WPC QPF MAY BE A BIT ON
THE CONSERVATIVE SIDE...AND MAY BE RAISED FOR THE FINAL ISSUANCE
THIS MORNING...ESPECIALLY ALONG THE EAST COAST OF THE PENINSULA.
WHILE MEAN STEERING FLOW WOULD CARRY CELLS WESTWARD AT 10
KNOTS...CORFIDI VECTORS ARE DIRECTED BACK EAST INTO THE INFLOW AT
15 KNOTS...WHICH COULD YIELD A BALANCE RESULTING IN SLOW NET
MOVEMENT. THIS IS SEEMINGLY SIGNALED IN SOME OF THE 00Z HI-RES
GUIDANCE WHICH PRODUCES HEAVY RAIN ALONG THE EAST COAST OF FLORIDA.

BURKE

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

24HR QP VT 24/12Z
 0.01 526936 524918 523907 522900 521891 520884 514871 507861
      503856 499852 495847 492845 488845 485848 482852 479860
      460910 457918 454925 447939 444945 440950 437955 431961
      423969 414976 394986 389989 382991 368997 357001 344006
      321014 317017 312019 305019 297017 272006 266004 263004
      263009 266014 264017 259018 254020 251021 250024 251029
      256032 261034 265039 264046 262052 260058 262064 266068
      275069 289067 298068 301070 306071 311074 318076 329075
      333073 340072 346071 351074 355079 356081 356085 353090
      351093 350098 352100 357100 364100 372098 380097 384095
      388094 389097 382106 377109 374114 371128 370137 372142
      380152 386155 393152 397144 396141 399138 410136 417135
      422134 429128 437117 441113 446108 453094 456087 459086
      458092 459100 460104 461107 462111 464113 466115 469113
      473111 475109 475106 474102 475098 479095 483092 485090
      485084 485080 481079 473078 467080 462082 460085 458082
      462077 471066 479056 482050 486045 487040 490033 497022
      509997 512991 515981 520962 526936
 0.01 511157 512152 511149 510145 507143 505142 502141 499140
      497142 496146 497149 499150 501152 504154 505156 508158
      511157
 0.01 500162 497160 495156 493150 491147 488143 485146 483151
      482155 483159 486163 491164 495163 496164 500162
 0.01 480264 481260 481256 479251 471241 458237 453237 449239
      441248 437252 434256 430262 430267 432268 435271 439271
      442272 455276 466275 471274 475271 480264
 0.01 487714 486704 483695 481690 474687 468689 464690 462693
      461698 463702 464708 464713 463716 464722 463725 460733
      457739 454745 454752 456754 459754 464750 469744 472738
      478724 482725 486717 487714
 0.01 450760 449755 447755 444755 440757 439759 437762 436765
      436768 437770 440771 442769 445767 446764 448763 450760
 0.01 423692 419688 415684 410681 405685 401690 398695 397698
      398703 402706 405711 412710 419708 421702 422694 423692
 0.01 367822 365817 362814 358814 356815 354821 351831 349833
      346834 342836 342838 340844 341851 338858 337861 335862
      332865 330872 328877 327884 326891 327894 329895 331898
      329901 329905 328908 326913 326917 337913 339909 340904
      340894 341886 341883 344882 350883 355886 359887 359876
      356874 355872 355866 357860 355855 354850 356846 358841
      363832 367822
 0.01 340093 340091 339089 337088 335088 333090 333092 333093
      334095 335095 336095 338096 338095 340094 340093
 0.01 328796 326792 323791 319790 317792 310798 303799 299797
      294791 288787 278784 275782 270783 264787 256785 251785
      248788 244796 241803 241813 243825 249833 254838 259844
      265852 268859 269866 270869 273878 274884 276888 278891
      276893 274896 271904 271909 272913 275917 279920 283921
      288921 294920 297918 299916 299911 301907 300903 306895
      310877 310865 310858 310852 312843 316836 320827 322822
      321817 326806 328800 328796
 0.01 326941 325937 323934 323930 323926 323924 321921 317921
      315923 314926 313928 313932 314935 317935 319937 321939
      325941 326941
 0.01 304002 301994 298983 296973 292964 290953 286952 283955
      280951 278947 270943 266941 263942 261943 259947 258952
      244963 244968 244973 250980 253983 259983 264981 268983
      272985 275989 280995 284999 287001 291005 295006 301006
      304002
 0.01 259006 257002 259998 258994 255991 251989 248991 245994
      243998 244002 245007 249009 254009 258007 259006
 0.25 505926 506919 505913 503901 500893 494892 493886 493878
      493872 491866 487865 484868 482873 480879 476901 473910
      469918 464926 458937 448952 437965 432971 426976 419981
      410988 403993 396996 387999 379001 371003 364006 356011
      352012 347013 338015 327018 320022 315028 298031 279038
      273043 268050 268055 272058 281055 285056 289058 293059
      297059 302059 306060 315064 324065 335064 345062 353061
      359062 361064 365070 371079 373083 377085 386083 395080
      411077 420076 423081 424085 424094 431101 439105 442104
      445099 444094 442090 439086 440080 445074 450068 462057
      468050 475039 484023 487015 490003 493992 497979 500967
      502956 504942 505926
 0.25 422105 422097 417094 414093 412096 411102 412106 411105
      409101 400108 391112 386114 381119 380125 381128 383130
      388129 394126 398124 405125 411124 416121 419117 421107
      422105
 0.25 392057 392055 392053 390052 389052 388052 386053 384053
      384054 383054 381055 380056 379058 380060 382060 384061
      386060 388060 389059 390059 391057 392057
 0.25 299870 300861 296854 297848 299840 295835 289832 280825
      276824 272824 269824 265825 263829 266835 270841 274845
      278849 280854 280863 283869 287874 292876 297874 299870
 0.25 293805 288797 279792 275791 269791 265793 260796 256795
      251796 248806 254814 257816 262815 268813 275813 285812
      290810 293806 293805
 0.25 285976 284976 283974 281972 279971 279970 277970 275969
      274968 273968 272968 272970 273972 274973 275974 275975
      277976 277977 279978 281978 283978 284977 285976
 0.50 501926 500915 498911 496909 491910 488912 484913 481914
      478918 476922 473924 462939 454951 445964 439970 434976
      421985 410993 399000 390002 381004 373006 365009 353016
      347018 342019 338018 310032 302032 296034 290037 286043
      285047 287049 294052 308051 309055 313058 320059 328060
      335058 352055 361055 366055 370053 376050 383047 397045
      414040 421037 424036 424040 418045 412048 409049 407053
      407061 410065 414067 420064 437060 444059 451057 461049
      467043 472034 474030 473027 471026 471019 477003 480995
      484989 493971 496963 497949 501926
 0.50 441101 442098 441096 440094 438093 436092 435090 434090
      433089 431088 430088 428089 428092 429093 430094 431096
      432097 434099 436099 437100 439101 441101 441101
 0.50 392121 393119 392118 390118 389118 388118 387120 386122
      388124 390123 392121 392121
 0.50 378076 379074 379071 378069 376068 375067 373067 372068
      371070 372073 372074 373075 374076 376077 378076 378076
 0.50 281802 280800 279800 279801 281802 281802
 0.50 277838 277836 275834 273834 272834 273836 275836 277838
      277838
 0.50 274805 273803 272801 272804 272806 273807 274805
 0.50 256799 255799 253799 253800 254801 255800 256799
 1.00 489962 490956 489951 488942 485926 481925 479928 474934
      467947 460959 457964 452969 429984 424987 419991 411999
      399008 393009 387008 379008 378012 376014 372017 370017
      368013 362015 356018 349022 341023 337022 334023 329026
      321035 315048 314052 318053 325055 337053 351051 365047
      376041 389037 394036 402035 409035 417032 429028 435026
      440026 442032 438038 429046 429049 434049 441048 446045
      448039 449033 451027 456022 459015 467999 473987 473982
      471979 467974 466970 467964 470958 474952 477949 481949
      482949 484953 485959 487965 489962
 1.00 308041 308036 306035 303034 299035 297037 295039 293041
      295044 296046 299046 302045 304044 307043 308041
 1.50 452986 452980 449978 443979 435983 429987 406007 400012
      393015 385019 378022 370023 364025 358026 358023 355022
      352024 344026 338025 333025 330027 325033 321040 318046
      333050 349048 364043 370039 376035 393030 402031 409030
      418027 425024 430020 436015 442008 446000 452986
 1.50 306038 304037 302037 301037 300038 299039 298040 298042
      298043 300043 301042 302042 304041 305040 306038 306038
 2.00 447988 446984 445983 440983 438984 427991 418999 408007
      404012 399015 393018 391020 390025 393027 397027 405027
      411025 418022 427016 436007 440002 444995 447988
 2.00 374026 364028 353031 348033 341033 336030 334029 331029
      327033 324038 324043 322043 331045 334046 338046 345046
      350045 356043 366039 369034 373028 374026
 2.00 345030 345028 344028 344030 344032 345030
 3.00 433999 433996 429996 427997 424998 422000 420002 418003
      415005 415007 417008 420010 423009 425008 427006 430004
      431002 433999
 3.00 363034 362033 361033 359033 357033 357036 359035 359036
      360037 362036 363034

$$




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