Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 261804
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
201 PM EDT FRI SEP 26 2014


PRELIM DAY 1 QPF DISCUSSION
VALID SEP 27/0000 UTC THRU SEP 28/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1...

INTERMOUNTAIN WEST
~~~~~~~~~~~~~~~~~~
A MID-LEVEL TROUGH AMPLIFIES THROUGH TONIGHT/SATURDAY MORNING AS
STRONG SHORTWAVE ENERGY OFFSHORE NORTHERN CA DIGS INTO THE BASE OF
THE TROUGH AND CLOSES OFF A MID-LEVEL LOW OVER CENTRAL CA/WESTERN
NV BY SATURDAY MORNING.  THIS DYNAMIC SYSTEM COULD BECOME A MAJOR
RAINFALL PRODUCER BEGINNING LATER FRIDAY AFTERNOON AND FRIDAY
NIGHT AND CONTINUING INTO SATURDAY DUE TO A COMBINATION OF HEIGHT
FALLS, INCREASINGLY FAVORABLE UPPER DIVERGENCE, AND STRENGTHENING
850/700 HPA SOUTHERLY FLOW OFF THE GULF OF CA/SEA OF CORTEZ INTO
PARTS OF THE INTERMOUNTAIN WEST.  UNIDIRECTIONAL FLOW WITH HEIGHT
THAT SHIFTS FROM SOUTH-SOUTHWESTERLY TO MORE SOUTHERLY WITH TIME
WILL BRING PRECIPITABLE WATER VALUES (PWS) OF 1.50-1.75" AS FAR
NORTH AS THE AZ/CA/NV BORDER AND LOCALLY ABOVE 1" ACROSS THE GREAT
BASIN -- WHICH IS CLOSE TO FOUR SIGMAS ABOVE THE AVERAGE FOR LATE
SEPTEMBER REGIONALLY -- HELPING TO SUPPORT THE NOTION OF LOCALLY
HEAVY RAINS FROM PORTIONS OF THE DESERT SOUTHWEST NORTHWARD NEAR
THE NV/UT BORDER INTO SOUTHEAST ID.

RECENT RAP RUNS INDICATE CAPE VALUES RISE >1000 J/KG ACROSS THIS
REGION AND 850-700 HPA INFLOW ON THE ORDER OF 25+ KTS TODAY AND
SATURDAY, WHICH SHOULD BE ENOUGH TO ORGANIZE CONVECTION ACROSS THE
REGION.  CLOSER TO THE DESERT SOUTHWEST, THE MESOSCALE QPF
GUIDANCE ADVERTISES LOCAL AMOUNTS OF 3-5" (CLOSE TO THE ANNUAL
AVERAGE RAINFALL FOR THE REGION), WHILE LOCATIONS FARTHER
NORTHWARD ACROSS THE GREAT BASIN HAVE ADVERTISED MAXIMA IN THE
2-3" RANGE.  THE FARTHER NORTH YOU GO WITHIN THIS REGION, THE MORE
LIKELY THIS COULD EVOLVE MORE INTO A LONGER DURATION FLOOD RATHER
THAN A SHORTER DURATION FLASH FLOOD EVENT AS LOW- TO MID-LEVEL
FRONTOGENESIS AND ITS ASSOCIATED INCREASING CLOUD COVER TONIGHT
AND SATURDAY COULD LIMIT AVAILABLE INSTABILITY TOMORROW.  CELL
TRAINING IS EXPECTED TO BE THE PRIMARY CAUSE OF ANY FLASH FLOODING
IN THIS REGION -- SOME DRY AIR IN THE LOW-LEVELS OF FORECAST
SOUNDINGS WITHIN THIS REGION SHOULD FOSTER FORWARD PROPAGATION
BEFORE THE ATMOSPHERE SATURATES ON SATURDAY.  USED THE 00Z GEFS-
AND CLIMATOLOGY-BASED QPF REFORECAST TO MODIFY THE 12Z WPC QPF
CONTINUITY WHICH LEADS TO A SOLUTION IN THE DIRECTION OF THE 09Z
SREF MEAN (TOWARDS SLIGHTLY LOWER AREAL AVERAGE AMOUNTS), WHICH
WAS A TREND NOTED WITHIN MUCH OF THE 12Z GUIDANCE.


TEXAS
~~~~~
AN UPPER-LEVEL VORTICITY MAXIMUM NEAR WESTERN TX (AT THE BASE OF A
REX BLOCK) IS LURING PWS OF 1.75-2" INLAND AND INCREASING
LOW-LEVEL INFLOW OFF THE GULF OF MEXICO ON THE ORDER OF 20-25 KTS
FRIDAY AND SATURDAY AFTERNOON AND EVENING ALONG WITH BUILDING
INSTABILITY NEAR A COASTAL FRONT/"PADRE TROUGH" WHICH COULD
ORGANIZE THUNDERSTORM ACTIVITY TOWARDS A MULTICELL CONVECTIVE MODE
ACROSS SOUTHERN TX NEAR THE SURFACE BOUNDARY.  THIS MOISTURE
EVENTUALLY WORKS NORTHWARD ALONG THE 100TH MERIDIAN TOWARDS
SOUTHWEST OK PER RECENT GFS GUIDANCE.  THE MESOSCALE QPF GUIDANCE
ADVERTISES LOCAL AMOUNTS OF 3-6" IN THIS REGION, WITH THE BEST
SIGNAL CLOSER TO PORT ISABEL/BROWNSVILLE TX WITHIN THE 00Z SSEO
NEIGHBORHOOD PROBABILITIES OF EXCEEDING THE THREE HOURLY FLASH
FLOOD GUIDANCE VALUES (FFGS), WHERE FFGS ARE CURRENTLY LOWER.
USED THE 00Z GEFS- AND CLIMATOLOGY-BASED QPF REFORECAST TO
SOMEWHAT MODIFY THE 12Z WPC QPF CONTINUITY WHICH LED TO A WETTER
SOLUTION HERE.


SOUTHEAST & GULF COASTS/FL
~~~~~~~~~~~~~~~~~~~~~~~~~~
AN AXIS OF ABOVE AVERAGE PWS WILL PERSIST THIS PERIOD FROM THE
EXTREME EASTERN CAROLINAS DOWN INTO THE FL PENINSULA NEAR A
FRONTAL BOUNDARY, WHOSE 850 HPA SLICE SLOWLY RETURNS NORTHWEST
TOWARDS THE EASTERN GULF COAST BY LATE TOMORROW.  TO THE NORTH,
THE HEAVIER RAINFALL TOTALS IN THIS HIGH PW AXIS WILL LIKELY
REMAIN OFFSHORE OF THE SOUTHEAST COAST DUE TO EASTWARD PROPAGATION
ANTICIPATED WITHIN MORE ORGANIZED THUNDERSTORM ACTIVITY NEAR THE
FRONT AND GULF STREAM PER 06S GFS CORFIDI VECTORS.  THE BEST
CHANCE OF HIGHER AMOUNTS OVER LAND ARE ACROSS THE FLORIDA
PENINSULA NEAR THE LINGERING FRONTAL BOUNDARY AND TOWARDS THE WEST
COAST IN THE AFTERNOON/EVENING DUE TO THE LOW-LEVEL EASTERLY FLOW
EXPECTED THROUGH LATE TOMORROW.  OVER FL, LOW-LEVEL INFLOW SHOULD
BE LIGHT ENOUGH TO PREVENT MUCH CONVECTIVE ORGANIZATION --
THUNDERSTORMS SHOULD REMAIN SINGLE CELL/PULSE/OUTFLOW DOMINANT.
USED THE 00Z GEFS- AND CLIMATOLOGY-BASED QPF REFORECAST TO MODIFY
THE 12Z WPC QPF CONTINUITY WHICH LED TO INCREASED AMOUNTS -- THE
18Z WPC FORECAST REMAINS WITHIN THE SPREAD OF THE AVAILABLE
GUIDANCE.

ROTH

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

24HR QP VT 28/00Z
 0.01 514266 515260 514255 511246 505228 502220 496214 490212
      482212 475214 468215 465216 463221 465225 470227 473229
      475233 478241 485246 487249 488254 493274 496282 499285
      502286 506285 507279 506274 508269 514266
 0.01 515153 513147 510145 506146 503147 502144 498141 496134
      493129 492122 492116 494106 498095 502079 505063 506058
      506052 503049 498051 490053 483062 476071 472073 466072
      456066 454066 452068 448070 448073 443081 441083 438083
      432082 428079 424075 423067 423063 425060 422057 418055
      409058 400064 389067 379065 377061 379056 384054 391055
      395055 394049 386045 381046 374046 362045 358047 355047
      352051 352055 355060 360067 365070 368076 368080 364083
      350098 345095 342090 341088 338089 333092 330093 325091
      318085 312083 306083 297080 292079 290084 286083 282083
      274083 271083 270085 267091 270095 282108 289114 300120
      305122 312124 318130 324139 327145 331150 339153 345155
      351156 365158 371160 375163 373170 371174 369176 367177
      363179 359182 361187 365192 368197 374203 386207 393208
      396208 399207 405199 412192 420188 430184 435183 439183
      440180 446174 451174 452176 454175 460166 465164 469160
      475161 478161 478153 479149 482149 488147 491148 494150
      498152 504153 511156 515153
 0.01 447925 447921 445917 445913 443911 441909 437908 431909
      428911 424911 421909 417909 415907 412908 409909 405910
      398920 398924 399927 402933 405939 410945 414949 421950
      433945 437942 442936 445930 447925
 0.01 369864 369858 366858 357862 347868 343870 337871 333873
      328871 323862 317852 316844 317836 318830 320826 324817
      333798 335786 339773 341762 340757 337751 333751 328753
      320758 313767 307774 299781 294784 287786 275788 269789
      263788 253788 247789 243793 240797 238799 238802 238807
      238812 242824 243827 245827 249831 253834 258838 265843
      267847 267852 264862 261875 259885 256897 255904 253909
      246929 241951 240962 239969 238976 241986 240993 240000
      252015 256016 261017 270021 292028 304026 309024 316024
      327027 336023 342017 352014 355010 355007 346002 344997
      339999 329005 325007 323009 321008 313002 302988 299983
      298978 296972 293968 290964 287963 285960 282948 283940
      284936 289927 291923 295921 301920 306918 316915 326911
      343902 348900 354897 359894 361887 366876 369864
 0.01 357834 357832 356830 355828 354827 353826 353825 351826
      349828 349829 348831 348833 347833 347835 347838 348840
      350840 352838 353838 355837 357835 357834
 0.01 268064 266059 265056 263055 256054 250056 246058 244060
      243064 245069 249074 253077 259078 263075 266070 268064
 0.25 491086 492082 492078 486079 480082 475086 469090 462092
      456093 448094 443095 438098 427105 421108 415109 412108
      409103 408100 406102 402106 398104 393104 391105 388103
      386100 387093 386091 382091 372103 363111 361113 357113
      349109 345104 339099 333100 325101 320097 318096 316098
      317105 320112 324118 328124 331130 333138 335144 341148
      348150 354149 360147 364148 367151 372155 380158 385161
      387165 387174 390176 391179 389182 386184 381183 379185
      374189 374193 376196 380200 386203 390204 393203 397198
      416177 423166 426158 430152 433150 436150 440155 442159
      446159 449158 453154 455150 460145 466141 470136 476131
      480126 482116 485105 491086
 0.25 336771 335767 334763 331761 327764 323765 317770 308782
      304788 298794 293798 289803 288807 284810 278811 262807
      257808 254810 253812 254816 258820 263823 269829 271836
      274844 275850 275856 275864 273873 271888 264904 260919
      257927 254935 251950 248969 248978 248988 247995 249998
      252000 258002 264005 270010 276013 283018 289020 296020
      301019 305017 308013 308008 307004 302998 298993 293987
      290979 281966 277954 277943 279934 284919 287911 291904
      299895 303888 305880 304836 306829 308822 312816 316810
      321804 325797 328791 332783 336771
 0.25 297094 297092 297091 296092 296094 296095 297094
 0.50 483100 483094 478093 470096 460098 450098 446099 443103
      435107 428111 417113 402109 384113 378114 370118 363119
      358117 349112 343107 338105 331104 326106 325111 330120
      338137 339140 343144 348146 353145 361143 368147 372152
      376153 388155 395153 403153 413155 417157 420154 425146
      431139 434139 437141 439144 441150 443151 447151 458137
      464131 471123 477112 483100
 0.50 396191 398187 395185 393186 389187 387188 385189 382190
      380191 379194 381197 382198 386200 389199 390197 392195
      394193 396191
 0.50 332774 331770 329769 323772 318778 314783 305794 301798
      297805 298813 295818 285819 279818 272816 264816 262818
      263821 269824 274828 275830 276835 280852 280873 280884
      278890 271900 269906 269917 269927 268932 267934 259935
      255942 254949 253956 252967 252976 251984 253991 257996
      262000 285013 291016 298014 302011 302008 298000 291991
      287987 283981 280974 277967 273952 272946 272937 279925
      289895 296887 300881 301876 301871 300861 298850 295834
      298821 301816 306812 313808 317803 322797 326790 329783
      332774
 1.00 468110 464108 461110 457111 454110 450110 447114 448119
      451122 455122 458119 460116 464113 468110 468110
 1.00 426127 426122 424119 420119 415120 413120 409121 407124
      405128 405133 408136 413138 417137 420134 424131 426127
      426127
 1.00 388146 389142 388137 386131 384126 382123 379122 374125
      369128 366133 364135 365139 370142 375145 382147 388146
 1.00 351132 352128 351126 347121 343116 340113 337111 333112
      333116 335123 338128 342133 345136 349139 351132
 1.00 323786 320786 318787 316789 314792 312794 311796 310799
      310801 312800 315798 317796 319794 320791 322789 323786
 1.00 297872 297868 295863 293857 292853 288854 287858 287864
      287870 287877 289882 294880 296877 297872 297872
 1.00 288841 286841 288841 288841
 1.00 281997 279991 275988 270985 268980 270976 272974 272970
      268958 267953 263947 261945 257952 258964 257978 258984
      260989 264994 268997 273000 279999 281997
 1.00 277914 278912 277911 275912 275913 275915 277916 277914
 1.50 383140 382138 379136 376135 376132 375129 373131 371134
      370136 370139 373140 377141 379142 380141 383140
 1.50 346127 345125 344124 343122 341121 340120 339119 339117
      338117 338118 339120 340122 341123 342124 342125 344127
      346127 346127

$$





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