Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 250657
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 AM EDT MON SEP 25 2017


PRELIM DAY 1 QPF DISCUSSION
VALID SEP 25/1200 UTC THRU SEP 26/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...SOUTHWEST TEXAS...

ONE OF THE MORE NOTEWORTHY AREAS OF PERSISTENT SYNOPTIC
FORCING...ENHANCED INSTABILITY...AND GROWING MODEL QPF SIGNAL
EXISTS OVER THE RIO GRANDE VALLEY...AROUND THE SERRANIAS DEL BURRO
RANGE IN COAHUILA...WITH THE PRECIPITATION SIGNAL BLEEDING OVER
INTO THE DEL RIO TEXAS AREA. EARLY MONDAY MORNING ORGANIZED
CONVECTION WAS INCREASING ON THE MEXICAN SIDE OF THE RIVER PER
RADAR AND SATELLITE IMAGERY. ALTHOUGH THERE IS LITTLE MOVEMENT OF
THE LARGE SCALE TROUGHING THROUGH TODAY...THE AREA OF FAR
SOUTHWEST TEXAS WILL REMAIN IN A GENERALLY DIFLUENT REGION OF THE
500-250 MB FLOW...AND THIS DIFLUENCE MAY BECOME ENHANCED LATE
MONDAY NIGHT AS AN UPPER JET STREAK TIGHTENS AND STRENGTHENS
UPSTREAM OVER EASTERN NEW MEXICO. THUS...AFTER ONE ROUND OF
DIURNAL CONVECTION SUBSIDES LATER THIS
MORNING...ANOTHER...POTENTIALLY MORE SIGNIFICANT ROUND...IS
POSSIBLE FROM THE AFTERNOON INTO THE OVERNIGHT HOURS.

A BALANCE OF SLOW CELL MOTIONS AND ENHANCED LOW LEVEL
INFLOW...PARTICULARLY DURING THE NATURAL BACKING AND STRENGTHENING
OF THE LOW LEVEL FLOW AT NIGHT...COULD LEAD TO VERY SLOW MOVING
CONVECTION WHOSE RAINFALL EFFICIENCY IS PEAKED BY THE INVOLVEMENT
OF HIGH LEVEL MOISTURE STREAMING OFF OF TROPICAL STORM PILAR.
THEREFORE NUMEROUS HI-RES MODELS START TO PRODUCE PROLIFIC
RAINFALL AMOUNTS APPROACHING 10 INCHES OR MORE...AT LEAST ON A
SMALL SCALE...AS OF MONDAY NIGHT. THIS IS PRIOR TO WHAT IS
EXPECTED TO BE A MORE WIDESPREAD HEAVY RAIN EVENT UP ONTO THE U.S.
SIDE OF THE BORDER LATER ON TUESDAY. THE DIFFICULTY ON DAY 1 IS
PREDICTING HOW MUCH WILL REACH THE U.S. SIDE...ALTHOUGH ALL OF IT
WILL FALL IN THE RIO GRANDE BASIN...EVENTUALLY FINDING ITS WAY
INTO THE RIVER.

FOR THE DAY 1 PERIOD...WPC LEANED ON RECENT WRF-ARW RUNS FROM 12Z
AND 00Z...AND THE 00Z NAM CONUS NEST AND NSSL WRF. THIS RESULTED
IN HEAVIER QPF...2 TO 3 INCH AREAL AVERAGE...STRADDLING THE RIO
GRANDE NEAR DEL RIO. SOME ISOLATED MUCH HEAVIER AMOUNTS APPEAR
POSSIBLE.


...SOUTHERN PLAINS TO UPPER MIDWEST...

THERE WILL BE SOME MOVEMENT WITHIN THE STABLE...POSITIVELY TILTED
LONGWAVE TROUGH TODAY AS A SHORTWAVE EJECTS FROM THE ROCKIES TO
THE UPPER MIDWEST...BUT DEEP LAYER FORCING WILL ONCE AGAIN
PRIMARILY OCCUR TO THE COOL SIDE OF THE ASSOCIATED SURFACE COLD
FRONT. THIS LACK OF WESTERLY FLOW AND ABSENCE OF STRONG FORCING
OVER THE WARM SECTOR HAS GENERALLY HAMPERED THE MAGNITUDE OF MID
LEVEL LAPSE RATES AND RESULTING INSTABILITY. ALTHOUGH RAIN WAS
WIDESPREAD WITH THIS SYSTEM...IT HAD NOT YET BEEN TOO FOCUSED OR
HEAVY. THE MODEL QPF SIGNAL IS SOMEWHAT HEAVIER FOR THE MONDAY AND
MONDAY NIGHT PERIOD...PARTICULARLY ALONG THE TX/OK/KS PORTION OF
THE FRONT...BEING BRUSHED BY THE SHORTWAVE EJECTING OUT OF THE
CENTRAL ROCKIES. STILL...IT IS DIFFICULT TO GO TOO HEAVY WITH THE
QPF WHEN SEEING CAPE DROP OFF DRASTICALLY WITH EASTWARD EXTENT
INTO THE WARM SECTOR. FORTUNATELY...FOR QPF PLACEMENT THERE WAS
GOOD AGREEMENT AMONG MULTIPLE GLOBAL AND HI-RES MODELS...AND GOOD
CONTINUITY WITH THE PREVIOUS WPC FORECAST. FOR THE UPDATE THIS
MORNING WE PUSHED SOME OF THE TIMING AND INTENSITY DETAILS TOWARD
A CONSENSUS OF THE 00Z NAM CONUS NEST...NSSL WRF...AND 12Z WRF-ARW
WHICH LOOKED A LITTLE MORE FAVORABLE THAN ITS 00Z RUN.


...ELSEWHERE...

A WEAK UPPER LOW WILL CONTINUE TO PROMOTE DIURNAL SHOWERS ALONG
THE CENTRAL GULF COAST...AND WARM ADVECTION WILL BRING SOME LIGHT
PRECIPITATION TO WESTERN WASHINGTON. MEANWHILE FLORIDA WAS CAUGHT
IN RELATIVELY WEAK DEEP LAYER FLOW...AND WITH SOME DRYING HAVING
OCCURRED AT MID LEVELS...DIURNAL SHOWERS WILL BE LIMITED IN SCOPE.

BURKE

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




24HR QP VT 26/12Z
 0.01 535206 535198 535190 530175 527169 524166 515158 512157
      510154 504153 500155 498157 497162 497170 500178 507186
      510191 512198 515205 517212 522215 528217 532213 533209
      535206
 0.01 517281 518270 518263 518249 516240 514235 509224 507219
      503214 498210 494210 488210 482208 474213 470215 466219
      463224 467225 473221 475222 477225 478229 476231 471232
      467232 465234 462232 459232 456234 453238 451240 449244
      454248 452255 452260 454265 458270 465279 475286 486291
      498295 504297 509296 511294
 0.01 507872 507860 507854 505849 501832 498824 492821 487818
      483816 475825 470832 467839 466848 464855 458866 449879
      439888 429897 420904 413914 405924 396933 386942 362956
      352962 342970 321983 316983 310981 303968 301962 297956
      294949 290947 287947 283950 282959 278964 273967 263968
      256969 255972 255976 259980 261987 254988 249989 244991
      238993 236996 235001 238017 248025 253028 259031 270037
      273040 278043 284048 285050 281050 275051 270054 271057
      273059 276061 278065 281067 289066 295067 299066 301064
      304058 309056 312054 316055 323057 328060 336060 348058
      363057 422062 434063 429068 427070 426075 425077 425082
      421087 425092 429099 432104 438103 440100 442096 440088
      437086 436083 440078 444078 446080 451083 452073 449066
      446053 445049 447050 449051 453047 452041 450039 447038
      424043 420046 413047 412045 414044 417042 422038 428035
      431031 438021 457003 479987 485975 488967 492961 494955
      497949 501932 507895 507881 507872
 0.01 486030 487021 487012 486006 485002 483001 479999 475001
      471004 468008 464018 459030 457036 456042 458047 462047
      468047 473047 478045 481042 486030 486030
 0.01 407110 407107 408105 408103 408100 406102 405105 405107
      405109 407110 407110
 0.01 282714 277726 276740 277748 279754 286762 294773 303781
      308783 314784 325782 333781 339778 347770 357761 364753
      372743 376738 379733 382727 384720 385715 384710 382709
      379707 376707 372711 368715 361717 355714 351710 346706
      343702 336694 332691 327688
 0.01 315892 315884 314880 312873 310869 300854 294847 288841
      281835 277836 275840 274846 274852 275865 276877 278888
      282899 285908 286915 288920 288931 293930 295929 298930
      303931 305928 308924 309918 312909 315892
 0.01 279792 278785 276781 273776 271774 267771 263769 258770
      254772 247778 243786 239795 238806 236815 236821 238826
      240839 242842 248841 253833 258826 267829 269827 269820
      266815 264813 261812 260809 264809 268812 272812 277811
      275807 272804 273800 277797 278792 279792
 0.25 501272 501265 500261 496255 492248 487241 482240 475242
      473246 473251 475260 480265 486271 492275 496276 499274
      501272
 0.25 492886 492879 491871 486864 483863 480865 475872 470873
      464877 458883 453888 439898 428909 423915 418921 409932
      403938 396944 385953 372961 366965 359969 346980 341983
      334987 326990 318992 302990 293991 284994 277997 273998
      268998 261996 254997 244997 242002 243008 247015 254020
      260024 266028 273032 280034 290034 298038 304042 308045
      311045 314042 318041 325042 331048 336049 340047 346044
      351039 364029 370025 378022 391015 397011 403006 413993
      424982 444959 455947 458944 462943 468939 479928 482921
      486912 489904 490898 492886
 0.25 434009 434004 431002 424006 419010 413014 407019 404026
      406028 410028 416026 423022 427018 432012 434009
 0.25 292709 286716 283724 282730 283736 284742 286747 297760
      303766 309770 313772 318772 326770 336767 343763 350757
      353748 353739 351729 346720 342711 337705 331698 324695
      314696
 0.25 308894 308884 306876 301869 295867 292868 290871 288879
      289889 290897 291901 295903 300902 306899 308894
 0.25 294060 295058 294056 292055 290054 289054 287054 285055
      283057 285059 286060 288060 290061 292061 294061 294060
 0.25 245817 245815 244814 243815 242817 242819 243821 243819
      244818 245817
 0.50 488257 489255 489252 489251 487249 486247 484247 483247
      482248 481249 481252 482253 483255 483256 484258 486258
      488257 488257
 0.50 464917 465912 465906 464900 462898 455897 448897 442900
      437904 429912 420923 413933 409939 405945 396950 375964
      365971 356978 346986 341989 335992 329993 323995 318997
      314998 311996 305993 296993 290995 285997 275003 271006
      267012 266015 267020 270025 275029 283030 290030 295028
      301030 305036 307038 309038 312035 314034 328033 332036
      334042 344039 354029 363021 381007 400991 417975 427964
      435955 442943 449935 456923 458921 462921 464917
 0.50 350742 349735 348731 343721 338714 334707 327701 320699
      310700 302704 295709 289715 286722 285727 285733 289742
      294749 304761 309764 312764 322765 327764 332763 340760
      346753 350745 350742
 0.50 305882 305880 304876 301874 299873 297874 295876 294880
      294883 294885 295889 297891 300893 302893 303890 304888
      305884 305882
 0.50 257010 258008 258006 258004 256003 255002 253001 251001
      249001 247002 248004 248006 249008 249009 250010 251011
      252012 254012 256011 257010
 1.00 448918 447918 446918 445920 445921 444923 445924 446923
      447922 448920 448919 448918
 1.00 413963 410963 407964 403959 397957 391960 380967 370973
      364976 359981 350989 340997 328000 322003 320008 322016
      322024 324024 327022 331018 337016 341016 342019 339027
      340032 345031 348026 353020 358016 367008 377000 382997
      387993 394982 403974 409968 413963
 1.00 345741 345735 343730 340722 336716 331711 326706 320704
      313703 305705 299710 294714 290721 289728 291736 295741
      305753 311755 318756 326756 335755 340750 344743 345741
 1.00 279026 288026 295023 300020 304018 309021 312020 312017
      310014 310004 308999 303997 297997 288001 280005 276009
      273013 272018 274023 279026
 1.50 392972 391972 390972 391974 392972
 1.50 389977 382971 373976 369978 365981 358987 355991 352996
      350001 351007 355010 359007 364005 367002 371999 375997
      380994 383991 387987 388981 389977
 1.50 342737 340729 337723 333717 329711 325708 319706 312706
      306707 300711 295716 292722 292729 295736 299741 304745
      308748 321750 328751 334749 339744 342739 342737
 1.50 335008 334006 333004 331005 329005 329006 328008 329009
      331010 333009 335008 335008
 1.50 306009 306004 304001 297000 291002 284005 279009 275015
      278022 281024 284024 291023 296019 302015 306009
 2.00 381981 380978 378979 374983 369985 364989 360994 358998
      356003 362001 366998 371995 375992 378987 381981
 2.00 340735 339729 336723 329713 325710 319708 313707 306709
      301712 297716 294721 293727 295733 300738 304742 309743
      321745 327746 333745 337743 340738 340735
 2.00 302011 303004 298003 293003 289004 286006 282009 280012
      278015 280017 281022 285023 289021 291018 295016 299015
      302011 302011
 3.00 336736 336729 335725 329718 323712 315710 310710 305712
      299717 297721 297726 298733 301736 304738 308739 318739
      326740 331741 335738 336736
 3.00 289010 293007 294006 291006 289007 285010 287010 289010
 4.00 334734 334729 333726 328720 323715 316712 309712 305714
      302717 299723 301730 305736 309737 312736 320738 327739
      332738 334735 334734
 5.00 333732 332727 330724 325719 320715 313713 308714 305716
      301723 301727 303729 308734 316735 321737 326737 331736
      333732
 6.00 331733 329725 325721 321717 317715 311715 307718 303723
      305727 309730 314733 319735 325736 329735 331733
 7.00 329731 327726 325722 321719 319718 315716 311717 308720
      306725 309728 312730 315732 319733 323734 327733 329731
 8.00 327729 325725 323724 321722 319720 317718 315718 312719
      310721 308723 309725 311727 313729 315730 317731 321732
      323732 326731 327729
 9.00 323730 323728 322727 321726 320724 320723 318722 317721
      316720 315720 314721 313721 312722 311724 312725 313726
      314727 315728 316729 317730 319731 321731 322730 323730
10.00 320728 319726 318725 316725 315727 317728 317729 319729
      320728 320728

$$




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