Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 211859
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM EDT SUN AUG 21 2016


PRELIM DAY 1 QPF DISCUSSION
VALID AUG 22/0000 UTC THRU AUG 23/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...NEW ENGLAND AND MID ATLANTIC...

A WELL DEFINED AND EASILY MODELED AMPLIFIED TROUGH WILL SWEEP
THROUGH THIS REGION THIS AFTERNOON AND TONIGHT...WITH SOME
POST-FRONTAL PRECIPITATION LINGERING ACROSS MAINE AND
MASSACHUSETTS EARLY MONDAY. A NARROW AXIS OF ABOVE AVERAGE PW
VALUES...2 TO 2.5 STANDARD DEVIATIONS ABOVE THE MEAN...WILL
PERSIST ALONG AND AHEAD OF THE SURFACE FRONT...AND STRONG FRONTAL
CONVERGENCE WAS ALREADY SUPPORTING WIDESPREAD MODERATE RAIN OVER
NEW YORK AND NORTHERN PENNSYLVANIA. SOMEWHAT GREATER HEATING AND
HIGHER TERRAIN OVER THE MID ATLANTIC WAS FOSTERING MORE ROBUST
CONVECTION WITH HEAVIER RAIN RATES AS OF 18Z. THE QUICK MOVEMENT
OF THE FRONT AND ASSOCIATED CONVECTION SHOULD BE A LIMITING FACTOR
FOR VERY HEAVY TOTALS. INSTABILITY IS ALSO MARGINAL WITH NORTHWARD
EXTENT...WITH THE MORE ROBUST CONVECTION LIKELY TO BE CONFINED
NEAR AND SOUTH OF A WEAK WARM FRONT OVER SOUTHEAST NEW YORK / NOTE
THAT A BETTER DEFINED WARM FRONT IS BEING ANALYZED AND DEPICTED BY
WPC DOWN TOWARD VIRGINIA. THERE MAY BE A NARROW CORRIDOR FARTHER
NORTH...INTO THE WEST FACING SLOPES OF THE MOUNTAINS IN WESTERN
MASSACHUSETTS AND VERMONT...IN WHICH RETURN MOISTURE ALONG WITH
HEATING AHEAD OF THE EXTENSIVE CLOUD SHIELD...WILL ALLOW FOR SOME
STRONGER CONVECTIVE RAIN RATES FOR A FEW HOURS. QPF IN THIS REGION
WAS DRAWN FAIRLY CONSERVATIVELY...WITH AREAL AVERAGE OF A HALF TO
ONE INCH ROUGHLY FROM THE DC/BALTIMORE AREA NORTHWARD INTO WESTERN
MAINE. THERE IS NOT TOO MUCH RANGE IN THE GLOBAL
GUIDANCE...ALTHOUGH A FEW OF THE HI-RES MODELS SUGGEST LOCAL
2-PLUS INCH AMOUNTS ARE POSSIBLE.


...SOUTH CENTRAL TO SOUTH TEXAS...

OVER SOUTH TEXAS...WIDESPREAD CONVECTIVE RAINS OVERNIGHT HAD
CONTINUED TO FEED BACK ONTO THE HEIGHT FIELD...REINFORCING A BROAD
CIRCULATION OR MCV...WHILE SMALLER SCALE MCVS WERE SHED EASTWARD.
THIS ENTIRE REGION OF MID/UPPER LEVEL FORCING HAD GENERALLY BEGUN
TO SHEAR AND WEAKEN AS A DEEP NORTHERN STREAM DEEP TROUGH STARTS
TO PULL AWAY FROM THE REGION...AND RETURN FLOW SETS UP AHEAD OF A
TROUGH OVER THE SOUTHWEST STATES. THE NET EFFECT OF THESE CHANGES
WILL BE TO LESSEN THE DEGREE OF ORGANIZATION TO THE CONVECTION
OVER DEEP SOUTH TEXAS...ALTHOUGH SMALL SCALE STORMS CONTAINING
HEAVY RAIN RATES WILL OCCUR ALONG THE FORCING / INSTABILITY
INTERFACE JUST INLAND FROM THE COAST.

FARTHER EAST...THE WEAK BUT PERSISTENT UPPER DIFLUENCE ALONG THE
INTERFACE BETWEEN THE NORTHERN STREAM TROUGH AND THE TEXAS
CIRCULATION...WILL SLOWLY WASH THROUGH WESTERN
LOUISIANA...ALLOWING FOR A LITTLE GREATER COALESCENCE OF SEA
BREEZE AND OTHER DIURNALLY DRIVEN CONVECTION. EXPECT ISOLATED
HEAVY DOWNPOURS...BUT MODEST AREAL AVERAGE TOTALS GENERALLY LESS
THAN ONE INCH.

MOVING FORWARD IN TIME...THE QPF SIGNAL BECOMES EVEN MORE
DIFFICULT TO READ. THE GLOBAL MODELS DEPICT A VERY BROAD AREA OF
LIGHT TO MODERATE RAINFALL OVER TEXAS AND ADJACENT STATES THROUGH
MONDAY AFTERNOON...OCCURRING GENERALLY WITHIN A DEVELOPING RETURN
FLOW / WARM ADVECTION PATTERN WITH SOME REMAINING EMPHASIS FOR
DIFLUENT UPPER FLOW AT THE TAIL END OF THE EASTERN U.S. TROUGH. IN
THE WAKE OF RECENT WIDESPREAD OVERTURNING...HOWEVER...IT IS
QUESTIONABLE HOW MUCH INSTABILITY WILL DEVELOP TO SUPPORT SUCH
WIDESPREAD RAINFALL...AND WHERE WILL HEAVIER RAIN OCCUR WITHIN
THIS BROAD AREA. THE CONSENSUS OF THE MODEL SIGNAL SUGGESTS MORE
FOCUS OVER THE BIG BEND AREA OF TEXAS AND OVER NORTHEAST TEXAS.
WPC QPF FOLLOWED A BLEND OF THE WRF-NMM...SREF MEAN...AND
CONTINUITY. THE SREF MEAN...AND ESPECIALLY QPF PROBABILITIES
DERIVED FROM THE SREF HAVE BEEN PERFORMING WELL RECENTLY.


...DESERT SOUTHWEST INTO THE SOUTHERN HIGH PLAINS...

A POSITIVELY TITLED MID LEVEL TROUGH HAVING SETTLED INTO
ARIZONA...WILL DRIVE A CHANNEL OF ENHANCED FLOW FROM SOUTHERN
ARIZONA...OPENING UP INTO A DIFLUENT PATTERN OVER NEW MEXICO AND
THE SOUTHERN HIGH PLAINS. WITH MOISTURE ALONG A FRONTAL ZONE AND
INCREASING AMOUNT OF RETURN MOISTURE GOING INTO MONDAY...EXPECT A
FEW AREAS OF ORGANIZED PRECIPITATION...SOME OF IT LOCALLY
HEAVY...SUCH AS THE UPSLOPE ENHANCED SMALL MCS THAT PROMPTED A FEW
FLASH FLOOD WARNINGS IN SOUTHEAST NM TODAY. ENHANCED FLOW ON THE
NORTH SIDE OF THE TROUGH MAY ALSO ALLOW FOR ORGANIZATION OF
CONVECTION COMING OFF THE TERRAIN IN UTAH AND NORTHERN
ARIZONA...HEADING DOWN THE COLORADO RIVER BASIN. WPC QPF IN THIS
REGION SOMEWHAT RESEMBLES THE 12Z ECMWF AND NSSL WRF.


...PACIFIC  NORTHWEST...

A TROUGH WILL FINALLY BEAT DOWN THE HEIGHTS OVER THE NORTHWEST AND
BRING A COLD FRONT THROUGH THE REGION. WITH NO REAL CONNECTION TO
DEEP MOISTURE...HOWEVER...MOISTENING THROUGH LIFT WILL OCCUR
MAINLY OVER CANADA. THIS WILL RESULT IN A FAIR AMOUNT OF
PRECIPITATION IN THE UPPER REACHES OF THE COLUMBIA RIVER
BASIN...WHERE WPC AND THE MODEL CONSENSUS PREDICTS SOMETHING JUST
SHORT OF ONE INCH AREAL AVERAGE THROUGH MONDAY.
CONSENSUS...SUPPORTED BY THE GEFS REFORECAST ANALOG CASES SUGGEST
LIGHT AMOUNTS OF RAIN IN THE NORTHERN CASCADES OF WASHINGTON AND
THE NORTHERN REACHES OF THE ROCKIES IN ID/MT.

BURKE

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

24HR QP VT 23/00Z
 0.01 553151 550143 550130 550118 550104 549095 543096 539102
      536106 532105 525104 519106 510118 502131 496135 492135
      489136 478129 476131 475139 476147 480155 480160 481163
      483168 486170 488177 490182 490188 491191 491197 489204
      487206 481209 477210 475212 473214 474218 482220 486222
      489225 495231 496233 500231 503229 507231 512236 515238
      516235 514228 513226 515225 519226 524225 531222 537218
 0.01 514670 513659 511653 509643 506637 503632 499628 494624
      488625 483625 477626 473624 467625 454629 440635 430642
      427645 423651 420657 421662 422664 423668 419673 412682
      407691 404697 402703 398708 395714 393720 392723 389725
      380731 359745 355748 352753 349758 348763 346771 347774
      350793 355793 359790 362785 364780 370770 375766 381763
      388761 395759 404754 418753 431751 444747 453742 464735
      469731 473727 482719 490711 494705 496699 496692 501686
      510681 514670
 0.01 518939 518920 518912 516902 514898 512892 511882 511877
      509874 509865 507859 506851 504844 496837 491835 486836
      484834 481834 478837 476844 476852 477861 479868 479887
      483900 485914 488920 491927 494942 496965 497960 501955
      506953 510955 515955 517951 517943 518939
 0.01 453850 446850 439854 435854 431852 424850 418851 415854
      415858 416862 419865 424867 433866 442866 444863 447863
      451855 453850
 0.01 433790 432776 430774 425775 422782 420787 418792 415802
      412812 414814 415821 416823 420821 423818 425813 427805
      430795 433790
 0.01 413798 412788 412786 408784 405785 400790 396793 392798
      388799 386801 385804 392803 393801 397800 404799 407799
      411800 413798
 0.01 398206 399195 398191 394192 388192 383186 380184 380179
      384175 389171 391165 390161 388154 389150 391146 392125
      394119 397115 399113 403111 407111 409108 410102 409098
      408095 405097 404103 400104 396110 390112 386113 383113
      378114 374116 370118 363115 361113 359112 361110 364110
      364107 364104 367102 371101 373097 379100 383098 385095
      390089 395082 399076 401072 404069 407066 408062 409059
      408055 395049 387048 379045 376044 375040 378031 381024
      382022 381017 379015 377014 372014 366019 354028 347030
      343031 340028 338025 339020 339009 338002 339990 341973
      341963 342952 342947 343943 348937 352931 353925 353922
      348916 344910 342907 340902 339897 338893 336889 334888
      332885 332881 329865 326856 325846 323838 322833 322829
      325811 325808 322803 319804 316806 313808 309809 299810
      294809 285808 281810 280812 284813 289816 291823 294831
      295841 298862 299872 298882 295901 287898 283900 284908
      288918 289927 290931 288935 275960 277964 281966 282968
      283972 281978 274981 266982 261986 256987 251988 245990
      240994 239998 240002 242006 245008 253010 260013 263015
      260017 252020 242027 235029 231033 228041 227045 228049
      228060 232068 236074 240080 251089 256094 262098 273106
      284115 286118 288117 294115 300112 311114 315114 318113
      323114 327117 332123 334128 336132 341135 345138 346143
      358144 367144 369147 368149 365150 361156 362162 368165
      370167 368169 366171 360176 358181 360185 365192 374197
      379202 386206 394208 398206
 0.01 358111 359109 357107 355107 355106 354105 352104 350106
      348108 350109 351110 353111 355112 357112 358111
 0.01 277811 277807 276803 272801 266799 259800 253802 251807
      250810 251813 255817 259821 265822 268821 272818 275817
      276813 277811
 0.25 546174 547163 545150 544140 540129 538127 534128 528132
      522136 517143 516147 514153 514168 512176 509178 507182
      505190 507201 509206 512208 517209 525209 532210 535208
      538205 541195 546174
 0.25 505657 505650 503645 498639 491636 485635 477635 473635
      469637 456648 449653 443659 433673 429680 428683 429687
      439687 441687 445690 444693 442696 436700 431703 426703
      418703 413704 410707 406713 403724 400730 399734 400738
      402741 406741 409740 411742 416742 421741 430738 434737
      439737 445735 448732 455727 467719 472712 477704 481697
      485690 489683 496677 503668 505661 505657
 0.25 393743 394738 391738 389740 386742 384743 380743 378746
      379750 381752 385750 388750 392750 393745 393743
 0.25 383195 381194 379193 379194 381195 383195
 0.25 375191 376189 375187 374186 373185 371184 370183 368183
      366183 365184 366186 366187 367188 369189 371190 372190
      372191 374191 375191
 0.25 381081 382074 381069 378066 373065 368063 365061 367051
      363049 358049 354050 350052 349057 352061 354064 355070
      362074 365077 369076 372079 373084 377086 380083 381081
 0.25 365121 363121 365122 365121
 0.25 360132 360131 360129 359127 357125 355124 354126 354128
      355130 356131 358132 360132 360132
 0.25 346074 343070 339067 336067 332071 327072 322072 313069
      307068 306071 307073 311077 311079 309080 304082 303085
      305087 308090 315091 319088 324088 332081 340077 346074
 0.25 339056 337054 334051 332050 329049 325051 324053 323057
      325060 326062 330063 332062 335060 337058 339056
 0.25 336949 337939 336928 335925 332922 329921 326923 321926
      318929 316932 313939 307942 304949 302958 303961 305958
      310952 313955 316962 318970 318982 320984 324985 329980
      334965 335955 336949
 0.25 320014 318006 315001 310994 304990 299986 296984 292985
      289983 288985 286987 280991 274993 269999 268004 269007
      274013 281024 281029 282033 285035 290035 303031 309028
      314024 320014
 0.25 320879 321872 321864 315855 313849 310852 308863 306876
      305888 305895 306903 305910 305914 308915 311915 313909
      315906 317902 316898 316891 318885 320879
 0.25 297970 296968 294968 295970 296971 297970
 0.25 285078 286073 284070 282067 278065 275062 275059 278051
      275044 269039 262036 258037 256041 252047 248049 243049
      238048 236051 234055 235061 238067 243072 255082 267091
      275095 280095 282093 282084 285078
 0.25 262811 262809 262807 261807 260805 258805 256806 255808
      255810 255812 257813 259814 260814 261813 262811 262811
 0.25 257998 257997 255997 253997 251997 249997 247997 246998
      246000 247001 249001 251001 253001 255001 256000 257999
      257998
 0.50 542179 544169 543160 541144 538137 537135 533136 526143
      522146 519151 519159 521166 520173 518182 515187 516193
      527201 531203 535201 539195 541187 542179
 0.50 500653 498646 494642 488640 482639 477640 474640 471642
      468649 467652 464654 453661 443669 440672 439674 438678
      440681 446681 454680 459681 461684 450694 433711 432714
      432718 432723 434727 442733 451724 462716 466712 470707
      472701 474693 475689 477687 481683 486676 490672 497665
      500658 500653
 0.50 430733 429730 427729 423727 421727 419726 418726 416729
      415732 413734 413739 416740 419738 421737 424736 426736
      429736 430733
 0.50 427712 426710 424707 422706 419707 417708 414709 412711
      409714 411717 415717 418717 420718 422718 424717 426715
      427712
 0.50 378078 379076 378074 378073 376072 374073 374075 374076
      375078 376079 377079 378078
 0.50 333949 334943 333936 330933 326936 325939 323943 321947
      321954 320960 321963 323964 328962 330959 331954 333949
 0.50 313888 313887 312886 312884 313884 313881 313879 313877
      313875 312874 312875 311877 311879 311882 310884 310886
      310888 310890 311892 312890 313888 313888
 0.50 309019 309013 308009 304002 300994 297991 293991 288992
      284993 277997 273999 272005 277011 280015 283017 287019
      290022 294024 299024 305024 308021 309019
 0.50 275090 276077 272072 268071 266068 269062 271054 270047
      266041 263040 260041 258047 256051 254053 249056 239053
      238062 242066 247070 251075 261083 266086 272089 275090
 1.00 535169 535166 535163 536161 535158 535155 533153 532152
      530154 528156 527159 527161 528163 528164 529167 530169
      531170 532171 533171 535169
 1.00 493653 490649 485647 482648 479650 477656 473662 469665
      465670 471670 476669 482667 487663 490658 493653
 1.00 300015 298010 295008 290006 291000 288997 284999 281001
      277003 276006 280009 283012 287013 292014 296016 300015

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