Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 111741
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 PM EDT WED OCT 11 2017


PRELIM DAY 1 QPF DISCUSSION
VALID OCT 12/0000 UTC THRU OCT 13/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...EASTERN U.S...

A TROUGH EXITING THE OHIO VALLEY INTO THE MID ATLANTIC STATES AND
SOUTHERN NEW ENGLAND...WILL PRODUCE A FAIRLY UNIFORMLY DISTRIBUTED
QUARTER TO HALF INCH AVERAGE RAINFALL FROM WESTERN NEW YORK DOWN
TO CENTRAL AND EASTERN VIRGINIA AND EASTERN NORTH CAROLINA.
SYNOPTIC FORCING WILL DIMINISH WITH EASTWARD EXTENT TOWARD THE
COAST AS THE ASSOCIATED MID LEVEL WAVE DAMPENS. MEANWHILE...THE
ONLY SUBSTANTIAL INSTABILITY IS LOCATED FARTHER WEST....NEAR THE
APPALACHIANS AND JUST TO THEIR LEE...INCLUDING OUT ALONG A
STATIONARY FRONT INTO SOUTHEAST VIRGINIA. THE GREATEST OVERLAP OF
INSTABILITY AND DEEP LAYER ASCENT IS SOMEWHERE IN BETWEEN...AND
SUPPORTS SLIGHTLY HEAVIER QPF ALONG THE CAPE GRADIENT FROM
SOUTHWEST PENNSYLVANIA TO SOUTHEAST VIRGINIA. THE DEFORMATION ZONE
ACROSS WESTERN NEW YORK MAY RESULT IN ANOTHER LOCAL MAXIMUM THIS
AFTERNOON BEFORE THE WAVE BECOMES MORE SHEARED.

SOME INGREDIENTS ARE IN PLACE TO SUPPORT LOCALLY HEAVY
RAINFALL...BUT ANY SIGNIFICANT ISSUES MAY BE VERY ISOLATED OWING
TO THE RELATIVE LACK OF INSTABILITY AND WEAKENING DEEP LAYER
FORCING. THE FLASH FLOOD GUIDANCE IN THIS REGION IS NOT
PARTICULARLY LOW...SO THE AREA CAN TAKE SOME RAINFALL.

SURFACE HIGH PRESSURE BUILDS SOUTHWARD BEHIND THE WAVE...AND ANY
LINGERING SHOWERS ON THURSDAY ARE NOT EXPECTED TO BE TOO
PRODUCTIVE EXCEPT PERHAPS IN AREAS ENHANCED BY EASTERLY UPSLOPE
WINDS MAINLY OVER VIRGINIA. ANOTHER ROUND OF RELATIVELY HEAVIER
DOWNPOURS IS POSSIBLE OVER EASTERN NORTH CAROLINA THURSDAY
AFTERNOON ON THE FRONT. OTHERWISE A FEW SHOWERS/STORMS WILL ALSO
EXTEND DOWN ALONG A WEAK TROUGH AXIS INTO SOUTHERN GEORGIA AND
NORTHERN FLORIDA...BUT THE SCOPE OF THESE SHOWERS WILL BE FAIRLY
LIMITED.


...PACIFIC NORTHWEST...

THIS AFTERNOON A LEAD SHORTWAVE WAS HELPING ESTABLISH A LONGWAVE
TROUGH OVER THE WESTERN STATES...WITH HEIGHT FALLS AND A FRONTAL
ZONE PRESSING OUT TOWARD CENTRAL MONTANA DOWN TO THE MIDDLE OF THE
GREAT BASIN AND ON INTO CENTRAL CALIFORNIA. THE TROUGH WAS DIGGING
FROM THE NORTHWEST...AND LACKED ANY CONNECTION TO SUB-TROPICAL
MOISTURE. AS SUCH...SHOWERS OF RAIN AND SNOW WERE LIMITED TO THE
AREAS VERY HIGH TERRAIN AND STRONG HEIGHT FALLS EAST OF THE TROUGH
IN THE NORTHERN ROCKIES...AND BENEATH THE COLD MID LEVEL
TEMPERATURES AND RELATIVELY MORE MOIST / UNSTABLE LOW LEVELS FROM
THE CASCADES WESTWARD. THE COASTAL AREAS WILL SEE ANOTHER ROUND OF
DEEP LAYER FORCING AS A SHORTWAVE DIGS ON THE BACK SIDE OF THE
DEVELOPING TROUGH TONIGHT AND THURSDAY. THE PREVIOUS WPC FORECAST
HAD A GOOD SPATIAL COVERAGE TO THE QPF...FITTING THE MODEL
CONSENSUS...WITH HEAVIEST AMOUNTS CONCENTRATED IN THE COASTAL
RANGE AND CASCADES OF OREGON...EXTENDING UP TO MOUNT SAINT HELENS.
FOR MAGNITUDE...THE GOING FORECAST WAS ALREADY TOWARD THE HIGH END
OF WHAT WOULD BE EXPECTED...WITH EXPECTATIONS TEMPERED BY THE
RARELY SEEN NEGATIVE PW ANOMALIES PERSISTING THROUGHOUT THE EVENT.
THEREFORE...WE MADE VERY LITTLE CHANGE TO QPF...BUT DID USE SOME
OF THE 12Z NAM CONUS NEST. WE ALSO NOTED THE PESKY PROBLEM OF THE
GFS PLACING A STRIPE OF HEAVIER RAIN OFFSHORE...WHEN IT SHOULD
OCCUR IN THE OREGON COASTAL MOUNTAINS PER THE PATTERN AND MODEL
CONSENSUS.


...SOUTH FLORIDA AND SOUTH TEXAS...

IN FLORIDA A BROAD EASTERLY WAVE WILL APPROACH FROM THE
BAHAMAS...RESULTING IN A GRADUAL INCREASE OF PRECIPITABLE WATER.
MID LEVELS OVER MUCH OF THE PENINSULA WERE DRY ENOUGH TO PREVENT
PRECIPITATION TODAY...BUT MOISTENING WILL OCCUR FROM SOUTH FLORIDA
UP TO ABOUT MELBOURNE TO PORT CHARLOTTE THROUGH THURSDAY.
MEASURABLE PRECIPITATION IS EXPECTED SOUTH OF THAT LINE...AND SOME
LOCALLY HEAVIER SWATHS WILL OCCUR TOWARD MIAMI AND THE
EVERGLADES...WITH MOIST EASTERLY FLOW AND A MODEST AMOUNT OF
SYNOPTIC SUPPORT FROM THE WESTWARD MOVING TROUGH.

MEANWHILE...WITH A FRONTAL ZONE HAVING MOVED OFFSHORE OF TEXAS THE
MODELS CONTINUE TO INDICATE A PATTERN OF PERSISTENT SHOWERS AND
STORMS EAST OF BROWNSVILLE...WITH VERY LITTLE OF IT DRIFTING
ONSHORE...AND DIMINISHING IN INTENSITY AS IT DOES SO. THIS LEAVES
QPF FAIRLY TAME...WITH PERHAPS A QUARTER INCH AREAL AVERAGE RIGHT
ALONG THE COAST.

BURKE

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


24HR QP VT 13/00Z
 0.01 532176 532170 530165 523159 519157 517155 513147 507142
      502138 498139 497145 493137 487132 480126 475124 471125
      466124 459118 461114 464112 467110 471111 473110 475106
      480099 486091 491087 495082 497077 496073 493071 490073
      487073 484075 480082 475087 468085 461088 455092 448094
      441098 440106 443114 450132 451137 450144 448147 444145
      441144 438146 437152 438157 446168 447174 445179 440188
      444194 445197 443201 438208 433212 427215 422220 419223
      418228 416233 417239 416245 417247 422253 424257 427260
      429262 434265 442267 450269 457273 464279 471282 475283
      477281 482273 484260 484256 485252 489244 491242 494245
      496249 501251 504244 505234 506224 504215 493204 490194
      489189 492184 504184 506182 510181 514184 516182 518181
      519175 520169 524170 527176 532176
 0.01 485153 485151 484150 484148 483147 481147 480146 478145
      476145 475144 473146 474148 476149 478148 478149 479151
      481152 481153 482154 484154 485153
 0.01 488889 486886 483889 480894 476897 473910 471915 467919
      460927 458931 458935 463935 467933 472931 474927 477922
      479917 480909 483904 485898 487894 488889
 0.01 476177 475174 473174 472174 470174 468175 466175 465176
      466179 468179 469179 471180 473178 474178 476177
 0.01 445785 444774 443760 442749 440741 428707 425698 421690
      414691 410696 407703 403709 398723 395726 393722 392716
      390712 386707 382707 379705 375701 371702 368704 363707
      358712 353717 349725 346732 345739 343748 342757 339771
      332802 330810 328815 318826 311830 305835 296844 293850
      289851 287853 281867 281869 283869 290864 292860 295862
      301863 306859 309855 318844 323839 328832 331828 336822
      351800 357797 359793 362789 366787 370788 373793 378798
      382803 384804 389804 396806 401809 406809 410810 414816
      416818 420819 427817 432812 441801 444793 445785
 0.01 376078 377073 376069 375066 373064 371062 370061 368063
      367066 369066 371068 372073 373075 374078 376078
 0.01 371810 369810 366813 361818 359823 356828 353835 352839
      354841 357837 360830 363825 367820 368815 371810
 0.01 309884 309877 307873 305869 303869 301876 301880 300884
      299891 296899 291906 290910 291914 299912 303905 306897
      308892 308886 309884
 0.01 293075 291071 288068 280068 273064 267058 265055 260055
      258059 258064 258072 264078 266081 271083 275085 281085
      286086 289083 290077 293075
 0.01 285798 279784 277775 272768 265766 262765 257766 251770
      245776 238789 233804 231813 231817 231822 236828 243830
      249829 252827 258824 271815 279811 283805 285798
 0.01 285968 284961 283958 281956 279956 279952 280945 280936
      280932 277931 270939 266945 261948 257949 255951 250955
      247961 244966 242969 242972 248975 253978 259981 265983
      272982 278980 283974 285968
 0.01 255008 255004 255001 253998 251997 249995 247994 246991
      244992 243996 244998 245002 245004 247006 251007 253009
      255008
 0.25 497231 497229 498226 497225 497224 496222 495220 493221
      492222 492224 492227 492230 493233 495233 496233 497231
 0.25 481219 483212 482209 479207 474207 469208 462208 449213
      443215 436218 431222 430225 431229 431233 430237 429241
      431244 437250 443253 450257 458260 465259 467257 469253
      472244 470236 469231 470228 472224 475222 481219
 0.25 483138 482136 481136 480137 480138 482138 483138
 0.25 475161 475156 474154 472151 471149 469148 466145 463145
      461146 459150 460154 462156 464159 466161 468162 470163
      473162 475161
 0.25 455103 454103 454104 455103
 0.25 431774 430760 428748 426739 424734 422731 418733 416738
      416747 414756 411764 407771 405774 401776 394773 391771
      389767 385759 386749 382743 383735 384725 381723 378722
      374722 370724 368727 368732 368738 367743 365751 357763
      356766 353762 352760 350762 349765 346773 346777 348778
      351777 354773 355769 358772 360775 363777 370775 380784
      384789 386792 391794 395793 400794 404794 407791 418782
      427779 431774
 0.25 281078 279077 278077 276077 277079 279079 281078 281078
 0.25 278803 277796 274791 270787 266782 262778 257778 253782
      250786 243795 237805 236810 236814 238815 246819 255811
      262810 269809 275807 278803
 0.25 273075 273073 273071 272071 271070 269069 267069 265069
      265070 265072 267074 269074 270075 272075 273075
 0.25 277970 277968 274966 270963 265961 260958 255959 252963
      250966 251970 255973 261976 266977 272975 276972 277970
 0.50 478215 478213 477212 476212 475212 474213 473214 472216
      473217 475217 476218 477217 478215 478215
 0.50 465241 466229 469218 465215 460215 452216 445218 440219
      438222 437227 440230 442232 441234 438236 437239 439243
      448247 453250 458249 464244 465241
 0.50 395787 394780 391777 388776 384772 381770 376770 375773
      376776 379778 383779 386783 387789 391790 394788 395787
 0.50 275801 273796 268796 264796 262790 261786 257784 254786
      251790 246796 241803 239806 240811 247813 254808 258807
      263806 269806 273803 275801
 0.50 269972 269970 268968 267968 266967 265966 264966 263965
      261964 259964 257965 256966 255967 255968 256970 257971
      259972 261973 263974 264974 265974 266974 268973 269972
 1.00 245802 244804 245805 246804 247802 246802 245802
 1.00 463223 464221 462219 461219 459219 457219 456219 454221
      455223 455224 456224 458225 460225 462224 463223
 1.00 456239 457236 456236 455236 453236 451235 450235 448235
      446236 444237 444239 445240 447240 449241 451241 452241
      454240 456239 456239
 1.00 448224 448223 446223 445223 446224 448224 448224
 1.00 255795 256793 255792 253794 252796 253797 255796 255795

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