Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 200659
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 AM EDT FRI OCT 20 2017


PRELIM DAY 1 QPF DISCUSSION
VALID OCT 20/1200 UTC THRU OCT 21/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1


...NORTHWEST INTO THE CENTRAL AND NORTHERN ROCKIES...

THE ONGOING ATMOSPHERIC RIVER EVENT WILL CONTINUE TO PUSH SOUTH
AND GENERALLY WEAKEN WITH TIME THIS MORNING. IN ITS WAKE A DEEP
TROUGH BRINGING IN COOLER TEMPERATURES ALOFT AND STEEP LAPSE RATES
WILL SUPPORT CONTINUED SHOWERY PRECIPITATION INTO THE NORTHWEST
AND NORTHERN ROCKIES THROUGH TODAY. AS THE TROUGH AXIS SHIFTS
EAST...PRECIPITATION WILL MOVE INTO PORTIONS OF CO/WY BY THIS
EVENING AS WELL. WITH PWATS LOWERING AND PRECIPITATION IN MORE OF
A SHOWERY FORM...RAINFALL RATES SHOULD GENERALLY REMAIN AT 0.1" IN
AN HOUR OR LESS WITH THIS POST FRONTAL PRECIPITATION.

BY 12Z SATURDAY THE NEXT ATMOSPHERIC RIVER EVENT WILL BE MOVING
INTO THE NORTHWEST...WITH RAIN RATES BEGINNING TO PICK UP BETWEEN
06Z AND 12Z SATURDAY MORNING OVER WESTERN WA/OR. THIS WILL BE AN
IMPRESSIVE ATMOSPHERIC RIVER EVENT WITH MOISTURE TRANSPORT...PWATS
AND LOW LEVEL WINDS ALL FORECAST TO BE WELL ABOVE NORMAL. THIS
WILL BE MORE OF A LONG DURATION MODERATE TO HEAVY RAINFALL
EVENT...AND THUS MOST OF THE FLOODING CONCERNS SHOULD BE AFTER 12Z
SATURDAY...WITH TOTALS GENERALLY BELOW 1.5" THROUGH 12Z SATURDAY.
RAINFALL RATES SHOULD BE PRETTY LIGHT FOR MOST OF FRIDAY
NIGHT...HOWEVER BY 12Z SATURDAY BEGIN TO SEE WINDS SHIFT MORE
WESTERLY ALLOWING FOR INCREASED OROGRAPHIC ASCENT...AND THUS MAY
BEGIN TO SEE SOME 0.25" IN AN HOUR TOTALS ALONG THE OR COASTAL
RANGES BY 12Z.


...MID TO UPPER TX COAST...

MODELS CONTINUE TO SHOW A CONCENTRATED AREA OF SOUTHEASTERLY TO
SOUTHERLY LOW LEVEL FLOW OFF THE WESTERN GULF AND INTO COASTAL TX.
AS THE WESTERN U.S. TROUGH PUSHES EAST...SOME OF THIS HIGHER
MOISTURE SHOULD BE PUSHED NORTHWARD INTO MUCH OF EASTERN TX. THIS
SHOULD SUPPORT SOME SCATTERED SHOWER AND EMBEDDED THUNDERSTORM
ACTIVITY. FOR THE MOST PART AMOUNTS SHOULD BE LIGHT...WITH
INSTABILITY LACKING THE FURTHER INLAND YOU GO.

HOWEVER WILL HAVE TO CLOSELY WATCH AREAS ALONG THE COAST IN THE
VICINITY OF HOUSTON. A CONCENTRATED AREA OF CONVECTION WILL
CONTINUE PUSHING NORTHWEST OFF THE GULF OF MEXICO. AT THE CURRENT
TIME THE HEAVIEST RAINFALL AMOUNTS HAVE GENERALLY REMAINED
OFFSHORE WITH THE BETTER INSTABILITY AXIS. HOWEVER THERE ARE
INDICATIONS THAT THE INSTABILITY AXIS MAY TRY TO SHIFT ASHORE AS
WE HEAD THROUGH THE MORNING HOURS...WHICH MAY ALLOW FOR SOME OF
THE HEAVIER CONVECTIVE CORES TO GET ONSHORE. LOW LEVEL WINDS
INCREASING TO AROUND 20 KTS AND ALIGNED WITH THE MEAN FLOW DOES
SUPPORT THE POTENTIAL FOR SOME BACKBUILDING AND TRAINING ALONG THE
COAST. PWAT VALUES ARE AROUND 1.8" IN A NARROW CORRIDOR AND ARE
SUPPORTIVE OF LOCALIZED HEAVY RATES. THERE IS A GOOD SIGNAL
AMONGST THE HIGH RES GUIDANCE FOR ISOLATED 3" AMOUNTS SOMEWHERE
BETWEEN PALACIOS AND PORT ARTHUR. RECENT HRRR RUNS HAVE SHOWN
LOCALIZED AMOUNTS AS HIGH AS 3-7" THROUGH 18Z. NOT CONFIDENT
TOTALS WILL INDEED GET THIS HIGH...BUT WILL HAVE TO CONTINUE TO
CLOSELY MONITOR THROUGH THE MORNING HOURS...AS THE HEAVY RAINFALL
SIGNAL DOES APPEAR TO BE GROWING IN A CONCENTRATED REGION NEAR
HOUSTON.

...FLORIDA...

NO SIGNIFICANT CHANGES EXPECTED TO THE CURRENT POST FRONTAL EAST
NORTHEASTERLY LOW LEVEL FLOW REGIME ACROSS FL DAY 1.  SCATTERED
SHOWERS LIKELY TO CONTINUE OFF THE WESTERN ATLANTIC AND ACROSS THE
PENINSULA THIS PERIOD.  CONFIDENCE LOW WITH QPF DETAILS IN THIS
PATTERN---WITH LIGHT TO MODERATE AREAL AVERAGE AMOUNTS DEPICTED
AND POTENTIAL FOR ISOLATED HEAVY TOTALS WHERE RAIN BANDS
CONCENTRATE.

...PLAINS...

AS THE WESTERN U.S. TROUGH PUSHES EAST A COLD FRONT WILL MOVE INTO
THE PLAINS FRIDAY NIGHT...WITH IMPRESSIVE 850 MB MOISTURE
TRANSPORT NOTED AS WELL. THERE APPEARS TO BE A PRETTY STRONG
LOW/MID LEVEL CAP IN PLACE HOWEVER...AND THIS IS GENERALLY
EXPECTED TO SUPPRESS MOST CONVECTIVE DEVELOPMENT THROUGH 12Z
SATURDAY. THERE MAY BE A FEW EXCEPTIONS...ONE ACROSS MN AND
ANOTHER AREA OVER PORTIONS OF NE/IA...WHERE MOISTURE CONVERGENCE
MAY BE ENOUGH TO GENERATE SOME SHOWER ACTIVITY. ALTHOUGH AT THIS
TIME NOT ANTICIPATING ANY SIGNIFICANT RAINFALL TOTALS THROUGH
FRIDAY NIGHT.


CHENARD


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

24HR QP VT 21/12Z
 0.01 461329 468330 473330 481327 485323 489316 491307 491299
      490291 488285 491279 496281 500288 505287 511281 514274
      517268 518259 518252 516248 511234 507219 512200 515200
      516203 520208 522211 526212 529211 531208 532200 531196
      531192 531187 529180 527174 524171 522169 521165 526159
      529154 530151 531146 533142 533136 537126 540119 537112
      534105 532103 529102 522101 520102 519101 518098 518091
      518081 517074 517067 516061 512061 510062 506062 503061
      498057 493053 490050 486050 479049 477052 474054 461052
      457052 454054 452056 451061 450067 448072 446071 441072
      442077 444080 443084 442089 440090 437092 433091 428088
      425090 425096 426099 424101 419104 414103 411102 408104
      404109 400114 390114 383121 382125 384126 389121 393116
      404120 417127 412141 402151 398155 394163 389172 388178
      392182 395184 397184 403183 413181 424179 434170 441170
      443173 443177 442183 440186 438190 435193 430194 424193
      421197 419198 417196 412195 409199 410202 409207 407210
      404212 396199 391198 388196 386191 380187 373184 361184
      356182 353180 350181 347184 345191 345200 345204 346207
      350206 354205 357205 364205 371204 374203 378204 385206
      396213 403218 406220 406224 405227 403228 397228 393230
      393235 395242 398246 403251 406257 409265 412271 414274
      413278 412286 414296 417301 421307 427312 432316 440320
 0.01 501144 502132 501126 498123 492104 487099 483097 480095
      479087 482082 483079 482075 475077 468081 466083 461083
      454086 452089 451091 452094 460097 475106 475109 473113
      472120 473123 475124 479125 482128 486129 489134 500145
      501144
 0.01 488200 489197 488193 487190 485184 483181 480177 477174
      470176 466177 463181 458188 452194 451199 456201 464205
      469206 473205 480201 488200
 0.01 498942 498927 497911 495904 493901 491904 489911 486921
      483926 479928 476930 471931 466932 462932 459928 459920
      458915 453918 448923 447925 447929 448935 451944 448957
      447961 447966 450970 452972 455972 458970 461967 465964
      468959 470956 476956 487955 494950 497945 498942
 0.01 455008 455005 452005 448005 446007 432006 423011 420015
      418017 417022 410033 408037 408040 410042 422046 432044
      441036 444031 447027 453013 455008
 0.01 437947 436941 433933 430930 424927 414923 409925 406931
      402943 397956 398964 402969 406971 414971 417968 421964
      430957 434953 437947
 0.01 425063 425058 422055 417054 411053 403054 398055 394057
      388062 382062 380065 373062 366063 370069 372080 375082
      380083 388081 392087 392098 392102 395103 399095 406090
      409089 410091 413094 416086 417078 419073 422068 425063
 0.01 378128 379126 379123 377123 377125 375127 375130 376130
      377130 378128 378128
 0.01 344180 345173 344169 341166 336164 331162 327161 324163
      322167 321169 324172 329174 335175 339177 341180 344180
 0.01 347947 345943 337942 330941 326940 323937 323930 315930
      312930 310932 305938 300936 296931 289930 281928 276926
      270925 261925 255927 251931 248937 246943 246954 246956
      249957 256959 264960 265963 263966 260970 261973 263975
      266976 271977 279978 286977 292975 298973 306975 314984
      317984 321982 326978 337974 339971 341967 341958 342954
      343951 347947
 0.01 302808 302804 301802 299802 298804 296807 295810 294813
      293816 294820 295822 298822 299820 301817 301815 301810
      302808
 0.01 305916 304909 303904 303899 301893 298886 292874 288868
      286866 284867 281872 279879 277886 275889 271890 267894
      265901 266909 270913 274917 279921 285923 288922 292920
      304916 305916
 0.01 281779 279778 276778 266779 252785 246788 240793 235797
      233800 233804 232811 232822 232828 236835 238836 241834
      245827 249823 253821 257820 266820 269821 272819 275813
      277805 279788 281779
 0.25 510180 510175 507169 507165 503160 499159 495161 491158
      485156 476151 471147 468142 465138 461135 456135 451139
      449144 447146 444147 440145 437146 434152 436158 440162
      445165 448167 449170 450175 453180 457182 460181 462178
      459175 456174 455169 459165 481163 486165 489170 493175
      498180 504182 510180
 0.25 499232 500226 500221 499212 483206 477208 471211 464211
      455213 449214 441213 426217 422220 420222 421226 422230
      413231 411233 409236 410240 413244 416247 417251 421260
      422270 424276 425285 425291 426295 430299 435300 442303
      446305 449308 452311 457312 463310 467305 468299 470295
      474284 477274 477265 479261 481258 483252 485250 485246
      482238 480231 478228 475227 473224 477223 481224 485222
      490226 493231 499232
 0.25 493150 491145 490141 489136 486133 481131 476131 471130
      470135 471140 475143 480143 485146 487149 491152 493150
 0.25 450114 450109 446107 444101 443098 439099 437102 434107
      434110 436112 440113 443116 446118 449117 450114
 0.25 414071 413070 412068 410068 408069 407070 407072 407075
      408076 410076 410075 411074 412073 413071 414071
 0.25 416954 417952 416950 414950 412950 410951 410952 410954
      410955 411956 412957 414958 415956 416955 416954
 0.25 405079 405072 403069 401065 398060 395063 392066 390070
      391075 394073 396073 399078 401081 404081 405079
 0.25 378196 378194 377193 376193 374193 374194 373195 374196
      375197 377197 378196
 0.25 332960 333955 330952 323948 314949 308949 305946 299942
      292939 285936 279935 274935 266937 262940 260943 259946
      259950 266954 275956 283959 290962 297962 300964 305963
      308961 312962 317968 321971 325971 327970 330967 332960
 0.25 292906 292904 292901 291899 290897 289896 289895 287893
      285893 284893 283894 283896 283898 284900 285902 286902
      288903 288904 290905 291906 292906
 0.25 273795 269795 266798 262798 257797 254796 251798 248802
      241809 238811 237816 236822 236826 239824 242819 244815
      247811 254806 258803 261801 265801 267806 269808 272803
      273797 273795
 0.50 484217 485215 486212 484210 483209 481209 479209 477210
      476212 475212 474214 474216 475217 476218 478220 479221
      481221 482219 483218 484217
 0.50 477238 477235 475234 469234 466231 466228 470223 473217
      471215 467213 455216 450216 444216 440215 438216 433220
      427220 425222 425225 431229 434232 432236 432240 431244
      430241 427238 423237 420237 418239 420245 424249 428264
      430270 433275 435281 434287 434293 445299 447302 452303
      455298 462287 465280 465272 464258 464253 465250 470246
      475244 477238
 0.50 486139 486136 484135 482134 481134 480135 479135 477135
      476135 474135 473136 472136 471138 472140 473141 475141
      477141 478141 480141 482141 484141 485139 486139
 0.50 473158 471152 466146 464143 460142 454146 450153 447155
      444152 441150 439150 438153 444157 447160 451161 454162
      457160 460158 463158 470160 473158
 0.50 329960 328957 328954 326952 323951 321952 317953 316955
      316957 317960 318962 320964 323966 325967 326966 328962
      329960
 0.50 301954 299947 296944 290942 283941 276943 271945 270947
      272949 276953 281955 287957 294957 299956 301954
 1.00 461220 459219 457219 457221 457222 459222 460223 460222
      461220
 1.00 453240 454238 453236 452235 450234 449234 448234 446235
      446236 445238 444239 443240 443242 445242 447243 448243
      450242 451242 452241 453240
 1.00 449224 449222 448220 448219 447218 445218 444217 442217
      441217 440218 439219 439221 441222 443223 444224 446224
      448225 449224
 1.00 297952 296949 294949 292948 290947 288947 287946 285946
      283946 281947 279947 280949 281950 282952 283952 285952
      287953 288953 290953 292953 294953 296953 297952

$$




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