Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 180706
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
305 AM EDT WED OCT 18 2017


PRELIM DAY 1 QPF DISCUSSION
VALID OCT 18/1200 UTC THRU OCT 19/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1


PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES

FLAT SHORTWAVE UPPER RIDGE AXIS WILL PUSH EAST OF THE NORTHERN
ROCKIES LATER TODAY...GIVING WAY TO AN AMPLIFYING UPPER TROUGH
THAT WILL APPROACH THE PAC NW COAST ON THU. INCREASING UPPER LEVEL
DIFFLUENCE AND DEEP-LAYER MOIST ISENTROPIC ASCENT WITHIN THE WARM
CONVEYOR BELT (WCB) AHEAD OF THE AMPLIFYING TROUGH WILL DIRECT AN
ATMOSPHERIC RIVER/ELONGATED PLUME OF DEEP-LAYER MOISTURE INTO
WESTERN WA AND EVENTUALLY WESTERN OR WEDNESDAY AND WEDNESDAY
NIGHT. SOUTHWESTERLY 850 MB FLOW INCREASING TO ~50 KTS WILL LEAD
TO ROBUST LOW-LEVEL MOISTURE TRANSPORT INTO THE COASTAL AND
CASCADE RANGES...WITH 850 MB MOISTURE FLUX ANOMALIES EXPECTED TO
TOP OUT BETWEEN 4-5 STANDARD DEVIATIONS ABOVE NORMAL ACROSS
WESTERN WA AND FAR NORTHWEST OR PER THE SREF AND GEFS.

IN ADDITIONAL TO THE FAVORABLE DYNAMICAL SETUP AND MOISTURE
PROFILE AHEAD OF THE TROUGH...STRENGTHENING RIGHT ENTRANCE REGION
FORCING VIA THE BUCKLING UPPER JET STREAK THAT WILL DROP SOUTH OF
B.C. AND INTO THE PAC NW LATER TODAY/TONIGHT WILL ENHANCE THE
DEEP-LAYER ASCENT AND LOW LEVEL FRONTOGENESIS. THIS WILL LIKELY
COMPOUND PCPN TOTALS OVER THE FAVORED HIGHER TERRAIN (WESTERN
SLOPES) OF THE COASTAL-CASCADE RANGES WED-WED NIGHT AS THE
GUIDANCE OF LATE HAS CONSISTENTLY SHOWN. TO THAT END...CONSIDERING
THE PROLIFIC TOTALS...CHANGES TO THE QPF FROM CONTINUITY (PREVIOUS
WPC FORECAST) WERE NEGLIGIBLE...WHICH YIELDED 5KM AREAL-AVERAGE
TOTALS OF 6-8 INCHES ACROSS THE OLYMPICS AND 3-5 INCHES OVER THE
NORTHERN WA CASCADES. LESSER AMOUNTS (1-3") WERE NOTED ACROSS THE
SOUTHERN WA COASTAL-CASCADE RANGES ALONG WITH THE NORTHERN OR
COASTAL MTNS. THE LACK (ABSENCE) OF DEEP-LAYER INSTABILITY WILL
INHIBIT SHORT-TERM RAINFALL RATES AND THUS LIMIT THE RISK OF FLASH
FLOODING...HOWEVER...THE VOLUME OF RAINFALL EXPECTED COULD VERY
WELL LEAD TO SOME LONGER DURATION RUNOFF ISSUES LATER IN THE
PERIOD (LATE WED-WED NIGHT) AS THE SOIL SATURATES.

FARTHER DOWNSTREAM INTO THE NORTHERN ROCKIES...THE CONSENSUS AMONG
THE MODELS CONTINUES TO POINT TOWARD 24 HR AREAL-AVERAGE QPF
BETWEEN 0.50-1.25" ACROSS THE WESTERN SLOPES OF THE NORTHERN
ROCKIES FROM FAR NORTHEAST WA INTO THE NORTHWEST TIP OF ID AND FAR
NORTHWEST MT.

HURLEY


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

24HR QP VT 19/12Z
 0.01 529242 522231 520225 521222 523224 524227 527229 530227
      532225 534221 537213 539205 540194 540184 539178 534165
      530161 525157 505143 494140 486130 479129 474131 472135
      472138 475140 481142 485146 485150 484153 481153 476150
      470152 468157 467165 469172 469177 467179 466181 465185
      465189 466192 470198 471201 469203 464205 459206 452215
      447216 444217 443220 442227 439231 431239 430241 426241
      420240 415241 412247 413253 413257 412260 407274 408282
      411285 414287 416286 420286 421289 428291 434291 436304
      440309 446311 451309 456306 473295 478293 485295 489295
      497298 503297 508302
 0.01 463178 463176 461175 461176 459177 459178 459180 461180
      462178 463178
 0.01 378226 376225 374225 374227 374228 376228 378226 378226
 0.01 370185 370183 370181 368180 367180 366180 365181 363181
      361181 360183 360185 360186 362188 364189 366187 367187
      368187 370185 370185
 0.01 374120 372118 368119 367115 367112 366110 364110 363114
      363119 362123 362126 366126 368124 370122 372122 374120
 0.01 352755 351749 345749 341751 337754 326770 322773 319777
      315785 309787 304788 301788 302785 305780 306771 303767
      299765 290763 284763 277764 273766 269771 268775 263778
      257778 253777 240779 237781 234785 230793 229804 230818
      229828 228835 229841 232851 234855 238859 243859 249859
      253857 256854 257848 256842 257836 259832 260827 260823
      263822 271817 277817 281819 289823 293824 298823 303821
      306818 320804 326797 331789 341773 347763 352755
 0.01 336058 329055 325050 323048 318046 311045 302044 300049
      305053 314055 319059 324064 327066 331066 332060 336058
 0.01 305083 305075 307068 305063 301061 288059 282059 279061
      277063 274063 270062 259058 256058 254060 254067 255072
      258076 268081 273082 279083 292084 296083 303083 305083
 0.01 283970 280965 276960 271956 267952 261939 257935 252932
      245930 241931 238936 239946 240952 243958 247963 252966
      257970 263972 269975 275976 280974 283970
 0.01 275884 275873 273865 270862 268861 265862 263866 261874
      260882 259891 260901 262903 266903 269898 273891 275884
 0.25 525257 516237 511213 510206 512204 515205 521211 528218
      531215 533209 536196 535190 534183 531173 529168 525163
      517156 510151 506148 501146 496145 493145 491147 490153
      486156 482157 479161 480167 479175 479182 482188 484187
      486184 487182 489183 491187 489192 482198 475203 471206
      467208 464209 459211 453218 453225 451230 443234 437241
      432249 428252 425256 423263 427268 432268 435266 444266
      448277 454280 460281 469282 489283 496287 502290 508291
      513289
 0.25 326788 326781 324779 321782 318786 315789 313792 311796
      312803 316802 318800 321795 323793 326788 326788
 0.25 303800 298796 293790 291785 292780 295778 295773 289770
      281768 276769 274772 273781 275790 274793 272797 259805
      256807 256812 258816 261815 260809 262805 265803 269804
      282811 289815 292816 297816 300813 302809 303801 303800
 0.25 250847 250842 246841 244837 243831 244821 245811 245807
      244803 240803 238806 234814 234822 234832 236842 237848
      239851 243853 249852 250847
 0.25 253952 252950 251950 250948 250947 248946 248945 246943
      245941 243941 242941 242943 243945 244947 245949 245950
      246951 247952 248953 250953 252953 253952
 0.50 522267 522261 520254 517244 514235 512228 510222 506212
      503202 502196 505193 514198 519201 521205 524209 528210
      531205 532197 531189 530183 527172 521163 515156 508151
      501156 498153 495157 488160 483160 483166 483174 483176
      486177 491180 493184 495189 493195 489197 485199 477204
      471209 462211 456217 455230 452233 448234 444236 441239
      441242 444244 449246 452257 457264 460270 463273 467276
      472277 481277 491280 499286 504287 509286 513283 518279
 0.50 482227 482226 480225 480226 480227 482228 482227
 0.50 319791 319790 317791 315794 314796 316797 317796 317795
      319793 319791
 0.50 298807 296800 293797 289792 286792 283794 277796 273799
      274803 276805 280808 286810 290812 296811 298807
 0.50 285779 284777 284776 284775 282773 280772 278773 277774
      277776 276778 276780 277782 277784 277786 278788 278786
      279784 280784 281783 283782 283781 284780 285779
 0.50 245847 246845 244843 243844 242845 241847 243849 245848
      245847
 0.50 240837 241835 241833 240831 240830 239832 238834 238836
      240837 240837
 0.50 238828 238826 237825 237826 237828 238828 238828
 1.00 518270 518263 518256 514242 510230 505218 500208 497203
      492201 483203 478205 474209 472213 466213 462215 458219
      461231 453235 450236 448239 453240 456241 460246 471263
      474268 479269 484269 488270 497278 501282 504283 506281
      509278 513276 516273 518270
 1.00 522184 522179 520173 517177 515176 509168 506165 501165
      499164 498167 494167 489165 485166 492173 497172 501175
      504179 506184 512189 519187 522184
 1.00 503257 504255 504253 503252 502250 502249 501248 499247
      498246 497247 498248 498250 499251 500253 500254 502255
      503257 503257
 1.00 485233 487231 486228 485227 484226 482224 481223 479222
      478221 476222 477224 478225 479227 479228 480229 481231
      482232 483233 485233 485233
 1.00 473224 472222 471223 470223 470225 470226 470225 472224
      473224
 1.50 516270 517264 516259 514250 511236 507229 505221 498208
      492205 489204 487205 480206 476211 474215 475218 481221
      485224 488225 492231 495238 499242 504248 507254 508263
      509267 511270 514272 516270
 1.50 503278 505273 505269 503262 497252 491240 487236 482235
      480231 475226 471228 467232 464231 462235 463240 465246
      468250 475254 479259 490264 497274 501278 503278
 1.50 470218 470216 469215 468214 467215 467217 468219 469219
      470218
 1.50 461238 460237 458235 457235 455235 454236 455237 456238
      458239 460239 461238
 1.50 463223 464221 462219 461219 460220 459222 460224 462225
      463223
 2.00 514266 514264 515261 514260 513258 513257 512257 511258
      511260 511262 512265 512266 513267 514266
 2.00 509243 509238 507232 503223 500214 498210 493207 490206
      486207 479209 477212 478218 484222 491225 494234 500241
      505244 509243
 2.00 503273 500261 495251 490240 487237 482237 480233 477228
      472230 469235 467241 469245 474249 480251 488258 491261
      495266 502275 503273
 3.00 496260 496257 494254 492251 491248 490245 489242 487240
      485240 484245 486247 488249 490252 491255 493258 494260
      496260
 3.00 500230 498222 495216 491213 486210 481211 479213 480217
      484221 488221 490219 494216 492222 494228 497231 500230
 3.00 481244 482242 482241 481239 481237 481236 480233 479233
      478231 476230 475230 473231 472233 471236 471238 471240
      472241 473243 474244 476245 478245 479245 481244 481244
 4.00 488218 488216 488213 487212 486213 484214 483214 482214
      481216 482217 483218 485219 486219 488218
 4.00 480241 480239 480236 479235 478233 478232 476232 474232
      473234 473236 473239 475241 476242 478243 480241 480241
 5.00 479238 479237 478236 478234 476233 474234 474237 475239
      476240 477240 478240 479238

$$





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