Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 160643
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
142 AM EST SAT DEC 16 2017


PRELIM DAY 1 QPF DISCUSSION
VALID DEC 16/1200 UTC THRU DEC 17/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

GREAT BASIN INTO THE NORTHERN ROCKIES

THE ELONGATED UPPER TROF INITIALLY STRETCHING FROM CENTRAL
CALIFORNIA INTO THE NORTHERN GREAT BASIN/NORTHERN ROCKIES REGION
WILL BE SPLITTING INTO TWO STREAMS WITH THE SOUTHERN PORTION
CLOSING OFF OVER THE NORTHERN BAJA--WHILE THE NORTHERN PORTION
FROM THE GREAT BASIN INTO THE NORTHERN ROCKIES REMAINS MORE
PROGRESSIVE TO THE EAST.  MODELS ARE SIMILAR WITH THE PRECIP
AMOUNTS AND DISTRIBUTIONS WITH THE PROGRESSIVE PORTION FROM THE
GREAT BASIN INTO THE NORTHERN ROCKIES--WITH GENERALLY LIGHT TO
MODERATE PRECIP TOTALS. THE GREATEST PRECIP TOTALS LIKELY ACROSS
WYOMING WHERE POST FRONTAL NORTHEASTERLY LOW LEVEL UPSLOPE FLOW
WILL ENHANCE TOTALS.

NORTHWEST MEXICO INTO THE SOUTHWEST

PRECIP WITH THE CLOSING OFF SOUTHERN PORTION OF THIS TROF WILL
INITIALLY CONCENTRATE ACROSS THE NORTHERN BAJA LATE SATURDAY
AFTERNOON INTO SATURDAY NIGHT WHERE THE STRONGEST ONSHORE WESTERLY
FLOW IS FORECAST.  PRECIP SHOULD WORK NORTHEASTWARD TOWARD THE
SOUTHWEST U.S. OVERNIGHT SATURDAY INTO EARLY SUNDAY.  THE 1200 UTC
DEC 15 ECMWF HAS BEEN MORE EMPHATIC ABOUT THIS NORTHEAST PUSH OF
PRECIP THAN MOST OF THE REMAINING GUIDANCE AS IT HAS HAD A
SLIGHTLY STRONGER AND FARTHER NORTH CLOSED LOW.  THE 0000 UTC
ECMWF HAS TRENDED TOWARD THE MAJORITY OF THE GUIDANCE WITH THE
FARTHER SOUTH CLOSED LOW POSITION AND HAS TRENDED WITH LESS PRECIP
INTO SOUTHERN AZ COMPARED TO PREVIOUS RUNS.  THIS SOLUTION IS
SUPPORTED BY THE LATEST 24 HR PQPF WHICH SHOWS LOW PROBABILITIES
OF .10-.25" AMOUNTS INTO SOUTHERN AZ WHICH WERE THE MAGNITUDE OF
THE PREVIOUS WETTER EC SOLUTION.

PACIFIC NORTHWEST

IN THE WAKE OF THE INLAND MOVING ELONGATED TROF EARLY DAY 1 ACROSS
THE GREAT BASIN/ROCKIES---DEEP LAYERED WESTERLY FLOW WILL BE
PUSHING EASTWARD FROM THE NORTHEAST PACIFIC SATURDAY AND IMPACTING
THE PACIFIC NORTHWEST LATE SATURDAY NIGHT INTO THE EARLY SUNDAY
MORNING HOURS.  STRENGTHENING ONSHORE FLOW AND INCREASING PW
VALUES WILL SUPPORT INCREASING PRECIP INTO THE PACIFIC NORTHWEST
LATE IN THE DAY 1 PERIOD WITH .25-.50"+ AMOUNTS ACROSS COASTAL
WASHINGTON AND .10-25"+ INLAND INTO THE WASHINGTON CASCADES.

SOUTHERN PLAINS TOWARD THE LOWER MS VALLEY

THE UPSTREAM FORMING CLOSED LOW OVER NORTHWEST MEXICO WILL EJECT
THE DOWNSTREAM CLOSED LOW OVER NORTH CENTRAL MEXICO NORTHEASTWARD
SATURDAY TOWARD THE BIG BEND/SOUTHWEST TX---ACCELERATING SATURDAY
NIGHT INTO EARLY SUNDAY INTO NORTHEAST TX---EASTERN OK AND
NORTHERN ARKANSAS.  STRENGTHENING SOUTHERLY LOW LEVEL FLOW OFF THE
WESTERN GULF AHEAD OF THESE HEIGHT FALLS WILL INCREASE PW VALUES
1-2 STANDARD DEVIATIONS ABOVE THE MEAN.  THIS AND FAVORABLE UPPER
DIFFLUENCE AHEAD OF THESE HEIGHT FALLS WILL SUPPORT A BROADENING
AREA OF MODERATE TO HEAVY RAINS ACROSS EASTERN PORTIONS OF THE
SOUTHERN PLAINS TOWARD THE LOWER MS VALLEY.  THE LACK OF
INSTABILITY AND THE PROGRESSIVE NATURE OF THE HEIGHT FALLS SHOULD
KEEP PRECIP TOTALS FROM BEING VERY HEAVY.  MODEL CONSENSUS IS FOR
MAX TOTALS IN THE 1-1.5"+ RANGE OVER EASTERN TX INTO WESTERN LA
AND SOUTHERN ARKANSAS.  THE MARGINAL RISK AREA WILL BE MAINTAINED
ON THE DAY 1 EXCESSIVE RAINFALL POTENTIAL OUTLOOK---ALTHOUGH THE
QUICK MOVEMENT---LACK OF INSTABILITY AND HIGH FFG VALUES SHOULD
KEEP ANY RUNOFF RISK VERY LOW.

EASTERN GREAT LAKES INTO THE NORTHERN MID ATLANTIC

WEAK ISENTROPIC LIFT TO THE NORTH OF THE FRONTAL BOUNDARY
STRETCHING WEST TO EAST TO THE SOUTH OF THE GREAT LAKES INTO THE
NORTHERN MID ATLANTIC WILL SUPPORT AN AREA OF OVERRUNNING SNOWS
PUSHING ACROSS THE LOWER LAKES INTO THE NORTHERN MID ATLANTIC
DURING SATURDAY.  PRECIP/SNOW TOTALS SHOULD BE LIGHT---SAVE FOR
AREAS TO THE EAST AND SOUTHEAST OF THE EASTERN PORTION OF LAKE
ERIE WHERE FAVORABLE WEST SOUTHWEST FLOW OFF THE LAKE WILL ENHANCE
SNOW TOTALS.

ORAVEC

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

24HR QP VT 17/12Z
 0.01 484339 489334 493329 500312 504306 507300 514285 535215
      537206 536196 531180 529177 528172 525168 520170 514170
      511169 508167 502167 492165 489164 486161 480160 471150
      481130 471122 475106 474098 471093 466089 464087 463084
      460076 458069 455067 453063 451055 446040 441025 439018
      436012 430010 427011 425013 423020 419025 410017 405014
      401012 397014 392020 391022 393025 397028 400030 403031
      410036 412043 419055 420057 419062 418069 414082 409087
      406094 404104 402107 399108 387113 382117 380118 379121
      378132 380134 378137 375141 377146 374159 374164 376165
      381167 386164 388163 393163 393169 391173 387177 380180
      377187 378191 380193 386198 388200 392199 395198 396194
      399188 403181 405176 410171 417163 421157 424150 437120
      440118 442120 445128 449134 448138 446140 445144 446147
      450153 451157 450162 449173 448178 445180 441182 440192
      442200 445201 447200 452195 458185 457178 456173 460170
      467172 473169 476168 477173 479180 484184 487188 488190
      489196 490201 488203 486206 483206 476208 471211 465214
      454216 455222 455225 454228 451231 449235 444237 442239
      441243 444250 446256 451261 455265 458270 462286 466300
      469317 471325 474334
 0.01 509212 509209 508206 507204 505203 504202 502202 500202
      499203 499206 500208 501208 503210 504212 506213 507213
      509212
 0.01 506973 506962 504957 498944 494929 491926 489924 486924
      482923 480922 478920 478914 481908 483902 489891 490884
      490881 486881 481884 479890 476895 475902 474907 472909
      469910 465904 463898 459893 454894 453896 453901 455908
      459920 465920 467922 469927 468937 469945 476955 481958
      485962 492972 494975 499975 506973
 0.01 476880 473875 471873 471868 470860 468853 467858 465861
      465866 464871 467878 469885 471890 473890 475885 476880
 0.01 461738 459721 458714 456709 452708 450711 447711 442708
      438712 441717 442721 441723 430725 428727 425727 420730
      421734 427733 433733 440732 446729 450730 451733 452736
      450738 447739 443739 440738 437739 434744 408749 406754
      408764 410770 410775 409779 408787 409794 411800 413807
      417821 421837 426867 430874 431876 429879 430883 432884
      439884 445886 449890 453888 456882 458876 459870 457867
      455866 452866 450869 446873 443873 442869 438856 434852
      433842 433833 432823 431821 430816 432807 437797 439791
      440788 440783 442769 442764 443761 448756 457750 459748
      461744 461738
 0.01 449833 449831 448830 447829 446828 445828 444827 443824
      441824 439824 439825 438826 437828 436830 436832 436833
      437835 438836 440836 442835 443835 445835 447835 448834
      449833
 0.01 391963 392953 391947 390944 388936 385930 380915 376898
      373892 370889 368889 365887 361887 355889 348892 343895
      340896 338894 335892 332893 322902 317906 311909 305911
      297910 294909 292911 289913 287916 287921 286924 280928
      269934 256940 246945 244948 245951 250956 256958 262956
      265954 268956 269963 266965 263966 261969 257969 251971
      245975 243991 240997 238001 233007 230013 228032 228041
      229048 232050 235050 240048 247044 253041 274028 283020
      298017 309015 314012 321011 333006 337991 339989 340991
      347993 353993 361992 366992 368990 373988 382977 388970
      391963
 0.01 349121 350118 349114 348110 346105 343100 341090 339085
      337082 332079 329080 323087 303084 297084 292085 281083
      272083 265084 260085 257088 256093 257096 261099 265102
      270105 273107 278108 287113 289116 288122 282126 278127
      275127 271124 268126 266131 269141 274146 282153 286155
      290158 298162 304170 313174 325176 329175 330170 319157
      313155 309152 306149 304144 309142 313144 320149 329147
      331145 334140 336136 337130 330123 331118 333116 339118
      344121 349121
 0.25 514274 517265 516257 511245 506234 500224 497219 493217
      488217 487220 488223 488231 488235 487237 482237 480232
      476230 472232 467234 463237 460242 458248 460253 463259
      472279 475294 478307 480313 482317 487319 492316 498306
      504297 510285 514274
 0.25 451078 450073 448070 443066 439062 437054 440039 436038
      433040 430047 425051 423054 423058 424066 423077 422081
      420084 418092 419095 422095 425095 429096 435098 440094
      439081 441078 445077 449079 451078
 0.25 423796 424791 424787 422783 421786 419790 419792 418797
      418799 418804 419808 421806 422802 423799 423796
 0.25 371947 370940 368934 364925 360918 353912 346906 335904
      327910 319915 302922 288933 280939 277941 276944 279944
      283947 286952 279956 277960 277967 276974 275978 268986
      264992 258000 251005 244010 238017 240022 246023 256025
      263021 270015 277010 279005 282003 289997 295990 302985
      308979 317974 323969 335967 339967 343964 350959 355949
      359949 364950 369950 371947
 0.25 312130 312128 311127 311126 310124 308122 306122 305121
      303121 301122 300122 299124 299126 300128 300129 302131
      303131 303132 305132 307133 309133 310132 311132 312130
 0.25 269009 267007 265008 265009 263009 262011 263012 265011
      266011 267009 269009 269009
 0.50 514269 514261 513256 510246 506238 500231 497229 496234
      496239 496243 495245 490243 485242 481243 480239 477234
      474234 471239 470246 470251 472256 474266 481285 483296
      487306 490309 493307 498300 504291 508283 511274 514269
 0.50 348930 349920 347913 343909 335909 315922 308924 303926
      293933 288937 287940 288943 290948 288954 284958 281963
      281978 273987 270990 267997 270998 274998 280996 285994
      290989 298982 308975 325960 335953 340950 343945 347937
      348930
 1.00 511262 510260 510257 509257 508255 508256 508257 509259
      509260 510262 511263 511262
 1.00 503283 504276 503270 502267 499263 496260 493259 491262
      491266 490273 490278 491284 495288 500287 502285 503283
 1.00 327945 325941 323941 318943 315945 308950 301955 294960
      289966 292975 301973 307969 312962 318956 323949 327945
 1.50 301966 301965 299964 297966 296967 294968 293968 294968
      296969 297969 299968 301966 301966

$$





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