Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 200657
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
156 AM EST FRI JAN 20 2017


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


DAY 1

...WESTERN U.S...

AN ACTIVE PATTERN CONTINUES IN THE WEST...PARTICULARLY CALIFORNIA
AND ARIZONA TO THE FOUR CORNERS AREA. BROAD SCALE CYCLONIC FLOW
EXISTS...WITH ONE BETTER DEFINED VORTICITY MAXIMUM AT MID/UPPER
LEVELS PUSHING THROUGH COLORADO THIS MORNING...AND A BETTER
DEFINED / DEEPER TROUGH DEVELOPING AND MIGRATING INTO CALIFORNIA
EARLY TODAY ALONG THE CYCLONIC SHEAR SIDE OF A RATHER STRAIGHT AND
RATHER STRONG 160-170 KNOT JET STREAK. THE LEAD WAVE THROUGH
COLORADO WILL FOSTER MAINLY LIGHT TO MODERATE RAIN/SNOW. THE
DEEPER TROUGH MOVING INTO CALIFORNIA WILL TAP INTO SUB-TROPICAL
MOISTURE AND PRODUCE DEEP ONSHORE FLOW THROUGH THE COLUMN...WITH
700 MB U-WIND COMPONENT ANOMALIES OF 3 TO 5 STANDARD DEVIATIONS
FROM CLIMATOLOGY ALONG THE COAST. THIS ALONG WITH STRONG HEIGHT
FALLS AS THE FLOW AMPLIFIES A BIT...WILL PROMOTE SOME HEAVY
RAINFALL FOR COASTAL CALIFORNIA...PROGRESSING NORTH TO SOUTH
DURING THE DAY. RAINFALL RATES WILL LIKELY EXCEED A HALF INCH PER
HOUR AT TIMES...LEADING TO EVENT TOTALS OF 2.0 TO 3.5 INCHES IN
THE FAVORED TERRAIN ALONG THE COAST...AS WELL AS SIMILAR LIQUID
EQUIVALENTS OVER THE SOUTHERN END OF THE SIERRAS. ALONG THE COAST
THE RAINFALL WILL BE FAIRLY EVENLY DISTRIBUTED FROM MONTEREY TO
SAN DIEGO...AS THE SYSTEM WILL REMAIN PROGRESSIVE. FLOODING /
FLASH FLOODING WILL BE POSSIBLE.

THE SUB-TROPICAL FEED...MEASURED BY INTEGRATED VAPOR TRANSPORT AS
MODELED OFF THE GFS...SHOULD PENETRATE INTO THE DESERT AREAS AND
TOWARD THE MOGOLLON RIM...SUPPORTING THE ONSET OF HEAVIER RAIN AND
HIGH ELEVATION SNOWS THERE. HEIGHT FALLS WILL BE CONCENTRATED
ALONG THE PATH OF THE UPPER JET INTO THE SOUTHWEST U.S...SUCH THAT
PRECIPITATION AMOUNTS FALL OFF WITH NORTHWARD EXTENT INTO THE
GREAT BASIN AND NORTHWEST STATES.

THE PREVIOUS FORECAST HAD A GOOD HANDLE ON ALL THIS. WE STARTED
WITH A 40/20/20/20 BLEND OF THE PREVIOUS WPC FORECAST / ECMWF /
UKMET / WRF-ARW. THIS APPROACH MAINTAINED A GOOD DEAL OF
CONTINUITY. PLEASE READ THE WPC HEAVY SNOWFALL
DISCUSSION...QPFHSD...FOR DETAILS OF THE WINTER WEATHER IMPACTS
OVER THE WEST.


...SOUTHERN STATES...

A QLCS PUSHING THROUGH NORTHERN FLORIDA SHOULD WEAKEN AS THE UPPER
LEVEL SUPPORT STARTS TO PULL AWAY THIS MORNING AND THE CONVECTION
RUNS AWAY FROM THE INSTABILITY AXIS PARKED BACK OVER THE CENTRAL
TO WESTERN GULF. ATTENTION THEN TURNS TO THE WEST...AND THE NEXT
IN A SERIES OF ENERGETIC AND PROGRESSIVE SHORTWAVE TROUGHS. THE
TROUGH OVER THE FOUR CORNERS REGION WILL PULL OUT INTO THE PLAINS
TODAY...ACTING TO TIGHTEN GRADIENTS AND STRENGTHEN A JET STREAK
WITHIN SSW - NNE FLOW OVER THE WESTERN GULF STATES. THE LOW LEVEL
RESPONSE WILL DRAW MOISTURE AND INSTABILITY RAPIDLY BACK NORTHWARD
INTO LOUISIANA AND ADJACENT PARTS OF TX / MS. THE GREATEST
MOISTURE FLUX SHOULD BE ORIENTED INTO SOUTHERN LOUISIANA BY 00-06Z
THE 21ST...WITH WINDS THEN BEGINNING TO VEER AS THE SYNOPTIC FLOW
REGIME REMAINS PROGRESSIVE. THEREFORE...WE FAVORED SOLUTIONS SUCH
AS THE NSSL WRF AND GEM REGIONAL WHICH DEPICT HEAVIER SWATHS OF
RAIN ORIGINATING IN SOUTHERN LOUISIANA AND EXPANDING EASTWARD.
THIS THINKING MATCHED WELL WITH THE PREVIOUS WPC FORECAST...SO WE
MAINTAINED ESSENTIALLY THE SAME FORECAST LOCATION WILL BUMPING UP
THE AMOUNTS AS CONFIDENCE STARTS TO INCREASE. THIS COULD CERTAINLY
LEAD TO HIGHER ODDS OF RAINFALL EXCEEDING FLASH FLOOD
GUIDANCE...AS THE AREA HAD RECEIVED LOCALLY HEAVY RAIN JUST
THURSDAY.


...GREAT LAKES TO MID ATLANTIC...

A NEGATIVELY TILTED...BUT OPEN...TROUGH...WILL START TO LOSE SOME
OF ITS PUNCH AS IT ENTERS A MEAN SHORTWAVE RIDGE POSITION OVER THE
NORTHEASTERN / EASTERN STATES. DEEP LAYER ASCENT AND FAVORABLE
MOISTURE CONTENT...HOWEVER...WILL LEAD TO WIDESPREAD LIGHT
PRECIPITATION...MOSTLY FALLING AS RAIN BUT WITH SOME ICE/SNOW OVER
THE UPPER GREAT LAKES. MODELS ARE IN GOOD AGREEMENT HANDLING THE
QPF...PRIMARILY LESS THAN A HALF INCH AREAL AVERAGE...FROM
MINNESOTA TO VIRGINIA. WHEREVER THERE WAS DOUBT WE LEANED TOWARD
SOLUTIONS SHOWING A LITTLE GREATER COVERAGE OF QUARTER INCH
RAINFALL...WITH SUPPORT FROM THE GEFS AND ECMWF ENSEMBLE
PRECIPITATION PROBABILITIES.

BURKE

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

24HR QP VT 21/12Z
 0.01 527204 528199 528194 527191 526188 524184 522183 519182
      517184 516187 516193 516196 517200 518203 520206 523207
      525206 527204
 0.01 507253 506249 502248 499249 495248 492246 490242 486235
      481227 475222 474219 476217 479216 487211 490207 493201
      495196 495189 496185 498182 500178 500172 497169 493173
      492182 492186 490188 485191 481192 476192 471194 466194
      462192 459190 457191 454189 454183 456172 457167 456162
      453153 443134 433116 424107 417106 413103 408093 406089
      408084 411081 414079 422075 434083 438084 442086 450088
      454090 457089 462089 466087 468085 470080 470073 468068
      454050 441034 428020 415010 410009 407007 398007 395009
      392004 394000 396989 398984 403982 422978 436978 442978
      445977 448976 450974 453967 456954 456947 457943 459945
      462949 464954 473969 477977 481983 482987 485990 490997
      497002 498007 499011 502015 505017 509019 514020 519016
      521012 524005 526997 527989 527981 524967 518942 516936
      515931 512921 500883 496871 492860 489851 486843 475826
      464818 457819 452818 450810 450804 449797 447790 439776
      436768 437765 440762 445755 449751 448744 447740 444737
      438730 434727 429726 425724 421719 416711 414707 409709
      402707 391703 377706 345721 321744 307765 302773 297781
      296786 298788 301788 306785 314784 320783 323780 329773
      335770 350762 357761 361763 363766 362770 357776 349782
      344790 345796 348796 350799 350802 350807 349811 346820
      342831 342837 345843 348846 354846 359841 370829 375825
      380824 383826 389831 390835 391839 391846 395854 397858
      394862 384881 381886 378893 376898 376906 380907 383905
      387902 389898 392892 392888 393884 395883 399881 403881
      407882 409887 413891
 0.01 413891 415897 416902 413903 412906 410912 410916 408922
      408927 407931 406937 404942 402945 396947 393954 390962
      388970 388975 387979 384989 381996 378007 375016 373026
      375031 373035 373038 374041 377043 379047 378052 374050
      365049 356051 351052 345052 338047 332045 326042 319041
      308040 304040 305042 307051 306057 304061 304065 303068
      300069 294066 288066 280068 276069 274073 276080 279088
      282107 284115 284124 285127 283132 283136 284140 286148
      290157 293165 297171 301176 305181 313193 317201 322207
      325216 327220 330223 338232 341235 346237 353240 367249
      372250 377253 387257 395264 402268 409269 444271 471270
      488270 491271 494266 499261 507253
 0.01 429039 430035 428035 423030 420029 418027 414027 412024
      407021 406020 404021 405023 409028 412033 415038 417043
      420045 424045 427042 429039
 0.01 360890 360884 358880 353871 348862 342853 337846 334834
      332820 330817 328818 325820 323822 322819 321814 319810
      314809 297819 289824 284831 281842 281849 280854 274902
      273906 273912 272921 269932 268937 271941 270947 268949
      262956 261961 262966 267968 269974 271978 275979 280979
      285978 289976 292972 296968 299963 306959 313953 321946
      326937 329929 335922 350908 356899 360890
 0.25 472249 472244 471241 464235 462231 461225 462217 461212
      457213 453215 449217 446221 442225 438226 435224 428216
      425208 420202 415205 412204 409199 400198 390192 382186
      374177 373173 375169 379167 383168 387165 389159 390155
      391147 389143 386139 384133 384126 384122 383118 381113
      384101 386085 379078 374071 371067 368066 366068 363072
      364078 365083 366087 364091 354086 346083 340079 333073
      332068 335063 337058 334054 330052 325053 322074 316079
      312080 307080 297077 292076 288078 286083 287089 289101
      293111 297119 301125 307130 310133 316134 320134 324136
      330144 327149 326150 321151 315149 311147 305145 300145
      296145 294147 294152 295157 300164 306170 313178 321186
      326194 330203 334209 339215 345222 353228 390252 397256
      407258 426261 431261 436260 444257 449255 454255 460256
      464255 469254 472249
 0.25 476922 475914 472906 465893 458881 455876 450871 445867
      441863 437861 435865 437869 439876 443882 447887 450894
      456908 457910 460913 464918 467923 474927 476922
 0.25 445179 445176 444173 441173 439174 437177 436179 435184
      435189 435192 436195 439195 440192 441188 443186 445181
      445179
 0.25 437849 437847 435844 433842 431840 428841 426842 425845
      424848 425851 427854 429855 432856 436855 437851 437849
 0.25 423813 422808 422806 420804 419804 417807 416811 417816
      417821 418825 420827 421822 421819 423815 423813
 0.25 420778 418766 414756 409749 405748 402753 402765 403769
      405774 404777 400779 400785 400793 403797 407798 412796
      414791 412786 411780 414782 417782 419780 420778
 0.25 373736 372731 367726 364724 360726 352732 351737 348742
      341750 334756 331759 335763 342759 351751 357745 368741
      372738 373736
 0.25 375792 376789 376787 374786 373787 371788 371789 370790
      370792 369793 369795 369797 370798 372797 373795 374794
      375792 375792
 0.25 374109 372105 368102 365100 361102 357103 353102 351098
      349100 349103 352107 354111 357113 362115 366115 370113
      373110 374109
 0.25 329857 329850 326847 324845 319846 317848 311853 307856
      303858 300858 298851 297843 295843 292849 289856 288866
      288873 287882 284898 281914 279921 279925 280929 282931
      283935 281943 278951 276960 277963 281962 286959 292955
      297950 301945 303943 306941 311937 316932 321919 324913
      327904 330900 330895 329892 329883 330872 329857
 0.50 436250 436245 435242 428236 421230 418227 418220 417217
      414213 410212 407208 401203 393197 387193 380188 374182
      365176 360172 357169 355170 351170 347168 345165 340161
      325156 315152 307149 303148 300150 298152 299157 305163
      311170 316175 323180 329187 333195 340208 345216 352222
      357226 365231 376235 383240 388245 397249 408252 418254
      427254 433253 436250
 0.50 378151 379142 379134 379124 378120 376117 371120 366119
      363119 360121 357121 355117 348108 345102 343094 340089
      336084 330079 325080 321083 319085 315085 308085 301082
      296081 294082 292086 294094 294102 300113 308124 312128
      319126 325123 329124 330127 332133 336137 346147 350150
      356151 358153 359156 360161 364162 367162 372159 378151
 0.50 332058 330056 329056 327056 326057 327058 328059 330059
      332058 332058
 0.50 326863 326857 323853 319853 315856 309863 303873 292889
      290893 288898 285910 284914 284921 287925 289931 286940
      284946 284950 287951 294946 301938 307931 310927 313922
      320900 322889 325876 326863
 1.00 423246 424241 421238 413231 414223 414219 411217 408217
      405215 402210 396203 388198 370183 367181 362179 356180
      352181 347184 345179 345171 343166 323158 312154 306152
      304153 304156 317169 326174 335182 339189 341201 343205
      348210 356217 363222 367223 371222 373222 373215 370211
      365207 358203 351195 351191 358193 363195 367199 373206
      377210 381212 388213 394216 399220 402220 404223 402227
      392230 389232 389236 391238 396242 402244 414246 419247
      423246
 1.00 374132 375127 375124 373127 372129 371134 370136 368138
      368142 369144 371145 373143 373138 374134 374132
 1.00 347134 347128 347120 346113 343107 338097 333094 329096
      324098 319101 309107 309110 310112 311115 314117 322109
      332116 335120 338126 341130 345134 347134
 1.00 319873 315871 308873 306876 304882 304888 302893 294899
      292904 290909 288914 290916 297923 301921 305918 307913
      310907 313897 317888 317881 319875 319873
 1.00 298933 298931 297929 296931 296932 295933 296935 297933
      298933
 1.50 400213 399210 396206 389201 381195 374189 368184 363182
      357181 354184 354187 356189 365193 369194 373197 379203
      386209 394213 398214 400213
 1.50 365218 365217 364216 363214 362213 360213 359214 360215
      361217 363219 364219 365218
 1.50 355207 354204 351201 350199 348196 347194 346191 343190
      343192 343195 344198 345202 347203 349205 352208 355207
 1.50 343182 343173 342169 339166 332164 324161 317158 310156
      312161 317165 323169 331173 336178 341183 343182
 1.50 339117 340115 340113 340111 339109 339108 338106 337105
      336104 334104 332105 330106 329107 329109 330110 331112
      333113 334114 334115 336116 337117 338117 339117
 1.50 309894 311890 311887 309888 307893 306895 306896 305897
      304899 306900 306899 308897 309894
 1.50 299912 304903 305900 304900 302901 300903 297904 295906
      294908 293909 293910 293911 294912 295913 297913 299912
      299912
 2.00 393207 392206 390205 389203 387203 386203 387204 387205
      388206 390207 392208 393207
 2.00 369190 369188 369187 368185 367185 366184 364184 363183
      361183 359182 357183 356185 356187 357187 358188 360189
      362190 363190 365190 367190 369190 369190
 2.00 335169 334167 332166 330165 329165 327165 325165 326168
      328168 330169 332169 333170 335169
 3.00 366187 364186 362185 361185 359185 358185 359185 360186
      362187 364187 366187 366187

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