Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 210651
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
151 AM EST SAT JAN 21 2017


PRELIM DAY 1 QPF DISCUSSION
VALID JAN 21/1200 UTC THRU JAN 22/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...SOUTHEAST U.S. TO THE MID ATLANTIC...

AN ACTIVE PERIOD IN STORE FOR THE GULF COAST STATES...WITH RAIN
ALSO SPREADING INTO THE SOUTHERN MID ATLANTIC. SURFACE GRADIENTS
WERE TOO DIFFUSE TO IDENTIFY ANY SYNOPTIC SCALE FRONTAL BOUNDARIES
TO THE SOUTH OF WAVE FRONT IN THE OHIO VALLEY...BUT WEST TO
SOUTHWESTERLY FLOW HAD ESTABLISHED A MID LEVEL BAROCLINIC ZONE
NEAR THE GULF COAST...WITH RICH MOISTURE AND MODERATE INSTABILITY
POSITIONED ACROSS THE FULL LENGTH OF THE NORTHERN GULF.
THUNDERSTORMS WERE ONGOING EARLY THIS MORNING IN THE FLORIDA
PANHANDLE WITHIN A MODEST WARM ADVECTION REGIME...BUT A MUCH
LARGER AREA OF ORGANIZED THUNDERSTORMS...INCLUDING SUPERCELL
MODES...WAS EVOLVING OVER LOUISIANA AND ADJACENT PARTS OF
TX/MS...WHERE LOW LEVEL FLOW HAD ACCELERATED IN ADVANCE OF A
TROUGH OVER THE PLAINS...TAPPING INTO THE STRONGER WELL OF
INSTABILITY OVER THE WESTERN GULF. THE PERIOD THROUGH BOTH
SATURDAY AND SUNDAY SHOULD PROVE PARTICULARLY ACTIVE...WITH THE
FIRST TROUGH BRUSHING ACROSS THIS REGION WITH SEASONABLY STRONG
DEEP LAYER FLOW...AND THEN A 3.5 SIGMA BOWLING BALL OF AN UPPER
LOW PUNCHING OUT AT LOW LATITUDE ON SUNDAY. ADD TO THIS SETUP THE
MORE SPRING-LIKE MOISTURE AND WARMTH...AND WE HAVE A RECIPE FOR
BOTH SEVERE WEATHER AND FLASH FLOODING. PLEASE REFER TO STORM
PREDICTION CENTER PRODUCTS AND THE WPC EXCESSIVE RAINFALL OUTLOOKS
FOR ADDITIONAL DETAILS.

FOR QPF...OBSERVATIONAL TRENDS IN THE SHORT TERM AND MODEL TRENDS
IN THE LONGER TERM ALL SUGGESTED KEEPING THE SHAPE OF THE GOING
FORECAST...BUT SHIFTING EXPECTATIONS A LITTLE FARTHER NORTH TO
SYNC UP WITH THE SYNOPTIC FORCING. WE WERE HESITANT TO GO TOO FAR
NORTH...AS THE CONVECTION ALWAYS FINDS THE STRONGER INSTABILITY TO
THE SOUTH GIVEN ANY SUFFICIENT AMOUNT OF FORCING...BUT RADAR
TRENDS CERTAINLY DICTATED SHIFTING THE MAXIMUM AMOUNTS DEEPER INTO
LA/MS EARLY ON...AND THEN MORE SOLIDLY INTO SOUTHERN GEORGIA IN
THE LONG RUN...THOUGH THE FLORIDA PANHANDLE WILL STILL SEE A
HEALTHY AMOUNT OF RAIN. MODELS HAD ALSO TRENDED WETTER INTO
SOUTHEAST VIRGINIA AS THE TAIL END OF THE INITIAL TROUGH AXIS WILL
SLIDE ACROSS THE BROAD MID LEVEL BAROCLINIC ZONE. AT 06Z SHOWERS
WERE ALREADY DEVELOPING OVER SOUTH CAROLINA...AS MOISTURE APPEARED
READILY AVAILABLE.

WPC BEGAN WITH A 50/30/20 BLEND OF THE PREVIOUS WPC FORECAST / 12Z
ECMWF / 12Z WRF-ARW...BUT ALSO NUDGED THE FORECAST TOWARD THE 00Z
GEM REGIONAL. THE 00Z NCEP SUITE OF HI-RES GUIDANCE WOULD HAVE
SUPPORTED A GREATER NORTHWARD SHIFT TO THE PRECIPITATION
AXES...BUT IT IS LIKELY THAT THE QLCS ORGANIZING OVER THE WESTERN
GULF STATES WILL EVENTUALLY SUPPRESS THE LOCATION OF PERSISTENT
CONVERGENCE / UPGLIDE LATER TODAY AFTER IT SWEEPS THROUGH THE
SOUTHEAST. THE 00Z GUIDANCE ALSO DEPICTED A DISTINCT MINIMUM SWATH
IN BETWEEN THE INSTABILITY GRADIENT ALONG THE COAST AND THE MID
LEVEL FRONTOGENESIS TO TAKE PLACE UP ACROSS NORTHERN AL/GA. IN
REALITY THE SOUTHERLY FLOW AND A BROAD FETCH OF UNSTABLE AIR
SHOULD SUPPORT THE FULL LENGTH OF THE DEVELOPING QLCS...SUCH THAT
WE WERE NOT IN FAVOR OF SUCH A DISTINCT MINIMUM AS SHOWN IN SOME
OF THE GUIDANCE.


...INTERMOUNTAIN WEST INTO THE SOUTHERN PLAINS...

THE VERY ENERGETIC OPEN WAVE THAT WAS PUSHING THROUGH ARIZONA THIS
MORNING WILL CARRY RAIN/SNOW THROUGH THE MOUNTAINS EARLY IN THE
DAY BEFORE BEING REPLACED BY STRONG HEIGHT RISES AS THE SYSTEM
MOVES INTO THE PLAINS. THE WAVE IS FORECAST TO DEEPEN AND FORM A
CLOSED CIRCULATION WITH 500 MB HEIGHTS CRASHING TO 3.5 STANDARD
DEVIATIONS BELOW CLIMATOLOGY OVER OK/TX BY SUNDAY MORNING.
MOISTURE AVAILABILITY IS ABOVE AVERAGE FOR JANUARY...WITH NO
FRONTAL SYSTEM INHIBITING FLOW OFF THE GULF...AND THE GFS
FORECASTS PW VALUES OF 0.75 INCHES TO WRAP BACK AS FAR WEST AS
ENID OKLAHOMA ALONG THE NORTH SIDE OF THE UPPER LOW TRACK. SIMILAR
TO THE SOUTHEAST U.S. REGIME...THE MODELS HAD TRENDED NORTHWARD A
BIT IN THEIR QPF. WPC INCORPORATED SOME OF THE TREND...AND
ESPECIALLY IN TERMS OF A NORTHWARD EXPANSION INTO KS/MO...BUT DID
NOT WANT TO UNDERPLAY THE PRECIPITATION FARTHER SOUTH ALONG THE
INTERSTATE-40 CORRIDOR GIVEN THE STRENGTH OF THE LOW. THE SYSTEM
IS PROGRESSIVE ENOUGH THAT PRECIPITATION AMOUNTS ARE MODEST...BUT
SOME OF THE TYPICALLY DRIER AREAS OF THE SOUTHWEST WILL CATCH UP
TO A HALF INCH AREAL AVERAGE LIQUID EQUIVALENT EARLY TODAY...AND
PARTS OF NORTHEAST OKLAHOMA INTO THE OZARKS MAY SEE SLIGHTLY MORE
IN THE FAVORABLE VERY STRONG ASCENT REGION NORTHEAST OF THE LOW.


...WEST COAST...

VERY COLD AIR ALOFT IN THE WAKE OF THE INTENSE JET STREAK DIVING
INTO THE SOUTHWEST STATES...WILL SUPPORT A SHOWERY REGIME OVER
CALIFORNIA...AND EVEN PARTS OF OR/WA EARLY TODAY. THE NEXT
ATMOSPHERIC RIVER QUICKLY ORGANIZES BACK OFFSHORE AND APPROACHES
SATURDAY NIGHT...WITH THE INITIAL ONSLAUGHT OF HEAVIER RAINFALL
AIMED AGAIN AT NORTHERN CALIFORNIA. ONCE AGAIN A DEEP AND
AMPLIFYING TROUGH WILL BRING THE RIVER ONSHORE...ALTHOUGH WITH
STEADY PROGRESSION THERE WILL NOT BE TERRIBLY LONG RESIDENCE TIME
OF THE ENHANCED MOISTURE FLUX AT ANY ONE LOCATION. CERTAINLY THERE
WILL BE CAUSE FOR CONCERN IN FLOOD-PRONE AREAS...HOWEVER...AS
MODERATE PW AND FLUX ANOMALIES DEVELOP...SUPPORTING HEAVY 1-HOUR
AND 3-HOUR RAIN RATES. A CONSENSUS FORECAST MATCHES REMARKABLY
WELL TO THE GEFS REFORECAST DATA BASED ON ANALOG CASES...AND THE
GRIDS REQUIRED VERY LITTLE CHANGE THIS CYCLE...INDICATING AREAL
AVERAGE AMOUNTS 1.5 TO 2.5 INCHES THROUGH SUNDAY MORNING IN THE
FAVORED COASTAL TERRAIN AND NORTHERN SIERRAS / SHASTAS. THE EVENT
WILL WORK DOWN INTO SOUTHERN CALIFORNIA TOWARD DAY 2.


...NORTHERN TIER / GREAT LAKES...

LIGHT PRECIPITATION WILL FOLLOW ONE UPPER LOW LIFTING SLOWLY
THROUGH NORTH DAKOTA AND ANOTHER LIFTING THROUGH IOWA TOWARD LAKE
SUPERIOR. WE ATTEMPTED TO KEEP CONTINUITY WHILE USING ENSEMBLE
PROBABILITIES AND DOWNSCALED CONSENSUS QPF...WEIGHTED TOWARD THE
HI-RES RUNS...TO TRY TO HONE IN ON MEASURABLE VERSUS TRACE
AMOUNTS. THE RESULT SOMEWHAT RESEMBLES A GFS/ECMWF BLEND.

BURKE

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

24HR QP VT 22/12Z
 0.01 544976 544959 542946 537924 533913 528904 523897 518887
      511868 504846 499834 495826 492825 488827 485831 484839
      480838 478833 475830 473825 468819 464809 455762 448756
      447757 444761 438781 433790 430800 429805 425809 421811
      416811 411810 408812 405815 402820 395816 387814 384811
      382807 380803 380795 382785 386774 387765 390755 392743
      391737 392731 391725 388719 383708 365707 359709 355712
      348718 342722 334726 326731 319738 314745 309753 307757
      305762 302772 298788 295797 291807 287816 283827 281836
      278846 275854 274858 275863 279871 282882 282892 283903
      284910 287914 289918 290925 290948 290956 288958 288962
      289966 292966 294964 296962 301960 305958 310958 317958
      321961 326967 340976 339983 336986 335996 341016 344024
      350024 353022 359025 361029 367039 367043 365045 361047
      351050 349047 348041 349039 347036 342033 333035 329037
      325041 319043 315039 308022 303021 296022 289031 285062
      282065 273069 271074 275082 279089 281099 283111 285116
      286119 289122 292125 296126 301127 304129 310130 314129
      319130 327127 332126 336129 344136 348139 355140 358143
      362143 373141 382140 389138 397135 403131 409131 414133
      418136 421140 423144 428145 430148 431154 434157 437160
      440168 442174 440177 439175 433174 431178 430184 431191
      430193 428193 425191 420185 411183 407180 405177 402172
      401167 399161 396159 392161 387162 378165 372164 369162
      362157 355157 348162 344162 340160 331156 327154 322152
      314149 303147 298149 296152 295155 296160 299165 302167
      313174 321180 324182 325187 320195 317205
 0.01 317205 317214 320221 323227 325235 328242 333247 345258
      351262 356266 370276 390282 399285 407289 424293 437294
      444291 450287 454282 456276 458272 462268 464264 468263
      475265 479265 483265 491266 494264 496260 500254 502246
      504241 506228 507219 507210 506200 502193 501188 501182
      502180 505179 507179 511178 513172 510165 507158 503149
      498143 493138 488131 480129 475128 472123 468117 463121
      468125 469128 471130 469131 464129 461131 460136 462140
      462142 460141 455135 452127 452123 454120 456116 459114
      465111 463105 461104 456102 453099 450095 446096 436095
      430097 425097 423094 421086 418078 419072 421069 419067
      421065 426065 426062 425058 421056 423060 420062 415059
      409055 401051 397050 390047 381042 378042 375039 374036
      375033 376030 381024 385008 383988 384979 388971 390963
      393955 397947 401938 399929 398924 396921 394917 393911
      394907 394901 394895 395891 399883 403877 405873 406870
      410865 415859 424845 428838 432830 435829 437832 440841
      441849 443854 443860 442866 442877 439887 439892 437896
      434904 431911 429919 428923 427930 426934 427938 428945
      429949 433955 436973 438974 457985 468991 472026 483048
      493071 512077 513076 519074 522071 522065 521059 519056
      513050 506046 503043 502039 501034 501029 499020 498014
      500011 500005 501002 503003 503010 503015 506027 510036
      514043 520046 528043 533040 536033 538030 539024 540020
      540014 544976
 0.01 494156 494153 493151 492150 491148 490148 488147 486147
      485149 486150 487151 488152 489154 491155 492157 494156
 0.01 484161 483156 481154 478154 474154 473150 471146 465142
      463144 465146 467149 470155 458153 453159 454163 454169
      457177 459179 459182 453188 452195 450198 452201 456203
      461200 467196 473191 475190 476184 473176 473173 475171
      477169 480170 482164 484161
 0.01 463703 462698 460696 458696 454697 451701 447707 444711
      443718 444725 446732 452733 456729 459724 461718 461711
      463703
 0.01 475962 475957 474954 472952 471947 471944 468944 466947
      466952 464954 465959 466962 467964 469967 472969 474964
      475962
 0.01 454747 454745 454742 453740 452740 451740 449740 449741
      448743 447744 448746 449748 450749 452749 453748 454747
 0.01 449080 449078 448075 446075 445072 443072 443074 444075
      446077 448078 449080 449080
 0.01 430171 431167 430164 427164 426166 423169 418168 418164
      421162 422156 420152 419152 417149 415148 410150 402153
      400157 403161 407165 407173 409175 410173 412174 412176
      414177 420178 427172 430171
 0.01 260793 261788 259786 256786 252787 250789 249791 248794
      248796 249798 252799 255798 257796 259795 260793
 0.25 480244 479233 476228 472229 467235 465230 465224 466219
      465216 462214 459214 456215 437215 431213 428211 419210
      411205 402200 370181 365178 360178 352182 349184 347188
      340195 338199 338204 336216 336222 338226 342235 346243
      352250 360257 366262 370265 374267 384269 392272 403278
      412282 421282 430281 433278 434271 435264 439261 446257
      459247 464245 466244 470244 476245 480244
 0.25 474905 470900 465899 462900 460903 456906 452908 447913
      444918 445922 447923 452922 457920 462918 465916 469916
      472912 474905
 0.25 401074 401073 399072 397072 396073 395076 396078 397079
      398078 399078 400076 401075 401074
 0.25 395115 394113 392114 390116 390118 392117 394115 395115
 0.25 388082 390077 388074 387071 383070 380070 378069 374064
      371062 368062 367065 367070 370075 371082 375087 379087
      385086 388082
 0.25 372733 371727 369725 366724 360724 356727 346735 343737
      340736 334736 324742 318750 314757 313763 313771 312777
      294822 290832 286843 285851 286858 288863 289870 288884
      289891 291899 293903 297907 300909 304907 308904 315895
      328889 345883 349883 351885 355888 361889 364887 365885
      366868 369855 371848 370840 366827 365810 364791 361784
      357781 352779 349774 346769 344767 343762 346756 349754
      353754 359756 361760 365775 366778 368776 371771 372756
      371742 372733
 0.25 366200 365198 364196 363195 361193 360192 359192 358191
      356191 355191 354192 353193 353195 353196 355198 357199
      358200 360201 362201 363202 364202 365201 366200
 0.25 383947 383943 381941 378941 375941 373939 371934 368928
      367922 367913 365907 362903 358900 348905 341905 336907
      333909 332912 331917 329923 331929 337937 338944 341950
      349956 352960 355966 356973 356980 360992 362998 365003
      368006 372006 373005 374000 374996 373990 372982 372977
      373974 376961 383947
 0.25 377918 378911 377904 375900 374896 372891 370887 367888
      367891 368898 368905 369909 371916 373919 377918
 0.25 348114 344107 342104 343098 340089 334084 330078 324078
      321079 318080 315079 307076 297074 292074 289076 282079
      283083 285087 287096 290102 296107 306109 314108 324109
      331106 336107 339109 343114 347115 348114
 0.25 334167 332165 330164 329164 329163 327163 326163 325163
      324165 325166 326167 328168 330168 332168 334167 334167
 0.25 336058 336056 334054 333053 332053 331052 329052 327052
      325053 324055 324057 325059 326061 328061 330061 332061
      334060 336059 336058
 0.50 459237 458237 457236 455236 456238 458238 459237
 0.50 455238 451236 448236 439237 434235 433230 438226 446226
      448223 445220 442220 438221 428221 425223 421221 416215
      408210 400204 370183 366181 361181 357183 358185 360187
      367193 371201 373204 377207 372209 366209 361207 358205
      352204 350206 348210 347215 347220 358235 356241 357245
      359250 362253 370258 374261 379262 389266 397270 408275
      413275 417273 423258 427255 431254 438250 447244 451240
      455238
 0.50 361738 361736 360734 359732 359731 357731 355732 354734
      354735 353737 353740 353742 355743 357742 359742 360740
      361738
 0.50 370958 370952 369947 366936 364927 361916 359913 355911
      350912 347914 345919 346923 348929 350932 355933 357937
      359941 360947 361952 363958 365961 369961 370958
 0.50 359816 360809 360803 358797 355794 350788 345786 340787
      334793 332796 327797 326793 325787 325780 328778 332776
      334772 336763 340754 335744 326747 322749 320753 318763
      319769 321776 322780 320782 316785 314789 305804 302812
      299821 292838 290847 290853 292857 293869 293883 293889
      295893 300895 305894 319883 332873 341871 346868 350868
      354869 357867 359863 360857 360846 358834 358824 359816
 0.50 307094 307089 306085 303082 299080 294078 290079 287083
      289087 291092 293094 296097 301097 305096 307094
 1.00 428242 415227 415219 413217 410217 405215 402211 398207
      394203 385198 377192 372190 374195 376198 380202 388209
      402223 393223 386222 381222 373227 378236 387243 398247
      403247 407246 418245 424245 428242
 1.00 363220 364218 363216 362213 361213 360212 358211 357211
      355211 355213 356216 357218 359219 361220 362221 363220
 1.00 355808 353803 349799 344794 342793 340795 338801 335806
      331811 327814 323813 321806 319797 316796 309805 305816
      302827 299834 298840 297846 297855 299863 299870 298876
      299884 301887 304887 309884 316877 323868 330859 336848
      338843 342838 347835 349829 353819 355808
 1.00 299086 299085 298084 297083 295083 295084 294086 295087
      296088 297089 299088 299086
 1.50 420240 415234 413231 412226 411223 409223 407228 404231
      399229 392228 386226 384228 386232 388235 393236 400239
      403241 406241 414240 420240
 1.50 400213 399211 399210 397208 395206 394205 392204 391204
      390206 392208 392209 393210 395212 396213 398214 399215
      400213
 1.50 350811 349807 347807 342807 335813 327819 322821 320817
      319810 316804 313806 311809 307819 304830 301842 300853
      303863 303876 303883 305883 309880 312876 317868 324860
      330853 334843 344825 348818 350811
 2.00 397210 396210 397211 397210
 2.00 345816 344814 341814 334818 329822 324825 320825 318821
      317817 315812 312813 308818 306827 303844 302852 305861
      306870 308874 310873 319862 327848 335837 342824 345816
 3.00 331830 335827 336825 335824 332827 331828 330828 331830
 3.00 315846 318838 315830 314827 313827 311833 310837 309839
      308842 307846 307850 311851 312849 315846

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