Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 200704
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
303 AM EDT FRI MAY 20 2016


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


DAY 1...

...GULF COAST...

WELL FORMED BOW ECHO WITH IMPRESSIVE RADAR PRESENTATION WAS
TRACKING ALONG THE GULF COAST AT 06Z. THE BROAD MESOSCALE
CONVECTIVE VORTEX ASSOCIATED WITH THIS WAS LOCATED INLAND...AND
MEAN STEERING FLOW IN THE 600-400 MB LAYER SHOULD GUIDE THE MCV
TOWARD SOUTHERN/CENTRAL GEORGIA BY EARLY AFTERNOON. IN THE SHORT
TERM WE FAVORED THE HRRR AND 12Z WRF-ARW FOR TIMING THE
PROGRESSION OF THIS SYSTEM. THE 00Z WRF-ARW SEEMED TO LOSE THE
INFLUENCE OF THE MCV PREMATURELY...ALTHOUGH THERE MAY BE A DIURNAL
MINIMUM OF INTENSITY / RAINFALL RATES LATER THIS MORNING...WITH
CONVECTION THEN FLARING UP AGAIN IN THE AFTERNOON OVER GEORGIA.
THE LARGER SYNOPTIC PATTERN FAVORS LOWER LEVEL CONFLUENCE BACK
OVER THE NORTHERN GULF INTO NORTHERN FLORIDA THIS EVENING...AND TO
MAINTAIN CONTINUITY WE HELD ONTO SOME PRECIPITATION THERE...BUT WE
DID CUT BACK ON AMOUNTS A BIT DUE TO UNCERTAINTY. THE SCENARIO IN
THE 00Z WRF-ARW AND NSSL WRF...THOUGH DIFFERING IN TIMING...WOULD
ALLOW THE TAIL END OF THE BOW ECHO TO TURN RIGHT AND PROPAGATE
WELL OUT INTO THE GULF...STABILIZING THE ATMOSPHERE PRIOR TO THE
ONSET OF MORE FAVORABLE SYNOPTIC LIFT THIS EVENING.


...TENNESSEE / KENTUCKY AND POINTS EAST...

WHILE THE FORECAST OF WIDESPREAD MODERATE RAINFALL HAS NOT
CHANGED...WE DID MAKE A FAIRLY BIG CHANGE IN THE LOCATION OF A
RELATIVE MAXIMUM SWATH OF RAINFALL...MOVING IT OUT OF EASTERN
TN...AND INTO NORTHERN TN/CENTRAL KY...GENERALLY FROM NASHVILLE TO
LEXINGTON. IT IS EASIER TO MAKE SUCH CHANGE WHEN THE MODEL
GUIDANCE WAS ABSOLUTELY UNANIMOUS IN THIS ASPECT. GLOBAL AND
MESOSCALE MODELS ALIKE APPEAR TO BE LATCHING ONTO MODERATE
SYNOPTIC FORCING WHERE SOME SENSE OF UPPER JET COUPLING COINCIDES
WITH A FEED OF SEASONABLY MOIST AND SUFFICIENTLY UNSTABLE AIR. THE
CONVERGENT NORTHERN EXTENT OF A LOW LEVEL JET IS FORECAST TO TRACK
STEADILY ALONG A PATH FROM WESTERN/NORTHERN TN INTO CENTRAL KY AND
SOUTHERN OH. MODELS GENERALLY AGREE TO 1 TO 2 INCH AREAL AVERAGE
RAINFALL ALONG THIS SWATH...WHILE THEIR FORECASTS HAVE DRIED
CONSIDERABLY OVER EASTERN TN...PERHAPS OWING BOTH TO CHANGES IN
ASCENT AND SOME MOISTURE ROBBING ASPECT OF THE GULF COAST
CONVECTION. FARTHER EAST THE FORECAST IS MORE STABLE...WITH
PRECIPITATION SURROUNDING A COASTAL LOW POISED TO AFFECT COASTAL
PARTS OF THE CAROLINAS...AND ADDITIONAL RAINFALL...SOME
CONVECTIVE...BREAKING OUT FROM THE MOUNTAINS TOWARD THE
PIEDMONT/COASTAL PLAIN IN NC/VA AS WELL DEFINED SYNOPTIC FORCING
OVERSPREADS THE REGION THIS EVENING/TONIGHT. FOR QPF THROUGHOUT
THE EAST...WPC STARTED WITH A BLEND OF THE GFS AND OUR IN-HOUSE
ENSEMBLE WITH THE PREVIOUS WPC FORECAST.


...PACIFIC NORTHWEST TO NORTHERN ROCKIES...

AN UPPER TROUGH WITH VERY BROAD 1.5 STANDARD DEVIATION ANOMALIES
BELOW THE 500 MB HEIGHT CLIMATOLOGY WILL REMAIN RELATIVELY PARKED
OVER THE NORTHERN GREAT BASIN AND EASTERN PARTS OF OREGON INTO
NORTHERN CALIFORNIA. STEEP LAPSE RATES AND A SHOWERY
ENVIRONMENT...ENHANCED BY SOME FOCUSED DIFLUENCE ALOFT...SHOULD
RESULT IN ONE RAINFALL MAXIMUM OVER ADJACENT PARTS OF OR/CA/NV/ID.
DOWNSTREAM...A JET STREAK WILL INCREASE FORCING THROUGH THE
NORTHERN ROCKIES...RESULTING IN PRECIP OVER THE MOUNTAINS OF
ID/MT...BUT ALSO A MORE CONVECTIVELY DRIVEN...LOWER BASED
THUNDERSTORM EVENT OVER SOUTHERN CANADA...WHICH MAY WELL EXTEND
DOWN INTO MONTANA NORTHEAST OF GREAT FALLS. INFLOW INTO THIS
REGION WILL BE QUITE STRONG...SO THAT ANY ESTABLISHED MCS COULD
PRODUCE HEAVY RAIN. THE PREVIOUS FORECAST HAD MANY OF THESE
ASPECTS WELL HANDLED. OUR PRIMARY CHANGE WAS TO REFLECT THE
HEAVIER CONVECTIVE RAINFALL EXPECTED OVER NORTHERN MONTANA. THIS
WAS DRAWN USING MAINLY A MASS FIELD / PATTERN RECOGNITION
APPROACH...WITH SOME SUPPORT FROM THE 00Z GFS QPF. THE 00Z WRF-ARW
THEN ALSO INCREASED ITS QPF SIGNAL IN THIS AREA.

BURKE

GRAPHICS AVAILABLE ON THE WEB AT WWW.WPC.NCEP.NOAA.GOV

24HR QP VT 21/12Z
 0.01 553127 550113 546101 540092 537088 532087 527086 523082
      521076 517072 512066 501065 482071 473073 469076 463077
      459078 453076 448073 444072 441072 444075 447080 447084
      443086 437086 431087 428087 421092 413096 410097 408096
      406095 406098 403102 400106 397110 401114 407115 410114
      413115 413119 414125 414128 412130 409134 402141 401144
      398145 394145 387159 381165 382171 386173 396171 401170
      404171 407173 406177 403180 396187 393192 388193 380190
      374187 371186 366187 365191 373200 377204 381208 386211
      388215 389221 391225 393227 391229 386229 384232 385235
      389239 394242 403248 409251 414254 420256 426256 430255
      436256 445254 454251 460247 464244 465237 462233 457232
      447232 437234 434232 432229 435228 444226 463226 467223
      471222 481222 484222 486225 488231 490237 494238 500245
      504250 507249 511249 511244 507230 516214 516207 512202
      507199 505196 506193 510190 513188 518186 521183 528175
      532168 539160 543157 545152 553127
 0.01 525741 524725 523719 521714 520702 517690 514686 510685
      508688 506692 505704 504708 505715 502737 498758 498763
      497768 495777 492799 491812 491824 491834 491848 492863
      495872 503888 524910 526913 530912 531908 531901 531886
      529882 529875 525851 523840 522826 521810 522806 522799
      521786 522780 522773 525741
 0.01 496260 495257 494254 493251 492248 490245 488243 485243
      486247 487249 490252 491255 491258 494261 494262 496260
 0.01 479241 479238 478235 477235 476234 475235 474236 473237
      474237 475238 476240 477240 478241 479241
 0.01 466655 464651 461649 457651 455654 451660 446667 443674
      441682 442687 446687 452682 457676 461669 464663 466655
 0.01 466021 463013 460008 457005 451998 446993 440987 438985
      434990 438997 443002 448010 454016 457020 461023 464023
      466021
 0.01 445041 443038 443036 443034 443033 442031 440031 438030
      438031 436033 436035 436038 438040 439043 441041 443041
      445041 445041
 0.01 428058 424053 419052 416050 407049 397048 381051 378049
      375050 365050 359054 365054 368052 370053 375053 379054
      382058 382062 380064 375064 374066 375071 375078 377080
      381081 384080 390082 391081 397078 401074 404073 408073
      412071 415069 417066 419063 423061 427060 428058
 0.01 419804 416789 415783 412777 407768 401760 389745 385735
      380727 376723 371721 365722 359725 352729 341730 335732
      332735 325741 319748 315756 304774 300782 297787 291786
      282785 276786 271788 265790 260790 255791 251793 246794
      242798 244803 246804 245808 245812 249814 257819 265822
      274825 278828 278832 277836 276842 270851 267855 267861
      266872 267886 266899 265911 266937 266944 271946 281942
      285940 288943 295948 299945 303941 307934 311925 317918
      325912 331911 338911 345911 348912 353914 358915 361915
      360917 354918 349919 345921 342923 344929 348939 355946
      359949 364950 368948 374947 379949 384950 388953 391956
      398961 403961 407959 407954 404949 396944 389936 384929
      382921 381916 378913 372913 367915 365914 366912 370911
      374907 377904 379900 380894 382891 386891 392890 395888
      399883 404882 407878 407873 409867 408859 409853 411848
      417828 418821 418814 419804
 0.01 300015 300011 299009 297004 291997 288993 286992 285988
      285983 281978 266968 263962 259962 257965 253968 250968
      249966 246963 242961 239961 237963 233965 233971 235976
      235981 231983 231990 231994 234999 237003 241006 249011
      255019 259021 263023 269025 273028 278029 285029 290028
      293024 298017 300015
 0.25 539132 539124 538118 537112 534109 521096 511079 507076
      502076 493078 479088 476089 471089 467090 464092 459094
      454095 450097 449102 445104 445112 443116 439117 432123
      425129 419135 417138 415144 418148 424149 427148 430149
      430151 432156 435158 438158 440161 446163 451166 453171
      451177 448182 448185 455183 459179 457172 459168 463166
      471165 475167 475172 478177 481181 486182 489182 493181
      497177 499168 500161 502155 509152 511150 512143 515139
      519137 525136 531136 539132
 0.25 517876 517870 515862 512848 507837 504824 501809 500813
      499819 501834 503843 505847 507853 508862 511874 514880
      516880 517877 517876
 0.25 493153 492150 490148 488146 486144 483141 480141 478142
      476144 476147 477151 479153 482155 484157 487158 489157
      491155 493153
 0.25 468127 469125 468125 466124 465125 463126 463127 462129
      463129 464130 466130 467130 468128 468127
 0.25 443188 441183 440177 439175 437175 431166 427164 424167
      422171 419174 417178 417182 415187 412191 407196 400199
      389199 384197 381194 379196 381199 394212 400218 404221
      407222 411223 416224 422219 429214 432209 432203 434196
      436191 438192 442190 443188
 0.25 429245 427243 426242 424241 423241 422241 420241 419241
      417241 417242 416244 418245 420246 421246 423246 425246
      427246 429245
 0.25 410812 409801 407792 401778 393768 384757 379752 375745
      371738 366735 359735 354735 350737 345740 337742 331746
      325751 320756 318762 311775 309781 309788 321794 323795
      322798 317803 310805 303806 297803 292799 286796 278795
      271794 263795 256798 253800 252804 253809 258813 261814
      266814 274814 281817 286820 289827 286834 283840 283848
      278864 276871 276881 278889 277898 279907 281914 282919
      285922 289922 294920 301910 311901 316897 322895 330896
      337895 343892 352892 361891 368889 372885 377880 392856
      397852 402847 405841 408834 410829 410822 410812
 0.25 280016 274008 267003 260994 258990 255991 251992 246990
      242993 244998 250004 256011 263018 268020 272022 277022
      280016 280016
 0.25 263988 263986 264984 264982 263980 263979 262978 261977
      259977 258978 257980 258982 258984 259985 259986 261987
      261988 262989 263988
 0.50 533125 532117 528111 523106 518103 513098 512095 512092
      512087 511084 506080 502079 499079 495082 489086 486090
      482099 482105 482111 484114 489118 502122 515128 529130
      532127 533125
 0.50 469160 469153 467150 464146 459144 455144 452146 450151
      451156 454158 458160 461161 466160 469160
 0.50 468103 469098 469095 467095 465097 462098 458098 457099
      454100 456103 458105 459106 461106 465105 466105 468103
 0.50 448128 449124 448120 442122 438124 433126 428130 425134
      423136 423140 430141 436140 441137 445133 448128
 0.50 428189 428185 425184 418190 412195 407201 403204 399205
      394205 393208 400214 403217 408218 410214 414213 419214
      422212 424208 423205 425200 428189
 0.50 407813 407806 406799 402791 398784 393778 384766 381763
      377762 372760 368759 365755 362745 360741 357739 347742
      339744 333750 323760 315774 313783 314787 319788 325791
      329789 330785 334779 339775 346770 350768 353772 354775
      352780 347785 342790 337795 325805 322807 319809 310812
      302812 295809 289806 286802 283801 276799 268798 255805
      256809 259811 263812 268812 276812 284814 290817 295822
      294826 293830 288839 287847 285855 282862 280871 282879
      285886 282903 285910 287912 291912 295905 302901 310890
      313888 318886 327885 333888 337888 342887 347887 352888
      359888 365885 371880 380865 385860 389853 398843 403835
      405827 407818 407813
 0.50 275017 275015 274014 273013 272012 271011 269010 267010
      266011 265013 267015 269016 270017 272019 274019 275017
 0.50 250998 249997 248996 248995 246996 247997 248998 249998
      250998
 1.00 506089 506085 503083 499082 495086 491089 488096 486103
      485108 488110 493107 495102 499096 502092 506089
 1.00 417201 416199 414200 412201 411202 410204 412205 414203
      415203 416202 417201
 1.00 403808 403802 401799 398797 395799 393802 388803 385801
      384797 389791 390787 388783 386775 381768 377767 373767
      366771 358783 354790 355795 357797 361798 362802 366809
      369812 374811 381808 384809 384814 384825 380832 374837
      368838 361841 354845 349850 344855 342858 343861 344864
      349869 351875 356879 360880 363878 375867 383857 393843
      396837 399827 402817 403808
 1.00 358752 356746 352744 339748 332757 330762 327767 324769
      324771 322771 319775 318778 319782 323786 326784 331772
      335768 340766 348757 358752
 1.00 343812 340808 340805 338804 335805 321816 315822 312825
      307826 298829 295836 293841 295845 302849 302855 302859
      302865 303869 310875 313877 316877 321870 324866 328864
      335858 337856 337850 341841 342836 341830 341818 343812
 1.00 270806 269805 267804 265805 263805 261806 260807 260808
      262808 262809 264809 265809 267809 269808 270806
 1.50 499090 499087 498087 497087 496088 494089 493090 492091
      492093 494093 496093 497092 499090
 1.50 394828 395820 394812 391811 390813 389820 388826 386831
      380839 372845 370850 367854 366862 364867 364869 367868
      371866 378859 385850 390842 393837 394830 394828
 1.50 381777 379775 375776 370779 368782 367786 369791 373792
      377792 379789 377785 377780 380780 381777
 1.50 357854 356853 354854 354855 353856 351857 353859 355858
      355857 356855 357854
 1.50 342758 346755 351752 355751 354748 351747 346749 341751
      337755 336756 335758 335760 335761 337761 339761 341760
      341759 342758
 1.50 328829 328824 327822 322824 318829 315833 314837 315841
      313847 314856 317857 318855 322851 327848 328844 327840
      326831 328829
 1.50 307837 306835 304833 302833 301834 300834 299836 299838
      300840 301841 303841 305840 306838 307837
 2.00 387843 386838 382840 379843 377846 374851 372854 370858
      370861 373860 375857 378853 381850 383848 386844 387843

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