Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 161856
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 PM EDT THU APR 16 2015


PRELIM DAY 1 QPF DISCUSSION
VALID APR 17/0000 UTC THRU APR 18/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...ROCKIES AND CENTRAL/SOUTHERN HIGH PLAINS...

AN UPPER LOW NEAR THE FOUR CORNERS REGION DRIFTS SLOWLY EASTWARD
THROUGH FRIDAY. A SHORTWAVE ROTATES TO THE EAST SIDE OF THE UPPER
LOW THROUGH FRIDAY MORNING...WHICH WILL STRENGTHEN DEEP LIFT AND
UPPER DIFLUENCE CO/WY/NE. MUCH OF THIS AREA WILL SEE LIFT ENHANCED
BY STRONG LOW LEVEL UPSLOPE...PERSISTENT NEAR-SURFACE WINDS OF
20-30 KNOTS FROM THE EAST TO NORTHEAST. GULF MOISTURE WILL WRAP
INTO THE SYSTEM AS THE WARM CONVEYOR BELT FORMS OVER THE HIGH
PLAINS AND WRAPS WESTWARD ACROSS THE DEEP FRONTAL SURFACE COMING
INTO PLACE OVER WESTERN KS/NE. ALL OF THESE THINGS COMBINE TO
PROVIDE REASONS FOR GENEROUS RAINFALL TOTALS AND LIQUID EQUIVALENT
OF SNOW IN THE HIGHER ELEVATIONS. SOME OF THE HIGHER RESOLUTION
GUIDANCE FEATURES PARTICULARLY INTENSE PRECIPITATION...WITH THE 27
KM GFS OUTPUT AND THE GEM REGIONAL MODEL AND OUR IN-HOUSE PSEUDO
BIAS-CORRECTED ENSEMBLE TRENDING UPWARD. ALL THESE SOURCES
INDICATE LOCAL 3 TO 4 INCH MAXIMA OVER THE COLORADO ROCKIES AND
OUT OVER NEBRASKA NEAR THE SURFACE FRONT IN JUST THE 24 HOUR
PERIOD ENDING 00Z SATURDAY. THESE AMOUNTS APPEAR TOO HEAVY GIVEN
THAT THIS SYSTEM IS STRONG BUT NOT ESPECIALLY ANOMALOUS IN TERMS
OF HEIGHTS/WINDS. AFTER THE ABOVE-MENTIONED SHORTWAVE ROTATES
THROUGH THE EAST SIDE OF THE SYSTEM...PRECIPITATION RATES SHOULD
DECREASE SOMEWHAT DURING THE DAY FRIDAY AS THE SYSTEM BECOMES
STACKED. THAT IS NOT TO SAY THAT THERE WILL NOT STILL BE
IMPRESSIVE AND GENEROUSLY WIDESPREAD PRECIPITATION...BUT THE ECMWF
AND NAM DID NOT SHOW THE SAME TREND TOWARD MUCH HEAVIER VALUES AS
SEEN IN THE GFS. THE PREVIOUS WPC FORECAST WAS ALREADY
APPROPRIATELY HEAVY...SO WE TRENDED ONLY SLIGHTLY IN THE DIRECTION
OF HEAVIER VALUES...WITH SOME 2.0 TO 2.5 INCH AREAL AVERAGE
FORECAST THROUGH 18/00Z IN THE UPSLOPE REGION AND THE MOUNTAIN
PEAKS OF NE CO/SE WY AND OUT OVER NE/KS WITHIN THE WARM CONVEYOR.

FORECAST CAPE IN THE NAM AND SREF CENTRAL PLAINS OF 500-1000 J/KG
WILL SUPPORT EMBEDDED CONVECTION MARCHING ONLY VERY SLOWLY
EASTWARD AS DEEP FLOW MAINTAINS A STRONG MERIDIONAL COMPONENT.
SOME S-N OR SW-NE CELL TRAINING MAY PRODUCE LOCALLY HEAVY
RAINFALL...BUT WITH DRY AIR AND MODERATE TO STEEP LAPSE RATES IN
THE SOUNDINGS INITIALLY...THERE SHOULD BE ENOUGH COLD POOL
DEVELOPMENT TO PUSH THE AXIS OF HEAVIER CELL DEVELOPMENT ONE
DIRECTION OR ANOTHER...AND IT MAY BE DIFFICULT TO REPLENISH A
SUPPLY OF MODERATE INSTABILITY ONCE IT BECOMES CONSUMED...GIVEN
RATHER CONTINUAL DEVELOPMENT OF PRECIPITATION IN THIS REGION
BENEATH THE STRONGLY DIFLUENT UPPER FLOW. WITH THIS AREA HAVING
BEEN DRY RECENTLY WE REFRAINED FROM INTRODUCING A RISK OF
EXCESSIVE RAINFALL...BUT ONE COULD BE CONSIDERED DURING LATER
UPDATES.


...TEXAS AND THE SOUTHEAST STATES...

THIS AFTERNOON/EVENING...MID/UPPER LEVEL DIVERGENCE WILL GENERATE
BROAD AND DEEPER ASCENT WHERE THE SOUTHERN STREAM OF THE POLAR JET
AND SUBTROPICAL JET SPLIT OVER MS/AL AND SE LA. THUNDERSTORM
DEVELOPMENT AT 18Z WAS INCREASING NEAR LOW LEVEL BOUNDARIES...A
LOOSELY DEFINED FRONT AND THE SEA BREEZE. BUT ORGANIZATION ON
LARGER SCALES SHOULD SUFFER AS THE DEVELOPING UPPER FORCING MOVES
OFF THE AXIS OF GREATER INSTABILITY LOCATED BACK ACROSS THE
WESTERN GULF COAST. EMPHASIS SHOULD GRADUALLY SHIFT BACK WEST WITH
TIME AS A LARGE UPPER TROUGH LEANS INTO TEXAS. DIFLUENT MID LEVELS
WILL COMBINE WITH AN INCREASING AXIS OF MOISTURE/INSTABILITY TO
PRODUCE GREATER
COVERAGE AND ORGANIZATION OF THUNDERSTORMS PRODUCING HEAVY RAIN
OVER THE TEXAS HILL COUNTRY TO THE UPPER TX COAST LATER TONIGHT
AND ESPECIALLY ON FRIDAY. PRECIPITABLE WATER VALUES WILL BE
SOMEWHAT ANOMALOUS...AND HEAVY RAIN RATES ARE EXPECTED...BUT OF
GREATER CONCERN WOULD BE THE POTENTIAL FOR REPEATED ROUNDS OF
CONVECTION SHOULD THE AXIS OF DEEPER MOISTURE...ORIENTED GENERALLY
WEST TO EAST...BECOME REINFORCED BY THUNDERSTORM
OUTFLOWS...PRODUCING A STRONGER LOW LEVEL FOCUS FOR REDEVELOPMENT
AHEAD OF THE SLOW MOVING UPPER TROUGH.

WE DEPICTED A RELATIVE MINIMUM DURING THE DAY 1 PERIOD OVER
NORTHEAST TEXAS. WARM ADVECTION SHOULD CONTRIBUTE TO SCATTERED
SHOWERS/STORMS THERE AND OVER ADJACENT PARTS OF OK/AR/LA. BETTER
DEFINED DEEP ASCENT WILL OCCUR FARTHER WEST...HOWEVER...ALONG THE
PACIFIC FRONT AND WITHIN THE STRONGER LOW LEVEL FLOW AHEAD OF THE
DEVELOPING CLOSED UPPER SYSTEM. THIS MAY ALSO BE A CASE IN WHICH
RICH MOISTURE AND INSTABILITY ARE INTERCEPTED OVER CENTRAL AND
SOUTH TEXAS...AS REFLECTED IN MOST OF THE OPERATIONAL MODEL
SOLUTIONS.


...OHIO VALLEY/MID-ATLANTIC/NORTHEAST...

A WEAKENING SOUTHERN STREAM SHORTWAVE WILL BE ABSORBED BY A
STRONGER NORTHERN STREAM WAVE DROPPING THROUGH THE GREAT LAKES AND
INTO NEW ENGLAND BY FRIDAY MORNING. BOTH OF THESE FEATURES WILL
CONTRIBUTE TO WARM ADVECTION...ESPECIALLY ABOVE THE
SURFACE...WHICH WILL TAP INTO A PLUME OF SATURATED MID LEVEL AIR
OVER THE SOUTHERN APPALACHIANS AND CAROLINAS. THOUGH INSTABILITY
WILL BE LACKING...THE ORGANIZED LIFT AHEAD OF THE NORTHERN STREAM
WAVE SHOULD BE SUFFICIENT TO SQUEEZE OUT WIDESPREAD 0.10 TO 0.25
INCH RAINFALL FROM THE UPPER OHIO VALLEY TO NEW ENGLAND AND PARTS
OF THE MID ATLANTIC. WITH DIURNAL HEATING AT THE TAIL END OF THIS
ACTIVITY ON FRIDAY...SOME LOW-TOPPED CONVECTION MAY DEVELOP OVER
VA/MD...AND WE FOLLOWED THE GFS IN DEPICTING THIS. ELSEWHERE...WE
BLENDED THE PREVIOUS FORECAST TOWARD THE 00Z ECMWF AND OUR
IN-HOUSE ENSEMBLE. THESE MODEL SOURCES CAPTURED THE TREND TOWARD
SOMEWHAT GREATER COVERAGE OF LIGHT...BUT NONETHELESS
SIGNIFICANT...PRECIPITATION...ESPECIALLY IN A SWATH ACROSS NE PA
AND SRN NY.

BURKE

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

24HR QP VT 18/00Z
 0.01 537210 540186 537180 532181 531177 530172 527166 521162
      516163 513162 510164 506169 498177 497187 502192 506198
      508204 510215 509225 499232 498235 498239 496243 493242
      490240 488243 488246 489251 489257 490264 493271 495278
      498287 501291 506292 510291 512288 515280 518273 520266
      521256 522251 522248 522242 521239 520231 521224 523219
      526222 529223 532221 537210
 0.01 481690 480675 478667 475662 470651 462643 456638 453636
      449635 441636 433641 428648 423655 418662 414670 407688
      404701 401711 399721 397733 395739 393743 394745 394747
      385753 382756 380759 377767 371774 370779 370782 371786
      372790 376794 375799 373800 372797 369794 364796 361799
      358801 355801 350801 348797 344789 341784 340781 343779
      349773 351769 353764 357755 361743 352731 348724 345721
      341720 323721 319724 318728 314738 290763 249810 252805
      257812 271820 279825 283832 287836 288843 290848 289854
      285862 281871 279876 278885 277891 275896 263929 261933
      262936 267945 267958 266964 261965 252967 248973 244981
      241990 239993 242996 249000 259996 264994 268994 269997
      269002 270005 271010 275013 281018 288022 298024 302026
      308027 319025 327023 336021 345018 355017 365017 368020
      368025 366029 365036 361049 357053 355058 355064 357067
      358072 355076 352079 353083 353088 353092 352095 352099
      352105 355107 357110 355118 357120 362124 370116 374115
      376120 375123 374130 376132 378130 385125 394122 396121
      402121 405126 408126 412123 417121 419116 416113 412109
      414106 416104 418097 419093 420090 423089 431097 432097
      434095 433092 430087 429084 430082 434080 436076 440067
      441062 441054 442040 444033 444024 444008 444995 443988
      442984 437964 431959 424954 421951 415951 403951 391951
      386947 381945 373941 368936 359921 354915 349907 344899
      340890 340886 342881 348874 351864 351853 352846 354843
      359835
 0.01 359835 374830 375841 375845 374848 369860 369865 372864
      377862 387855 397848 407841 409839 412838 417834 427827
      437820 442817 447813 453809 457805 455786 454777 453773
      453768 459756 464751 465746 468739 470731 473716 474709
      476702 481690
 0.01 326796 324795 322793 319791 315792 312794 310795 306796
      305797 307799 310799 312800 316800 319799 323799 326796
 0.01 340089 342094 346105 349113 352116 353118 351120 348119
      346118 345114 344109 343106 341103 338100 336096 336091
      338089 340089
 0.25 445656 441653 436657 432662 429668 424679 420691 417705
      416712 418712 425701 431690 436680 441669 444662 445656
 0.25 427733 427730 426729 423730 418738 413746 410754 407764
      406769 407775 409778 413776 418769 421760 427753 428748
      427743 426738 427733
 0.25 432056 433047 434036 434024 435013 433996 432990 430984
      428978 424973 421966 416963 395970 389970 383969 376966
      371962 366958 361956 355956 351956 343951 337951 334957
      332965 335972 336975 336980 334986 330990 323992 317992
      311992 319985 320979 319974 319962 319945 323935 326930
      328924 325908 325898 326889 329877 332864 337851 339844
      339837 335826 327818 317822 311825 307827 305826 302819
      299815 292808 282790 275797 264802 267807 271812 277816
      281821 286824 292825 296826 299827 299831 300838 298845
      295859 286881 281893 277909 276916 278921 280927 280934
      275947 275964 273976 273982 275989 281000 284005 290010
      298016 305018 310017 321010 327008 331008 343007 355005
      360004 368004 377006 379011 375024 376028 378033 379036
      378040 374045 369048 367052 368055 373059 369063 373073
      374080 378086 381087 382092 377094 376099 379103 384103
      388100 394100 399096 401092 402086 419076 427067 430062
      432056
 0.25 408100 408098 408096 407098 407100 408102 408100
 0.25 343746 340740 338736 334732 329735 327740 325747 324749
      321750 318750 311753 308757 306763 305770 308775 313777
      319778 326776 331773 335769 340765 342759 343752 343746
 0.50 429058 429051 429043 429033 431021 432009 430996 428987
      424980 418973 416970 410969 403972 395975 387977 379974
      373970 368965 362964 357965 350969 347977 344984 342997
      346001 352001 359000 369997 375997 381004 383007 384012
      384025 388031 389038 386043 380047 377050 377055 379059
      380065 377069 376076 377081 381080 394078 399069 405072
      408074 413073 419067 425064 429058
 0.50 337758 337751 334749 332752 329756 326758 323759 321759
      317762 316765 318768 322768 327767 330764 334761 337758
      337758
 0.50 327853 328846 327839 322833 314835 310837 306839 302847
      301856 298863 294872 287887 282904 281910 283916 286918
      287922 288933 287939 285943 281944 279948 279959 277982
      278989 280993 285999 296010 300012 304013 309009 311007
      308005 306002 301996 304985 308978 310971 310960 309947
      311937 314930 317920 322879 327853
 0.50 294818 292814 289810 286808 283806 280803 276802 273805
      275809 278813 281817 283819 287820 292820 294818
 1.00 425058 426054 426049 424044 422032 426004 424992 421987
      417984 412980 409977 401980 392985 385991 392011 395024
      405028 405033 403037 399041 395043 390046 388050 390054
      395057 398060 404062 412066 425058
 1.00 368985 368981 366978 364978 361977 358978 357980 354983
      352985 352989 354991 357992 358991 362990 364988 366987
      368985
 1.00 321860 321854 320850 319848 314848 310848 307850 304857
      303864 300870 295883 289894 286901 286906 291910 297912
      303911 307905 311900 313894 316879 319871 320864 321860
 1.00 301004 300002 299000 297999 295998 294000 295002 296004
      297004 298006 300006 301004
 1.00 301971 302968 301967 300966 299966 299968 301971 301971
 1.00 300937 301935 301933 301931 300928 300926 300924 299922
      297924 296926 295928 295929 295931 295933 295935 296937
      297938 299938 300937
 1.00 293993 295985 295977 295968 295960 292954 290952 287954
      285958 284966 282972 280978 281985 284990 288994 291995
      293993
 1.50 424053 420046 419043 415041 410042 404044 397047 392050
      393052 397055 402059 411060 414061 416060 421057 424053
 1.50 419008 418999 414991 412989 408987 406985 401986 396989
      393991 391994 390998 392001 396007 400014 401018 402019
      409015 413015 416013 419008
 1.50 316866 316860 315856 311854 308856 306865 301874 299882
      295891 293895 292899 300902 304900 306897 310888 312877
      315869 316866
 1.50 293966 293964 293962 292960 292959 291960 291962 291964
      291966 292968 293966
 1.50 290987 291985 291983 290981 290980 289979 288977 288976
      286976 284976 283978 283981 283983 284985 285985 286987
      287987 288988 290988 290987
 2.00 418055 420050 418048 416048 413050 411051 408050 404049
      401049 397050 397053 399054 400056 404058 407057 410056
      413055 416056 418055
 2.00 412005 411003 410999 408997 406996 403993 401992 398992
      396994 395998 397000 399002 401003 403005 405007 408008
      410008 412005

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