Quantitative Precipitation Forecast
Issued by NWS

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120
FXUS04 KWBC 210659
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 AM EDT THU MAY 21 2015


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


DAY 1

...SOUTHERN PLAINS...

EVOLVING MCS ACROSS CENTRAL AND SOUTH TX EARLY THIS AM CONTINUES
TO PROGRESS E-ESE AT A FAIRLY DECENT CLIP...AS THE ~20 KT S-SE LOW
LEVEL INFLOW AND WEAK SW-WSW MEAN FLOW IS LEADING TO INCREASED
DOWNWIND PROPAGATION PER THE LATEST RAP MBE/CORFIDI VECTORS. THE
MODELS HAVE HAVE BEEN DOING A POOR JOB IN HANDLING THIS FEATURE
(AT LEAST IN TERMS OF QPF)...INCLUDING MOST OF THE HIGH RES RUNS
OUTSIDE OF RECENT HRRR RUNS. FOLLOWING THE MCS...CONSIDERABLE
SPREAD IN THE GUIDANCE CONTINUES WITH THE QPF  LATER THIS MORNING
AND AFTN. WPC CONTINUED TO 2 AXES OF HEAVIER AMOUNTS...ONE ACROSS
SOUTH TEXAS ALONG THE SURFACE FRONT (WHICH WILL BECOME
STATIONARY)...WHERE THE CONTINUED AVAILABILITY OF PWATS OF
1.75-2.00 INCHES...MODEST DEEP-LAYER INSTBY (MUCAPES GENERALLY
1000-2000 J/KG)...AND THE PRESENCE OF A LOW-LEVEL BOUNDARY TO
FOCUS MOISTURE CONVERGENCE WILL ALLOW FOR LOCALLY HEAVY RAINFALL
AS MUCH OF THE HIGH RES GUIDANCE SHOWS ISOLATED TOTALS OF 3-6+
INCHES.

FARTHER NORTH...A RATHER ATYPICAL SETUP FOR MID MAY WILL BE THE
SHARP BAROCLINIC SETUP NORTH OF THE SURFACE BOUNDARY WITH THE WELL
BELOW NORMAL SFC-850 MB TEMP PROFILE WHILE PWATS REMAIN CLOSE TO 2
STANDARD DEVIATIONS ABOVE NORMAL. SE LOW-LEVEL INFLOW WILL VEER TO
THE SOUTH OVERNIGHT AND INCREASE TO 20-30 KTS ACROSS THE TX
PANHANDLE...WHERE THE MODELS CONTINUE TO SOME ELEVATED INSTBY TO
WORK WITH ALONG WITH THE UPSLOPE LOW-LEVEL FLOW AND UNSEASONABLY
FAVORABLE (OPTIMAL) ISENTROPIC ASCENT.


 ...MID ATLANTIC STATES TO LONG ISLAND AND ADJACENT COASTAL SRN
NEW ENGLAND...

MODEL CONSENSUS IS FOR A WELL DEFINED 700 MB WAVE TO TRACK FROM
THE MID MS VALLEY ACROSS THE OH VALLEY AND ACROSS THE CENTRAL TO
SOUTHERN APPALACHIANS THIS AFTERNOON/EVENING...THEN OFF THE COAST
BY 12Z FRI. 700 MB THETA-E ADVECTION AHEAD OF THE WAVE HELPS TO
PRODUCE WIDESPREAD RISING MOTION.  ABOVE AVERAGE PW VALUES WILL
PERSIST AHEAD OF THE COLD FRONT EXPECTED TO MOVE EAST ACROSS THE
TN VALLEY AND APPALACHIANS. OVERRUNNING RAINS TO THE NORTH OF THE
ASSOCIATED WEAK SURFACE WAVE PUSHING EASTWARD WILL BRING LIGHT TO
MODERATE PRECIP AMOUNTS FROM THE OH VALLEY AND THE CENTRAL TO
SOUTHERN APPALACHIANS AND VA/NC. WPC UTILIZED A MULTI-MODEL BLEND
WITH THE QPF (ECMWF/GFS/NAM/RGEM)... WEIGHTING MORE TOWARD THE
ECMWF WHICH HAS EXHIBITED BETTER RUN-TO-RUN CONTINUITY OVER THE
PAST 2 RUNS. THE 00Z NAM IN FACT HAS TRENDED NICELY TOWARD THE
ECMWF WITH THE QPF OVER THE MID ATLANTIC REGION.


...CALIFORNIA/PACIFIC NW...GREAT BASIN...CENTRAL/SOUTHERN
ROCKIES...

A REGION OF ABOVE AVERAGE PW VALUES WILL REMAIN ANCHORED FROM
NORTHERN CALIFORNIA/OREGON INTO THE NORTHERN GREAT BASIN WITH
STANDARDIZED ANOMALIES OF 1-2 STD DEVIATIONS ABOVE NORMAL OVER THE
SOUTHERN OR CASCADES INTO ADJACENT NORTHWEST CA.  SCATTERED SHOWER
ACTIVITY LIKELY AGAIN IN THIS ABOVE AVERAGE PW AXIS WITH 700 MB
VERTICAL VELOCITY MAXIMA OVER THE SOUTHERN OR CASCADES LEADING TO
A RAINFALL MAXIMA IN THAT REGION. THIS COINCIDES WITH A MAX REGION
OF UPPER DIFFLUENCE.  ELSEWHERE...MAXIMA IN THE RANGES OF
NORTHEAST OR/SOUTHERN ID/NORTHWEST WY/NORTHERN NV COINCIDE WHERE
ASCENT IS AUGMENTED BY UPSLOPE FLOW AS 700 MB CONVERGENCE MAXIMA
ROTATE AROUND THE BROAD CIRCULATION CONTINUING ACROSS CA/NV AND
ADJACENT PORTIONS OF THE GREAT BASIN.  MANUAL QPF USED A
MULTI-MODEL BLEND...HIGHLIGHTED BY THE ECMWF AND IN-HOUSE PSEUDO
BIAS CORRECTED QPF.

HURLEY

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

24HR QP VT 22/12Z
 0.01 387233 393238 401239 410242 416247 425250 428249 433249
      448247 454243 456241 458237 460232 464232 467230 471231
      473234 474238 476242 481241 486236 493233 500230 516224
      519217 520215 520212 516207 512204 506203 500206 497207
      494207 491200 488199 486201 479201 472200 466201 460201
      457199 457196 457192 458190 462194 464193 467190 469185
      467172 465166 468165 471165 473164 474159 472152 471147
      473143 477137 476134 472127 469112 463102 460098 455093
      453083 450082 448077 446075 443074 437072 431068 428063
      423059 421052 420042 419034 414007 412001 408997 398988
      392980 388976 382974 363958 346946 345930 345923 345919
      343917 335908 331921 328927 324927 323923 323904 322889
      321874 319865 319856 318848 319843 319834 319830 320826
      322823 322819 324812 329801 328795 322793 315800 307807
      302804 296803 290801 283801 283789 284781 283778 280775
      277776 273781 270787 269794 268796 265797 260796 253797
      248801 246806 248811 250815 252814 277818 284818 286826
      286831 290835 293839 295845 297852 298860 298868 297876
      296880 296887 293895 289893 285895 285904 287910 288919
      293931 293939 292945 287956 284961 279964 271970 259972
      255977 250981 244983 237983 232985 230991 229007 230015
      232021 240027 246034 255041 260045 265046 271048 277049
      292051 297052 303053 312061 318069 326076 337082 342085
      348086 355087 360086 365088 371091 375094 375103 383097
      389099 389107 392109 392112 386114 381115 377119 373123
      373129 378130 382126 386123 394124 398129 394135 390138
      388139 387143 386157 384160 382160 376163 374168 370171
      366170 365168 361167 360170 360174 358176 354180 350183
      346188 345191 347198 352202 356206 364213 369215 376218
      377214 374212 370210 370207 374207 379207 385209 390212
      396214 402217 408219 406224 400225 395224 390227 388229
      387233
 0.01 513683 513678 511675 510671 508657 506654 502655 493657
      490659 488665 486668 483669 470678 469684 470691 472695
      471699 468703 465702 459709 458712 457717 457730 457742
      455752 453764 454775 456785 455798 456808 455812 456819
      459828 462830 465827 467832 471833 476829 481809 482804
      482796 484786 483773 481768 481761 478749 479744 481739
      487734 492727 503713 512697 513683
 0.01 514744 512739 509734 507732 503733 500737 497740 497745
      499747 503749 506751 511750 512747 514744
 0.01 440667 438656 437651 435648 431645 423647 416650 409654
      398661 391665 384669 377672 372675 365678 359683 355688
      352694 336715 333720 331724 330727 324740 317752 310763
      302770 299773 298777 299782 301785 307788 311787 315785
      319782 325779 332779 335782 337784 339791 344796 356802
      360807 361810 361814 359821 356829 353835 352842 357840
      364836 374834 379830 384826 392815 396808 399801 402796
      404793 407792 409789 413788 419783 417767 415760 412764
      411767 408770 401769 399766 400762 404755 407749 409740
      412735 417729 424718 427712 429705 433698 435691 437685
      438679 440667
 0.01 458886 458880 456876 456871 454867 453862 452857 448853
      443853 441849 440837 439825 437818 434818 430821 427829
      426836 426842 425846 429864 431871 435878 439885 442894
      444898 446899 451903 455898 456893 457889 458886
 0.01 345182 345178 344175 344171 343169 341168 339169 337170
      335171 337172 340173 343175 343180 344182 345182
 0.25 485705 484702 482701 479704 477709 476715 472716 472723
      473730 474734 475732 475727 476724 478723 481718 482715
      484710 485705
 0.25 475738 473734 469736 466742 465752 463762 463772 463782
      468780 471772 472763 473753 474743 475738
 0.25 464224 465221 465219 464217 463217 461217 461218 459219
      458219 458222 459222 460223 462224 464224 464224
 0.25 463178 463175 461174 456174 453171 449173 447176 445179
      444186 445191 449193 451190 453186 455181 460180 463178
 0.25 445221 443216 443211 445207 446204 444202 441197 438197
      434197 433195 430190 431186 430184 427184 425186 419194
      417200 419204 422209 425213 428214 429217 427219 426222
      428224 434225 438225 443223 445221
 0.25 439207 438206 437204 437203 436204 435205 434205 433207
      432210 432212 432213 433212 434212 436211 438209 438208
      439207
 0.25 423231 424229 424227 423226 422226 421226 419227 418228
      417229 416229 417232 418234 420234 421233 422233 423231
 0.25 421673 420666 418662 415662 410663 396671 381679 373684
      368689 362697 360704 358713 359718 358721 356724 353726
      347732 340733 337734 334737 331745 329753 327762 329766
      334765 336765 340767 342770 343774 344780 345785 351789
      357794 364796 372795 377792 380789 385784 389776 395761
      401744 403735 407727 414710 419694 421684 421673
 0.25 414231 415229 414227 412227 411228 410230 411232 413231
      414231
 0.25 398203 397196 394188 392185 388183 384183 380185 378187
      375187 372185 368183 364184 362186 365191 372196 378201
      384205 392208 396208 397205 398203
 0.25 411061 410057 410049 408038 406028 402019 399011 393003
      386998 378995 375994 371995 367998 361996 355993 349987
      342982 335978 331977 330971 330959 331954 331947 329945
      325948 323956 321967 319971 318977 319986 320990 319992
      317995 309000 305000 302998 299994 297989 296979 299970
      305951 307940 307936 308928 306918 307913 311910 312906
      312901 311890 307887 304889 300895 296903 297910 299914
      301918 300923 299935 297944 295954 292961 288966 285968
      279973 276975 272977 268979 266983 264988 263994 264996
      262999 258001 255999 248995 240993 238996 236999 237003
      241012 253024 258028 264029 270028 287035 298036 306036
      310036 315039 320046 325052 328054 332053 336054 339057
      342060 343064 346068 347073 350077 354078 361073 363070
      366071 368076 368081 369085 372086 380083 383079 387078
      390080 394078 401074 407068 409063 411061
 0.25 375064 374062 373061 372060 371061 371062 373064 375064
      375064
 0.25 373046 373044 374042 373039 372039 371040 370041 370043
      371044 372046 373046
 0.25 262807 263805 261803 259802 257803 256803 256804 254806
      254808 256808 258808 260808 262807 262807
 0.50 414684 414679 412676 406675 399677 393680 381687 376691
      372697 370703 370710 372713 375711 383709 385713 383716
      381722 378727 374732 369737 368743 366749 365757 364765
      365769 367772 367781 364787 366790 370789 374785 382777
      386771 388765 393752 397739 399733 402727 408715 412701
      413692 414684
 0.50 393202 391199 388194 385191 382190 378191 373188 369186
      367187 371190 375193 378196 381199 385202 389203 392203
      393202
 0.50 407056 407051 406048 404046 401046 395047 390045 386047
      383051 383054 385056 387059 386061 383063 385065 390066
      395064 400060 405058 407056
 0.50 372718 370713 366716 361724 358728 356734 354739 347740
      339745 338750 340755 343758 348759 351755 353751 359742
      363739 365733 365727 369723 372720 372718
 0.50 359067 359065 359064 357063 355064 353066 352068 351070
      350073 351073 353074 354073 355073 356071 358069 358067
      359067
 0.50 358025 359022 358020 356018 352014 348011 344006 339997
      336991 333989 330990 326995 324000 320005 319011 316018
      318025 324034 328039 335040 348038 353037 356031 358025
 0.50 294014 295009 294006 291000 287993 281989 278988 275989
      274994 275999 270005 267007 266011 266016 269019 274022
      283023 291023 292017 294014 294014
 0.50 289979 289977 289974 288973 286973 285974 284974 283976
      282976 282978 282981 283982 284982 286982 288981 288980
      289979
 1.00 399716 399714 399712 398711 396711 394712 394713 393715
      393718 393720 393722 392723 392725 392727 393727 395727
      395726 396724 397721 399719 399718 399716
 1.00 400055 401053 400053 399054 398055 399055 400055 400055
 1.00 390732 390729 386730 383734 380740 379746 376753 374758
      379757 382755 383752 385749 387749 385749 384745 384742
      386740 389735 390732
 1.00 334019 334018 334017 334014 333012 331010 329008 327007
      326007 325007 325010 324011 323012 323014 323016 325018
      326018 327019 329019 330020 332020 334019 334019
 1.00 287014 288010 287008 284005 282005 280006 276007 275007
      272009 272013 274015 277015 280016 283017 286016 287014
 1.50 284012 284010 282010 280010 278010 276010 274011 276012
      278013 279013 280014 282014 283014 284012

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