Quantitative Precipitation Forecast
Issued by NWS

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203
FXUS04 KWBC 221900
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM EDT SAT APR 22 2017


PRELIM DAY 1 QPF DISCUSSION
VALID APR 23/0000 UTC THRU APR 24/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1...

...S-CENTRAL APPALACHIANS...MID ATLANTIC...SERN US...

IT REMAINS THE CASE THAT THE SLOW MOVING...LARGELY W-E ORIENTED
UPPER TROUGH CURRENTLY ACROSS THE CENTRAL CONUS WILL PIVOT INTO
THE LOWER MS VALLEY BY THE END OF THE PERIOD...DEEPENING AND
IN-TURN BECOMING MORE NEUTRALLY-TILTED TO NEG-TILT LATER PERIOD.
THE MODELS ARE FAIRLY WELL CLUSTERED MASS FIELD WISE DURING THE
DAY 1 PERIOD...BOTH ALOFT AND AT THE SURFACE...WITH THE EVOLVING
PATTERN STILL LEADING TO A MODEL CONSENSUS OF A ~1008 MB SURFACE
LOW IN NORTHWEST GA BY 12Z SUN. THE DECELERATING SYSTEM ALONG WITH
INCREASINGLY FAVORABLE DYNAMICS (UPPER DIFFLUENCE COUPLED WITH
PROLONGED RIGHT ENTRANCE REGION (FRONTOGENETIC) FORCING VIA THE
UPPER JET STREAK OVER THE NRN MID ATLANTIC-NORTHEAST) WILL FAVOR A
BROAD AREA OF OROGRAPHICALLY-ENHANCED HEAVY RAINFALL ACROSS ERN
TN/KY EASTWARD INTO THE CENTRAL-SOUTHERN APPALACHIANS...AND
SPREADING IN ERNEST NEWD ACROSS THE MID-ATLC/SE SUN WITH SLOW
SYSTEM TRANSLATION ALOFT. THE ROBUST DEEP-LAYER DYNAMICAL FORCING
WITHIN A SHARPENING LOW-MID LEVEL FRONTOGENETIC ZONE AND MATURING
WARM CONVEYOR BELT (WCB) WILL CONTINUE THE HEAVY RAIN THREAT
OVERNIGHT SAT-SUN...MAINLY FOCUSING ALONG/NORTH OF THE SURFACE LOW
AND ASSOCIATED STATIONARY FRONT...EVEN AS THE ELEVATED INSTABILITY
DIMINISHES PER THE MODELS. THIS ESPECIALLY ACROSS THE
AFOREMENTIONED HIGHER TERRAIN AREAS...WHERE THE UPTICK IN
SOUTHERLY LOW-LEVEL MOIST UPSLOPE FLOW ALONG WITH INCREASINGLY
HEAVY PW AND MOISTURE FLUX ANOMALIES AS PER THE GULF OF MEX AND
OFF THE WRN ATLC. THIS WILL FAVOR OROGRAPHIC AUGMENTATION WITH THE
RAINFALL RATES. LATEST WPC QPF WAS COMPOSED OF A MUTLI-MODEL BLEND
WITH A GOOD DOSE OF WPC OVERNIGHT CONTINUITY AND THE REASONABLY
CLUSTERED 12 UTC ARW ALONG WITH SOME INPUT FROM THE 12 UTC
GFS/NAM/NMMB. THIS YIELDED AREAL-AVERAGE MAX TOTALS OF 1-3 INCHES
CENETRED ACROSS ERN TN...SE KY...SW/SRN VA...SRN WV...WRN/CENTRAL
NC...NW SC...AND NRN/CENTRAL GA. PER THE ARRAY OF HIGH-RES CAM
GUIDANCE...LOCALIZED AMOUNTS OF 3-5" ARE ANTICIPATED THAT COULD
LEAD TO SIGNIFICANT RUNOFF ISSUES LOCALLY THAT SPREAD INTO DAY 2.

IN TERMS OF THE EXCESSIVE RAINFALL OUTLOOK FOR DAY 1 INTO DAY
2...WPC DELINEATED A FAIRLY BROAD SLIGHT RISK AREA WHICH
ENCOMPASSED NOT ONLY THE AFOREMENTIONED MAXIMUM DETERMINISTIC
QPF...BUT ALSO TOOK INTO ACCOUNT THE LATEST NATIONAL WATER MODEL
(NWM) SOIL MOISTURE GUIDANCE...LATEST FFG VALUES...AND THE SSEO 40
KM NEIGHBORHOOD PROBABILITIES ABOVE 30% WHERE 3 AND 6 HOURLY SSEO
MEAN QPF EXCEEDS THE CURRENT FFG.

...KEYS/SOUTH FLORIDA...

SLOW MOVING WEAK UPPER LOW WEST OF THE FL STRAITS WILL ALLOW FOR A
PERSISTENT AREA OF UPPER LEVEL DIFFLUENCE ACROSS SOUTH FL WILL
MAKE FOR A RATHER NARROW CORRIDOR OF HEAVY RAINFALL FOCUSED OVER
THE KEYS AND THE FAR SOUTHERN PORTION OF THE FL PENINSULA...AND IN
PARTICULAR THE WESTERN KEYS CLOSER TO THE LOW-MID LEVEL
CIRCULATION AND THUS MOST CONVERGENT LOW-LEVEL MOIST INFLOW.
MUCAPES OF 1000-1500 J/KG COUPLED WITH PWATS NEAR 2 INCHES (WHICH
IS ABOUT 3 STANDARD DEVIATIONS ABOVE NORMAL FOR LATE APRIL) WILL
PROVIDE A RICH THERMODYNAMIC PROFILE THAT WILL COINCIDE WITH THE
FAVORABLE DYNAMICAL FORCING IN PRODUCING HIGHLY EFFICIENT RAINFALL
RATES. WPCQPF...USING A MULTI-MODEL BLEND WHICH INCLUDED HIGH-RES
GUIDANCE/MEANS...AND LEANING ON THE 12 UTC ARW AND WPC CONTINUITY
INDICATED POTENTIAL FOR A MAX OF 2-5+" OVER THE WRN KEYS. THIS IS
ALSO WHERE THE LATEST SSEO 40 KM NEIGHBORHOOD PROBABILITIES SHOW A
>30% CHANCE OF 3 HOUR QPF EXCEEDING THE FFG...PARTICULARLY IN THE
AFTERNOON INTO THE EARLY EVENING AND WPC UPGRADED TO A SLIGHT ERO
THREAT AREA.

HURLEY/SCHICHTEL

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

24HR QP VT 24/00Z
 0.01 549159 550151 549145 547139 545133 542124 540118 539112
      535101 531093 526084 521076 516069 510062 504040 492992
      489982 487969 483943 481916 481909 482900 485890 499864
      523835 524811 510789 492781 485750 484716 485672 483660
      483653 480648 476639 473636 469634 458638 450637 442635
      432637 429639 427644 425648 427657 431668 433672 437676
      443679 451682 456683 460685 466693 472698 474699 474702
      472705 468713 464724 461733 459744 458751 459759 458765
      459774 460781 462786 461797 461805 460810 461827 462834
      461839 461855 460870 457880 454891 454905 455921 456927
      457936 460961 465986 470004 473016 475029 481051 484060
      485065 487069 493079 495082 499081 502082 503084 506091
      507096 509101 511106 512111 515123 519132 520135 519138
      514139 511140 506139 502139 500144 496145 493142 485135
      476133 473129 474120 474113 472107 472100 467099 458098
      456099 454098 450096 445096 440097 429096 426099 424104
      419107 415108 413115 422112 430112 435112 437117 442125
      434133 429140 426144 426148 431152 433156 427165 426177
      427175 430171 432167 435165 438170 438176 438182 440185
      443188 446189 446193 450195 455195 459193 461189 464186
      466182 464179 462180 460178 462173 466170 470169 476170
      480173 482175 487185 489190 489198 487202 484205 476210
      468212 453213 437216 432218 428220 421228 428232 420233
      411234 407236 405240
 0.01 405240 405244 409247 413247 419249 430249 440251 446252
      452253 458255 463259 473264 477266 481270 486272 490276
      493277 496282 503290 506291 508290 511286 513280 517275
      519270 521261 524249 527242 528234 533220 536207 537198
      539192 542173 543166 545162 549159
 0.01 523240 522237 522235 521232 520234 520236 521239 522242
      523240
 0.01 460714 456710 452707 447707 444712 439712 432713 431716
      434716 436717 439717 441718 444720 445722 447725 451724
      452722 457718 460714
 0.01 367898 375876 382840 392798 392773 397742 387724 360729
      331770 295785 268776 252774 238781 234784 233788 232800
      230809 230816 231823 233827 236830 240833 245834 249831
      252828 261828 271830 275831 278834 282838 284842 286846
      285851 282862 279871 280874 279875 276879 265892 253907
      249915 247926 240946 237955 236967 235979 235986 236990
      241997 247004 251006 254006 261009 265009 267008 270004
      272000 275995 277992 278985 278971 278959 279952 281948
      288940 296935 302928 308923 323912 339902 344900 349901
      354902 357905 361908 364905 367898
 0.01 291077 291070 288066 281063 275062 270060 263059 259060
      262064 267068 271071 276074 281077 289078 291077
 0.25 538145 537144 536142 534141 533143 531143 531146 530149
      530150 531151 532154 533154 534155 535156 536155 536153
      536150 535149 535147 536145 537147 538145
 0.25 513266 514254 513246 511238 508230 503218 498212 493209
      488211 483214 481217 482220 486225 488229 489233 488236
      484236 479231 478229 472226 472224 478217 471218 467218
      460217 448219 436223 440225 446225 454226 460230 459235
      457237 451239 451241 455242 462244 475251 481255 486260
      494270 500276 505279 513266
 0.25 519183 519180 518178 517177 516177 515176 514176 513176
      512176 510176 509177 509180 509182 511183 512183 514183
      516183 517183 519183
 0.25 484017 484992 482972 479950 477929 476917 474908 470909
      469912 467922 466935 467947 469967 471977 473987 477005
      480013 482017 484017
 0.25 383798 383789 382782 381766 376753 372744 367741 362741
      357743 354747 348755 343765 334783 332795 331809 327818
      323821 318823 309827 305830 301834 298845 296855 298860
      302859 310855 318861 319875 305889 291905 292915 308908
      327886 351881 367854 374837 380814 383798
 0.25 273803 271797 266794 259787 255782 251779 246781 243785
      240791 239797 235808 234814 235820 238826 243828 249826
      254823 261822 265819 268814 270808 273803
 0.50 509254 509249 508243 506234 503228 500220 498217 494215
      490216 487218 491224 493233 496242 501248 505254 509254
 0.50 501269 502263 501259 497255 495251 490244 487241 483242
      480238 478233 474231 472234 470238 471242 476245 481246
      487254 491260 497268 500270 501269
 0.50 476964 476959 476954 475952 475947 474942 473939 472935
      472939 472944 472949 472952 473957 474962 474964 476964
 0.50 379780 378771 375761 372754 367749 363749 361750 357756
      354762 353771 352782 352785 349789 347790 342790 340793
      341799 342805 338812 334818 328822 316830 310835 306839
      303846 304849 308848 321842 326841 328844 329855 330863
      331868 334871 337873 341873 349870 354865 358860 366847
      372833 377817 379809 380800 380788 379780
 0.50 266802 266799 264797 261795 254791 250788 247787 243790
      241793 240797 239802 236812 237820 240823 243826 248825
      251822 257817 259816 259813 258811 264804 266802
 1.00 376801 376793 375786 374772 372766 369762 365766 364771
      361781 358790 350809 345817 338823 334826 332829 336832
      335837 336849 341858 342863 344865 347865 353859 359851
      363843 367833 370824 374813 376801 376801
 1.00 258801 253799 248798 244795 242799 240805 239811 240819
      243824 247824 248822 251816 252810 255806 258801
 1.50 372801 372791 371787 369784 363789 360794 354806 348818
      344824 341830 339836 340843 343850 346855 349855 351853
      356848 359843 362837 368824 370817 371810 372801
 1.50 250812 250808 248805 247802 246800 243801 243805 242807
      242809 241813 241817 242821 244823 245823 248821 249818
      249814 250812
 2.00 369802 368795 366793 362797 360802 355810 350820 345829
      344835 344842 345848 346851 349851 355843 360834 364825
      367813 369802
 2.00 248816 248814 248812 248810 247809 246809 245807 244809
      243809 243811 242813 242815 242817 243819 244821 244822
      246821 247819 248817 248816
 3.00 360821 360814 357815 354819 352823 352828 350833 349837
      350840 353836 355832 357828 359823 360821

$$





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