Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 201845
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
244 PM EDT THU APR 20 2017


PRELIM DAY 1 QPF DISCUSSION
VALID APR 21/0000 UTC THRU APR 22/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1...

...OHIO VALLEY...GREAT LAKES...NORTHEAST...MID-ATLANTIC...

AN AMPLIFIED NRN STREAM SHORTWAVE TRAVERSING EASTWARD FROM THE
GREAT LAKES DAY 1 WILL PROVIDE A SWATH OF MODERATE WAA PCPN WITH
EMBEDDED HEAVIER AMOUNTS WITHIN AREAS OF CONVECTION. PER A
MULTI-MODEL BLEND...AN AREA OF 1-1.25" AMOUNTS WAS NOTED ACROSS
N-CENTRAL NY. DESPITE THE ANOMALOUS MOISTURE AVAILABILITY AND
VIGOROUS DEEP-LAYER DYNAMICAL FORCING...INSTABILITY BECOMES MORE
LIMITED N-NE OF THE OH VALLEY (MUCAPES DROP TO UNDER 500 J/KG).
THIS IN-TURN ALONG WITH THE PROGRESSIVE NATURE OF ACTIVITY MAY
MITIGATE SHORT-TERM RAINFALL RATES. HOWEVER...GIVEN THE LOWER FFG
VALUES/ANTECEDENT WET SOILS OVER THESE AREAS...MAINTAINED A
"MARGINAL" EXCESSIVE RAINFALL RISK OVER PORTIONS OF NY/NRN PA AND
VICINITY. LOCAL ACTIVITY ALONG/AHEAD OF A TRAILING COLD FRONT DOWN
THROUGH THE OH VALLEY WILL SPREAD ONWARD WITH FRONTAL PROGRESSION
ACROSS THE APPALACHIANS AND MID-ATLANTIC/NEW ENG FRI. MAINTAIN
CLOSE WPC QPF CONTINUITY...BLENDING PRIOR AMOUNTS WITH THE 12 UTC
ARW/NAM CONEST/UKMET.

...S-CENTRAL PLAINS ENEWD THROUGH THE MID-MS VALLEY...

IT REMAINS THE CASE THAT THE INITIAL SHORTWAVE PROGRESSING SLOWLY
ENE ACROSS THE UPPER MS VALLEY TODAY...ALONG WITH THE PRE-FRONTAL
CONVECTION AND ATTENDANT OUTFLOW BOUNDARIES...WILL ALLOW THE
SURFACE FRONT TO DROP INTO SOUTHERN OK-CENTRAL AR BY LATE IN THE
DAY. THIS BOUNDARY WILL BE THE FOCUS FOR POTENTIALLY HEAVY
RAINFALL FROM DURING DAY 1...AS A VIGOROUS NW-SE ORIENTED UPPER
LEVEL JET STREAK DROPS INTO THE 4 CORNERS REGION AND AMPLIFIES THE
UPPER TROUGH OVER THE CENTRAL-SOUTHERN ROCKIES. THE 12 UTC MODELS
HAVE REASONABLY TRENDED SLIGHTLY MORE AMPLIFIED WITH THIS FEATURE
CONSIDERING UPSTREAM WATER VAPOR IMAGERY. THE DEVELOPING LEE-SIDE
LOW AND DOWNSTREAM UPPER DIFLUENCE...ALONG WITH CONTINUED FORCING
WITHIN THE RIGHT-ENTRANCE REGION OF THE UPPER JET STREAK DRAPED
OVER THE CENTRAL PLAINS...WILL MAKE FOR A DYNAMICALLY-FAVORED
ENVIRONMENT (STRENGTHENING UPPER DIVERGENCE AND LOWER LEVEL FGEN
ALONG THE STATIONARY BOUNDARY) FROM OK E-ENE INTO SRN MO AND NRN
AR. MEANWHILE... A POOL OF ANOMALOUS MOISTURE (PW AND 850-700 MB
MOISTURE FLUX STANDARDIZED ANOMALIES AROUND +2) ADVECTING ACROSS
THE QUASI-STATIONARY BOUNDARY...ALONG WITH MODEST DEEP-LAYER
INSTABILITY (MUCAPES 1000-1500 J/KG)...WILL PROVIDE A FAVORABLE
THERMODYNAMIC ENVIRONMENT FOR AREAS OF HEAVY RAINFALL ACROSS THE
REGION...PARTICULARLY OVERNIGHT AND ON FRIDAY WITH HEIGHT FALLS
AND CELL INTERACTIONS. FURTHERMORE... WHILE NOT OVERLY
ROBUST...THE STRENGTHENING LOW-LEVEL WSW FLOW AHEAD OF THE FRONT
WILL BECOME MORE PARALLEL AND CLOSE TO THE MAGNITUDE OF THE MEAN
850-300 MB FLOW BETWEEN 00-12Z...ENHANCING THE POTENTIAL FOR
UPWIND PROPAGATION AND THUS CELL TRAINING.

AS A RESULT...WPC CONTINUES TO CARRY A "SLIGHT" RISK OF EXCESSIVE
RAINFALL INHERITED FROM THE OVERNIGHT OUTLOOK...THOUGH BASED ON
THE LATEST GUIDANCE TRENDS...HAVE EXTENDED THE OUTLOOK SLIGHTLY
SWWD ACROSS OK GIVEN CONVECTIVE SUPPORT. LATEST WPC QPF HAS BEEN
BASED ON A COMPOSITE OF A WELL CLUSTERED BLEND OF OVERNIGHT WPC
QPF ALONG WITH A COMPOSITE OF THE 12 UTC ARW/NAM CONEST/ AND
UKMET. THIS YIELDS A STRIP OF 2"+ AREAL-AVERAGE TOTALS ACROSS THIS
AREA. BASED ON THE AFOREMENTIONED FAVORABLE DYNAMICAL AND
THERMODYNAMICAL PARAMETERS...SOME OF THE HIGHER LOCALIZED AMOUNTS
(2-4+ INCHES) ARE REFLECTED ACCORDINGLY IN THE HIGH-RES CAMS. ALSO
HELPING TO DELINEATE THE SLIGHT RISK AREA INCLUDED THE RELATIVELY
LOWER FFG VALUES PER THE RFCS AND HIGHER SOIL SATURATION VALUES
PER THE NATIONAL WATER MODEL...BOTH OF WHICH WOULD BE MORE
CONDUCIVE TO LOCALIZED RUNOFF ISSUES.

...N-CENTRAL ROCKIES/HIGH PLAINS...

UPPER JET AND SHORTWAVE ENERGIES/HEIGHT FALLS DIGGING SEWD THROUGH
THE N-CENTRAL ROCKIES WILL PROVIDE DYNAMICS TO ENHANCE INHERENT
FRONTAL/UPSLOPE FLOW AS FUELED BY MODEST POOLED MOISTURE. THE 12
UTC ARW/NAM CONEST WERE BLENDED WITH THE WPC OVERNIGHT PACKAGE QPF
TO MAINTAIN GOOD CONTINUITY THAT INCLUDES AN EXPANSIVE NW-SE
ORIENTED SWATH OF PCPN WITH SOME TERRAIN ENHANCED POCKETS OF
.5-1"+ MOST LIKELY FROM THE MOUTAINS OF NW WY SEWD TO NERN
CO/VICINITY WITH MAX SUSTAINED LIFT. WINTER WEATHER
SPECIFICS/REASONINGS CAN ALSO BE FOUND VIA PRODUCTS FROM THE WPC
WINTER WEATHER DESK.

HURLEY/SCHICHTEL


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

24HR QP VT 22/00Z
 0.01 518167 519164 517162 515158 517148 518132 519114 520096
      523081 521075 520073 518073 514073 511073 511075 510079
      508081 504086 496084 491083 488084 477083 473081 471079
      470075 468069 466065 456049 445038 440030 432023 427016
      420009 415003 413000 412994 399955 398947 397940 396923
      396909 396900 397892 397882 397875 399871 410855 420842
      426836 434832 440830 443830 445832 445841 444848 442851
      444853 444856 447856 451855 453859 457869 459881 459898
      460905 462910 466915 471915 474913 477912 481909 487899
      489895 491889 495881 496869 498859 500853 500848 501842
      501833 500814 500805 501799 506792 511782 512775 511766
      509750 505727 504720 503712 501704 499697 488687 483679
      478672 474669 470667 467666 462668 458670 454671 447670
      443674 438674 433672 430668 423662 415660 412661 408664
      403670 398678 396683 395689 396712 396716 395720 392728
      388731 382729 377730 374733 374740 371743 365750 361758
      359761 358768 358774 357780 354790 351798 347805 340825
      332841 328848 329860 331867 332876 332880 330882 329887
      325896 324902 324908 324912 322915 319912 316908 312905
      310902 305902 299908 293914 291923 290934 290940 290946
      293951 296954 299955 302953 305949 306945 311937 323924
      327920 330922 334930 335937 335946 336958 335963 334970
      331982 331994 331000 332004 339024 343029 347037 351042
      353046 355055 357061 360063 365061 370061 373064 374071
      375077 377080 383087 385092 388095 392096 395097 397100
      397104 393107 383118 384122 386125 390125 395127 411134
      417135 418138 417142 416155 416158 418159 423159 424151
      424144 424137 426132 430128 433127 438149 441160 443167
      443171 444176 445180 443183 442187 442193
 0.01 442193 444196 448197 453198 455196 456192 460188 466182
      468180 470178 473179 483181 491183 494179 498177 501183
      503182 511183 512176 515171 518167
 0.01 498263 498261 499258 499256 499253 499250 498248 496248
      494247 493247 492248 491250 492252 492253 493256 494259
      494260 495262 496262 497264 498263
 0.01 498232 498221 497215 493209 485204 481203 477203 462210
      444215 436217 429221 426225 427230 431232 436232 444229
      454229 456230 455233 453236 453241 459243 469246 474247
      479246 482244 482239 480233 479231 481229 489229 494229
      495231 498232 498232
 0.01 266798 255798 251800 246803 241811 240816 241821 243824
      245824 248820 255826 259828 263826 266822 264815 261812
      256810 254807 258804 266798 266798
 0.25 506151 500139 496133 493130 489128 488125 488120 485112
      481105 476100 471093 465088 456075 447064 435053 432048
      430040 426033 421027 413017 402007 391995 385979 383971
      383960 383948 384936 384928 385918 384906 385894 386877
      387868 390860 394854 398845 400834 402825 402822 405819
      411822 414823 416822 418819 423814 431804 443807 448808
      454812 457818 460825 467847 471855 472859 475862 479860
      482857 485851 488842 489831 489811 490802 491789 491779
      491768 489749 489743 488737 482732 477725 473718 476711
      478707 478701 474695 471693 467692 461692 457688 442687
      429684 423682 418678 414679 412684 411693 410713 410724
      408733 405739 399744 395749 394754 395758 397764 402770
      405778 405784 404787 391792 378803 370807 365813 360818
      358825 357835 355844 353851 352859 352870 350879 346893
      344902 345913 345919 344923 342927 341933 340943 339956
      338976 339986 340995 343001 347005 354008 361012 366016
      369022 369033 373037 383049 387055 388064 389069 390073
      393077 397079 402080 405078 413076 418076 422081 424091
      428097 434110 440114 446119 457131 466146 475147 482146
      490148 497151 503153 506151
 0.50 482801 482789 481783 479779 475772 473768 471765 465760
      462753 461741 459736 455733 450728 448719 449711 450704
      446700 440698 433699 428695 424694 421696 418702 417712
      420721 420728 419733 418743 415749 413758 410767 410771
      411776 415782 418784 420788 421794 423798 443783 448782
      452781 455778 457780 459784 463793 471807 471813 473819
      477822 480819 481812 482801
 0.50 458103 459100 458097 456093 450087 453080 451075 448070
      445068 442067 439069 437074 435078 435083 435090 436097
      441103 444108 447111 450112 454110 458103
 0.50 427056 425049 422043 419036 416030 407021 395015 393013
      390012 383014 379014 377016 377024 385035 393045 396051
      398058 402063 409063 414061 421063 425061 427056
 0.50 379886 380875 378867 375859 372857 369856 367845 368840
      370832 371828 369825 366827 365831 365841 357854 356863
      356873 356883 353892 347928 343944 342952 341965 342985
      344993 349998 356000 361997 369983 373977 375969 377949
      378928 378907 379895 379886
 1.00 439760 438751 438746 437738 435735 435729 434727 431728
      430735 428741 426748 427758 430764 432765 436765 439760
 1.00 414047 413043 413040 412037 410033 409031 407030 403030
      401030 399032 398037 399041 401042 403044 405047 408049
      410049 412050 414047
 1.00 372949 372938 371925 371905 370895 369890 365892 361899
      358907 356917 353926 348943 346952 345965 345976 345982
      347987 350989 353990 359985 363978 368970 370962 372951
      372949
 1.50 368949 369942 368934 365923 364920 362919 359923 354934
      351945 348958 347971 347979 350984 353984 355983 359978
      363969 366958 368949
 1.50 366909 366907 366905 366904 365905 364907 364909 364910
      366910 366909
 2.00 365952 366941 364932 362930 360931 358934 355941 353949
      350958 349967 349972 349978 351981 354980 358974 361967
      363958 365952

$$





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