Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 030638
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 AM EDT MON AUG 03 2015


PRELIM DAY 1 QPF DISCUSSION
VALID AUG 03/1200 UTC THRU AUG 04/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1...


...NORTHERN AND CENTRAL ROCKIES INTO THE CENTRAL PLAINS...

MOISTURE AND INSTABILITY STRETCHED OUT ALONG A FRONTAL BOUNDARY
EXTENDING FROM THE NORTHERN ROCKIES INTO THE CENTRAL PLAINS FEED
CONVECTION THAT COULD PRODUCE HEAVY TO LOCALLY EXCESSIVE RAINFALL
DURING DAY 1. THERE WAS DECENT MODEL AGREEMENT CONCERNING THE
OVERALL SYNOPTIC PATTERN...THOUGH THERE WAS SOME SPREAD ON THE
FRONTAL POSITION ACROSS NE LATE IN THE PERIOD. IN AN ATTEMPT TO
MITIGATE SOME OF THE PLACEMENT DIFFERENCES WITH THE FRONT ACROSS
THE CENTRAL PLAINS...THE WPC QPF WAS BASED ON A BLEND OF HE 00Z
GFS/12Z ECMWF...AND HIGHER TERRAIN AMOUNTS WERE AUGMENTED BY THE
00Z WRF ARW.

A LOW LEVEL UPSLOPE FLOW ACROSS THE NORTHERN AND CENTRAL ROCKIES
INCREASES DURING THE DAYLIGHT HOURS...REACHING 15 TO 30 KNOTS
ACROSS WESTERN WY INTO EASTERN ID AND WESTERN CO BEFORE 03/21Z.
THE LOW LEVEL INFLOW TRANSPORTS 0.75 TO 1.00 INCH PRECIPITABLE
WATER VALUES INTO THESE AREAS (WHICH IS ABOUT TWO STANDARD
DEVIATIONS ABOVE THE MEAN). SYNOPTIC SCALE LIFT IS SUPPLIED BY A
SHORT WAVE RIDING NORTH OUT OF CENTRAL UT EARLY THIS MORNING TO A
POSITION OVER CENTRAL WY BY THE END OF THE PERIOD. THE MAIN
INGREDIENT MISSING FOR THE POTENTIAL FOR HEAVY RAIN COULD BE
INSTABILITY. 00Z GFS MODEL SOUNDINGS SHOWED MARGINAL INSTABILITY
ACROSS WESTERN WY (GENERALLY AROUND 500 J/KG OF SBCAPE)...PEAKING
AROUND 04/00Z.

MUCH OF THE 00Z GUIDANCE SHOWS THE POTENTIAL FOR AREAS OF AN INCH
OR SO OF BASIN AVERAGE QPF...AND SOME OF THE HIGH RESOLUTION
GUIDANCE (SUCH AS THE 00Z NSSL WRF AND 00Z REGIONAL GEM) SHOULD
MAXIMUM QPF AMOUNTS OVER 2.00 INCHES. ONE AND THREE HOUR FLASH
FLOOD GUIDANCE VALUES ARE AS LOW AS AN INCH OR LESS OVER PORTIONS
OF WESTERN WY (MAINLY IN THE TERRAIN)...AND GIVEN HIGHLY
ANOMALOUSLY MOISTURE IN PLACE...HEAVY RAINFALL IS POSSIBLE. A SEE
TEXT WILL BE ISSUED FOR PORTIONS OF EASTERN ID/WESTERN WY INTO
NORTHERN CO TO ADDRESS THE FLASH FLOOD POTENTIAL. IF INSTABILITY
WERE FORECAST TO BE MORE ROBUST...A SLIGHT RISK AREA MAY HAVE BEEN
WARRANTED.



...SOUTHERN PLAINS...

AN INCREASING LOW LEVEL INFLOW FEEDS MOISTURE AND INSTABILITY
ACROSS NORTH TX/WESTERN OK/WESTERN KS DURING THE SECOND HALF OF
DAY 1...AND THERE IS A MULTI MODEL INDICATION THAT AN MCS COULD
DEVELOP AFTER 04/00Z. THERE WAS DECENT MODEL AGREEMENT WITH THE
OVERALL PATTERN HERE...SO THE QPF WAS BASED PRIMARILY ON A BLEND
OF THE 00Z GFS/12Z ECMWF.

AN EARLY MORNING COMPLEX OVER NORTH TX SHOULD FADE AS THE LOW
LEVEL INFLOW WEAKENS AND INSTABILITY BECOMES ELEVATED. AN MCV FROM
THE COMPLEX COULD RESULT IN LIFT FOR CONVECTION ACROSS NORTH TX
THROUGH THE MORNING HOURS...BUT HEAVY RAIN WITH THIS SYSTEM IS
UNLIKELY AFTER 03/12Z.

THE PATTERN APPEARS TO REPEAT ITSELF TONIGHT...AS A 20 TO 30 KNOT
INFLOW OVER NORTH TX/WESTERN OK/WESTERN KS TRANSPORTS MODERATE TO
STRONG INSTABILITY AND PRECIPITABLE WATER VALUES IN EXCESS OF 1.75
INCHES INTO NORTH TX. THE 00Z NAM SIMULATED SATELLITE IMAGERY
SHOULD THE MCS DEVELOPING OVER NORTH TX/WESTERNMOST OK BETWEEN
04/00Z AND 04/06Z...THEN TURNS SOUTHEAST AS IT FOLLOWS THE BEST
LOW LEVEL INSTABILITY. MOST OF THE REMAINDER OF THE 00Z GUIDANCE
FORMS A CONVECTIVE COMPLEX OR MCS FURTHER NORTH INTO WESTERN
OK/SOUTHWEST KS. GIVEN THE FACT THAT THE CONVECTIVE COMPLEXES THAT
DEVELOPED IN NORTHEAST NM TRACKED ACROSS NORTH TX...THE WPC QPF
WAS PLACED SOUTH OF THE MODEL CONSENSUS...CLOSER TO THE 00Z
REGIONAL GEM PLACEMENT.

DUE TO HEAVIER RAINFALL ACROSS NORTH TX AND WESTERNMOST OK THE
PAST COUPLE OF NIGHT...ONE AND THREE HOUR FLASH FLOOD GUIDANCE
VALUES ARE AS LOW AS 1.50 INCHES. SOME OF THE HIGH RESOLUTION
GUIDANCE PLACES AS MUCH AS 3 INCHES OF RAINFALL WITH THE MCS
(INCLUDING THE 00Z WRF ARW/NMMB AND R00Z REGIONAL GEM).
CONSIDERING THAT PRECIPITABLE WATER VALUES TOP OUT BETWEEN 1.75
AND 2.0O INCHES...THIS IS PLAUSIBLE. A SLIGHT RISK AREA WILL BE
PLACED OVER PORTIONS OF NORTH TX/AND WESTERN OK FOR THE FLASH
FLOOD POTENTIAL.


...MID ATLANTIC/SOUTHEAST/FL...

THE DEEP MOISTURE ASSOCIATED WITH A SURFACE WAVE THAT CROSSES
NORTHERN FL AND MOVES ALONG THE SOUTHEAST COAST TO THE COASTAL MID
ATLANTIC FEEDS CONVECTION ALONG A SURFACE TROUGH...AND THE
RESULTANT CONVECTION COULD PRODUCE HEAVY TO LOCALLY EXCESSIVE
RAINFALL FROM NORTH FL THROUGH THE COASTAL CAROLINAS. THERE WAS
SOME SPREAD CONCERNING JUST HOW QUICKLY THE SURFACE WAVE MOVES OUT
OF NORTHERN FL AND TO THE SC COAST...WITH THE 00Z GFS HAVING THE
SUPPORT OF THE 12Z/18Z ENSEMBLE GUIDANCE...SO THE WPC QPF WAS
BASED PRIMARILY ON THE 00Z GFS.

THE NEXT SURGE OF CONVECTION TIED TO DEEP TROPICAL MOISTURE (WITH
PRECIPITABLE WATER VALUES BETWEEN 2.25 AND 2.50 INCHES) IS
APPROACHING THE CENTRAL PORTION OF THE WEST OF FL EARLY THIS
MORNING. THE BULK OF THE HIGH RESOLUTION GUIDANCE SUGGESTS THAT
THE BEST THRUST OF MOISTURE OCCURS IN THE 03/12Z TO 03/18Z TIME
FRAME...DURING WHICH AN ADDITIONAL COUPLE OF INCHES OF RAINFALL IS
POSSIBLE. FOR THIS REASON...A SLIGHT RISK AREA WILL NEED TO BE
RETAINED UNTIL THE DEEPER MOISTURE IS SCOURED BY A DEVELOPING
SURFACE WAVE OFF THE SC COAST DURING THE AFTERNOON.

AS MENTIONED EARLIER...THERE IS SOME SPREAD CONCERNING HOW THE
SURFACE WAVE EVOLVES...AND HOW THE DEEP MOISTURE BECOMES INVOLVED
IN THE DEVELOPMENT OF ADDITIONAL CONVECTION NEAR THE COAST.
FOLLOWING THE SEQUENCE OF EVENTS FROM THE 00Z GFS (WHICH APPEARED
TO HAVE THE BEST SUPPORT FROM THE 12Z ENSEMBLE
SOLUTIONS)...CONVECTION DEVELOPS ON A FRONTAL BOUNDARY/SURFACE
TROUGH AHEAD OF THE SURFACE WAVE...STRETCHING OVER COASTAL SC/NC.
IT IS UNCLEAR...BASED ON THE 00Z GFS (AND THE PREPONDERANCE OF
OTHER 00Z GUIDANCE SOLUTIONS)...WHETHER THE HEAVIEST RAINFALL
OCCURS ALONG THE COAST OR JUST OFFSHORE. THE BEST INSTABILITY
SHOULD GET ONSHORE AHEAD OF THE SURFACE WAVE...AND THE CONVECTION
SHOULD TAP THE DEEP MOISTURE TO PRODUCE AN AXIS OF 1.50 TO 2.25
INCHES OF QPF OVER THE COASTAL CAROLINAS.

THREE HOUR FLASH FLOOD VALUES ALONG THE COASTAL CAROLINAS IS HIGH
(GENERALLY ABOVE 3.00 INCHES)...SO AT FIRST LOOK IT WOULD APPEAR
THAT THE THREAT FOR FLASH FLOODING IS LOW. HOWEVER...MOST OF THE
HIGH RESOLUTION GUIDANCE (FROM THE 00Z WRF ARW/MMB TO THE 00Z
REGIONAL GEM) SUGGEST THE POTENTIAL FOR 2-4 INCHES OF
QPF...ESPECIALLY IF A CONVECTIVE COMPLEX FORMS IN THE STRONG
SOUTHERLY INFLOW NEAR THE NC COAST. THE AIRMASS PRODUCED LARGE
RAINFALL AMOUNTS ACROSS NORTHERN FL THE PAST FEW DAYS...SO IT IS
CAPABLE OF SUPPORTING RAINFALL AMOUNTS NEAR 4 INCHES. GIVEN THIS
INFORMATION...A SEE TEXT OR EVEN A SLIGHT RISK AREA WILL BE ISSUED
FOR PORTIONS OF THE SC/NC COAST LATER THIS MORNING.


...NORTHEAST...

MOISTURE AND INSTABILITY TRANSPORTED AHEAD OF A COLD FRONT INTO
THE NORTHEAST STATES FEEDS DEVELOPING LINES OF CONVECTION FROM
WESTERN PA INTO NORTHERN NEW ENGLAND DURING THE AFTERNOON AND
EVENING HOURS...RESULTING IN LOCALLY HEAVY RAINFALL FROM UPSTATE
NY THROUGH NORTHERN NEW ENGLAND. THE 12Z ECMWF APPEARED TO BE A
BIT SLOW WITH THE SURFACE FRONT...ESPECIALLY ACROSS NEW ENGLAND.
OTHERWISE...THERE WAS GENERALLY GOOD MODEL AGREEMENT...SO THE WPC
QPF WAS BASED ON A MULTI MODEL BLEND.

CONVECTION AHEAD OF A COLD FRONT STRETCHING FROM SOUTHWEST QUEBEC
INTO IA EARLY THIS MORNING BECOMES REINVIGORATED THIS AFTERNOON
AND EVENING FROM WESTERN PA/WV INTO UPSTATE NY STATE AND MUCH OF
WESTERN AND CENTRAL NEW ENGLAND. AHEAD OF THE FRONT...THE
ENVIRONMENT BECOMES CONDUCIVE FOR DEVELOPMENT AS A 20 TO 30 KNOT
LOW LEVEL SOUTHWEST FLOW TRANSPORTS 1.50 INCH PRECIPITABLE WATER
AIR AND MODERATE INSTABILITY INTO THE REGION. MODEL SOUNDINGS
SHOWED GOOD INFLOW AND STEEP MID LEVEL LAPSE RATES...SUGGESTING
THE CONVECTION TAKES ON AN OUTFLOW DOMINATED MODE THROUGH AT LEAST
04/00Z.  A LARGE AREA OF 0.50 TO 1.00 INCHES OF QPF WAS EXTENDED
FROM UPSTATE NY INTO NORTHERN VT/NORTHERN NH AND WESTERN ME...WITH
LESSER AMOUNTS TOWARD THE COAST.

SOUNDINGS ACROSS UPSTATE NY INTO NORTHERN NH SUGGEST THAT THE
COLUMN MOISTENS WITH TIME...AND ANY TRAINING CELLS COULD LEAD TO
LOCAL FLOODING ISSUES. SOME HIGH RESOLUTION GUIDANCE PLACES AS
MUCH AS 2 INCHES OF QPF ACROSS THE WHITE MOUNTAINS OF NH WITH THE
FRONTAL PASSAGE. THREE HOUR FLASH FLOOD GUIDANCE VALUES ARE
GENERALLY ABOVE 2.50 INCHES (EXCEPT ACROSS THE ROOFTOP OF
ME...WHERE THEY LOWER TO 1.50 INCHES)...SO WHILE LOCAL ISSUES ARE
POSSIBLE...ORGANIZED FLASH FLOODING IS NOT EXPECTED.


HAYES

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

24HR QP VT 04/12Z
 0.01 530243 530240 532235 531230 530226 524219 521210
      517201 512194 509191 506192 499194 496195 495192 494188
      489186 480183 473179 465176 463180 464185 463193 460198
      456202 455205 457206 460209 464210 469210 477211 480210
      482211 477215 464224 458227 452229 421232 413231 410225
      399209 393204 391201 389197 388175 388166 389160 390157
      394147 396143 395140 393140 388139 386140 384142 382142
      379140 376137 372136 369126 373119 374114 379112 387109
      390108 391103 391098 386097 380101 377102 374103 373091
      368074 365067 364062 360061 357060 355056 357053 361051
      363048 362044 357040 343070 346077 347081 347087 348092
      347096 345107 338106 333104 328105 325106 323110 322115
      320117 311115 307113 305109 304106 307103 312094 314091
      314085 316080 316076 315069 313065 312071 310082 308091
      303096 300098 294097 277095 270092 265088 257084 250078
      244072 238066 229055 228052 230050 239051 276058 284059
      293061 297061 299059 302056 306054 310056 311061 313059
      314052 313041 313031 313024 316021 323016 327014 327008
      328997 329988 330982 333980 345970 350966 358964 374960
      382955 383952 384946 387925 384916 382911 381906 379902
      378899 376898 374893 374889 372885 371879 370876 370872
      370865 369860 370853 369846 369834 370831 370824 371815
      373807 377797 380788 383779 388772 395757 396750 397747
      400741 408726 412720 414715 417712 422708 428702 438689
      442681 448675 460664 467659 472652 484638 491629 495625
      502622 519668 519676 519684 514689 516696 516704 514712
      513718 509724 505728 500727 497728 494730 491734 486738
 0.01 486738 465763 455776 445791 442799 439803 436805 432812
      432816 437813 444812 449820 455825 460832 470846 473854
      474858 475865 468898 463898 460899 456896 453889 451877
      450863 446855 446849 443846 438839 433833 431829 430823
      431820 431817 430815 424822 419829 414835 409841 404848
      398854 394863 392871 392877 393881 404893 415907 419914
      423923 429940 432947 435957 441978 443986 446998 449017
      452039 453051 456061 459071 461080 465100 468107 469113
      472116 475120 480122 488126 495122 502121 509123 515119
      521117 524113 527113 536115 541116 544119 555135
 0.01 534840 530833 523828 520826 517822 511817 509815 506815
      503821 504828 506834 509843 515851 523855 528854 532854
      534848 534840
 0.01 411699 407672 405670 399671 396673 391676 384682 380688
      375697 369705 355716 349721 340726 327736 323738 320743
      315751 304764 298769 294771 289772 283774 273774 267775
      263777 257779 253781 239787 232791 229793 226797 226800
      228803 233804 233810 236814 239819 243825 246819 248817
      250818 253822 260839 262844 263850 265858 268864 269869
      270882 270903 273912 273925 269945 269951 268956 268962
      271966 272968 277966 283961 285958 287954 292947 298901
      298891 303884 307873 307870 307866 309867 312871 314869
      317860 315834 318824 324818 331813 336807 347794 350791
      353786 357777 365760 369753 375748 387735 399719 405710
      409704 411699
 0.01 308041 308040 306038 304038 302038 302040 304042 306043
      306042 308041 308041
 0.25 550165 548166 547166 546166 545168 544169 543171 542173
      541176 541178 541181 542182 543184 544185 545186
 0.25 505670 504661 501656 497652 492654 487658 482662 475670
      469673 466677 459686 445703 430720 427724 424730 421734
      417738 410747 408752 407759 406764 409768 411774 415780
      399791 397790 394790 391794 385804 382810 380815 381823
      384825 387822 389816 391813 395814 400814 409809 411818
      415818 418814 420807 422799 431793 437785 448765 452765
      456761 462751 467742 470736 472729 477719 482716 484719
      487718 502700 504693 506686 505670
 0.25 457150 457134 457125 456115 456106 456101 454097 450092
      444087 437084 432080 427077 422072 414060 405049 400045
      396044 393046 392047 388046 386049 385068 386074 390079
      394086 395094 398100 398108 406119 409115 412114 415116
      427124 433121 440120 443120 445123 443131 440139 441143
      443147 446150 451152 455152 457150
 0.25 451080 451078 450075 448073 447073 446072 445071 443070
      443069 441069 440072 441073 442074 443076 444077 446079
      447080 448080 449081 451081 451080
 0.25 432215 432212 431212 430214 432215 432215
 0.25 433004 434998 433991 433985 432980 428972 424964 416949
      409934 405936 404941 405952 403959 402966 402972 404983
      407991 410000 414008 417016 419027 421035 424037 425032
      427021 430011 433004
 0.25 422100 422099 420099 419100 418100 417098 415098 414099
      415100 416101 417102 418102 420102 422100 422100
 0.25 409089 409088 407086 405086 404086 402085 400085 400086
      398087 400088 401089 403090 403091 405092 407093 408091
      408090 409089
 0.25 379716 378713 375712 370714 364717 359720 349727 338736
      329743 322753 316762 308773 302783 294792 292797 293802
      293806 289806 282804 277801 271800 265799 258800 253802
      251806 252810 254812 257813 264813 271814 270819 269832
      268838 268845 270853 273859 280870 281887 282903 283910
      285913 288912 291905 292898 292881 292874 290865 289858
      291851 300827 303823 309820 315817 321814 326810 330806
      338797 345788 352776 357765 363754 369744 375731 379716
 0.25 386027 387012 385999 382990 379987 375983 367980 361980
      357982 351988 348992 347998 346005 345009 343013 338015
      334019 335023 340023 345025 352031 360034 364037 367041
      372049 379055 383056 385049 383044 380040 376037 378034
      384031 386027
 0.25 380078 379076 379074 378071 377069 376067 375065 373064
      371065 370066 370068 371069 371070 372073 373073 373075
      373077 374079 374080 375082 377082 379080 380078
 0.25 335058 334056 332055 330054 329054 327055 326057 327057
      328058 330059 332059 334058 335058
 0.25 299080 298073 294071 289071 280070 271071 265069 261069
      261073 266078 270083 277087 284090 288090 292090 297086
      299080
 0.50 498683 497664 495661 491662 485668 465688 456699 447710
      442715 440722 436727 433735 432740 431743 427748 424751
      421752 417754 414758 416762 418765 426765 430769 432768
      434765 442754 445747 449741 454737 456740 459739 462733
      464730 462728 459726 461723 466718 474705 478700 481694
      483692 484696 486699 489698 493695 496691 498683
 0.50 448109 447102 446097 443096 440096 434093 430090 428088
      425089 426096 430101 431104 429105 422105 419106 416105
      413106 411103 408100 404107 404111 406113 410109 414110
      419113 424117 429118 434118 438114 448109
 0.50 414987 414982 414977 413975 412971 410969 409968 405968
      405970 405973 406977 407980 408984 410987 412989 414987
 0.50 401072 402069 401068 400069 399070 399071 399073 401072
      401072
 0.50 394073 394071 394070 392070 392071 391073 391075 392077
      393075 394073 394073
 0.50 368732 369728 368724 364724 358726 353729 346737 337743
      330751 325761 318770 315774 312779 308789 302798 301803
      306805 313813 318813 323811 331804 337795 343785 353766
      358756 363746 367738 368732
 0.50 377078 377076 376074 374075 375078 376079 377078
 0.50 374017 372008 374005 376999 375993 373990 369987 364985
      359987 357990 355994 354000 351011 352022 354027 359029
      368031 372023 374017
 0.50 298817 298812 293813 287816 281819 276825 274832 273841
      275849 277851 282851 287846 291841 294834 296826 297819
      298817
 0.50 293081 293077 291076 287075 283075 280076 278076 275077
      272079 274082 277084 279084 282085 286085 288084 290083
      293081
 0.50 275807 274804 272803 270801 266801 263801 259802 256803
      254805 254808 256809 258809 262810 265809 269809 273808
      275807
 1.00 437112 436112 435111 435112 436112 437112
 1.00 431097 431096 429094 431097 431097
 1.00 426113 426110 424110 424112 426113 426113
 1.00 365021 365018 365016 365014 364012 363010 362010 360010
      358011 356013 356014 355016 356018 356020 357022 357023
      359024 361023 362023 363023 365022 365021
 1.00 355750 354746 351745 347746 343748 339752 335757 328768
      319778 318783 317788 318793 323795 320801 319804 321807
      327803 335793 341782 348771 352757 355750
 1.00 294822 295819 294816 290820 287822 283824 280827 279832
      278836 279840 282841 284841 288838 290835 292830 293826
      294822
 1.50 362018 361016 360015 358015 357016 358017 358018 359020
      361019 362018
 1.50 345765 344762 341760 336767 333772 333783 329789 326795
      325801 330796 334791 336784 341777 344771 345765
 1.50 291824 289824 287825 284827 282829 280831 280834 281838
      283839 286837 287835 289833 290831 291826 291824
 2.00 287831 286830 284830 283831 283833 284834 285833 286833
      287831

$$




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