Quantitative Precipitation Forecast
Issued by NWS

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340
FXUS04 KWBC 220701
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT FRI SEP 22 2017


PRELIM DAY 1 QPF DISCUSSION
VALID SEP 22/1200 UTC THRU SEP 23/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...WESTERN U.S...

A LARGE...TWO TO THREE STANDARD DEVIATION TROUGH IN THE WEST WILL
GRADUALLY SLIDE INTO A MORE NEUTRAL TILT. AT HIGH ELEVATIONS THIS
STORM IS BRINGING NOTEWORTHY SNOWS TO THE NORTHERN ROCKIES.
OTHERWISE THE SYSTEM IS REMOVED FROM ANY SUB-TROPICAL MOISTURE
CONNECTION...AT LEAST UNTIL TAPPING INTO A PLUME OVER SOUTHWEST
MEXICO THAT WILL ADVECT UP INTO THE PLAINS STATES STARTING FRIDAY
NIGHT. THROUGH THE INTERMOUNTAIN WEST...PRECIPITATION IS FAIRLY
LIMITED IN SCOPE...WITH HIGH ELEVATIONS FAVORED...AND A CONTIGUOUS
BAND OF LIGHT RAIN/SNOW TIED TO THE HEIGHT FALLS AND DEEP LAYER
ASCENT EAST OF THE TROUGH AXIS. UPSLOPE ENHANCEMENT WILL BE MOST
EFFECTIVE ACROSS PARTS OF WY/ID/MT THIS MORNING...BEFORE HEIGHT
FALLS DIMINISH...AND THE TROUGH BECOMES A BIT MORE
STAGNANT...WAITING FOR A SHORTWAVE TO DIVE INTO THE BASE OF THE
SYSTEM ACROSS ARIZONA FRIDAY NIGHT. MODEL QPFS ALL TELL A SIMILAR
STORY / STRONG CONSENSUS...AND GIVEN THE GENERAL LACK OF
MOISTURE...WPC QPF REMAINED ON THE CONSERVATIVE SIDE. GEFS
REFORECAST DATA SUGGEST AROUND 0.75 INCH LIQUID AMOUNTS IN SOME OF
THE UPSLOPE-ENHNACED TERRAIN OF THE NORTHERN ROCKIES DURING THE
NEW DAY 1 PERIOD. WE AIMED FOR SUCH AMOUNTS...AND USED THE 27KM
GFS AND 4 KM NAM CONUS NEST TO PROVIDE A LITTLE MORE DETAIL PRIOR
TO THE DOWNSCALING / POST-PROCESSING.


...SOUTHERN HIGH PLAINS / GREAT PLAINS / UPPER MIDWEST...

EARLY FRIDAY MORNING THUNDERSTORMS WERE BREAKING OUT IN A WARM
ADVECTION REGIME ACROSS CENTRAL MINNESOTA / SURFACE WARM
FRONT...NORTHERN MINNESOTA / ELEVATED WARM FRONT...AND NORTHEAST
SOUTH DAKOTA / NOSE OF THE PLAINS LOW LEVEL JET. THE 00Z SOUNDINGS
HAD BEEN CONDITIONALLY UNSTABLE...THE HRRR INSISTED ON MCS
DEVELOPMENT...AND MANY OF THE 00Z HI-RES MODELS CAME IN WITH
SIMILAR SOLUTIONS...WHICH AIDED CONFIDENCE. WPC THEREFORE WENT
WITH A FAIRLY AGGRESSIVE FORECAST...EXPECTING AN MCS TO RIDE NEAR
AND NORTH OF THE SURFACE WARM FRONT THROUGH MIDDAY...CROSSING
CENTRAL MN INTO NORTHERN WISCONSIN. OTHER CLUSTERS OF STORMS WILL
OCCUR FARTHER NORTH IN A MORE ELEVATED FASHION. WE TAPER OFF THE
INTENSITY EACH 6 HOURS AND WITH EASTWARD PROGRESSION...AS
CONFIDENCE STARTS TO WANE BY THE 18-00Z PERIOD...AND THE
CONVECTION COULD STRUGGLE TO BE MAINTAINED AS LARGE SCALE FORCING
FAVORS RE-ORGANIZATION BACK TO THE WEST.

A FRONTAL WAVE OF LOW AMPLITUDE BUT OCCURRING BENEATH ENERGETIC
UPPER FLOW...IS EXPECTED TO FORM ACROSS THE CENTRAL PLAINS AND
LIFT NORTHEASTWARD. THIS SHOULD PROMOTE ELEVATED CONVECTION IN THE
ZONE OF 850-600 MB LIFT ACROSS EASTERN SOUTH DAKOTA INTO MUCH OF
NORTH DAKOTA AND WESTERN MINNESOTA. A FEW SURFACE-BASED /
WARM-SECTOR STORMS ARE ALSO POSSIBLE. SIMILARLY...PEAK HEATING
ALONG THE TRAILING FRONT AND TROUGH...COMBINED WITH STRENGTHENING
LOW LEVEL INFLOW...SHOULD PROMOTE THUNDERSTORMS IN NEBRASKA AND
FROM CO/KS DOWN THROUGH EASTERN NEW MEXICO. THE ACTIVITY IN NEW
MEXICO COULD BE PARTICULARLY HEALTHY AND LONGER LIVED INTO THE
NIGHTTIME HOURS...AS A PRONOUNCED SHORTWAVE TROUGH ROUNDS THE BASE
OF THE LARGE WESTERN U.S. TROUGH...PUSHING THROUGH ARIZONA...AND
ENHANCING THE DEEP LAYER ASCENT OVER NEW MEXICO. AT THE SAME
TIME...THIS VERY DEEP WESTERN U.S. TROUGH MAY BEGIN TO TAP INTO
MID AND HIGH LEVEL MOISTURE EMANATING FROM A TROPICAL WAVE ALONG
THE WEST COAST OF MEXICO...PER 500-200 MB RELATIVE HUMIDITY FIELDS
FROM THE GFS. THIS INFLUX OF HIGH LEVEL MOISTURE SHOULD BOOST
PRECIPITABLE WATER VALUES AND MAKE FOR A MORE EFFICIENT RAINFALL
PROCESS. THE PATTERN ALSO FEATURES A STRONG MERIDIONAL COMPONENT
TO THE DEEP LAYER FLOW...WHICH COULD ALLOW FOR TRAINING FROM SOUTH
TO NORTH...AND A RISK OF FLASH FLOODING OVER EASTERN NEW MEXICO
AND ADJACENT STATES FRIDAY NIGHT. NOTE THAT A COUPLE OF HI-RES
MODELS...WRF-ARW AND NSSL WRF PRODUCE SPOTTY 4-INCH TOTALS IN NEW
MEXICO DURING DAY 1.


...ELSEWHERE IN THE SOUTHERN AND EASTERN U.S...

EASTERLY FLOW ACROSS FLORIDA SHOULD BE MOIST ENOUGH...ALTHOUGH NOT
UNIFORMLY MOIST...TO YIELD AREAL AVERAGE RAINFALL AT LEAST A
QUARTER INCH FOR MUCH OF THE EASTERN / CENTRAL / SOUTHERN
PENINSULA. OTHERWISE DIURNAL CONVECTION MAY BE CONFINED TO A ZONE
OF RICH MOISTURE AND MODERATE CAPE FROM WESTERN SOUTH CAROLINA
TOWARD THE CENTRAL GULF COAST. AND POST-TROPICAL STORM JOSE IS SET
TO PRODUCE ONE LAST GASP OF PRECIPITATION AROUND A HALF INCH AREAL
AVERAGE OVER SOUTHEAST MASS. AND OFFSHORE ISLANDS.

BURKE

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

24HR QP VT 23/12Z
 0.01 525158 492122 490115 489103 492081 498064 501057 505047
      508041 511040 513038 520025 526014 529008 530996 530984
      530971 526964 521958 517952 514949 515943 517934 518923
      518914 517905 517893 515882 514874 512866 507851 499839
      490827 484823 480824 477827 474833 472840 470860 463872
      460872 454875 450879 447885 442892 442897 443901 444907
      444914 443925 439943 437960 426966 422971 418979 413990
      406002 401006 398000 396997 393997 386999 380002 374006
      361014 356018 350020 334023 329024 326028 323034 318037
      306043 299048 295053 288055 286057 283055 271047 264045
      262045 260049 253051 250052 248054 247062 249067 258075
      264078 272082 279085 284085 288083 298074 302070 308069
      320066 333061 344057 356055 364056 359062 357064 358067
      360073 362075 366079 370086 373091 380094 386095 390093
      396110 402118 407131 413136 417137 423134 427132 430134
      432138 432142 430151 430163 432169 435175 441176 447173
      456175 459175 459167 464163 467162 470160 473153 478145
      481143 485144 490146 493148 505156 510161 515160 518162
      520162 525158
 0.01 466006 465998 464994 461994 457998 451001 443007 434016
      427023 417030 412031 408029 402030 395030 389034 385035
      380037 376042 369051 368053 371053 379055 386056 392055
      404053 409049 412046 421038 428030 430028 432027 436027
      438026 444023 447019 456012 462009 466006
 0.01 462822 459813 457808 457803 455801 450801 443807 438813
      436817 432821 429831 431833 435833 443835 446832 452831
      455830 459827 462822
 0.01 432689 430677 428670 426664 414651 409649 405649 395648
      387654 381661 379666 380672 383676 385678 383681 379689
      376698 375710 378723 381729 384729 389728 391726 394725
      400723 403721 408720 415720 419720 423718 425714 428709
      430704 431699 432689
 0.01 433076 433072 429071 428069 424068 420072 415076 411078
      408077 406079 400082 400085 402087 405088 407086 412085
      418083 425083 429080 433076
 0.01 424108 423105 421103 420103 419102 418100 417100 415101
      415102 413103 413106 413108 414110 414111 415113 417112
      419113 420112 421111 423110 424108
 0.01 425846 425841 424836 423834 421834 419837 419839 418842
      418846 418849 420853 422853 423851 424848 425846
 0.01 397208 396205 394202 390196 387193 387189 381183 377178
      374177 371179 366182 364184 366187 370192 377197 382202
      388207 392208 397208 397208
 0.01 403160 405153 405148 401145 399148 397152 395158 391160
      389164 388169 391170 394166 398164 401164 403160
 0.01 366818 366812 361814 357819 346831 343835 341840 341839
      344818 343813 339812 337808 338804 341794 342790 345785
      345783 342781 339782 337786 331792 326799 324802 323807
      323812 322816 319826 317836 318846 317852 315855 304869
      301886 301898 302912 305912 306908 308899 312891 316882
      320875 326871 330864 338858 341856 342852 344849 348848
      352845 355841 358832 359827 362823 366818
 0.01 354120 355117 355115 354115 353115 351115 349116 349117
      351117 352118 354120 354120
 0.01 313811 303778 295769 290768 287770 282775 279782 274786
      268790 258792 251795 246798 239801 236803 233806 232819
      231822 233825 236826 238824 245824 249820 253824 252828
      254831 257839 262842 274850 276852 278857 280863 284869
      288871 292871 297868 299860 294843 291837 296837 301833
      304825 313811
 0.01 299998 299991 298985 299980 300973 299967 296964 285961
      272961 268963 265967 263970 263974 264978 268980 272984
      273985 277985 279983 284985 292990 293995 297998 299998
 0.01 299910 299905 297903 297899 295899 293901 291904 291906
      291910 291914 293916 295916 297914 299912 299910
 0.01 292023 292018 289015 285013 282012 276011 272011 270015
      270020 274024 277025 283026 286027 290025 292023
 0.01 266007 264000 258995 256993 251993 249991 245992 240997
      239000 241004 245008 248011 249014 250019 251022 254024
      259024 262022 264019 264014 265009 266007
 0.25 524986 522984 519984 514987 511985 507980 505975 504966
      503958 504949 505940 506933 509921 510912 509901 508894
      506885 502871 498860 495855 491853 488852 484854 480859
      477871 476880 474883 472889 470896 466900 462899 457897
      456895 454897 452902 451908 450917 449924 446940 447948
      449954 453955 457952 459945 461938 465927 468921 469918
      471921 472926 473935 471951 468967 466973 467977 470978
      479977 482980 484988 485993 484998 482004 477015 474021
      474026 476029 482027 487026 491030 494033 497033 502030
      504027 508022 513011 515004 518999 521992 524986
 0.25 482128 482120 481115 480102 479089 477083 473080 468079
      464081 460079 456076 450070 446070 444072 444077 449083
      451088 449095 446099 448102 452112 446119 442130 439135
      438141 439147 443152 446153 449150 452148 456142 462138
      471133 475134 478134 482128
 0.25 461974 462968 460966 454968 443973 439975 436975 429976
      421987 419994 417002 415009 414013 416017 420017 425013
      429008 433002 436996 441991 452984 456981 460975 461974
 0.25 425686 423675 420666 410657 404655 395658 393661 394665
      394671 394676 391682 385687 382694 380702 380709 381714
      384717 389714 393708 396706 399707 402709 406710 412712
      415713 419713 422710 423706 424696 425686
 0.25 394009 393004 387003 379009 372015 363020 345028 336031
      332032 326035 320041 312047 305053 304056 305059 310061
      320060 330056 338052 349049 357046 366041 372034 380027
      387021 393011 394009
 0.25 381081 382076 382072 381069 379067 377066 373065 371068
      372073 372076 373080 373083 377084 380083 381081
 0.25 337826 337823 336822 334822 332823 332824 331826 331827
      331828 330831 330833 331834 333834 334832 335830 336828
      336827 337826
 0.25 306808 306801 305797 300787 297783 293784 292789 288792
      277795 273796 266797 262796 257797 253798 248802 246805
      246808 247810 251812 255816 261821 263826 267829 273832
      277835 281838 284837 282833 282828 277826 270822 272819
      273814 283814 292816 299817 303814 306809 306808
 0.25 284076 285072 284070 281068 280064 277060 272056 267056
      262058 257060 257062 258065 262068 267071 272074 278077
      284076
 0.25 269806 269805 267805 265805 263806 263807 263809 264809
      265809 266808 267808 269808 269806
 0.25 259006 259004 258003 257002 256001 255000 253999 251999
      249999 247998 246000 246002 247004 249005 250006 251007
      251008 252009 254010 256010 258008 258007 259006
 0.50 504916 504903 503890 500880 497870 494862 490861 486861
      483869 481879 480890 479904 478915 479927 479937 477950
      475960 475967 479969 486970 489969 493967 494963 495957
      497946 499936 502925 504916
 0.50 499985 498980 497972 494970 490972 490980 489987 488992
      489997 492001 495998 497993 499988 499985
 0.50 476129 478122 478114 475105 473101 473093 471089 468086
      464087 461090 461101 463105 464111 463114 460117 457119
      456123 457129 461128 471130 476129
 0.50 470113 470110 469109 468109 467110 466112 467113 469113
      470113
 0.50 461925 461920 459920 457923 456925 454928 452929 451932
      450935 449940 450945 452945 454942 454940 455935 455932
      457929 460927 461925
 0.50 422687 421676 419671 417667 406659 400659 397662 398667
      397676 395685 391690 389690 386692 384699 382704 383706
      385710 387710 389701 394696 396693 400692 405690 408690
      408694 406698 405702 407704 413706 418706 419703 419697
      420693 422687
 0.50 390009 388006 386008 379014 374019 365023 349028 341031
      333034 326038 320044 314050 315053 319055 328053 336050
      343048 353044 359041 366034 377024 383018 389011 390009
 0.50 378078 379076 379074 378071 376070 375071 374073 374075
      375078 375080 377080 378078
 0.50 304806 302798 298792 296790 294792 288796 284797 279798
      274803 274805 276807 284808 290813 297814 302810 304806
 0.50 261815 260813 258811 257807 258805 260803 261801 259799
      255801 256804 254807 253809 253810 255812 257815 259817
      261815
 0.50 255006 255004 253003 251004 253005 254006 255006
 1.00 497921 498914 497906 496901 494899 492900 489904 487909
      486914 485919 486927 487932 489935 491932 494928 496924
      497921
 1.00 493883 493881 493878 492876 492873 491871 489872 488874
      488875 487876 486879 487881 488884 490886 491887 493886
      493885 493883
 1.00 474123 473122 473121 472118 470118 469119 467120 466120
      467120 468122 468123 470124 471125 473124 474123
 1.00 416677 415674 415672 414670 413670 412668 411667 410666
      409665 407666 406667 405668 405670 405672 404673 404675
      405676 406677 407677 409677 411677 412678 413678 415679
      416677
 1.00 361029 355030 348033 341034 334036 328040 326042 325046
      331045 335045 338044 346042 351040 357034 361029
 1.00 300804 300803 299802 298801 296801 294801 293801 292801
      290801 289801 289803 290805 291807 293808 295809 296808
      298807 300805 300804
 1.50 346037 344036 342036 341037 340037 339037 337038 335038
      334038 335040 336041 337041 338041 340041 341041 342040
      344039 346037 346037

$$





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