Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 201933
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
233 PM EST TUE FEB 20 2018


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


DAY 1

...LARGE SCALE HEAVY RAIN / FLOOD EVENT...

...EASTERN PLAINS / MID-UPPER MS VALLEY / GREAT LAKES / UPPER OHIO
VALLEY...

A SYNOPTIC PATTERN THAT SHOULD SPARK GREAT CONCERN OVER HEAVY
RAINFALL CONTINUES TO COME INTO PLACE...WITH LARGE SCALE
AMPLIFICATION OF THE WESTERN U.S. TROUGH...BLOCKED BY A 594 DM
RIDGE IN THE ATLANTIC...ALLOWING FOR PROLONGED ELONGATED MOISTURE
TRAJECTORIES EMANATING FROM THE CARIBBEAN BEFORE ENCOUNTERING A
SLOW MOVING FRONTAL ZONE IN THE MIDDLE OF THE NATION. PWAT VALUES
REMAIN WELL ABOVE NORMAL...WITH NEAR RECORD TO RECORD VALUES
STRETCHING FROM EAST TX ALL THE WAY INTO THE GREAT LAKES REGION.
SYNOPTICALLY HAVE SHORTWAVE ENERGY EJECTING INTO THE NORTHERN
PLAINS...HELPING INTENSIFY THE UPPER JET OVER THE AREA. INCREASED
ASCENT IN THE RIGHT ENTRANCE REGION OF THIS JET WILL HELP MORE
WELL DEFINE THE COLD FRONT OVER THE MIDDLE OF THE COUNTRY...AND
HELP PUSH IT EASTWARD WITH TIME. FROM THE MID MS VALLEY NORTHEAST
INTO THE OH VALLEY AND GREAT LAKES...THE FRONT WILL BE MORE
PROGRESSIVE IN NATURE HELPING CAP RAINFALL MAGNITUDES. STILL LOOKS
LIKE A BROAD SWATH OF MODERATE RAINFALL TOTALS THOUGH...AND SOME
WEAK INSTABILITY MAY TRY TO MOVE NORTH AHEAD OF THE EASTWARD
MOVING FRONT. THIS COULD RESULT IN SOME EMBEDDED CONVECTIVE
ELEMENTS AND LOCALLY HEAVY RATES INTO PORTIONS OF MO/IL/IN/MI INTO
THIS EVENING. GIVEN THE DEEP FROST DEPTHS AND INCREASINGLY
SATURATED CONDITIONS OVER THIS AREA...SHOULD THESE HIGHER RATES OF
BETWEEN 0.5"-1" IN AN HOUR MATERIALIZE...A FLASH FLOOD THREAT IS
POSSIBLE ON TOP OF THE ONGOING AREAL FLOODING.

THE FOCUS FOR HEAVIEST RAINFALL THROUGH THE DAY 1 PERIOD IS FROM
NORTHEAST TX INTO SOUTHEAST OK...AR AND NORTHERN LA. IT IS ACROSS
THIS AXIS WHERE THE COLD FRONT SHOULD BECOME NEARLY STATIONARY (OR
AT LEAST SLOW) THIS EVENING. CONTINUED MOISTURE TRANSPORT INTO
THIS BOUNDARY SUPPORTS TRAINING CONVECTION INTO TONIGHT. ON
WEDNESDAY AN ADDITIONAL WAVE APPROACHES FROM THE WEST ALONG WITH
THE LEFT EXIT REGION OF THE SUBTROPICAL JET. THIS SHOULD SUPPORT
AN INCREASE IN 850 MB MOISTURE TRANSPORT INTO THE
BOUNDARY...RESULTING IN INCREASING CONVECTIVE COVERAGE/INTENSITY
THROUGH THE DAY. CONVECTION SHOULD BE ABLE TO TAP INTO ENOUGH
INSTABILITY TO SUPPORT A CONTINUED EASTWARD PROGRESSION WITH TIME.
FOR THIS REASON FAVORED A BIT MORE OF THE PROGRESSIVE GUIDANCE
ACROSS TX/AR/LA ON WEDNESDAY. THIS INCLUDED THE 12Z RUNS OF THE
HRW ARW/ARW2/HRRR EXPERIMENTAL AND 0Z UKMET. ALL OF THESE
SOLUTIONS WERE A BIT MORE PROGRESSIVE THAN OUR PREVIOUS FORECAST
ACROSS THE LOWER MS VALLEY AND SEEMED TO FIT OUR EXPECTATIONS
BEST. THE DAY 2 (12Z WED-12Z THU) MODERATE RISK WILL THUS BE
SHIFTED A BIT SOUTHEAST TO MATCH THIS QPF AXIS. IT SHOULD BE NOTED
THAT SOME UNCERTAINTY WITH THIS AXIS ON WEDNESDAY REMAINS...WITH
SOME GUIDANCE EVEN MORE PROGRESSIVE THAN OUR NEW FORECAST...AND
OTHERS STILL SLOWER. THUS WILL NEED TO CONTINUE TO MONITOR TRENDS.
FOR NOW OUR 30 HOUR TOTALS (18Z TUE-0Z THU) SHOW 3-6" FROM
NORTHEAST TX INTO SOUTHEAST OK...CENTRAL AND WESTERN AR AND
NORTHERN LA...WITH A 4-7" MAX OVER NORTHEAST TX.


...ELSEWHERE...

LITTLE CHANGE TO THE FORECAST OUT WEST BENEATH THE DIGGING UPPER
TROUGH. THE SAME BLEND USED FOR THE EASTERN U.S. WAS APPLIED HERE
AS WELL. SOME OF THE HEAVIER SNOWFALL SHOULD OCCUR IN
WESTERN/CENTRAL COLORADO AND NORTHERN NEW MEXICO... SEE QPFHSD FOR
DETAILS.

CHENARD

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



THIS DISCUSSION WILL TRANSITION TO MIXED-CASE FEB 26, 2018.  THE
LISTING OF ISOHYET POINTS CONTAINED BELOW WILL ALSO BE ELIMINATED
FROM THE PRODUCT FEB 26, 2018.  ISOHYET GRID INFORMATION WILL
CONTINUE TO BE GENERATED IN A VARIETY OF BINARY FORMATS AND MADE
AVAILABLE THROUGH THE WPC GIS PAGE.

24HR QP VT 22/00Z
 0.01 397304 409305 412305 415304 419301 422295 424287 424280
      424273 423270 425266 430266 443265 448264 454265 463264
      466265 467268 470269 472268 474267 477263 478254 479248
      477240 478232 478225 476210 473204 472201 469199 463196
      459192 453185 461154 463149 462143 453136 449138 445142
      442144 439141 436141 435142 435149 437154 439158 443164
      445169 445173 442175 440177 436177 432180 428183 425188
      424193 422195 421200 413207 412217 408224 407233 404239
      404244 403246 400246 386242 379239 373236 369237 364241
      359249 358255 360262 367272 374281 379289 384296 389302
 0.01 528721 527716 526711 523701 516680 512669 505659 496645
      492639 489637 485635 480632 477632 472633 465634 459636
      454638 451637 449638 446643 443650 442653 443660 443664
      445669 447682 448690 447695 444706 435723 429728 427730
      425727 421725 418728 415731 414734 411740 409747 405752
      398757 397766 397771 396775 396783 393785 389787 384788
      379789 377791 374796 373801 369802 370797 368795 365798
      358798 354799 351801 347816 338825 335829 331830 322832
      313833 305833 294834 293837 295839 303842 303846 305849
      311855 319860 325863 330868 334868 333873 331876 328880
      322882 314883 309883 306882 302886 298893 296895 296900
      296912 293920 280931 276940 273949 270955 271961 271970
      270973 266975 264978 265981 264985 262986 258988 253988
      244986 242985 240989 241996 246003 248012 250020 254023
      257027 260027 263023 268016 280011 285011 289013 294019
      304028 317033 329025 341015 345017 349016 348020 345023
      333036 331038 332041 333047 334046 346037 354028 359023
      360018 361012 363002 366996 377983 382975 382970 379965
      376957 373954 374950 378944 382941 392929 401919 412905
      420893 430879 439864 446856 452851 463842 467837 473833
      478828 480826 484825 491843 507875 512869 519862 526855
      526842 525836 527831 526820 525808 526802 526797 525784
      525776 526770 524744 525728 528721
 0.01 477157 478152 476149 475146 473145 470143 468142 466142
      466145 467150 469152 470155 472156 473159 475159 477157
 0.01 450112 449109 447106 446106 444103 443101 439100 437102
      436105 435107 435110 438111 440113 443115 445116 447114
      449114 450112
 0.01 432169 431168 429165 428163 426163 424165 422167 420168
      418170 417175 417177 419178 423176 425175 426175 430173
      431171 432169
 0.01 402214 403207 402202 402200 400199 395197 387193 383190
      378188 372183 366182 363184 365190 374194 380200 386206
      394212 400215 402214
 0.01 410045 410038 408037 405035 401035 398036 394036 389038
      383044 381051 382055 384058 390058 393057 397055 402051
      408047 410045
 0.01 381078 382073 382069 377064 377059 376056 372053 363052
      359054 355055 352055 347055 338053 332051 330053 327053
      328059 333064 339065 341068 340071 337073 336075 343076
      349075 356074 363075 367075 370077 375080 380080 381078
 0.01 343180 345169 343166 341168 336166 331162 322159 319157
      315156 307155 309158 312161 316166 320167 324169 331172
      334174 338175 343180 343180
 0.01 288808 285804 282802 275798 268795 262795 258794 256791
      252792 250796 247798 244802 243807 244809 249810 258806
      262804 267804 274806 283808 288808
 0.25 513704 512695 511687 507681 503679 496665 492658 489654
      481648 476647 471647 468651 466657 465670 467678 470682
      471687 471691 465694 461698 458705 452718 447726 448730
      449738 447744 445752 447755 446761 443772 441779 438785
      435792 431797 422804 410807 403815 397823 394828 391831
      384833 380836 375839 371844 362854 355862 342879 336887
      331896 322902 315911 312917 308921 303926 299930 295933
      292938 291943 290949 289956 287963 283972 278981 279987
      282993 298012 302015 307018 313018 317015 323009 330001
      342986 346982 350977 354971 356969 356964 357957 360953
      366945 380931 395913 410893 421876 433857 438846 445835
      451825 458811 460805 462799 463793 463784 463777 464771
      466765 469761 476752 477747 474741 471739 470735 474730
      482721 486721 489726 494738 497743 501741 504737 507732
      509726 511718 513704
 0.25 465219 463214 460212 457212 451211 448212 444215 441220
      442222 442227 447230 451229 454228 458225 461223 464221
      465219
 0.25 453243 453239 451238 447239 444240 441237 437235 435237
      433241 433246 437249 441247 444247 448246 452244 453243
 0.25 357837 357831 356826 354823 350822 346829 342834 337840
      332844 332848 334851 340854 347856 353853 356846 355841
      356839 357837
 0.50 494686 493682 491675 489670 486666 484662 480660 478662
      478666 480672 482676 485682 487686 489689 493691 494686
 0.50 474713 474710 473710 471709 470709 468709 466711 466712
      466715 466717 467718 469719 471718 472716 473715 474713
      474713
 0.50 453791 453786 451784 445789 436802 429816 426820 421825
      417830 415833 412833 412831 407831 402835 397840 392844
      384845 378848 342890 338895 332900 326904 320909 313921
      310926 306930 301936 298942 292959 291968 288975 282986
      285991 289996 295001 298004 302006 308007 311002 315997
      320992 325989 330984 334977 337973 341971 347962 356952
      377930 384921 392910 411884 418875 425862 439832 445821
      447814 449804 453791
 0.50 354830 353827 351826 349828 348831 347833 346836 344838
      344842 347844 348842 350839 352837 353833 354830
 1.00 419853 419849 418847 415848 407857 401864 395872 386875
      380874 377869 372868 368871 362876 356884 352885 340898
      333904 324913 319917 313926 303945 299955 297966 294979
      293985 295991 298994 301995 303994 305990 308987 317984
      323982 328977 334970 339964 353947 359942 366935 372927
      380919 389902 404885 409878 414870 417861 419853
 1.50 410868 409867 407869 405872 404874 402877 400879 398881
      396883 394885 397887 399885 401883 403880 405878 407875
      408873 409870 410868
 1.50 392890 392889 390888 389888 390888 391890 392890 392890
 1.50 389890 386889 382890 379888 375888 363892 355893 349897
      345901 339904 334908 330913 326917 321920 316925 313932
      307943 303958 302965 300973 299980 301983 306982 312980
      317979 324977 329972 337962 354943 363934 370924 378914
      382902 389890
 2.00 366923 368916 367908 361903 358899 352900 347906 344909
      340908 334913 328919 321923 317925 315930 311937 310941
      310948 307958 309969 315974 321975 326973 332967 342954
      354941 364927 366923
 3.00 354932 352929 350923 346917 341919 338921 333921 329930
      330934 333936 322945 321931 318933 314937 315941 317943
      320944 320946 318951 316958 315963 319966 320969 323969
      330963 334958 344945 350939 354932 354932
 4.00 342939 339937 335941 330944 326947 323952 321960 325962
      330958 334954 337949 339943 342939
 5.00 334949 335947 334946 332946 330947 328948 327949 327950
      325952 325953 324954 324956 325958 326958 327958 328957
      329956 330955 331954 332952 333952 334950 334949

$$





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