Quantitative Precipitation Forecast
Issued by NWS

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345
FXUS04 KWBC 151900
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST MON JAN 15 2018


PRELIM DAY 1 QPF DISCUSSION
VALID JAN 16/0000 UTC THRU JAN 17/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...SOUTHERN AND EASTERN U.S...

THE ARRIVAL OF ANOTHER LARGE ARCTIC AIR MASS INTO THE SOUTHERN AND
EASTERN U.S...WILL YIELD A BROAD SWATH OF LIGHT
PRECIPITATION...TRANSITIONING FROM ICE TO SNOW IN SOME SOUTHERN
LOCATIONS...AND FALLING PRIMARILY AS SNOW FARTHER NORTH AND EAST.
THE DISTANCE LAG BETWEEN THE MID-UPPER LEVEL TROUGHS AND THE
ARCTIC FRONT WILL FAVOR PREDOMINATELY ANAFRONTAL
PRECIPITATION...AND WHILE OVERALL LIGHT GIVEN THE ABSENCE OF
SUBTROPICAL CONTRIBUTION (NEGLIGIBLE PW AND LOW-MID LAYER MOISTURE
FLUX ANOMALIES)...THIS EVENT WILL CREATE WINTER WEATHER IMPACTS.
PLEASE REFER TO THE LATEST QPFHSD.

A TENTH OF AN INCH OF LIQUID EQUIVALENT IS LIKELY IN MOST PLACES
FROM TEXAS TO NEW YORK BETWEEN MONDAY AND TUESDAY AFTERNOON.
SOMEWHAT HEAVIER AMOUNTS...ABOVE A QUARTER INCH ON AVERAGE...ARE
EXPECTED BENEATH THE UPPER JET ENTRANCE REGION OVER TEXAS AND THE
LOWER MISSISSIPPI VALLEY...AND FROM THE CENTRAL APPALACHIANS
NORTHEASTWARD. IT IS HERE THAT THE UPPER FLOW IS FORECAST TO
BUCKLE AND INFLECT...LEADING TO FRONTAL WAVE DEVELOPMENT...AND A
COASTAL LOW TRACKING RIGHT ALONG THE NORTHEAST COAST. THIS
EVOLUTION WILL LEAD TO A SOMEWHAT HEFTIER PRECIPITATION EVENT FROM
LATE DAY 1 INTO DAY 2. ONE OF THE MORE CHALLENGING AREAS FOR QPF
IS OVER THE TEXAS HILL COUNTRY AND SOUTH TEXAS WHERE THE NCEP
GUIDANCE IS MUCH MORE AGGRESSIVE WITH QUARTER-INCH-PLUS
AMOUNTS...WHEREAS OTHER GUIDANCE IS DRIER. THE MAIN THRUST OF MID
LEVEL ASCENT / JET CIRCULATION ASSIST APPEARS TO BE FARTHER EAST
FROM THE PINEY WOODS TO THE MISSISSIPPI RIVER. FORECAST
SOUNDINGS...HOWEVER...DO SHOW A DEEP MOIST LAYER LINGERING BACK
OVER SOUTH TEXAS...AND GENERALLY CYCLONIC AND SOMEWHAT CONFLUENT
MID LEVEL FLOW COULD SUPPORT OCCASIONAL LIFTING AT THE TOP OF THE
MOIST LAYER...IN ADDITION TO WHATEVER CONTRIBUTION THERE IS FROM
LOCAL TERRAIN EFFECTS IN THE SATURATED LOW LEVELS. WPC TRIED TO
STRIKE A BALANCE...INCLUDING TO MAINTAIN CONTINUITY. THROUGHOUT
THE EASTERN U.S...QPF WAS DERIVED PRIMARILY FROM A BLEND OF THE
PREVIOUS WPC FORECAST AND THE 12Z HREF MEAN...WHILE USING A SMALL
PERCENTAGE OF THE MORE AGGRESSIVE 12Z GFS.


...PACIFIC NORTHWEST...

A LOW LEVEL FRONT AND PRE-FRONTAL DIFFLUENT UPPER LEVEL FLOW WILL
CREATE AN UPTICK IN LOW-LEVEL MOISTURE TRANSPORT/FLUX
CONVERGENCE...AND AN ELONGATED...LARGELY N-S AREA OF SHOWERS
DRIFTING IN FROM THE PACIFIC OCEAN. THE PARENT UPPER LEVEL SYSTEM
IS DEFLECTED NORTHWARD BY THE WESTERN U.S. RIDGE AND THE
RE-LOADING TROUGH OFFSHORE...SUCH THAT PRECIPITATION SHOULD
GENERALLY DECREASE IN COVERAGE AND INTENSITY OVER TIME AS THE
FRONT ADVANCES INLAND AND PAST THE CASCADES. MODELS ARE IN GOOD
AGREEMENT SUCH THAT BIAS CORRECTED TOOLS AND HI-RES ENSEMBLE MEANS
LIKE THE HREF SHOULD PERFORM WELL. THE HI-RES TOOLS INDICATE A
LOCAL MINIMUM THROUGH THE WILLAMETTE VALLEY AND ENHANCEMENT ALONG
SOUTH FACING SLOPES OF THE CASCADES...GIVEN PREDOMINANTLY
SOUTHERLY LOW LEVEL FLOW. WE LOOKED TO REFLECT THIS IN THE WPC QPF
USING THE WRF-NMMB...WHEREAS SOME OTHER SOURCES SUCH AS THE
WRF-ARW AND NAM CONUS NEST FEATURED AMOUNTS THAT ARE LIKELY TOO
HIGH.

HURLEY/BURKE

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

24HR QP VT 17/00Z
 0.01 535220 535211 533202 531194 527187 521181 517177 507169
      502165 495163 491162 488159 486156 483155 470148 463146
      456144 454146 451146 445149 441149 439150 430149 422147
      420145 417144 413143 409140 404141 397140 393144 391155
      391164 387171 387176 388178 390181 391186 387191 385193
      381191 375188 370187 371190 374197 376201 375205 374210
      372212 369213 367216 364225 362231 364234 365238 366245
      362251 364254 367256 373257 387257 400256 408258 410258
      415259 441259 468259 473262 476265 477269 481277 484282
      488288 494291 499289 502288 504285 506282 508275 508266
      508257 511252 513244 514238 514234 514229 513225 510222
      509218 507209 509204 511204 516207 520213 527224 532225
      535220
 0.01 483887 483874 479867 477862 474860 466861 463865 461863
      461859 460843 459836 460830 460825 461820 463814 462808
      462803 463800 468791 467788 469784 468779 467769 465763
      465756 464752 466750 465743 464737 462733 461729 462725
      465717 465709 464704 459698 456695 450696 445698 443698
      440697 438695 433696 431697 430694 428693 425693 420693
      414695 413699 410702 410705 413709 417710 426711 421719
      416724 411732 395761 390769 387776 385781 383786 377794
      372801 367806 362812 358819 349833 339847 337851 336854
      331861 328870 325874 324877 319886 316894 309911 306919
      302927 297933 289936 270941 260941 254941 252943 243955
      241957 240964 240974 238986 242994 252006 263019 270024
      275025 279026 283026 287029 294033 300038 306042 309047
      318052 326054 335056 346057 355058 357060 362058 368055
      377053 383054 386054 388052 387047 382047 378044 375040
      375035 373030 368030 366032 362038 355042 351048 347052
      342052 337051 333049 329046 323045 320043 317039 314037
      312032 310026 311020 313015 315011 318008 328993 335979
      341963 345956 348947 352938 357932 363924 366921 368916
      373898 375887 379880 387862 388858 390854 395846 403834
      408827 415821 418825 419829 418840 416851 416859 411861
      406866 407873 415879 414882 415890 417910 420914 422918
      428926 430928 434928 442930 445929 447925 450923 450918
      450913 447908 442903 435897 432894 431890 431887 435886
      441885 445885 449883 452881 456881 458882 459885 459892
      458898 458906 457913 458917 459921 462924 464925 467922
      472915 474907 483887
 0.01 443861 443858 441856 439854 438855 436855 435856 434857
      433859 433861 435863 436863 438863 440863 441862 443861
 0.01 385735 384729 382726 376721 367721 358724 341732 328743
      323750 317757 312762 309767 307771 312775 320774 329769
      336763 342758 353756 357757 362756 368755 371752 377747
      380744 383741 385735
 0.01 308793 304791 297791 286797 283798 279797 281790 280786
      281782 285779 286774 281771 276773 273777 266786 263790
      258791 245793 238795 235799 232804 230808 229822 229830
      230834 233835 235834 240830 244819 253812 257809 259808
      263807 269804 274806 286809 291810 296807 304801 307797
      308793
 0.01 293887 293878 292874 291872 286869 282869 277873 275877
      272890 269902 267909 267917 266921 270927 270931 272933
      277933 281931 283925 286912 288906 289899 291892 293887
 0.25 429733 429733
 0.25 505245 506238 506232 503221 491206 490203 486202 482202
      478203 475208 473213 474217 478219 479221 475222 472225
      469225 471215 463214 460215 456218 448219 440221 434219
      430217 427215 424217 422222 418220 415216 412213 407211
      404209 396204 391203 389203 387206 387210 387212 389216
      388222 385226 381233 380240 380245 385248 389248 398247
      408249 417249 427250 434248 442249 451249 460249 470251
      479256 484263 490271 494274 497273 499269 500265 501255
      505245
 0.25 443230 442227 441226 440226 439227 438228 436230 436232
      438233 440232 441232 443230
 0.25 424756 422751 420747 417748 416750 412754 408759 405764
      403771 405773 410772 414771 415768 417762 421758 424756
 0.25 368732 363730 357732 350734 345737 339740 335744 334746
      334750 338752 345750 350749 357746 362742 365737 368732
 0.25 342904 343901 340902 338905 332913 321926 317929 316934
      313939 310942 305950 301959 292975 290981 290985 293988
      296985 303979 308971 323960 328953 332945 334940 335933
      338923 337917 339911 342904
 0.25 288006 288999 287995 285991 282988 277987 273989 271993
      270999 271003 275006 278008 282010 285009 288006
 0.25 286889 285887 282887 280890 279892 278894 277898 276900
      276904 279906 282906 284902 284900 285896 285891 286889
 0.25 283962 283960 281958 276959 272960 268960 266955 263957
      259960 258964 261966 265964 267964 270966 272968 276968
      280966 283963 283962
 0.25 242809 242807 241806 239806 238807 237808 237810 236811
      236812 236814 236816 237816 238816 239815 240813 242811
      242809
 0.50 360736 358736 356736 354736 353737 352738 350741 348743
      346744 346746 348745 352745 355743 357741 358740 360738
      360736 360736
 0.50 502241 503233 501226 498220 495219 493221 491230 492237
      493242 487239 482240 480234 478231 475230 471235 467240
      468242 471245 476248 479249 481252 487262 492266 495268
      497267 499258 498250 498247 499245 502241
 0.50 459240 459237 458236 457235 455236 453237 452238 451239
      449239 447240 445240 444240 445243 446243 447243 449242
      450242 452243 453243 454242 456242 457241 458241 459240
 0.50 428245 428240 423236 418230 412228 408227 405231 399230
      394231 391232 387236 386240 390242 395242 402245 409244
      420245 425247 428245
 0.50 406220 405217 403215 402213 400211 397208 395207 393209
      393210 394213 396215 398217 401220 404220 406220
 1.00 494259 495257 495256 495254 494252 493251 492250 491248
      491247 489246 488246 487246 486248 487251 487252 488254
      490257 490258 491259 492260 494260 494259
 1.00 498234 498232 498229 497226 496225 495225 494227 494228
      494230 495233 496235 498234 498234

$$





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