Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 190632
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
132 AM EST SUN NOV 19 2017


PRELIM DAY 1 QPF DISCUSSION
VALID NOV 19/1200 UTC THRU NOV 20/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1


...GREAT LAKES/NORTHEAST...

A NEGATIVELY TILTED LONG WAVE WAVE TROUGH CROSSES NEW ENGLAND
DURING THE FIRST PART OF DAY 1...PUSHING A COLD FRONT ACROSS THE
NORTHEAST. AHEAD OF THE LONG WAVE TROUGH AND FRONT...A STRONG LOW
LEVEL SOUTHWEST FLOW TRANSPORTS DEEP MOISTURE AND MARGINAL
INSTABILITY THAT SUPPORTS CONVECTION PRODUCING LOCALLY HEAVY
RAINFALL ACROSS PORTIONS OF ME.  BEHIND THE LONG WAVE
TROUGH...COLD AIR ADVECTION FOSTERS LAKE EFFECT CIRCULATIONS AND
UPSLOPE FLOW. THERE WAS GENERALLY GOOD MODEL AGREEMENT WITH THE
SYNOPTIC SCALE EVOLUTION...SO THE WPC QPF WAS BASED PRIMARILY ON A
MULTI MODEL BLEND. THE 00Z NAM AND 00Z HREF MEAN WERE USED TO
BETTER DEFINE THE EXTENT OF LAKE EFFECT PRECIPITATION...
ESPECIALLY ACROSS THE LOWER LAKES.

AHEAD OF A DEVELOPING LONG WAVE TROUGH OVER THE LOWER GREAT LAKES
AND OH VALLEY EARLY THIS MORNING (AND ITS ASSOCIATED SURFACE COLD
FRONT)...A 40 TO 50 KNOT LOW LEVEL FLOW TRANSPORTS 1.25 INCH
PRECIPITABLE WATER AIR (WHICH IS BETWEEN TWO AND THREE STANDARD
DEVIATIONS ABOVE THE MEAN) ACROSS CENTRAL AND EASTERN ME...MAINLY
BEFORE 19/18Z. BOTH 00Z GFS/NAM MODEL SOUNDINGS SHOWED MARGINAL
INSTABILITY INSTABILITY IN PLACE IN THE MOISTURE PLUME (AS THE 00Z
HREF MEAN SHOWED AN AREA OF 250 J/KG MUCAPE JUST AHEAD OF THE
SURFACE FRONT). THE MOISTURE AND INSTABILITY...AUGMENTED BY
DIVERGENCE IN THE LEFT FRONT QUADRANT OF A 130 KNOT JET STREAK
EXITING THE MID ATLANTIC COAST...SHOULD BE CAPABLE OF SUPPORTING
LOW TOPPED CONVECTION OVER CENTRAL AND EASTERN ME...WHERE THERE
WAS A MULTI MODEL SIGNAL FOR 0.50 TO 1.00 INCHES OF QPF.

AFTER THE LONG WAVE TROUGH EXITS NEW ENGLAND...THE LOW LEVEL
NORTHWEST FLOW SUPPORTS UPSLOPE FLOW ACROSS THE FAVORED LOCATIONS
OVER THE HIGHER TERRAIN OF VT/NH AND WESTERN ME. THE 00Z NBM/HREF
MEAN SHOWED AXES OF 0.50 TO 0.75 INCHES OF QPF OVER THE HIGHER
TERRAIN HERE (A MIX OF CONVECTIVE PRECIPITATION AND
UPSLOPE)...WHICH LOOKS REASONABLE GIVEN THE STRENGTH OF THE
UPSLOPE FLOW AND THE DEPTH OF THE LOW LEVEL MOISTURE DEPICTED IN
MODEL SOUNDINGS.

FURTHER WEST BEHIND THE LONG WAVE TROUGH...THE BOUNDARY LAYER
NORTHWEST FLOW BECOMES MORE CONDUCIVE FOR LAKE EFFECT CIRCULATIONS
TO DEVELOP DOWNWIND OF LAKES ERIE AND ONTARIO. 00Z NAM MODEL
SOUNDINGS SHOWED MIXED LAYERS INCREASING TO NEARLY 850 MB DURING
THE PEAK OF THE COLD AIR ADVECTION...WITHIN AN AREA OF LOW LEVEL
VERTICAL MOTION. THESE FACTORS SUPPORT MORE ORGANIZED LAKE
CIRCULATIONS...AND THE 00Z NAM/00Z HREF MEAN SHOWED AREAS OF 0.40
TO 0.60 INCHES OF ON THE DOWNWIND SIDE OF THE LAKES. THE SHORT
FETCH (DUE TO THE BOUNDARY LAYER NORTHWEST FLOW) SHOULD LIMIT THE
EXTENT OF THE CIRCULATIONS...WHICH WEAKEN LATER IN THE PERIOD.


...PACIFIC NORTHWEST/NORTHERN ROCKIES...

A POSITIVELY TILTED LONG WAVE TROUGH OFF VANCOUVER ISLAND EARLY ON
DAY 1 SENDS SHORT WAVE ENERGY INTO THE PACIFIC NORTHWEST AND
NORTHERN ROCKIES. THE SHORT WAVE ENERGY TAPS DEEP PACIFIC MOISTURE
TO PRODUCE HEAVY TO LOCALLY EXCESSIVE PRECIPITATION ACROSS THE
HIGHER TERRAIN OF WESTERN WA AND OR. FOR THE MOST PART...THERE WAS
GENERALLY GOOD MODEL AGREEMENT WITH THE EVOLUTION OF THE LONG WAVE
TROUGH...SO THE WPC QPF WAS BASED ON A BLEND OF THE 00Z GFS/12Z
ECMWF. BOTH THE 00Z HREF MEAN AND THE 00Z NBM WERE USED TO BETTER
DELINEATE THE HIGHER RAINFALL AMOUNTS IN THE HIGHER TERRAIN.

AS A POSITIVELY TILTED LONG WAVE TROUGH APPROACHES THE PACIFIC
NORTHWEST DURING DAY 1...SHORT WAVE ENERGY EJECTED FROM THE LONG
WAVE TROUGH INTERACTS WITH 1.25 INCH PRECIPITABLE WATER AIR
TRANSPORTED TO THE WA/OR COAST ON THE NOSE OF A 50/60 KNOT LOW
LEVEL SOUTHWEST FLOW. THERE IS A MULTI MODEL SIGNAL FOR THE BEST
LOW LEVEL MOISTURE CONVERGENCE TO OCCUR IN THE 20/00Z TO 20/06Z
TIME FRAME (WHEN THE MOISTURE FLUX IS EXPECTED TO PEAK BETWEEN
THREE AND FOUR STANDARD DEVIATIONS ABOVE THE MEAN). THE STRONG
UPSLOPE FLOW...COUPLED WITH SYNOPTIC SCALE ASCENT IN THE LEFT
FRONT QUADRANT OF A 110 KNOT JET STREAK APPROACHING THE OR
COAST...SHOULD BE SUFFICIENT TO PRODUCE AXES OF 2.50 TO 4.00
INCHES OF QPF...WITH THE HIGHEST AMOUNTS ACROSS THE HIGHER TERRAIN
OF THE WA OLYMPIC RANGE (WHICH IS FAVORED IN THE LOW LEVEL
SOUTHWEST FLOW).

THE MOISTURE PLUME IS NOT QUITE AS ROBUST ACROSS THE WA/NORTHERN
OR CASCADES...BUT THE UPSLOPE FLOW AND SYNOPTIC SCALE ASCENT
SHOULD MAKE THE MOST OF THE MOISTURE IN THE PLUME TO PRODUCE 2.00
TO 3.00 INCH QPF AMOUNTS ALONG THE AXIS OF BEST UPSLOPE OVER THE
WA CASCADES.

AS THE BEST SYNOPTIC SCALE LIFT AND WHAT REMAINS OF THE PACIFIC
MOISTURE PLUME REACHES THE NORTHERN ROCKIES LATE IN THE
PERIOD...UPSLOPE FLOW FOCUSES THE MOISTURE ON THE HIGHER TERRAIN
ACROSS THE BITTERROOTS IN ID AND THE ROCKY MOUNTAIN FRONT RANGE IN
MT. THERE WAS A STRONG HIGH RESOLUTION SIGNAL (LED BY THE 00Z NAM
CONUS NEST AND THE 00Z HREF MEAN) FOR 0.75 TO 1.25 INCHES OF QPF
ACROSS THE NORTHERN BITTERROOTS IN ID...WITH LESSER AMOUNTS
(BETWEEN 0.50 AND 0.75 INCHES) OVER THE CENTRAL BITTERROOTS IN ID
AND THE NORTHERN ROCKY MOUNTAIN FRONT RANGE.

HEAVY SNOWFALL IS EXPECTED OVER PORTIONS OF THE PACIFIC NORTHWEST
AND NORTHERN ROCKIES. PLEASE REFER TO THE MOST RECENT SUITE OF WPC
WINTER WEATHER PRODUCTS FOR MORE INFORMATION.


HAYES


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

24HR QP VT 20/12Z
 0.01 476618 490620 496628 500637 509653 511658 513666 514672
      515679 516689 516695 514702 512707 508719 506730 504735
      504742 504748 500751 498751 492752 488755 485753 470761
      460764 456765 450767 444774 443779 446783 449787 450791
      454800 457811 458818 460824 465831 468835 471838 477847
      482857 483865 482868 479868 475870 472875 474884 473896
      472900 469905 466904 465898 464891 465885 465877 464872
      460862 457860 452860 449863 444864 433864 428862 423863
      420863 417865 415863 413859 413852 415849 418849 420851
      424853 427857 434856 437852 440846 444842 447841 448838
      447834 444831 438826 432821 426815 424812 420815 416823
      412826 408826 404822 401817 398814 396812 393813 389815
      384816 381821 377821 367822 364824 362828 357837 352843
      349844 348841 351831 356823 379800 386793 394788 399787
      402785 406783 410780 418773 419759 415749 407741 402738
      392739 385740 379742 374745 366747 360752 352757 346765
      333781 327789 323797 313812 302827 292837 286838 283836
      279836 277839 274845 269852 267856 264858 257866 250871
      247879 242887 240890 237889 232886 231881 230878 231870
      234861 234856 232852 233845 235837 238829 242819 244817
      250816 251820 254820 258826 260830 263828 275813 277808
      278805 274804 272802 266800 261802 256803 250803 248802
      248800 253792 258785 261778 266773 271766 279761 284760
      287756 293750 298745 302742 306742 308746 309752 308756
      306760 303763 303766 309767 312769 315770 317765 322756
      331737 334730 339724 345718 351710 372683 383669 394663
      399661 404659 416654 427650 442637 457625
 0.01 475618 474620 472620 471622 469623 467623 466623 464624
      462623
 0.01 429316 432313 437315 442317 446318 453315 460311 467305
      472299 478295 487294 494293 503292 511293 514290 527250
      528247 528245 528242 529240 529237 530235 531233 532232
      532230 533228 534228 535225 540206 542192 542181
      539167 532160 525154 517149 513146 508144 499139 492135
      485128 476122 471121 468123 468129 467136 462129 459130
      457130 456133 455142 452148 449150 443149 441152 440159
      443170 444176 443181 444185 445187 444191 441192 442198
      443204 443209 432210 429207 424205 415203 419212 420214
      418216 412215 403214 407222 408225 406227 401227 396228
      393230 386234 383236 380241 379243 379250 387259 395263
      404267 410269 411272 410276 405288 403295 401306
 0.01 499960 499954 496949 492942 486936 480929 475922 473918
      470917 470922 472925 472930 475939 479949 484957 489962
      497962 499960
 0.01 469200 469198 467198 465198 464197 462197 461198 462200
      463201 465200 467200 468201 469200
 0.01 430212 429209 427209 425210 425213 426214 428214 428213
      430212
 0.01 231973 235979 238980 242980 248976 252972 254964 254956
      254947 253943 250940 242941 237946 233951 231959 231965
 0.25 537202 537193 535184 532176 528171 523163 518158 506150
      500147 495143 486132 481130 479133 475132 475135 477137
      482140 484143 480147 476147 471148 468146 465147 461143
      459142 458145 459150 462158 463168 459173 456172 453170
      451171 451174 455181 461182 467180 477183 482189 495189
      498191 500190 503193 501195 499195 496195 494197 486196
      475204 428221 426222 428225 433231 433234 431237 429239
      424238 416234 412235 412240 417246 421252 423259 424263
      427266 430271 430280 430289 431295 433297 435297 442294
      450297 456299 459299 462296 472290 495278 506273 510270
      515265 518256 519242 520230 521223 524222 528220 532216
      535208 537202
 0.25 519218 519216 518215 517212 516210 515208 513206 512205
      512204 510203 509203 508203 508206 508207 509209 509210
      511211 511212 512213 514214 515216 517217 518218 519218
 0.25 506688 506677 503669 496652 489641 486636 481631 475631
      470634 462638 457642 448650 442664 438670 437677 435684
      435689 436695 437706 438716 438721 435724 430727 427728
      426732 428734 432735 440734 447734 452735 457739 464738
      470740 473740 477738 483735 487729 494726 498721 503707
      505698 506688
 0.25 484227 484225 482224 481223 479223 477222 476222 475222
      475224 475225 477225 479226 480228 480229 482229 483229
      484227
 0.25 460160 459160 458158 457157 456156 455157 455159 456160
      458160 459161 460160
 0.25 447809 447807 447805 447802 447800 446797 444797 444798
      444800 445802 445805 445807 446809 447811 447809
 0.25 440757 440753 436751 435750 431750 429750 428751 427755
      427758 427761 428764 429768 431771 433773 435770 436765
      436763 438760 440757
 0.25 420683 420679 418675 415672 410673 403675 394678 385685
      378692 371700 359716 353724 347734 343742 340751 344750
      347746 355738 362732 371726 390716 399710 407703 413696
      419685 420683
 0.25 425793 426789 424786 422787 420790 418792 416795 416797
      416802 416807 419807 420805 422801 423799 424796 425793
 0.25 392796 391795 390795 388796 387797 386799 386800 388800
      390799 391797 392796
 0.50 533201 533189 532184 529180 519163 513158 505156 508159
      507161 506161 496162 493160 489158 484156 479154 477156
      478162 481165 485173 493177 496174 497172 500173 504182
      507187 509190 516198 521204 522208 525213 529213 531210
      533201
 0.50 513258 515248 516238 515230 513223 495203 486200 475205
      471210 466209 459211 455214 443215 439219 440229 438241
      437248 434256 435262 438267 442274 442278 444282 453289
      460292 466288 474281 484276 492271 498270 504268 509263
      513258
 0.50 501687 500677 498670 495661 491654 485643 481639 478639
      474642 469644 463646 455650 452654 447667 445673 444677
      445683 452693 455699 455703 453706 441711 440713 440719
      444719 446719 445722 442726 435727 434730 436732 439731
      449725 454721 456720 458722 465730 470731 477729 486721
      495710 497705 499699 501687
 0.50 501152 499151 498150 496149 496148 495147 493145 493147
      493148 494150 494151 496152 497154 499155 500155 501153
      501152
 0.50 485230 486228 486225 484223 483222 481221 479221 478220
      476220 474220 473221 472221 472223 472225 474226 475226
      477226 478227 479228 480230 481231 483231 485230 485230
 0.50 490142 490139 489138 488136 487135 486134 485133 484133
      484135 484136 485138 486139 487140 488141 488142 490142
 0.50 474161 474159 473158 472156 472155 471153 470152 469152
      468152 468155 468157 468159 468160 469162 469164 471164
      473163 474161
 0.50 463178 461176 459176 458177 459179 461180 462179 463178
 0.50 425244 425242 424240 423239 423238 421237 420238 419240
      420241 422243 424244 425244
 0.50 433768 433766 433764 432763 432764 432766 433768 433769
      433768
 0.50 418239 417239 417237 416236 415236 414238 415240 417239
      418239
 0.50 396694 395689 391688 384693 378698 373703 369709 366715
      364718 367721 373717 380712 385707 389702 394696 396694
 1.00 523181 523179 522176 522175 521173 520170 519168 517167
      517169 517172 518175 518177 519179 521181 522181 523181
 1.00 509254 511245 511237 510228 508223 504219 501214 498210
      493207 487205 481206 476207 472212 472214 469213 465212
      462213 460215 451217 442219 445223 449225 451222 453222
      458226 461229 457231 452231 448234 444239 447243 452244
      458244 461246 464247 466249 467255 471257 473256 478257
      484260 497264 501261 502257 507256 509254
 1.00 512181 513178 512176 512175 511173 510171 510170 509169
      507168 506168 505169 505171 505172 506174 507176 507177
      508178 510180 511181 512181
 1.00 491235 490229 489226 486223 481220 476218 471218 469220
      467227 469229 471229 475228 479231 482234 484235 489235
      491235
 1.00 485666 485663 485661 484659 483656 483657 482659 483662
      483664 484666 485666
 1.00 491170 491169 490168 489166 488165 486165 485166 486168
      487168 489169 489170 491171 491170
 1.50 507245 508239 508232 504226 500218 498214 494210 490210
      486208 478208 475211 474213 475216 480217 485220 491224
      493234 494238 493242 486236 483238 481235 478231 473231
      471235 472239 474244 477247 484251 491257 493260 498261
      498256 495252 498247 502247 506246 507245
 1.50 466237 466233 464230 462233 460233 457233 454233 452233
      449234 447236 447240 451241 454241 456241 459241 461239
      463238 466237
 1.50 469217 468214 465214 463215 461217 459218 456218 454218
      455220 457222 460224 464224 465221 466218 469217
 2.00 504241 505238 505234 503231 501226 499222 497216 492215
      491217 491220 492226 493231 495236 498239 502242 504241
 2.00 496260 497256 495253 493246 490242 486238 483243 480237
      476233 473234 473239 476243 479245 483246 487250 491255
      494260 496260
 2.00 488218 490216 490214 489212 487211 486210 484210 483209
      481209 479209 478210 477211 476212 477214 479214 480215
      482216 483217 485217 487218 488218 488218
 2.00 460237 460235 459234 457234 456234 455234 453234 452235
      451235 450235 448236 449239 451239 453239 454239 456239
      458239 460238 460237
 2.00 462223 462222 460221 459221 458222 459222 460223 462223
      462223
 3.00 500235 500234 499232 499230 498229 498226 497225 497223
      496222 495221 494223 494225 494226 494228 495231 495232
      496234 498235 499236 500235
 3.00 495257 495256 494254 494253 493251 492250 491250 491253
      492254 493256 495257 495257
 3.00 479241 478239 478238 477236 476235 474236 473237 474237
      475239 476240 477240 478241 479241

$$





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