Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 200624
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
124 AM EST MON NOV 20 2017


PRELIM DAY 1 QPF DISCUSSION
VALID NOV 20/1200 UTC THRU NOV 21/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1


...PACIFIC NORTHWEST/NORTHERN AND CENTRAL ROCKIES...

A CLOSED MID LEVEL LOW OFF THE PACIFIC NORTHWEST COAST EARLY ON
DAY 1 WEAKENS AS IT CROSSES THE NORTHERN AND CENTRAL ROCKIES
DURING THE SECOND PART OF THE PERIOD. THE SHORT WAVE ENERGY
INTERACTS WITH DEEP PACIFIC MOISTURE THAT BECOMES FOCUSED ON THE
HIGHER TERRAIN BY A STRONG LOW LEVEL FLOW TO PRODUCE HEAVY TO
LOCALLY EXCESSIVE RAINFALL...MAINLY OVER SOUTHWEST OR AND
NORTHWEST CA. THERE WAS FAIRLY GOOD MODEL AGREEMENT WITH THE
OVERALL SYNOPTIC SETUP...WHICH RESULTED IN A SOUTHWARD PROGRESSION
OF THE HIGHEST QPF FOR DAY 1 INTO NORTHERN CA. THE WPC QPF WAS
BASED ON A BLEND OF THE 00Z GFS/12Z ECMWF...AUGMENTED BY THE 00Z
HREF MEAN/NBM TO BETTER DELINEATE HIGHER TERRAIN QPF MAXIMA.

THE FIRST SLUG OF DEEP PACIFIC MOISTURE IS EXPECTED TO AFFECT
SOUTHERN WA/NORTHERN OR DURING THE FIRST PART OF DAY 1. A 55 TO 65
KNOT LOW LEVEL SOUTHWEST FLOW TRANSPORTS 0.75/1.00 INCH
PRECIPITABLE WATER AIR ONTO THE HIGHER TERRAIN OF THE OR COASTAL
RANGE...MAINLY BEFORE 20/18Z. THE STRONG UPSLOPE FLOW...AUGMENTED
BY MARGINAL INSTABILITY (DEPICTED AS MUCAPE VALUES BETWEEN 100 AND
250 J/KG BY THE 00Z HREF MEAN)...IS EXPECTED TO PRODUCE AN AXIS OF
1.50 INCHES OF QPF ACROSS THE OR COASTAL RANGE. FURTHER INLAND
ACROSS THE OR CASCADES...THE UPSLOPE FLOW IS MORE EFFICIENT...AND
THE LOW LEVEL FLOW IS MORE PERPENDICULAR TO THE TERRAIN. THERE WAS
A MULTI HIGH RESOLUTION SIGNAL FOR 2.50 TO 3.25 INCHES OF QPF OVER
THE CENTRAL OR CASCADES...WHERE MINIMAL INSTABILITY COULD PRODUCE
AT LEAST SOME CONVECTIVE ELEMENTS TO THE PRECIPITATION CHARACTER.

THE FOCUS FOR HEAVY RAINFALL DROPS SOUTH AFTER 20/18Z...WHERE A 40
TO 50 KNOT LOW LEVEL SOUTH SOUTHWEST FLOW TRANSPORTS 1.25 INCH
PRECIPITABLE WATER AIR (WHICH IS BETWEEN TWO AND THREE STANDARD
DEVIATIONS ABOVE THE MEAN) ACROSS FAR SOUTHWEST OR INTO NORTHWEST
CA. THE SOURCE FOR THIS MOISTURE PLUME CAN BE TRACED BACK TO SOUTH
OF HI...
AND THE LOW LEVEL FLOW FOCUSES THIS MOISTURE ON THE HIGHER
TERRAIN. MODEL SOUNDINGS FROM THE 00Z GFS SHOWED MARGINAL
INSTABILITY IN THE COLUMN EMBEDDED IN THE PACIFIC MOISTURE PLUME
(WITH MUCAPE BETWEEN 100 AND 250 J/KG)...WHICH AUGMENTS THE STRONG
UPSLOPE FLOW.

THERE WAS A MULTI MODEL SIGNAL FOR 4.00 TO 5.25 INCHES OF QPF
ACROSS FAR SOUTHWEST OR AND NORTHWEST CA...WHICH REPRESENTS A
SOUTHWARD DISPLACEMENT FROM THE PREVIOUS MODEL SOLUTIONS. THE BEST
LIFT AND HIGHEST RAINFALL RATES ARE EXPECTED BETWEEN 20/18Z AND
21/06Z...DURING WHICH TIME FLOODING IS POSSIBLE...ESPECIALLY IN
BURN SCAR AREAS...POSSIBLY RESULTING IN ROCK SLIDES. A SLIGHT RISK
WAS PLACED OVER NORTHWEST CA AND FAR SOUTHWEST OR ON DAY 1 AS A
RESULT.

AS THE SHORT WAVE ENERGY CROSSES THE NORTHERN ROCKIES DURING THE
SECOND HALF OF DAY 1...THE PACIFIC MOISTURE PLUME REMAINS AT LEAST
PARTIALLY INTACT...AS PRECIPITABLE WATER VALUES RISE TO BETWEEN
0.50 AND 0.75 INCHES. 00Z GFS MODEL SOUNDINGS SHOWED MARGINAL
INSTABILITY AS LAPSE RATES STEEPEN...AND THE COMBINATION OF
MOISTURE AND INSTABILITY WILL MAKE THE MOST OF THE MOISTURE IN THE
COLUMN. AREAS OF 1.00 TO 1.50 INCHES OF QPF WERE PLACED OVER THE
SAWTOOTH RANGE AND THE NORTHERN BITTERROOTS IN ID...AS WELL AS THE
GRAND TETONS IN WY. LOWERING SNOW LEVELS SHOULD PRECLUDE THE
POTENTIAL FOR FLASH FLOODING...EVEN WITH THE POTENTIAL FOR
ISOLATED CONVECTION.

FINALLY...AS THE SHORT WAVE ENERGY CROSSES THE CENTRAL
ROCKIES...THE MOISTURE PLUME IS NOT AS ROBUST AS IN THE NORTHERN
PLAINS. HOWEVER...STEEPENING LAPSE RATES AND UPSLOPE FLOW SHOULD
COMPENSATE...PRODUCING LOCAL 0.25 TO 0.50 INCH QPF AMOUNTS OVER
THE BIG HORN RANGE IN WY...AS WELL AS THE NORTHERN CO ROCKIES.

HEAVY SNOWFALL IS EXPECTED OVER THE HIGHER TERRAIN OF THE NORTHERN
ROCKIES. PLEASE REFER TO THE MOST RECENT SUITE OF WPC WINTER
WEATHER PRODUCTS FOR MORE INFORMATION.


...NORTHERN PLAINS/GREAT LAKES....

FAVORABLE LAKE EFFECT CONDITIONS ACROSS THE LOWER GREAT LAKES ON
DAY 1 WILL RESULT IN QPF DOWNWIND OF LAKES ERIE AND
ONTARIO...MAINLY DURING THE FIRST HALF OF THE PERIOD. A
STRENGTHENING SHORT WAVE DIVING OUT OF CENTRAL CANADA INTO THE
UPPER GREAT LAKES WILL DRAG A COLD FRONT ACROSS THE NORTHERN
PLAINS AND UPPER GREAT LAKES...MAINLY DURING THE SECOND HALF OF
THE PERIOD. THERE WAS GOOD MODEL AGREEMENT WITH RESPECT TO THE
SYNOPTIC SETUP...SO THE WPC QPF WAS BASED ON A BLEND OF THE 00Z
GFS/12Z ECMWF. THE 00Z NAM/HREF MEAN WERE USED TO BETTER DELINEATE
THE LAKE EFFECT PRECIPITATION OVER THE LOWER GREAT LAKES.

ONGOING LAKE EFFECT CIRCULATIONS ACROSS THE LOWER GREAT LAKES ARE
SUPPORTED BY REASONABLY DEEP MIXED LAYERS (REACHING BETWEEN 750
AND 700 MB DURING THE FIRST PART OF THE PERIOD). THE WEST
NORTHWEST BOUNDARY LAYER FLOW IS CROSSING THE SHORT AXES OF LAKES
ERIE AND ONTARIO...BUT AS THE FLOW BACKS WITH TIME...THE LAKE
EFFECT SNOW CIRCULATIONS SHOULD BECOME MORE WEST/EAST ORIENTED.
THIS IS EXPECTED TO PRODUCE LOCAL 0.25 TO 0.50 INCH QPF AMOUNTS
DOWNWIND OF LAKE ONTARIO...WITH THE HIGHEST AMOUNTS IN THE HIGHER
TERRAIN.

FURTHER WEST...A STRONG SHORT WAVE DIVING OUT OF ALBERTA DURING
THE FIRST PART OF THE PERIOD EVOLVES INTO A LONG WAVE TROUGH THAT
CROSSES THE NORTHERN PLAINS AND UPPER GREAT LAKES...MAINLY AFTER
21/00Z. SURFACE LOW PRESSURE ASSOCIATED WITH THE TROUGH IS
EXPECTED TO REMAIN NORTH OF THE BORDER...BUT A COLD FRONT
ASSOCIATED WITH THE LOW CROSSES MN/WI AFTER 21/0Z. GENERALLY LIGHT
QPF AMOUNTS (UNDER 0.10 INCHES) ARE EXPECTED IN THESE AREAS WITH
THE FRONTAL PASSAGE.


...FL...

A DEEP EASTERLY FLOW ALONG AND NORTH OF A SLOWING FRONT BOUNDARY
ACROSS SOUTH FL DURING DAY 1 WILL ACT AS A FOCUS FOR MOISTURE AND
INSTABILITY TO FEED CONVECTION CAPABLE OF PRODUCING HEAVY
RAINFALL. THERE WAS GOOD MODEL AGREEMENT WITH THE PLACEMENT OF THE
FRONT...SO THE WPC QPF WAS BASED PRIMARILY ON A BLEND OF THE 00Z
GFS/12Z ECMWF.

A SLOWING COLD FRONT BECOMES NEARLY STATIONARY ACROSS FAR SOUTH FL
DURING DAY 1. ALONG AND AHEAD OF THE FRONT...A DEEPENING EASTERLY
FLOW WILL FOCUS 1.50 INCH PRECIPITABLE WATER AIR AND MARGINAL TO
MODERATE INSTABILITY OVER FAR SOUTH FL...MAINLY AFTER 21/00Z. THE
00Z HREF MEAN SHOWED MUCAPE VALUES BETWEEN 1000/1500 J/KG OVER FAR
SOUTH FL AND THE KEYS BETWEEN 21/06Z AND 21/12Z...WHEN THE BEST
CONVECTION IS EXPECTED. AN AREA OF ABOUT AN INCH OF QPF WAS PLACED
OVER THESE AREAS.

MOST OF THE 00Z HIGH RESOLUTION GUIDANCE SHOWED MAXIMUM QPF
AMOUNTS BETWEEN 1.50 AND 2.00 INCHES OF QPF OVER FAR SOUTH FL...AS
THE FRONT MOVES SLOWLY NORTH AS A WARM FRONT. THE 00Z WRF ARW
SHOWED AMOUNTS OVER 5.00 INCHES NORTH OF KMIA...BUT THIS COULD BE
HIGH...CONSIDERING THAT PRECIPITABLE WATER VALUES DO NOT APPEAR AS
THOUGH THEY TOP 1.50 INCHES.


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

HAYES

24HR QP VT 21/12Z
 0.01 543006 544995 544985 544968 541946 538931 532901 530891
      529881 527872 527862 525845 524826 520807 516792 510780
      507775 504771 499768 497765 494766 481768 477772 475777
      475786 478792 486823 487831 488836 486838 485840 483839
      479836 473834 468833 465837 466846 470853 473855 481862
      484869 486877 486884 485894 478920 477927 479935 483941
      486947 490959 494970 497978 500983 503990 505993 505998
      507013 508016 510019 514022 519025 524025 535023 540016
      543006
 0.01 516153 515147 515140 513131 510126 507123 502118 496110
      492101 486093 479086 475078 469071 466062 465052 463045
      460042 451036 442031 440030 435030 434036 434043 435048
      436052 437058 435064 432073 434077 439079 444082 448085
      448089 447090 442090 435088 426086 422087 421090 424097
      423101 419102 416103 413103 411099 409094 406093 404098
      404104 401110 396112 394112 394115 398116 401118 406119
      409126 413130 414131 415134 404148 401152 399158 398167
      398171 396174 392176 393179 396182 399181 404187 408196
      407201 403203 398201 395199 387194 378189 376194 378199
      382206 385209 385215 382220 380223 377226 374231 372248
      374256 373269 373275 374279 377288 379291 383294 385296
      390298 402303 408304 412302 417296 422297 426295 433291
      439286 450277 459271 467268 472262 477251 479238 482233
      486234 491240 494244 497244 500243 501241 503236 505221
      507206 508198 509196 510191 513171 514158 516153
 0.01 473887 473882 473878 473875 471873 469875 469878 469883
      468885 466888 466893 467898 467900 468900 470898 472893
      472890 473887
 0.01 456707 455702 453702 452705 448706 445708 444710 442711
      440714 438717 440720 443719 446717 450717 452716 453713
      454710 456707
 0.01 456796 456786 454780 453775 451772 448768 442767 443760
      445751 445744 446742 444740 444737 441738 435741 430745
      428750 428756 427765 426772 423777 419782 417785 419787
      417790 418797 419806 422806 426793 429788 429780 427777
      428774 430770 431773 433776 434780 437783 440789 442796
      443804 438806 436808 436813 437816 440818 449816 453822
      455825 457825 456818 456809 455803 456796
 0.01 445730 444727 443729 440728 438726 435726 432726 428727
      426729 425732 427732 429734 433733 436733 439732 443731
      445730
 0.01 443771 443769 441767 441769 441772 442773 443771
 0.01 428061 427058 423055 415052 410051 406052 397053 389057
      386060 385065 390073 392076 395079 400079 404078 409078
      413077 416075 419071 421065 424063 428061
 0.01 402687 401674 400667 398662 394659 392661 387668 386673
      387680 390693 392697 393704 394710 396715 397721 399721
      400716 400709 399703 400697 402687
 0.01 302810 295807 291805 287805 276790 269773 269768 265766
      261766 259768 242800 238806 235815 232824 232836 233848
      236856 237865 240870 242872 248872 252871 262869 267867
      273866 278866 284867 297876 300874 300868 301857 300851
      298847 291845 286841 284837 282832 280829 274828 271828
      260829 253830 250829 249826 250821 252818 255815 260814
      268810 278806 287806 291810 295811 302810
 0.01 294887 293883 289879 281879 279878 277884 276888 275892
      273894 269896 266900 265913 268917 272919 278919 283917
      290912 292907 293901 293895 294887 294887
 0.01 290962 291954 287949 282948 277952 273953 271951 268943
      265939 263937 259937 255937 254939 250945 248951 248960
      248968 248972 250976 255987 259988 266984 270984 272983
      275982 277980 285970 288966 290962
 0.25 528981 528973 527964 525946 524937 524927 524915 523906
      520866 518849 515832 513824 510819 507820 506823 503829
      501834 500842 498851 498860 498865 498870 496876 495881
      498883 500888 502895 503905 504914 506921 513952 515967
      520983 522987 525990 527989 528984 528981
 0.25 497151 496144 494139 487131 482128 476125 472123 468119
      468111 466105 464102 459100 454096 448094 444095 438094
      434094 432092 428092 426094 428099 427102 415113 416117
      421119 425122 429123 438117 442118 446117 450117 453122
      452126 449129 443130 441137 434143 430144 429146 429153
      426154 426148 423143 420144 420148 421152 419153 416153
      414155 412157 410161 410164 411169 410172 412176 415179
      417176 413172 414168 420168 430172 434176 436181 438196
      440202 442205 445206 446204 448198 453189 453183 454185
      458185 466181 473176 480170 486167 487164 487160 485156
      486151 488151 493153 497151
 0.25 482214 483209 480208 472210 467211 462208 459205 457209
      453213 450213 440210 437207 432209 428206 425203 418198
      414198 411200 409206 408209 405209 398204 390199 382197
      383201 385205 391212 394216 397219 402223 386228 383232
      383237 385247 387258 388262 388268 387279 389288 393293
      396295 404297 409294 414285 418283 422283 431282 442272
      445268 447261 446255 449253 455249 460242 463238 464232
      465226 467225 475218 482214
 0.25 481145 480143 479142 478142 477141 476141 475142 474144
      475144 476145 478145 480146 481145
 0.25 451178 451177 449176 448175 447174 446174 444174 443176
      444178 445179 447179 449179 450180 451178
 0.25 452080 453078 451076 450075 448074 446072 445070 443070
      442069 441069 440072 441073 442074 443075 444076 445077
      446078 448080 449081 451082 452080
 0.25 438760 438758 437756 435756 434758 434760 434761 434762
      434763 435765 436766 437765 437763 437762 438760
 0.25 431164 431163 431161 431159 430157 429157 427156 425156
      424155 424154 422155 423157 424160 425160 426163 428164
      429165 431164 431164
 0.25 410152 408151 407152 406152 405154 406155 408155 408154
      410153 410152
 0.25 416064 415062 414061 412060 411060 409060 408061 409061
      410063 412065 414066 416064 416064
 0.25 412071 412069 412068 410067 409066 409065 407065 405065
      403065 401066 401067 401069 399070 398071 398074 399075
      401074 403072 405071 406072 408072 410072 412071 412071
 0.25 407058 405057 404056 403056 402055 401055 401058 402058
      404059 405059 407058
 0.25 397062 397060 397059 395059 393061 392064 393066 394065
      396064 397062
 0.25 282858 282854 280852 276850 274847 268844 263841 260839
      255839 253841 250845 249847 250853 256855 264856 273857
      279859 282858
 0.25 263805 264796 262788 259783 256785 254787 252792 248796
      245801 243807 244811 246814 248815 253812 258810 262807
      263805
 0.50 487139 486133 480130 474128 470124 464135 459138 456144
      455147 456149 459155 463161 464166 466169 465172 460173
      454175 452169 453157 443148 439145 434147 433150 432154
      435160 437165 440169 448171 452176 454181 459182 464179
      467174 470170 475167 477165 479162 479157 478154 474151
      471146 470143 471140 477139 487139
 0.50 463223 464217 461214 455214 450215 446214 437212 425216
      417215 413213 409213 403211 397206 391202 385201 404226
      391230 386230 385234 389241 395254 397264 396276 393287
      397293 400291 402288 406281 411280 414279 420276 424275
      426272 430265 434257 438251 444246 450243 456240 458237
      459233 450232 448229 451228 463223
 0.50 446233 445231 445230 444233 445233 446233
 0.50 448187 448185 448182 446184 447187 448187 448187
 0.50 445111 442105 441103 440098 436098 432094 429094 429096
      431102 430104 427104 425105 425109 429112 434115 438112
      442113 445111
 0.50 424234 425232 424229 422229 422231 422232 423234 424234
 0.50 427208 426206 426205 424204 423203 422202 421202 419201
      418201 417201 416201 414201 412201 411202 412204 412205
      413207 415208 417208 418209 420210 422210 424210 425210
      427208
 0.50 261801 261799 259795 257794 255796 253798 250799 247800
      246803 246807 248808 251810 254808 256807 260806 261803
      261801
 1.00 469157 468156 468155 467153 467152 466150 465149 464148
      463147 461148 461151 462152 463154 463155 465156 465157
      467158 468158 469157
 1.00 456219 454216 452217 444215 437216 435218 431219 425220
      422221 423224 430228 435230 440227 448226 454221 456219
 1.00 462178 462176 461175 459176 458177 457179 457180 459180
      461179 462178
 1.00 451237 450236 448235 446235 445235 444236 443236 441237
      440238 440239 442240 444240 446239 447239 448239 449238
      451237 451237
 1.00 447162 446160 445160 444157 443157 443156 441155 440156
      439158 440161 440162 442163 443163 445164 447162
 1.00 430246 429241 426237 423236 415228 413222 410218 405214
      403214 403218 407222 408225 406229 404231 401230 397232
      394233 394237 397242 403252 407255 411254 416251 421249
      426248 430246
 1.00 400213 398211 398210 397208 396208 395207 395209 395210
      396212 398214 400215 400213
 1.50 449222 447217 442216 438216 434220 431221 427222 425223
      430226 435226 438223 443224 448224 449222
 1.50 429243 424238 420235 415230 410228 407232 400232 397236
      399241 403247 407248 413246 418245 425246 429243
 2.00 447219 445218 444217 442216 440216 439217 438218 437218
      436220 436222 438222 439221 441221 443220 445220 447219
 2.00 431224 430223 429223 428223 429224 430224 431224
 2.00 425244 426242 424239 421237 417234 413232 409232 406234
      401235 399239 401242 403244 405243 410242 413243 418243
      423245 425244
 3.00 425242 423239 420238 418236 414235 412236 409236 405236
      408239 409239 412240 415241 419241 422243 425242
 4.00 423241 422241 421240 419240 417238 416237 414237 412237
      411237 412238 414239 415240 417240 419240 421240 422241
      423241

$$





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