Quantitative Precipitation Forecast
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

000
FXUS04 KWBC 200649
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
248 AM EDT MON MAR 20 2017


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


DAY 1...

...WESTERN U.S AND NORTHERN PLAINS....

SYNOPTIC OVERVIEW:

DEEP-LAYER WAA/MOISTURE WITHIN THE INITIAL WARM CONVEYOR BELT
(WCB) EARLY IN THE PERIOD WILL SEGUE TO ANOTHER (MORE MERIDIONAL)
WCB ACROSS THE WESTERN CONUS DURING DAY 1. THIS AS THE UPPER FLOW
BECOMES INCREASINGLY DIFFLUENT AHEAD OF AN AMPLIFYING (REINFORCED)
UPPER TROUGH OFF THE COAST...AS THE UPPER LEVEL JET STREAK ROUNDS
THE TROUGH BASE AND APPROACHES SOUTHERN CA BY THE END OF THE
PERIOD (12Z TUE). THE PERSISTENT BROAD-SCALE QS VECTOR CONVERGENCE
AND ATTENDANT DEEP-LAYER WWA FORCING/MOIST ISENTROPIC ASCENT WILL
GENERATE ADDITIONAL MODERATE-HEAVY PCPN ACROSS NORTHERN CA AND FAR
SOUTHWEST OR...WITH THE HEAVIEST AMOUNTS ONCE AGAIN TIED TO THE
TERRAIN. THIS INCLUDES THE COASTAL RANGES...SHASTA/SISKIYOUS...AND
NORTHERN SIERRA...AREAS THAT WILL BENEFIT THE MOST AT THE LEADING
EDGE OF THE SUBTROPICAL MOISTURE PLUME (PWS AOA 1.0").
AREAL-AVERAGE QPF TOTALS ARE EXPECTED TO RANGE BETWEEN 1-2+" OVER
THE OROGRAPHICALLY-FAVORED RANGES...WITH THE ASSORTMENT OF
HIGH-RES GUIDANCE SUPPORTIVE OF LOCALLY HIGHER AMOUNTS (3-4
INCHES) ACROSS THE AFOREMENTIONED NORTHERN CA-SOUTHWEST OR RANGES.

FARTHER DOWNSTREAM INTO THE GREAT BASIN...NORTHERN ROCKIES...AND
SOUTH PORTIONS OF THE NORTHERN PLAINS...MOISTURE ANOMALIES ARE
JUST AS HIGH DESPITE THE LOWER PW ENVIRONMENT TO WORK WITH (CLOSER
TO 0.50"). THE DEEPENING MOIST ISENTROPIC ASCENT OVER THIS REGION
ALONG WITH THE UPSLOPE ENHANCEMENT AND A PERIOD OF LOW-MID LAYER
FRONTOGENESIS VIA THE RIGHT ENTRANCE REGION OF THE UPPER JET
STREAK WILL GENERATE LIGHT-MODERATE PCPN TOTALS...GENERALLY
AVERAGING 0.25-0.50 INCH. THIS WILL ALSO INCLUDE A RELATIVELY
NARROW AREA ACROSS THE NORTHERN PLAINS (PARTICULARLY FROM NORTHERN
NE INTO SD)...WHICH WILL BENEFIT FROM THE INCREASING LOW-LEVEL
EASTERLY FLOW (GRADUAL UPSLOPE) ON THE BACKSIDE OF THE SURFACE
HIGH.

MODEL PREFERENCES:

HIGH FORECAST CONFIDENCE IN A NON-GFS GENERAL MODEL
COMPROMISE...WITH EMPHASIS ON THE HIGH-RES MEANS (INCLUDING THE
HREF... IN-HOUSE BIAS CORRECTED HIGH-RES ENSEMBLE...AND PARALLEL
NBM) GIVEN THE BETTER SENSITIVITY OVER THE HIGHER TERRAIN. THE GFS
WAS A NOTICEABLY WET OUTLIER OVER FAR NORTHWEST CA AND SOUTHWEST
OR...DEPICTING A POCKET OF AREAL-AVERAGE TOTALS OVER 2 INCHES.

EXCESSIVE RAINFALL POTENTIAL:

MARGINAL ACROSS NORTHERN CA AND FAR SOUTHWEST OREGON...INCLUDING
THE COASTAL...SHASTA/SISKIYOUS...AND NORTHERN SIERRA RANGES
THEREIN. LOCALIZED TOTALS OF 3-4"...THE BULK OF WHICH EXPECTED TO
FALL WITHIN 12-18 HOURS MON AFTERNOON AND OVERNIGHT...WILL
POTENTIALLY LEAD TO LOCALIZED SHORT-TERM RUNOFF
ISSUES...PARTICULARLY IN AREAS OF MORE RAPID SNOWMELT.


...OHIO VALLEY / APPALACHIANS / MID ATLANTIC...

SYNOPTIC OVERVIEW:

THE SHORTWAVE TROUGH OVER THE EASTERN CONUS EARLY IN THE PERIOD
WILL GIVE WAY TO SHEARED ENERGY/VORT LOBES WITH ENSUING FLATTENING
(ZONAL) FLOW ALOFT. THE DEGREE OF UPPER DIVERGENCE AND DEEP-LAYER
ASCENT BEHIND THE DEPARTING UPPER RIDGE WILL BE TEMPERED SOMEWHAT
BY THE BROAD RIGHT-EXIT REGION FORCING FROM THE STRAIGHT UPPER
LEVEL JET STREAK -- WHICH WOULD FAVOR INCREASED SUBSIDENCE.
BELIEVE THE COMPETING SYNOPTIC FORCINGS ARE RESPONSIBLE FOR THE
CONTINUED MODEL QPF DISCREPANCY...BOTH IN TERMS OF AMOUNTS AND
LATITUDINAL PLACEMENT. MOREOVER...THE MODELS ARE EXHIBITING
DIFFICULTY HANDLING THE CONVECTION BREAKING OUT EARLY THIS AM
ACROSS THE UPPER GREAT LAKES REGION. BELIEVE THE STEEP MID LEVEL
LAPSE RATES (7-8C/ KM BETWEEN 700-500 MB) ARE CHIEFLY
RESPONSIBLE...WHICH IS ANOTHER COMPONENT IN THE EXIT REGION OF A
BROAD...STRAIGHT UPPER JET STREAK. DESPITE THE DIFFERENCES IN THE
DETAILS... THE MODEL CONSENSUS IS FOR MODEST QPF (AVERAGING
0.25-0.50 INCH FOR MOST) ACROSS MUCH OF THE OH VALLEY INTO THE
WESTERN SLOPES OF THE APPALACHIANS (WITH THE UPSLOPE WESTERLY
LOW-LEVEL FLOW)...BUOYED AT LEAST TO SOME DEGREE BY THE MODEST
MOISTURE ANOMALIES ALONG WITH THE STEEPENING MID LEVEL LAPSE
RATES. PER THE SREF AND GEFS...BOTH PW AND 850-700 MB MOISTURE
FLUX ANOMALIES ARE EXPECTED TO AVERAGE AROUND 2 STANDARD
DEVIATIONS ABOVE NORMAL.

MODEL PREFERENCES:

A BLEND OF THE 00Z ECMWF...UKMET...AND RGEM...ALONG WITH HIGH-RES
MEANS (HREF...IN-HOUSE BIAS CORRECTED HIGH-RES QPF...AND PARALLEL
NBM) GIVEN THE CONVECTIVE CONTRIBUTION. THE GFS IS A DRY OUTLIER
ACROSS IL-IN-OH...WHILE THE NAM AND PARALLEL NAM ARE TOO FAR NORTH
WITH THE HEAVIER QPF.

EXCESSIVE RAINFALL POTENTIAL:

NONE.

HURLEY

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

24HR QP VT 21/12Z
 0.01 340272 357273 372274 376275 379274 386276 401281 418287
      425290 428291 432289 438285 446283 450285 452288 454292
      455296 454302 454306 456315 460321 468325 476327 481327
      492324 497319 501313 509296 511283 511273 507256 503216
      500212 495213 491212 490209 491199 490194 491187 492176
      493161 491152 490147 487146 484143 482143 475145 473141
      474136 468033 469026 468021 466013 464008 460007 455011
      453005 451998 449990 445983 436970 432961 428952 425945
      424940 423937 419938 417940 415947 414957 413969 412975
      411978 406984 405986 404992 404002 408005 411007 411010
      414020 415025 415031 415038 413040 410040 406040 404042
      401050 399055 392061 387067 386077 386081 390081 393083
      395085 394087 393093 392098 395103 397102 397099 396094
      398090 402084 405083 408086 406096 404105 403107 401107
      399107 394112 394115 398115 406116 410113 411110 411100
      411094 412088 417083 423084 427080 433076 435080 435085
      434091 430089 424089 426094 428097 431099 430104 425108
      428111 429113 427117 423124 421143 422148 422154 424161
      425165 423167 419171 416172 415175 414179 416177 418180
      416183 413185 408184 400187 393191 388193 382189 375186
      371184 366183 361183 360186 362193 356197 351195 349193
      343190 339193 330201 319213 315219 313223 314227 319233
      322235 326236 338245 341247 339250 336253 332258 330263
 0.01 518790 514776 509775 504780 498789 495794 492800 482824
      477837 476844 477855 479860 482865 487869 489870 490874
      489890 488898 490906 493911 497914 500911 500901 499898
      499893 500887 506873 510860 513843 514835 514828 516811
      518790
 0.01 467717 465708 463704 460701 455701 450705 445711 441718
      437725 436728 432730 426734 417735 403738 385742 372749
      367753 363759 361765 362774 363780 365783 369789 370792
      371798 367802 362809 360816 353826 351828 351833 350837
      350843 351864 352874 353878 354883 355890 356897 358903
      358907 361915 363924 366930 369932 372932 374928 375925
      375916 377913 377909 380889 382880 385875 386871 388870
      390878 390885 390893 396899 402902 404904 409904 415901
      425891 428886 431881 433873 435863 435851 435845 436842
      438835 440830 440825 439816 438811 437808 436802 435800
      434795 431792 430788 429783 434779 439774 444769 448764
      451758 458744 464730 466723 467717
 0.01 445646 439644 431647 425651 421653 418656 413661 412664
      413668 416670 419669 425663 428661 431658 434657 437654
      441652 444649 445646
 0.01 436129 436124 436120 433121 432123 430128 428130 427134
      426136 427141 430140 431137 433135 435131 436129
 0.01 415156 417154 415151 413153 411155 411157 409159 408161
      409161 411160 411159 413158 414158 415156
 0.01 307032 307030 307028 306028 305027 303027 302027 301029
      301032 302034 303034 304034 305034 306033 307032
 0.01 292027 293023 292018 291016 289015 285015 282015 280017
      280018 281021 283023 285024 288027 290027 292027
 0.01 276801 277797 275794 268794 262797 257799 252803 248806
      247811 253809 258806 265805 270803 276801
 0.01 235820 236818 236816 235815 234814 233813 231813 230814
      229815 228817 228819 229821 229822 230823 232823 234823
      234822 235820 235820
 0.25 491302 490278 487264 484257 481252 475241 468234 458224
      455220 449217 441212 432217 427218 422222 419222 418220
      416214 409212 404207 397202 384197 379194 373193 370197
      366203 356204 350204 345207 337214 328220 328224 331225
      336223 346220 350220 354221 357223 358226 364234 366239
      369243 372248 374251 374255 372259 374262 377263 390268
      402271 408272 415272 425271 444267 451267 455266 460268
      464274 466280 468285 468294 465301 466310 471315 478316
      482314 488308 491302
 0.25 459180 458177 457175 456172 455169 452166 450168 448172
      447177 447182 448187 451185 453183 455181 457181 459180
 0.25 463109 464104 463099 461094 458087 458079 458068 457061
      454054 453044 452036 450031 446025 440023 437023 434020
      432016 427009 425011 424015 424026 424034 425038 427040
      430035 435033 437038 444050 446056 445064 441069 441074
      443076 451083 454089 453092 450094 440109 444110 446112
      448118 453122 457120 459114 462111 463109
 0.25 423843 423837 421832 416823 416813 413807 410803 409796
      407793 403789 400786 393782 389783 385788 382796 379807
      377819 380825 383829 386832 387838 389843 393847 397856
      399869 401874 403878 407880 411879 416872 420860 422852
      423843
 0.25 377868 377866 377864 377862 376860 376859 374859 374860
      373860 372862 372864 371867 371868 371869 371871 371873
      372874 373875 373876 374875 375875 376873 377871 377870
      377868
 0.50 457249 458245 457242 455238 451234 445231 439229 434229
      425232 419230 416228 416221 416217 414215 408214 404211
      400207 396205 390204 387206 386211 388217 384220 381224
      379231 378235 382245 383259 387262 393264 398265 404264
      413264 422261 430258 441256 450256 454254 457249
 0.50 412859 412854 412849 410842 408836 408831 405831 404834
      404841 402846 400850 401860 403866 403870 407870 409863
      412859
 0.50 392221 392220 390218 388220 390221 391221 392221
 0.50 362215 362213 361210 361209 359208 357208 355207 354207
      352208 351208 351210 351211 353213 354214 356216 358216
      359217 361217 362215
 1.00 428245 426239 420236 415233 413231 413226 413221 412220
      407222 403228 399231 394233 391233 388232 388234 390235
      393242 394248 389254 392256 398256 408251 418248 423247
      428245
 1.00 401216 401215 401214 400212 399211 398210 397210 396210
      395210 393212 394213 395214 396215 398216 399217 401216
      401216

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.