Quantitative Precipitation Forecast
Issued by NWS

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000
FXUS04 KWBC 240654
QPFPFD

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
153 AM EST FRI FEB 24 2017


PRELIM DAY 1 QPF DISCUSSION
VALID FEB 24/1200 UTC THRU FEB 25/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1

...EASTERN U.S...

THE SOUTHERN AND EASTERN STATES WERE IN THE MIDST OF RECORD
SETTING WARMTH...WHILE THE TROUGH OVER THE NORTHWESTERN HALF OF
THE NATION WAS EQUALLY IMPRESSIVE IN HOW COLD IT WAS ALOFT...WITH
500 MB TEMPERATURES COLDER THAN -30 C NOTED AT MANY UPPER AIR
STATIONS. THIS JUXTAPOSITION HAD PRODUCED SOME VERY STEEP LAPSE
RATES ON BOTH THE COLD AND WARM SIDE OF THE BAROCLINIC ZONE...AND
WILL CONTRIBUTE TO CONVECTIVELY ENHANCED PRECIPITATION WITHIN THE
ZONE OF UPGLIDE AND DEEP HEIGHT FALLS FROM THE MIDWEST INTO THE
GREAT LAKES. PRECIPITATION TYPES ALSO GO THROUGH A TRANSITION IN
THIS ZONE...ACROSS IA/WI/MI. THE HEAVIER AMOUNTS...EXCEEDING ONE
INCH...OVER SOUTHERN AND EASTERN LOWER MICHIGAN WILL FALL AS
MOSTLY RAIN. DEEP LAYER FORCING WILL BE ESPECIALLY LONG LIVED
HERE...WITH WARM ADVECTION FOLLOWED LATER BY STRONG HEIGHT
FALLS...WITH THE SURFACE LOW ALSO TRACKING TOWARD CENTRAL LOWER
MICHIGAN.

GENTLER UPGLIDE...MAINLY ON THE 290-295 K ISENTROPIC
SURFACE...WILL EXTEND DOWNSTREAM INTO NEW ENGLAND...SUPPORTING
BROAD 0.10 TO 0.40 INCH AREAL AVERAGE PRECIPITATION THROUGH
SATURDAY MORNING. MEANWHILE IN THE WARM SECTOR AN ENTIRELY
CONVECTIVELY DRIVEN EVENT IS EXPECTED FRIDAY AFTERNOON / NIGHT.

THE RELATIVELY NARROW ZONE OF HEAVY SNOWFALL WITH THIS SYSTEM HAD
NOT MOVED MUCH IN THE GUIDANCE...SO WE WERE ABLE TO MAINTAIN A
GOOD DEAL OF CONTINUITY THERE...FROM NE/IA NORTHEASTWARD. WE DID
REDUCE QPF A BIT OVER NORTHEAST WISCONSIN...AS THE SYSTEM WILL
BECOME WRAPPED UP AND AMPLIFIED ENOUGH TO DEVELOP A RELATIVE DRY
SLOT DURING THE DAY. FOR BOTH THE COLD AND WARM SIDE OF THE SYSTEM
WE FAVORED THE 00Z GFS...WRF-NMM...AND NAM CONUS NEST...AND NUDGED
THE PREVIOUS WPC FORECAST TOWARD THESE. CONFIDENCE IN PLACEMENT IS
HIGHEST IN THE COLD SECTOR...AND ALONG THE NOSE OF THE LOW LEVEL
JET INTO LOWER MICHIGAN. FARTHER SOUTH IT WILL BE DIFFICULT TO
ACCURATELY CAPTURE MULTIPLE NARROW SWATHS OF HEAVIER PRECIPITATION
FROM THE OUTBREAK OF STRONG TO SEVERE STORMS EXPECTED PER THE
STORM PREDICTION CENTER DAY 1 OUTLOOK. RAPID STORM MOTION WILL
LIMIT OVERALL RAINFALL POTENTIAL...BUT UNSEASONABLY RICH MOISTURE
AND INSTABILITY ARGUE FOR RESPECTABLE SHORT TERM RAIN RATES. WPC
TRENDED TOWARD SOMEWHAT GREATER QPF FROM OHIO TO TENNESSEE PER A
CONSENSUS OF SOME OF THE MORE AGGRESSIVE GUIDANCE...WHICH WE SIDED
WITH BASED ON THE AVAILABLE MOISTURE...INSTABILITY...AND DEEP
LAYER FORCING.


...ROCKIES...

RESIDUAL MID LEVEL MOISTURE WITHIN THE BASE OF THE ELONGATED
WESTERN/CENTRAL U.S. TROUGH WILL SUPPORT SNOW SHOWERS IN THE
ROCKIES. LARGE SCALE FORCING IS RELATIVELY NEUTRAL HERE...AND
WINDS MAINLY LIGHT EXCEPT FOR TERRAIN EFFECTS...SO PRECIPITATION
POTENTIAL IS LIMITED. WPC NUDGED THE INHERITED FORECAST TOWARD
NDFD AND TOWARD A DOWNSCALED VERSION OF OUR IN-HOUSE ENSEMBLE
WHICH MAKES USE OF THE HI-RES MODELS.


...PACIFIC NORTHWEST AND NORTHERN CALIFORNIA...

A DEVELOPING CLOSED LOW IS FORECAST TO SKIRT THE OREGON COAST AS
IT DIGS SOUTHWARD. VERY COLD AIR ALOFT WILL YIELD A SHOWERY
REGIME...PARTICULARLY FOCUSED OVER WESTERN OREGON WHERE MODEST
ONSHORE FLOW WILL DEVELOP AS A 700 MB TROUGH FORMS JUST OFFSHORE.
THIS FEATURE STARTS TO REFORM FARTHER OFFSHORE OF CALIFORNIA AS
THE SYSTEM SLIDES SOUTHWARD...PER GFS FORECASTS...RESULTING IN A
MORE ANEMIC FLOW PATTERN OVER NORTHERN CALIFORNIA. STILL...A
SUFFICIENTLY MOIST COLUMN COMBINED WITH DIFLUENT UPPER LEVEL FLOW
EAST OF THE LOW CENTER...SHOULD PRODUCE SCATTERED RAIN/SNOW
SHOWERS OVER NORTHERN CALIFORNIA AND FAR NORTHWEST NEVADA. WPC QPF
REMAINED CLOSE TO CONTINUITY.

BURKE

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

24HR QP VT 25/12Z
 0.01 536199 537185 537178 536174 533166 528161 524154 520149
      513146 507142 486128 481124 477119 474113 475106 475101
      474096 469090 457085 450072 445067 439065 436063 435060
      432054 427049 422046 418047 411048 406047 401048 385050
      376049 372050 369052 373054 377054 381056 382060 378062
      375062 370061 359064 358067 360068 364068 367066 372069
      374077 374085 378085 381084 386085 390084 393085 395087
      397087 404082 407080 410081 414088 404097 401104 397105
      396107 391112 386116 386119 389121 394121 399122 404122
      410127 415132 417136 418141 417147 419149 422150 423146
      427141 429137 432137 433141 433147 432152 435153 439158
      443156 449158 451161 453160 453154 453149 454147 459143
      461140 465139 469138 472141 480143 484149 483153 480152
      476151 473153 471154 470157 471160 474163 476167 478168
      478172 480174 481178 485179 486175 489175 494180 494189
      494193 493198 489202 481201 478204 473203 468206 461206
      457207 455210 450211 447212 443211 441209 440204 437203
      435206 432207 430204 425198 422192 422176 419178 415182
      413187 410189 406196 403200 401201 392201 390202 388205
      391210 395216 398218 402220 403224 401226 396227 394226
      390227 384228 379232 376237 376242 378247 384253 390258
      396262 404267 418267 430266 441261 446257 452255 462254
      468253 473254 482256 486257 491259 498261 498256 496252
      495248 497244 498241 500244 503246 506248 508248 510244
      508237 507234 508229 508222 507218 509208 510205 512203
      514203 518204 519207 528205 536199
 0.01 505761 505749 502741 498734 496725 493716 492705 492697
      491687 490677 487670 485663 481658 478655 472652 465650
      461642 459638 456635 453634 447640 444645 443652 441659
      441667 440672 439674 436675 434674 428683 426697 426712
      423749 423758 422765 417769 415771 416776 410787 405791
      400795 380804 375809 373811 369810 368806 369804 366804
      364807 359811 355816 352819 349826 335841 320857 301878
      297881 294885 290890 288897 286904 287907 292917 295922
      300926 305928 308926 327909 335902 340898 346895 357891
      361888 366887 370885 371888 368893 369897 372898 376898
      380896 384897 385902 388902 397903 402906 409915 410921
      410926 408933 405938 403945 403950 402954 403960 399989
      393023 394039 398039 400037 400033 402030 404023 407017
      411012 415009 420006 424002 429994 434988 437981 439973
      442966 447951 449945 453940 460930 466921 472910 478900
      482895 485887 489871 489861 492852 495848 498842 501836
      503828 505822 506814 505779 505767 505761
 0.01 499113 500099 499090 497081 497069 498062 497058 497046
      495043 493044 490045 488050 487044 485041 483039 479038
      470038 468046 473061 475072 475078 476081 476086 477092
      480100 484105 488106 490109 493107 496110 499113
 0.01 463178 462176 461175 458177 454175 453171 451170 450170
      449173 451176 454179 454181 455185 457184 459182 461181
      463178
 0.01 452183 450180 449180 447179 445179 445181 443183 442186
      443186 444186 446184 448185 450185 451185 452183
 0.01 363054 361053 359053 359054 357055 357056 359056 361056
      363054 363054
 0.01 346730 343725 338724 330725 325727 320731 316735 313740
      311745 309752 308758 310763 312767 317771 322772 328770
      332766 335761 336754 338747 340742 344737 345732 346730
 0.25 481703 481699 480696 475695 471696 469691 460673 458669
      455666 452670 452676 452687 451696 444703 442707 441714
      443728 443733 441737 435754 430771 429777 429785 424793
      411802 399810 392815 384818 374823 367828 361832 357835
      354838 351846 347853 346858 348862 355864 361865 367864
      372863 378862 385856 393855 401850 403857 403861 401865
      396870 390878 392880 395878 399877 403878 405883 407887
      411888 424879 431878 435879 437882 422916 419926 419936
      421944 423949 424952 428952 433948 438941 443933 446924
      450918 455911 465898 469888 473878 477857 479836 485817
      487804 488790 487779 484766 480748 479721 481703
 0.25 469240 464234 459229 452230 447232 434236 418233 413233
      411235 406238 404242 403247 408253 411255 415257 421257
      429256 435254 446248 453245 459244 469240
 0.25 411223 412221 411220 411221 410223 411223 411223
 0.50 480789 479779 478773 473762 469752 467747 463744 460738
      459736 456736 452746 447748 446752 439759 436765 435770
      435777 436783 433792 428800 424804 417804 409810 395821
      390826 390832 391836 388838 384841 378846 374850 372855
      376857 380855 383852 391846 392852 397850 400847 408839
      411841 410844 411847 412853 412859 410870 409875 412875
      417873 425868 433865 439865 445863 452873 456876 459876
      463868 464862 463856 465842 469831 473821 477812 479805
      479799 480789
 0.50 443242 445240 444238 440238 435239 430239 424239 417239
      413243 411245 412248 419251 424250 430249 435248 439245
      443242
 0.50 450906 450899 449896 446894 443894 438898 433904 430912
      428921 428930 431933 435932 440926 444921 447913 450906
 0.50 377832 376829 373830 369833 364837 359841 356844 353850
      353855 356856 362852 365848 368844 371839 375835 377832
 1.00 469784 468777 464772 459767 454770 451775 447783 437800
      433810 431821 432833 431838 428841 422851 420855 420859
      425855 429853 439851 446850 452843 456832 459822 462812
      467801 469791 469784
 1.50 463787 461782 459778 457777 455779 452782 448790 444798
      442803 442808 440820 442827 450825 454817 457806 460797
      463787
 2.00 454796 455793 455791 454789 452791 452792 451793 450794
      449797 449799 450800 451800 453799 454796 454796

$$




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