Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 240819
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
418 AM EDT SUN MAY 24 2015

...VALID 12Z SUN MAY 24 2015 - 12Z MON MAY 25 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 NW KVAF 10 WSW KMIU 25 NNW ALI 10 ENE HLR NFW 15 WSW DUC
20 N JWG 20 NNE EWK 20 WSW BIE 30 WNW SUX 15 S MML MKT 10 NW CCY
OTM 15 ESE JEF 20 NW CGI 30 SW CIR 20 W BYH 20 NE SGT BQP
25 W BTR 25 S KVNP 35 NW KVAF.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 N TOR 20 SSW OGA 35 N GLD 15 SE ITR 15 ESE LIC 30 SSW PUM
25 W HLD 10 ENE WRL 10 WSW DHS 40 N TOR.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 ESE 3T5 25 SSE PSN 15 W OSA 30 SE AQR 20 NNW ADH 20 NNW GCM
35 ENE JLN 20 N BPK 20 WNW LZK 25 NE IER 20 WSW LFT 30 SW KVBS
15 N KBQX 20 NNE PKV 25 ESE 3T5.


...SOUTHERN PLAINS NORTH TO CENTRAL PLAINS AND EAST TO WESTERN
GULF COAST...


...HEAVY RAINFALL POTENTIAL SHIFTS SLOWLY EASTWARD ACROSS EASTERN
PORTIONS OF THE SOUTHERN AND CENTRAL PLAINS AND TOWARD THE LOWER
AND MID  MISSISSIPPI VALLEY...

THE LATEST SYNOPTIC AND MESOSCALE MODEL GUIDANCE CONTINUES TO
SUPPORT A SIGNIFICANT...HIGH-IMPACT MULTI-DAY HEAVY RAIN EVENT
CONTINUING TODAY AND INTO EARLY NEXT WEEK AS THE WESTERN CONUS
LONGWAVE TROUGH CONTINUES TO "RE-LOAD" WITH ADDITIONAL SHORTWAVE
ENERGY THAT ROUNDS THE TROUGH BASE AND EJECTS EAST-NORTHEASTWARD.
WIDESPREAD CONVECTION ORIENTED IN A SSW-NNE FASHION EARLY THIS
MORNING IS ALIGNED PARALLEL TO THE MID-UPPER LEVEL FLOW...PER THE
HIGHLY AMPLIFIED TROUGH/RIDGE ORIENTATION...AND AS SUCH HAS
EXHIBITED SLOW EASTWARD PROGRESSION EARLY THIS MORNING.
MOREOVER...THE AMPLIFICATION OF THE PATTERN CONTINUES TO SUPPORT
LARGE-SCALE UPPER DIVERGENCE AND DEEP LAYER VERTICAL BETWEEN THE
UPPER TROUGH/RIDGE AXES OVER A BROAD AREA STRETCHING FROM THE
SOUTHERN PLAINS NNE INTO THE LOWER MISSOURI VALLEY.

THE NEXT IN WHAT HAS BEEN A SERIES OF SHORTWAVES ROUNDING THE
TROUGH BASE...CURRENTLY APPROACHING THE TX BIG BEND PER SATELLITE
WV LOOPS...WILL LIFT NORTHEAST ACROSS THE RED RIVER AND INTO THE
MID MISSISSIPPI VALLEY BY THE END OF THE PERIOD (12 MON).
DYNAMICAL FORCING ACROSS THE SOUTHERN PLAINS ASSOCIATED AHEAD OF
THIS SHORTWAVE/HEIGHT FALLS CONTINUES TO GET A BOOST EARLY TODAY
WITHIN THE RIGHT ENTRANCE REGION OF THE CONFLUENT UPPER FLOW (S-N
ORIENTED JET STREAK) ACROSS THE SOUTHERN-CENTRAL HIGH PLAINS. THIS
ALONG WITH THE ROBUST LLJ (40-50 KTS) AND ANOMALOUS PW VALUES OF
1.75 AND 2.00 INCHES (~2.5 STANDARD DEVIATIONS ABOVE NORMAL) IS
MAINTAINING THE WIDESPREAD ORGANIZATION (MULTIPLE QUASI-LINEAR
SEGMENTS)...THOUGH ON AVERAGE THE RAINFALL RATES HAVE DECREASED A
BIT WITH THE LOWERING MUCAPE (ESPECIALLY NORTH OF CENTRAL
TX)...EVIDENCED BY THE WARMING CLOUD TOPS PER SATELLITE IR LOOPS.

OUTSIDE OF THE NEAR TERM (12Z AND BEYOND)...THE MODELS ARE ONCE
AGAIN STRUGGLING WITH THE DETAILS IN TERMS OF THE EASTWARD
PROGRESSION/FORWARD PROPAGATION OF THE QLCS. WPC DID UTILIZED THE
RGEM AND OTHER HIGH-RES GUIDANCE (SUCH AS THE WRF-ARW) TO NUDGE
THE ACTIVITY A BIT MORE TO THE EAST DURING THE 12-00Z TIME
FRAME...GIVEN THE ANTICIPATION OF STRENGTHENING DEEP-LAYER
INSTABILITY DOWNSTREAM WITH MUCAPES CLIMBING BETWEEN 2000-3000+
J/KG INTO NORTHWEST LA AND SOUTHWEST AR THIS AFTERNOON. WILL
RE-EVALUATE THE TIMING WITH SOME NEWER GUIDANCE (INCLUDING THE 00Z
ECMWF AND 06Z MODEL RUNS) AND MAKE ANY NECESSARY EDITS TO THE
FINAL DAY 1 QPF PACKAGE ISSUED AT 10Z.

FARTHER NORTH INTO EASTERN KS/NE AND MUCH OF MO/IA...AHEAD OF THE
SHORTWAVE TRACKING TO THE NORTHEAST...THE DEEP-LAYER INSTABILITY
WILL NOT BE AS STRONG...AND AS A RESULT HAVE CUT DOWN ON THE
AREAL-AVERAGE QPF A BIT FROM THE PREVIOUS WPC FORECAST (WIDESPREAD
AMOUNTS CLOSER TO 1-1.5" ON AVERAGE INSTEAD OF 1.5-2.0 INCHES PER
THE PREVIOUS FORECAST). THIS IS CONSISTENT WITH THE TRENDS IN THE
BULK OF THE GLOBAL AND HIGH-RES GUIDANCE...INCLUDING THE NEW (00Z)
ECMWF. STILL A HEALTHY AMOUNT OF WATER NONETHELESS FROM A
BASIN-AVERAGE STANDPOINT...AND CERTAINLY GIVEN SOME MODEST
INSTABILITY (MUCAPES GENERALLY UNDER 1500 J/KG) ALONG WITH THE
ANOMALOUS PW AND 850-700 MB MOISTURE FLUX...LOCALLY HIGHER AMOUNTS
ARE EXPECTED PER THE HIGH RES GUIDANCE. AS A RESULT...THE SLIGHT
RISK FOR EXCESSIVE RAINFALL WILL CONTINUE ACROSS THESE AREAS.


...CENTRAL HIGH PLAINS...

SCATTERED TO LOCALLY NUMEROUS SHOWER ACTIVITY IS LIKELY AGAIN IN
THIS ABOVE AVERAGE PW AXIS WITH 700-500 MB VERTICAL VELOCITY
MAXIMA ROTATING AROUND THE BROAD CIRCULATION LEADING TO A LOCALLY
HEAVY RAINFALL OVER PORTIONS OF CENTRAL AND SOUTHEAST WY INTO FAR
WESTERN NE AND NORTHEAST CO. THIS COINCIDES WITH A MAX REGION OF
UPPER DIFFLUENCE AS WELL AS SOUTHEAST-EAST LOW-LEVEL UPSLOPE FLOW
AND FAVORABLE MOISTURE TRANSPORT. LOCALIZED HEAVY RAIN ARE
POSSIBLE WHERE CELLS MOVE SLOWLY...AND CONSIDERING THE RECENT
HEAVY RAINS (LOW FFG VALUES OF 1.5" OR LESS IN 6
HOURS)...ADDITIONAL LOCALIZED SHORT-TERM RUNOFF ISSUES ARE
ANTICIPATED. MANUAL QPF USED A MULTI-MODEL BLEND...WHICH
MAINTAINED GOOD CONTINUITY FROM THE PREVIOUS WPC FORECAST.

HURLEY
$$





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