Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 040650
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 AM EDT MON MAY 04 2015

...VALID 06Z MON MAY 04 2015 - 12Z TUE MAY 05 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
GDP 25 WNW ROW 30 NNE 4CR 25 NNW CQC 20 NNE SKX 30 NNW VTP
25 NE MYP 15 N CCU 25 NE 20V 40 W FNL 20 WSW FNL 15 NNW BJC
10 SW MNH 15 ESE PUB 35 S LHX 15 ENE SPD 20 N PYX 30 ESE HHF
55 S CDS 60 SSE MAF 25 NE E38 GDP.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 NE PVW 50 E LBB 20 N BPG 15 E INK 25 E CNM 40 E ROW
35 ESE CVN 15 NE PVW.


...SOUTHERN HIGH PLAINS OF TX/OK/NM...

AS A SOUTHERN STREAM SHORTWAVE STRENGTHENS AND APPROACHES FROM THE
WEST...FLOW FIELDS AND MOISTURE TRANSPORT WILL INCREASE...LEADING
TO WIDESPREAD PRECIPITATION. SEASONABLY STRONG HEATING AND SURFACE
DEWPOINTS INCREASING TO THE UPPER 50S TO NEAR 60 DEGREES WILL
CONTRIBUTE TO CAPE VALUES PEAKING AT THE LOWER END OF
MODERATE...AROUND 1000-1250 J/KG PER THE SREF MEAN AT 05/00Z OVER
SE NM/SW TX. THE MODELS HAVE CONSISTENTLY ADVERTISED AN ORGANIZED
HEAVY RAIN EVENT IN THIS AREA. OFTEN THE MODEL QPFS HERE ARE
OVERDONE...AS MIXING AND MID LEVEL DRY AIR HAVE A TENDENCY TO
PROMOTE OUTFLOW AND DOWNSTREAM PROPAGATION. IN THIS
CASE...HOWEVER...THIS EFFECT MAY BE OFFSET BY VERY STRONG INFLOW
AND FAVORABLE TIMING OF THE ARRIVING SHORTWAVE. THE LOW LEVEL JET
IS FORECAST TO INCREASE ABOVE 50 KNOTS FROM THE SSE AFTER
00Z...MAXIMIZING MOISTURE TRANSPORT INTO WHAT WILL LIKELY BE A
REGION OF UPSCALE CONVECTIVE GROWTH AS SCATTERED STRONG STORMS
COMING OFF THE HIGHER TERRAIN BEGIN TO MERGE. THE MODELS HAVE
CONSISTENTLY PLACED THE MAXIMUM CAPE AXIS AND 850 MB MOISTURE
TRANSPORT OVER FAR SE NM AND SW TX...BETWEEN LUBBOCK AND MIDLAND
IN THE 00-09Z TIME FRAME. MORE AND MORE MODELS...INCLUDING RECENT
GFS RUNS...WRF-ARW...NMM...AND NSSL WRF...ARE NOW PLACING A QPF
MAX THERE AS WELL...WHICH INCREASES CONFIDENCE IN PLACEMENT OF THE
GREATEST HEAVY RAIN THREAT. SOME OF THESE MODEL SOLUTIONS PRODUCE
EXCEPTIONALLY HEAVY TOTALS...OVER SIX INCHES. THIS MAY BE
OVERDONE...WITH THE BOUNDARY LAYER NOT BEING PARTICULARLY
MOIST...AND WITH PW VALUES PEAKING ONLY NEAR 1.25 INCHES...OR 2
STANDARD DEVIATIONS FROM CLIMATOLOGY. STILL...THE MODEL QPF SIGNAL
IS STRONG...AND LINES UP WELL WITH THE SYNOPTIC PATTERN. WPC IS
FORECASTING AREAL AVERAGE RAINFALL OVER 3 INCHES IN A SMALL REGION
BETWEEN LBB AND MAF...WHERE IN KEEPING WITH CONTINUITY FROM
PREVIOUS OUTLOOKS...AND IN COORDINATION WITH THE LOCAL
OFFICES...WE WILL CARRY A MODERATE RISK OF RAINFALL EXCEEDING
FLASH FLOOD GUIDANCE.

A BROAD SLIGHT RISK AREA SURROUNDS THE MODERATE...AND INCLUDES
MUCH OF EASTERN NM AND THE OK/TX PANHANDLES. SLOW MOVING
SUPERCELLS WILL POSE SOME RISK OF HEAVY RAIN EARLY IN THE PERIOD
OVER NM...AND MOISTURE AND FORCING MECHANISMS INCREASE UP THROUGH
THE PANHANDLES OVERNIGHT.


...FRONT RANGE OF THE ROCKIES / SANGRE DE CRISTOS / SANDIAS...

LIGHT POST-FRONTAL UPSLOPE WINDS ARE FORECAST IN NORTHERN
COLORADO...AND PASSAGE OF A MODERATELY STRONG MID LEVEL WAVE WILL
PROMOTE A PERIOD OF UPSLOPE FLOW WITHIN THE WARM SECTOR OVER NEW
MEXICO. THE SURFACE HIGH OVER THE NORTHERN PLAINS IS NOT VERY
STRONG AND WILL BE WEAKENING...BUT THE UPSLOPE IT PROMOTES IN
COLORADO WILL COINCIDE WITH ARRIVAL OF A DIFLUENT MID/UPPER FLOW
PATTERN AND ASSOCIATED INCREASE OF LOW LEVEL MOISTURE
TRANSPORT...WITH PW VALUES RISING TO NEAR 0.75 INCHES OR 2
STANDARD DEVIATIONS FROM CLIMATOLOGY. SIMILAR MOISTURE CONTENT IS
EXPECTED IN NEW MEXICO ALONG THE EASTERN SLOPES OF THE SANDIAS AND
SOUTHERN SANGRE DE CRISTOS. DRY AIR ENTRAINMENT AND WEAK
INSTABILITY WOULD ARGUE FOR CELL MOTION AND MODEST RAIN
RATES...BUT MEAN 0-6KM WINDS AND PREDICTED SUPERCELL MOTION VERY
LIGHT...AND VERTICAL WIND/ASCENT PROFILES COULD PROMOTE SOME
TRAINING / BACKBUILDING. SEVERAL FORECAST MODELS INDICATE LOCALLY
HEAVY RAINS NEAR AND JUST DOWNWIND OF THE MOUNTAIN PEAKS...WHERE
FLASH FLOOD GUIDANCE IS ALSO RELATIVELY LOW AT THE CURRENT TIME.

BURKE
$$





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