Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jackson MS
342 PM CDT Wednesday may 6 2015
diurnal cumulus the rule across the area this afternoon with temperatures
in the lower to middle 80s. Scattered rain showers continue to develop in the Florida
parishes of southeast la and far southeast MS and work north into Highway 98 corridor
before dissipating. Trends and hrrr indicate that this activity will
likely to continue to fester into far southern sections of our area
this evening...so will keep a 20 pop for rain showers. Other primary weather
issue for tonight is dense fog potential. Relatively shallow low
level moisture coming into southern areas on light southeast flow below dry
middle level air could potentially set stage for areas of dense fog.
Latest hrrr model shows areas of less than 1/4 Michigan visibilities in Pine belt
region by 09z...and lamp/mav guidance supports this as well. Have
included mention of dense fog in severe weather potential statement and have fog in grids as well.
Main forecast issue for Thursday is potential for rain showers/thunderstorms and rain primarily in
far western areas. Models suggest surge of moisture...daytime heating
and combo of weak upper wave and diffluent flow aloft will support
some scattered convective activity during the afternoon. While most
of this activity will likely remain west of our area...high res
models suggest potential for activity to build into at least far
western areas. Have carried low probability of precipitation here to account for this
possibility. Rest of area should remain dry.
Thursday night into Friday looks to be pretty much a Carbon copy of the
next 24 hours. Some potential for fog in southeast sections late Thursday
night into early Friday...followed by some limited convective
potential in far western areas Friday afternoon. Weak lapse rates and
minimal shear suggest any convection both Thursday/Friday afternoons will
remain generic and subsevere in nature.
As far as temperatures...went with bias corrected raw guidance next
few days given generally stagnant conditions that will persist.
Diurnal ranges have generally been larger than grasped by MOS
guidance of late given lack of appreciable rainfall last 7 to 10 days
necessitating lower mins and higher maxes than guidance. Mins in
particular seem to be overachieving especially in eastern MS where
conditions have been driest and surface ridge has greatest influence.
Cut British Columbia guidance a few degrees for mins in this area.
forecast through the weekend into early next week will be dominated
by a gradual increase in convective potential. Significant trough
over southwest Continental U.S. Resposnible for a multiday period of active
convection over plains and Midwest will continue to slowly eject
northeast into Monday. This will enable a front to slowly sag toward
our area into Monday. While best middle level height falls will pass
well to our north...approach of front and increasingly favorable
upper jet support should result in increased convective potential
particularly late Sunday into Monday. Decent lapse rates should
support seasonable instability...and passing trough results in modest
increase in shear with 500 mb flow forecast by European model (ecmwf) to reach 30-40
knots by Monday. This should mean some increased potential for organized
convection with some risk for stronger storms. However...given that
best support for severe weather remains to our north and west and that
severe potential will be highly dependent upon mesoscale developments
will leave severe weather potential statement clear for now. Probability of precipitation gradually increase through the
weekend to reach high chance/likely most areas Monday into Monday night.
Models have trended toward less of a push with front into Tue/Wed...
resulting in probability of precipitation lingering and less of a cooling trend. Accepted
model blend for this period...but if this trend persists in later
operational/ensemble model guidance may need to trend a bit
warmer/wetter through this period.
main focus for tafs is potential for IFR/LIFR conditions due to fog
and some stratus late tonight into early Thursday morning. Greatest risk
per hrrr/lamp guidance for LIFR conditions is in khbg area...but have
carried some IFR conditions as far north as I-20 primarily due to a
few hours of stratus. Conditions should improve rapidly to VFR all
sites in the 13z-15z timeframe.
Preliminary point temps/pops...
Jackson 58 85 62 86 / 8 9 5 5
Meridian 56 86 61 86 / 4 9 4 5
Vicksburg 61 85 63 85 / 7 14 6 8
Hattiesburg 60 87 64 87 / 17 9 5 5
Natchez 62 84 64 85 / 18 14 8 11
Greenville 62 85 63 87 / 5 9 7 14
Greenwood 60 86 61 86 / 3 9 5 9