Area forecast discussion
National Weather Service Birmingham Alabama
332 am CDT Thursday Jun 20 2013
Discussion...
Current water vapor imagery indicates a closed upper low across the
Pacific northwest with a ridge across the central Continental U.S.. closer to
home...across the southeast...a few shortwave troughs can be noted
in the northwesterly flow on the eastern side of the ridge. These
subtle features will be key for shower and thunderstorm development
over the coming days. At the surface...a weak frontal boundary is
located just to the south of the County Warning Area and stretches back to the west
into eastern Texas. Last nights 00z sounding indicated a sharp
decrease in precipitable water down to 1.17 inches. Most of the year this would be a
respectable precipitable water value but for late June this around the 25th
percentile. For today...the highest probability of precipitation will be across the
southeast where the lingering surface front could provide additional
lift to parcels. Areas south of I-85 will also have the highest precipitable water
values running in the neighborhood of 1.5 inches. Further to the
north...coverage should be fairly isolated at best with precipitable water values in
the 1.25 area. Will hold on to the slight chance for afternoon
showers and thunderstorms further north as a shortwave trough moves
through the northwesterly flow. Model soundings indicate that cape
will be rather skinny with weak flow aloft so no strong or severe
storms are anticipated. Convection should be diurnally driven with
some isolated shower and thunderstorms possibly lingering into the
evening hours. With a fairly dry atmosphere for late June and no real
source of surface lift removed probability of precipitation during the overnight period.
Moisture will slowly increase late in the week and into the weekend.
Rain chances of Friday will creep northward. Best chances again will
be across the southeast decreasing to the northwest. The upper level
ridge will become amplified across the eastern half of the Continental U.S.. the
main challenge with this forecast is all of the models indicate a
weakness in the ridge across the southeast. Some of the models
indicate what appears to be a weak upper level low. Low level winds
will become more southerly by the weekend as the upper level ridge
at low level amplifies across the Atlantic. These southerly winds
will provide a fresh supply of Gulf moisture with precipitable water increasing to
near 2 inches by the end of the weekend. With the lack of any real
surface feature...convection should be diurnally driven with highest
chances during the afternoon with only slight chance to no chance
during the overnight hours. Temperatures will run a couple of
degrees below normal during this period with increased cloud cover
and precipitation. Upper level heights will increase during the
middle of the work week but continued southerly low level flow
should provide sufficient supply of moisture for rain chances to
continue. Models indicate a more potent upper level trough will
rotate through the ridge middle to late next week but differ slightly
on strength and timing.
05/Massachusetts
&&
Aviation...
06z taf discussion.
Winds have diminished across much of the area tonight...with surface
moisture remaining elevated. Patchy fog is possible...especially
across the southern half of the area. Very isolated areas of 3-4kft
cloud decks have developed across the south. There is weak lift
noted in forecast models...which weakens after 09z. Will include scattered
clouds at mgm and toi above 3kft for several hours...before light
fog develops.
Lower visible and ceilings will lift with sunrise Thursday morning. Front
should be shifting south of the area during the morning hours. This
will lower any rain chances across the south...and will only include
scattered 3kft ceilings at mgm and toi for tomorrow.
14
&&
Preliminary point temps/pops...
Gadsden 89 65 89 66 86 / 10 10 20 10 20
Anniston 88 67 88 68 86 / 10 10 20 10 20
Birmingham 90 69 90 70 87 / 10 10 20 10 20
Tuscaloosa 92 70 91 71 89 / 10 10 20 10 20
Calera 89 69 90 70 86 / 10 10 20 10 20
Auburn 88 68 88 69 85 / 20 10 30 20 30
Montgomery 91 70 92 72 90 / 20 10 30 10 30
Troy 90 69 90 70 88 / 30 10 30 20 40
&&
Bmx watches/warnings/advisories...
none.
&&
$$
